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Ice core records of atmospheric methane show that on orbital and millennial timescalesmethane closely follows changes in Greenland temperature, presumably driven by variationsin tropical precipitation/hydrology. Over the last glacial period, warm events referred to asGreenland Interstadials (GI), noted in Greenland ice core δ18O records and other globalclimate archives, are characterized by a coeval rise in atmospheric methane. At the onset ofthese events methane rises by 50-300ppb from Greenland Stadial (GS) concentrations. Inaddition to the GI/GS methane variations, there are distinct, though smaller, increases inmethane during Heinrich Stadials 1, 2, 4 and 5. These Heinrich Stadial features inthe methane record are unique as there is no coeval change in Greenland waterisotopes. Using the Inter-Polar Difference (IPD) of atmospheric methane, we investigate theseperiods and determine how latitudinal source distributions change between GS/IS cycles, totest a hypothesis that the Inter-Tropical Convergence Zone, normally positioned north of theequator, shifted southward during Heinrich Stadials, causing an intensification of monsoonsand tropical wetland methanogenesis in the southern hemisphere and drying in the northernhemisphere. We measured high-resolution records of CH4 from the GISP2 and WAIS Divide ice coresand calculated the IPD for the periods, GS 10 through GI 8 and GI 13 through GI 11. We alsoreanalyzed previous IPD measurements covering the LGM and Bølling/Allerød. Forthe first time, our records incorporate a correction for excess methane productionassociated with dust in Greenland cores. This correction implies an overall reductionin the IPD relative to previous studies. We furthermore resolve centennial-scaleCH4 variability in both records for the first time, greatly reducing chronologicaluncertainties. We show that the tropical to boreal source ratio between GS and GI periodsremains relatively constant, indicating a coeval response in both regions during a GSwarming event. Heinrich Stadials by contrast are characterized by a significantincrease in the tropical to boreal source ratio, suggesting a likely shut down theboreal sources and a potential increase in Southern Hemisphere or tropical sources. [ABSTRACT FROM AUTHOR]

During the last glacial cycle, the Antarctic Ice Sheet (AIS) has passed from an interglacial state, warmer than present day (PD), slowly into a glacial state, known as the Last Glacial Maximum (LGM) and then deglaciated on a faster timescale into the Holocene and PD conditions. Although we have proxy data of the size and extent of the ice sheet for the LGM, neither the oceanic temperatures of the Southern Ocean, nor the precipitation fields are well constrained. Also the time evolution of the ice volume during the glacial cycle is not fully clear. It is well assumed that it follows a sawtooth pattern, but from a modelling perspective different combinations of parameters and boundary conditions can give rise to plausible Antarctic configurations. Here we aim to study the uncertainty in AIS evolution resulting from ice-sheet model parameters, as well as the imposed climatic fields used as forcing. For this purpose we use the three-dimensional thermomechanical hybrid ice-sheet-shelf model Yelmo, which treats ice dynamics via the shallow-ce and shallow-shelf approximations, and accounts for basal melt below ice shelves and a subgrid parameterisation for treatment of the grounding line. We will focus on the effect of different climatic fields, such as precipitation and oceanic temperatures, as well as the effect of different enhancement factors and basal drag choices for reproducing consistent Antarctic configurations in the LGM and the PD. Improving our understanding of the effect of different ice-dynamics configurations in various climatic scenarios will help to better understand the past evolution of the AIS and potentially constrain its future evolution as well. [ABSTRACT FROM AUTHOR]

Atmospheric CO2 concentrations (pCO2) varied on millennial timescales in phase withAntarctic temperature during the last glacial period. A prevailing view has been that carbonrelease and uptake by the Southern Ocean dominated this millennial-scale variability inpCO2. Here, using Earth System Model experiments with an improved parameterization ofocean vertical mixing, we find a major role for terrestrial and oceanic carbon releases indriving the pCO2 trend. In our simulations, a change in northern hemisphere insolationweakens the Atlantic Meridional Overturning Circulation leading to increasing pCO2and Antarctic temperatures. The simulated rise in pCO2 is caused in equal partsby increased CO2 outgassing from the global ocean due to a reduced biologicalactivity and changed ventilation rates, and terrestrial carbon release as a response tosouthward migration of the Intertropical Convergence Zone. The simulated terrestrialrelease of carbon could explain stadial declines in organic carbon reservoirs observedin recent ice core δ13C measurements. Our results show that parallel variationsin Antarctic temperature and pCO2 do not necessitate that the Southern Oceandominates carbon exchange; instead changes in carbon flux from the global oceanand land carbon reservoirs can explain the observed pCO2 (and δ13C) changes. [ABSTRACT FROM AUTHOR]

The deposits of the Jeju Strait shelf can be divided into twelve sedimentary facies that are grouped into four depositional units, which formed in response to late Pleistocene to Holocene sea level changes. The deposits of the shelf can be grouped into four depositional units, each with different sedimentary facies and structures: 1) shelf sand, 2) estuarine sand/mud, 3) fluvial sand/mud, 4) shelf sand/mud. The Unit 1 shows massive to slightly bedded sandy shells with oyster fragments and is regarded as shelf sand developed under the shelf environment during the last interglacial. OSL date of the base of the unit is 124.4 ka. Unit 2 is characterized by thinly periodic parallel laminated mud, suggesting tidal signatures in tidal flats. The sediment color of this unit sediments is also characterized by moderate brownish, strongly suggesting extreme weathering trace after the depositions. OSL dates of this unit range from 81.1 to 74.2 ka. Unit 3 consists of lower cross-bedded sand and laminated mud with fining-upward successions. This unit is interpreted to be products of channel deposits in the fluvial environment. The OSL ages of Unit 3 range from 50.6 to 26.1 ka belonging to the Weichselian glacial period. The Unit 4 is composed of homogeneous mud and massive sand with molluscan shell fragments developed in the modern shelf environment. OSL and 14C-AMS age of Unit 4 ranges from 0.32 to 11.2 ka. [ABSTRACT FROM AUTHOR]

The Himalayan-sourced Ganges-Brahmaputra river system and the deep-sea Bengal Fan represent Earth's largest sediment-dispersal system. Recent work has developed a detrital-zircon (DZ) U-Pb provenance record from the Bengal Fan, from cores collected during IODP Expedition 354 located 1350 km basinward of the shelf margin. This dataset consists of 25 DZ samples from Early Miocene to Middle Pleistocene medium- to fine-grained turbidite sand, as well as samples from the modern Ganges and Brahmaputra Rivers, which serve as benchmarks against which the older record can be compared. These data record the strong tectonic and climatic forcing associated with, and inherent to, the Himalayas and Ganges-Brahmaputra system: after up to 2500 km of river transport, and 1350 km of transport by turbidity currents, the DZ U-Pb record faithfully represents Himalayan and Tibetan sources. Here we discuss possible signals of climate change within the Plio-Pleistocene part of the DZ U-Pb record. First and foremost, present-day sediment transfer to the land-sea boundary is closely coupled to the monsoon. However, for large rivers with broad shelves, delivery of sand to the deep sea is limited during global interglacial sea-level highstands like that of the Holocene, hence the sand-rich turbidite record is biased towards glacial periods when rivers extended across the shelf in response to climate-forced sea-level fall, and connected directly with slope canyons and the shelf margin. Second, sandy turbidites of the Bengal Fan displays the same DZ age populations and U-Pb age peaks that are present in modern river samples, but their proportions are significantly different. Pleistocene Bengal Fan data include (a) higher proportions of the <300 Ma population from Tibet, (b) higher proportions of the ca. 400-600 Ma population, which can be derived from Tibet and/or the Greater Himalaya Sequence, and (c) lower proportions from the Lesser Himalaya Sequence and/or peninsular India. We speculate these differences reflect contrasts in the loci of sediment production in the modern interglacial climate with strong monsoon rains, vs. a glacial climate where monsoon strength may be reduced and erosion is strongly tied to higher-elevation cold-climate and glacial processes. [ABSTRACT FROM AUTHOR]

Correlation of glaciations in disparate mountainous regions commonly relies on radiocarbon. Although it is the most common geochonological method used in Quaternary, archeological and geomorphic studies, the method is not without issues. A blind comparison of seven different radiocarbon laboratories was carried out to test reproducibility of radiocarbon age determinations. Lab A and E utilize the radiometric method, and Labs B, C, D, F and G utilize the accelerator method. Duplicate samples were sent to the laboratories without their knowledge that they were participating in the test. The results are provocative as there are significant differences among the laboratories:Three separate macrofossils from the same sample - 18,380±100 (Lab B), 17,380±130 (Lab C), and 17,820±140 (Lab C).A single Picea sp. (spruce) branch - 19,600±170 (Lab A), 19,500±170 (Lab A), 18,420±110 (Lab B), 17,290±130 (Lab C), and 19,300±150 (Lab D).A single Picea sp. (spruce) branch used as a standard by the GSC Radiocarbon Laboratory was analyzed five times resulting in an average age of 25,100±~150. The same log yielded ages of 25,320±400 (Lab A), 24,000±160 (Lab C), 25,160±100 (Lab D), 25,210±120 (Lab D), 24,710±170 (Lab E), 24,790±170 (Lab F), and 24,950±170 (Lab G).A single Salix sp. (willow) twig - 30,400±480 (Lab B), 28,310±280 (Lab C), 33,240±230 (Lab D), and 33,140±230 (Lab D). A single Salix sp. (willow) twig - - 24,930±940 (Lab C) and Lab D (>44,000). A second Salix sp. twig from the same sample - 33,290±380 (Lab C). A third Salix sp. twig from the same stratigraphic level - Lab D 46,500±1200 (Lab D). The differences between laboratories generally become larger with increasing age, raising the possibility that some labs introduce a small amount of modern carbon during processing. Because chronologic control is vital for many Quaternary studies, these results are disturbing. Radiocarbon users are cautioned that different laboratories may provide significantly different ages, making correlation potentially problematic. The problem is especially acute for samples at or near the limit of radiocarbon dating. The issue of laboratory consistency aside, we also advise caution in interpreting radiocarbon ages, as they are, in reality, a probability distribution. Internal testing at the GSC Radiocarbon Laboratory demonstrates that variation between samples processed and analyzed at the same facility in some cases can exceed the combined error. This is important when researchers are trying to determine lags and leads to climate forcing. [ABSTRACT FROM AUTHOR]

Recent climatic warming has resulted in rapid retreat of glacier margins in the northern hemisphere exposing landforms which record changes in glacier extent and behaviour through their sedimentology and geomorphology. These modern glacial systems can be used as analogues for paleoglacial deposits, such as those found throughout Europe, Canada and the northern USA. Large ice sheets that covered land masses in the northern hemisphere during the Quaternary are known to have hosted fast-flowing ice streams that controlled ice dynamics and behaviour. However, the former positions of these ice steams are difficult to determine in paleoglacial deposits. This study focuses on documentation of sedimentological and geomorphological characteristics of the proglacial fields of western Slettjökull and Öldufellsjökull, northern outlet glaciers of the Mýrdalsjökull Ice Cap in southern Iceland. These glaciers were selected as they have both experienced periodic episodes of fast ice flow and rapid marginal advance (surges) during the last century. It is believed that surging ice margins can be used as analogues for rapidly moving paleoice streams common within the Laurentide and Scandinavian Ice Sheets during the last glaciation. A combination of landsystem analysis, whereby landforms are classified into genetically related landform-sediment assemblages, and architectural element analysis (AEA), a hierarchal method of examining sedimentary deposits, is applied in this study. This methodology allows a detailed model of the process-form relationship of landforms and sediments exposed in front of the retreating glaciers to be created. Initial mapping of the proglacial fields of Sléttjökull and Öldufellsjökull was completed using high resolution digital elevation models (DEM) obtained from the Icelandic Meteorological Office to investigate the types, scale and distribution of glacial landforms. These maps were ground checked in the field using a portable geographic information systems (GIS) unit. Sedimentological data were collected from exposures along river banks and terraces to identify the sediment types associated with different landform types. An unmanned aerial vehicle (UAV) was also used to collect high resolution imagery of the proglacial fields, focusing in particular on areas impacted by the most recent surge events. Field and remotely sensed data were combined into a GIS to examine the spatial relationship between the various landforms and their associated sediments. The proglacial fields of these two outlet glaciers show overall similarities in the distribution and morphology of landsystems tracts connected with end moraine development. However, the proglacial field of Sléttjökull has a larger sandur proximal to the glacier margin and a greater amount of glaciofluvial sediment compared with Öldufellsjökull. The areas of the proglacial fields impacted by surges that occurred in the 20th century show a distribution of landforms that is similar to that described from other surge-type glaciers, including hummocky terrain and kettle holes. However, these proglacial fields lack the prominent glaciotectonized end moraine frequently reported at surge-type glaciers. The model developed for these proglacial fields may be utilized to help identify areas affected by fast-flowing ice and the position of former ice streams in previously glaciated regions. [ABSTRACT FROM AUTHOR]

Marine Isotope Stage 2 (MIS 2) is the latest glacial period and includes the Last Glacial Maximum, which is known as the period when global ice volume reached its maximum and global temperature lower than today. An advantage of MIS 2 is the availability of radiocarbon dating to make it possible to compare sea-level data with other paleoclimatic proxies. However, the number and accuracy of sea-level records during MIS 2 is currently lacking. Here we present the history of MIS 2 sea-level and ice-sheet change as recorded in the Bonaparte Gulf, northwestern Australia, by reconstructing relative sea level and then modeling glacial isostatic adjustment. The isostatically-corrected global sea-level history indicates that sea-level plateaued around 23 cal kyr BP prior reaching its minimum (~19 cal kyr BP). These large changes in ice volume over such a short time indicates that the continental ice sheets never reached their isostatic equilibrium during the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The radioisotope ratio 231Pa/230Th in Atlantic bulk sediments is commonly used as a proxyfor ocean circulation in the geologic past, particularly during the last (de)glacial periods. Theability for these particle-reactive isotopes to constrain circulation requires, among otherassumptions, that 231Pa is primarily affected by the flow, while 230Th is primarily affected byscavenging onto sinking particles. Deep oceanic regions of intense currents may violate thisassumption, as these currents may prevent 230Th from reaching a reversible exchangeequilibrium with settling particles, which is estimated to occur on a time scale of theorder of 10 yr at abyssal depths. Indeed, previous studies have shown that the DeepWestern Boundary Current (DWBC) ventilates deep layers in the western NorthAtlantic on decadal time scales with Labrador Sea Water, characterized by particularlylow activities of both isotopes. In our presentation, we will address the followingquestion: to what extent can transport of 231Pa and 230Th by the DWBC explain watercolumn observations of both radioisotopes in the Northwest Atlantic. This questionwill be tackled by comparing the distribution of 231Pa and 230Th simulated by aregional ocean circulation model (the Princeton Ocean Model) with water column231Pa and 230Th data gathered during (pre-)GEOTRACES cruises. The circulationcomponent of the model is constrained from (i) a 1/4-degree resolution hydrographicclimatology used to force the model via surface restoring, (ii) estimates of DWBC andGulf Stream inflows and outflows derived from various oceanographic programs,and (iii) surface wind stresses deduced from satellite altimetry. The scavengingcomponent of the model assumes that Pa and Th exchange reversibly with slowlysettling particles. In this description, adsorption of both metals onto particles isgoverned by a prescribed distribution of particulate matter which is derived from acompilation of nephelometer and transmissometer data. In our presentation, thesensitivity of modeled 231Pa and 230Th to changes in the volume transport of theDWBC will be examined. Model results will be compared to (pre-)GEOTRACES231Pa and 230Th data in order to provide an estimate of the effects of DWBC on theactivities of both radionuclides along the continental slope and in the abyssal basinsoffshore. [ABSTRACT FROM AUTHOR]

The maximal extent of the Laurentide Ice Sheet (LIS) on eastern Baffin Island during the Last Glacial Maximum (LGM; about 20 000 years ago) has been widely debated during the last decades as different palaeo-glaciological models have been proposed. Spatial and temporal variability of ice sheets extension during Quaternary glaciations complicate the establishment of a reliable reconstruction of the ice margin. Furthermore, the lack of geophysical data in most of the fjords, and seaward, makes it difficult to reconcile the proposed terrestrial and marine glacial margins. Here we use high-resolution swath bathymetry imagery, combined with acoustic stratigraphy data and sediment cores collected during various oceanographic expeditions, focusing on the ice dynamics in the area of Clyde Inlet since the LGM. Our data reveal possible positions of the maximal extent of the LIS near the continental shelf edge. The deglaciation on the shelf was rather slow and episodic, as indicated by the presence of grounding-zone wedges, recessional moraines, as well as time-transgressive glacial lineations. Ice retreat in the fjord occurred more rapidly, most likely due to increased water depths. However, the presence of multiple moraine systems reveals periods of ice-margin stabilizations. This study provides additional information to the terrestrial data and, thus, helps improve the models of glacial dynamics in the northeastern sector of the LIS. [ABSTRACT FROM AUTHOR]

A complex ice stream network occupied the European Alps during the last glacial maximum (LGM, MIS 2, Würmian Pleniglacial) with large valley glaciers extending as piedmont lobes into the northern and southern forelands. A completely different situation is reported for the easternmost Alps, where only a patchy pattern of isolated glaciers, confined to minor valleys, localized cirques and small plateaus could develop. Although the Alpine LGM glaciation was intensively studied, data sets vary considerably in the easternmost Alps (e.g concerning the numbers of local glaciers as well as extents) and systematic analyses of the glacial record are missing for the entire region. Consequently, equilibrium line altitudes (ELAs) and ELA depressions (ΔELAs) for these paleo glaciers remain unknown as well, though such data can be extremly useful to provide information on the variance of atmospheric circulation patterns over glacial to interglacial timescales. Characterized by relatively simple geometries and obviously rather simple source area relations (compared to the ice-stream network in the central Alps), they are most suitable for paleo-glacier reconstruction and ELA modelling – and can provide a robust dataset on ELA depression variabilities during the LGM. Such analysis is hardly possible for the ice-stream network occupying most of the central Alps at the same time.To fill this gap, we provide a new GIS-dataset of the LGM glaciation at the Eastern Alps based on the principal work of van Husen (1987), a number of case studies, geological maps, and the analyses of multiple orthophoto and DEM data. First systematic analyses on ELAs and ELA depressions of these low elevated isolated glaciers highlight the highly variable glacier response across the Eastern Alps to topographic and climatic forcing. [ABSTRACT FROM AUTHOR]

The Cryogenian (720 – 635 million years (Ma) ago) was a period in Earth's history of prolonged and severe glaciations, known as "Snowball Earth". The two main glaciations were probably near-global in extent, and the first of these (the Sturtian glaciation) lasted over 55 Ma, from about 715-660 Ma. The second, the Marinoan, "only" lasted 15 Ma, between 650-635 Ma. Recent results on the deep time history of Earth's tides, especially the discovery of a supertidal cycle linked to the tectonic supercontinent cycle, show that the tides are weak during a supercontinent arrangement because the ocean basins are not in tidal resonance due to their size. The Cryogenian was a period of a slow breakup of the supercontinent Rodinia between 750-633 Ma, and most of the period was spent with the continents only weakly scattered. Furthermore, the presences of nearly 1 km of ice may effectively have dampened out the tide. We can therefore expect the tides to be weak during the Cryogenian, but how weak? Did Snowball Earth kill the tides?Using an established a well-constrained numerical tidal model and the latest reconstructions of the tectonic configurations for the period, we show that the tides were indeed very weak throughout the Cryogenian. This is especially true during the glaciations, when a lowstand in sea-level of about 800m led to significantly reduced tides compared to an ice-free Earth with the same continental and orbital configuration. The 150 Ma simulated here are the most tidally quiescent of the 1 Byr now simulated, and they further support the idea of a supertidal cycle linked to the supercontinent cycle. The results further show that the tides were more energetic before the onset of the glaciations, and that they rapidly increased at the end of the Marinoan. We therefore conclude that the extensive glaciations did dampen the tides to very low levels due to changes in sea-level, with consequences for the Earth system at the time. The snowball did indeed kill the tides, with a sea level low stand during a supercontinent. [ABSTRACT FROM AUTHOR]

The aim of this paper is to showcase an ancient (Late Palaeozoic) striated surface in South Africa, and discuss its interpretation in the context of a soft-bedded ice sheet during the retreat phase. The quality of glacial geomorphic evidence, preserved in semiarid terrains of Africa, is extremely high, and allows special insight into aspects of an ancient glaciation that has gone to completion. The Dwyka Formation evidences multiple cycles of glacial advance and retreat which include a thick succession of diamictites and heterolithic strata. Painstaking work in the 1970s and 1980s produced regional palaeogeographic reconstructions, among which complex ice flows were identified. Trunk glaciers and / or ice streams appeared on a variety of palaeogeographic maps, many of which highlighted highly complex flow structures within the ice sheet. Nowhere are complex ice flow directions more apparent that in the Northern Cape Province, which exposes an outstanding soft-sediment striated surface at Oorlogskloof. Using a combination of field observations, aerial photograph interpretations, and new digital elevation models collected from an Unmanned Aerial Vehicle (UAV), we map the macrostructure of the surface. The inventory of structures, which include grain flow lobes at the flanks of flutes, suggests that the surface was largely generated at the ice-sediment interface, with local evidence for internal deformation and shearing of the sediment pile. Most importantly, the aerial images reveal two features that reveal a composite history to this pavement. Firstly, flutes and grooves to have high length to width ratios, potentially implying rapid ice flow. Secondly, the UAV images reveal a discontinuous network of bulbous ridges which traverse, fold and distort the striations and flutes. The latter features are interpreted to result from bulldozing beneath a floating ice mass. Collectively, therefore, the assemblage of structures may record two distinct phases in the he construction of this spectacular pavement. [ABSTRACT FROM AUTHOR]

Located between Melville Peninsula and northwestern Baffin Island (69.9247° N, 84.5121° W), the Fury and Hecla Strait region plays a key role in the understanding of the postglacial evolution of the Canadian Arctic. The absence of paleolimnological data in the region as well as the strategic position of the strait itself, given its location at the junction of the Atlantic Ocean currents coming from Foxe Basin and those of the Pacific Ocean through the Gulf of Boothia, make it a prominent region for Quaternary research. Although some studies have suggested a timing for the regional deglaciation, results remain extrapolated and do not provide high-resolution data for the region. This project aims to analyze sediment cores of lakes located on the southern shore of the Fury and Hecla Strait, in the Canadian Arctic, in order to reconstruct past climates and landscapes since the end of the last glacial period. A multi-proxy approach based on physical, chemical and biological core parameters, allowed high-resolution paleoenvironmental reconstructions of the region, including natural climate fluctuations, past extreme climate events and major landscape changes induced by glacial retreat, marine inundation and glacial isostatic readjustment.Various radiometric dating methods (210Pb, 137Cs and 14C) were used to establish a chronology for the reconstructed changes, pointing towards a glacio-marine phase that lasted from 8250 cal. BP, at its latest, to 6675 cal. BP, followed by a gradual transition towards freshwater conditions and the establishment of a lacustrine phase at 6125 cal. BP. An extreme event, marked by major geochemical and sedimentological shifts, also appears to have happened at 3950 cal. BP, but the nature of this abrupt change remains unknown. The results were also correlated with regional temperature data from previous studies to explore the relationship between diatom assemblage changes and environmental fluctuations. This study is crucial to respond to many unsolved questions in oceanography, biogeography, genetics or even anthropology, by providing a high-resolution chronology of geophysical changes, namely regional deglaciation and the opening of the strait. Furthermore, it improves our understanding of paleoenvironmental variability in the Foxe Basin throughout the Holocene, including climatic and physico-chemical shifts, enabling us to predict ecosystem responses to future global change. [ABSTRACT FROM AUTHOR]

The EastGRIP (East GReenland Ice core Project) Ice Core is drilled in a highly dynamic area, the North East Greenland Ice Stream (NEGIS), with a surface velocity of 55 m/yr, representing high flow rates in this area. All previous deep ice cores in Greenland were mainly drilled to find undisturbed ice for climate reconstruction. In contrast, the main purpose of this ice core is to increase our understanding of ice flow and linking it to deformation features shown in the physical properties. Some of these deformation features can be made visible using the line scanner device. It scans a polished ice core slab illuminated by an indirect light source (similar to dark field microscopy) and thus makes internal features (e.g. impurities, bubbles, hydrates and partly grain boundaries) visible, creating a 10x165 cm image of the core. Light traveling though the core is reflected and scattered at these features thus causing the camera to detect a bright section where the impurity content is high ("cloudy bands"), whereas ice with a low impurity concentration will not reflect light and contribute a dark layer in the image ("clear bands"). This is used to make layering, i.e. the stratigraphy, visible. Ice from the last glacial period has a well layered stratigraphy resulting from fairly regular annual dust storms in spring to summer. As deformation increases and deformation modes change towards the bottom of the core, these layers will show disturbances and folding. A strong relationship between the δ18O of the water isotopes in the ice core and the impurity concentration, derived from the visual intensity of different layers, can be observed. The correlation of these two makes way for a very precise correlation of the visual stratigraphy and their δ18O age, to analyze differences in deformation modes of ice from different climatic periods.Main deformation in the upper part of the ice sheet is pure shear (stretching along the horizontal and thinning in the vertical) and simple shear in the bottom parts. The gradual change from pure to simple shear is seen in the development of small scale disturbances in the layers, such as wavy patterns. The evolution of these features into z- and s-folds is expected in greater depth. Hereby the layer will deform into a z- or s-shape, overturning a section of the layer. Wavy features, such as the ones seen here, have not been observed in other cores and could be associated to the highly dynamic drill site in NEGIS. [ABSTRACT FROM AUTHOR]

Over the last 30 Myr, Earth&#x2019;s climate system evolved considerably. The Oligocene-earlyMiocene (30-17 Ma) was characterized by a unipolar Antarctic icehouse world, whichvirtually disappeared during the warm Miocene Climatic Optimum (MCO; 17-13.9 Ma).Following the Antarctic reglaciation ∼13.9 Ma and further late Miocene-early Plioceneglobal cooling (7-5 Ma), a bipolar Icehouse world was established at ∼2.7 Ma.The evolution of orbital-scale climate dynamics across this substantial intervalremains relatively unscrutinised. High-resolution carbonate records in particular canprovide insight into carbon cycle dynamics by constraining carbonate production anddissolution over time. Carbonate variability in the Equatorial Pacific Ocean has beenfairly well-documented. However, relatively few Atlantic records of comparablequality exist, limiting our understanding of the palaeoceanographic evolution of thisbasin. Here we present the first continuous South Atlantic carbonate record spanning the last 30million years. We generated new high-resolution (1-2 cm) X-Ray Fluorescence (XRF)records for the 0-17 Ma interval at Walvis Ridge ODP Site 1264 (2505 m water depth), whichwere combined with published data (Liebrand et al., 2011 Climate of the Past, 2016 EPSL) toobtain a single continuous 30 Myr record. We revised the shipboard splice usingpredominantly the XRF ln(Ca/Fe) record, most notably for the late Miocene-early Plioceneinterval, and generated an precession-obliquity tuning (8-0 Ma) that connects to aneccentricity tuning for the Oligo-early late Miocene interval (30-8 Ma). The ln(Ca/Fe)data was finally converted to %CaCO3 and CaCO3 mass accumulation rates toinvestigate carbonate production and dissolution in this South Atlantic since theOligocene. At Site 1264, CaCO3% generally varied between 92-97.5%. The lowest values (92-93%)occur during the MCO, suggesting increased dissolution due to widespread global warmth.The highest values (96-97.5%) are found between 8-4 Ma, indicating high carbonateproductivity during the Late Miocene Biogenic Bloom (LMBB). The timing of theLMBB at Site 1264 broadly agrees with the timing of the LMBB in the Pacific. Theimprint of long-term (400 kyr) eccentricity is visible throughout. The shorter-termorbital variability of the CaCO3 record is characterised by two intervals of distinctlydifferent pacing. Prior to 8 Ma, short-term eccentricity (100 kyr) dominates the CaCO3dynamics. After 8 Ma the record displays stronger obliquity and precession-drivencyclicity. These high-resolution carbonate records will allow us to investigate howthese orbital pacing regimes relate to the broader climatic trends of the last 30 Myr. [ABSTRACT FROM AUTHOR]

A study on the deepest part of the Talos Dome Ice Core (TALDICE) is presented. The need to better understand the in situ post depositional processes that take place in deep ice has risen due to the possibility to retrieve an ice core that goes back to 1.5 million years before present (Beyond Epica – Oldest Ice Project). Such a project poses significant challenges, one of these is related to the signal preservation in the bottom part of the core. To construct reliable climatic and environmental records it will be necessary to understand the post-depositional processes occurring in deep ice and that affect the original signals present in ice [1-2-3].Post-depositional processes may involve both the physical and chemical behavior of dust entrapped in ice. We study the effect of increasing depth and rising pressure on the microscopical behavior of dust: when recrystallization of ice occurs, solid impurities are excluded from the ice lattice leading to the formation of dust aggregates. These has been first noticed at depths lower than 2900m in the EPICA Dome C ice cores [1]. We present the dust record of the deepest part of TALDICE, analyzed through Coulter Counter, which shows the presence of dust aggregates, despite a climate related signal, associated to the succession of glacial and interglacial periods, seems to be preserved.Increasing depth doesn't affect only aggregation, but dust geochemistry also. Indeed, the composition of dust shows some anomalies [4]. In particular, the relative abundance of specific elements (iron, sulfur, calcium and magnesium) is different when comparing shallow and deep dust samples. We present a preliminary chemical analysis on dust grains performed through SEM/EDS, coupled to additional geochemical data.Bibliography[1] Tison, J.L.; de Angelis, M.; Littot, G.;Wolff, E.; Fischer, H.; Hansson, M.; Bigler, M.; Udisti, R.;Wegner, A.; Jouzel, J.; et al. Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core. Cryosphere 2015, 9, 1633–1648. [2] Faria, S.H.; Freitag, J.; Kipstul, S. Polar ice structure and the integrity of ice-core paleoclimate records. Quat. Sci. Rev. 2010, 29, 338–351. [3] De Angelis, M.; Tison, J.L.; Morel-Fourcade, M.C.; Susini, J. Micro-investigation of EPICA Dome C bottom ice: Evidence of long term in situ processes involving acid-salt interactions, mineral dust, and organic matter. Quat. Sci. Rev. 2013, 78, 248–265. [4] Baccolo, G.; Cibin, G.; Delmonte, B.; Hampai, D.; Marcelli, A.; Di Stefano, E.; Macis,S.; Maggi, V. The contribution of synchrotron light for the characterization of atmospheric mineral dust in deep ice cores: Preliminary results from the Talos Dome ice core (East Antarctica). Condensed Matter, 2018, 3(3), 25. [ABSTRACT FROM AUTHOR]

Speleothems from the northern rim of the European Alps (NALPS) have provided a number of important, high-resolution, precisely 230Th-dated records of both orbital and millennial-scale climate variability during the last glacial and interglacial periods. The isotopic signatures of such records have helped improve fundamental understanding of the effect that changes in atmospheric and North Atlantic circulation have on European climate, whilst the robust chronologies have provided important information about the timescales upon which the climate can change in this well-populated region. Furthermore, the pattern and timing of isotopic excursions in δ18O as recorded in the calcite of northern Alpine speleothems during the last glacial cycle has been shown to be synchronous within dating uncertainties with the sawtooth-pattern of changes in the δ18O of Greenland ice cores (known as Dansgaard-Oeschger cycles), thus reflecting the shared North Atlantic moisture source and integrated climate system. Here we present a revised chronology over the interval 120-60 ka. We have added an additional 5,000 δ18O measurements dated by 145 precise U-Th ages to the NALPS chronology of Boch et al. (2011), and subsequently taken the most reliable and precisely dated records for the final NALPS19 chronology. Within the interval 118.3 to 63.7 ka, the record is now 90 % complete, compared to 76 % in Boch et al. (2011). Where speleothems grew synchronously, major transitional events between stadials and interstadials (and vice versa) are all in agreement within uncertainty. The NALPS19 chronology is considered with respect to other Northern Hemisphere climate records. Furthermore, we consider the controls that operated on δ18O during the entire NALPS record over the interval c.120-20 ka. [ABSTRACT FROM AUTHOR]

The glacial extents of western Eurasian ice sheets is rather well established for the past 450 ka or so, essentially reflecting 3 major glaciations classified in continental Europe as Elsterian (MIS 12), Saalian (MIS 6), and Weichselian (MIS 2-5). This is because the western-southern geographical expansion of each glaciation became progressively less from the oldest to the next youngest glaciation. A very similar temporal pattern is also recorded in the amount of iceberg-rafted debris (IRD) in polar-subpolar marine sediment cores from all along the western European margin. As the glacial IRD input also decreased over time a direct relationship between the volume of iceberg discharge into the ocean and ice-sheet size over the adjacent continent may be inferred. By contrast, along its northern periphery, the North Eurasian shelf edge of the Barents-Kara seas, ice sheet activity there remained rather inactive before Saalian times. This latter finding is contrary to field evidence from southern and eastern Russia where the existence of several major glaciations predate both the Weichselian and the Saalian. We explain this temporal/spatial asymmetry in terrestrial glacial evolution between the Arctic and the regions farther south to have been caused by enhanced oceanic heat available in the mid-latitudes which eventually enabled significant amounts of moisture to be transported via atmospheric circulation into the European high Arctic only as late as the Saalian time. [ABSTRACT FROM AUTHOR]

Geomorphological evidence shows that during the last glacial period glaciers reached far intothe foreland of the Alps. How frequent such advances took place, how long the glaciersremained in advanced position and how fast they advanced or retreated, however, is difficultto reconstruct from geomorphology. Models of glacier flow are increasingly used to assess icedynamics during the last glacial period. Driving such models relies on a series ofestimates, including ice rheology, the forcing climate and glacier mass balance.Thereby, the latter strongly depends on climate and the equations used to describe theirconnection. Here, we focus on reconstructing surface melt of the Rhine glacier (∼16,000 km2) at thelast glacial maximum (LGM). Given large uncertainties in our knowledge of the LGMclimate, we base our estimates on (i) analogies from Arctic present-day climate and massbalance and on (ii) theoretical considerations. Thereby we investigate which are the keyclimatic characteristics that need to be specified to simulate LGM glacier melt. We find thatchanges in the amplitude of annual air temperature substantially influence simulatedablation-area mass balance gradients db∕dz, and thus glacier-wide mass balance. While thisinfluence has been shown in earlier research, it has not yet been considered in reconstructionsof glacier mass balance during the last glacial. Paleoclimatic evidence from Central Europe suggests that during the LGM annualamplitude of air temperature was larger than today. We show that computing LGM glaciermass balance while assuming no change in amplitude compared to present-dayclimate can result in an overestimation of db∕dz (∼0.4 m w.e. (100 m)−1 yr−1 vs.∼0.55 m w.e. (100 m)−1 yr−1). It remains to be explored how these differing db∕dz couldinfluence simulated glacier dynamics during the last glacial. [ABSTRACT FROM AUTHOR]

Although it is well documented that the late Paleozoic experienced one of the most severe ice ages of Earth's history, the exact timing and frequency of glaciations is still debated. This is in part due to the difficulty of accurately dating glacial deposits that are often barren, with no faunal recovery, and riddled with stratigraphic hiatuses. In order to circumvent these limitations, one alternative way to reconstruct the evolution of grounded ice volume during the Early Carboniferous is to use far-field reconstruction of eustatic sea-level fluctuations.In this study, we report on a detailed sedimentological investigation of Early Carboniferous strata from Western Libya. In the Late Paleozoic, this region was part of the Saharan platform, on the Northern margin of Gondwana, that formed a widespread, extremely low-angle, tectonically stable ramp. During the Early Carboniferous, extensive and thick exposures of siliciclastic-dominated sediments were deposited along a N-S orientated outcrop belt, parallel to depositional dip.A total of 4800m of sedimentary section was logged over a ca. 400km-long transect. Fieldwork observations and integrated subsurface data allow establishment of a detailed sequence stratigraphic framework. During the Tournaisian, Visean and Early Serpukhovian, six lowstand system tracts are identified, composed of incised valleys filled with fully amalgamated fluvial sandstones, capped by open marine packages. These incised valleys can reach a thickness of 50m. Given that they are embedded within shoreface to offshore marine deposits, total sea-level fluctuations of at least 70-80m can be estimated from these deposits. Due to the stable tectonic nature of the Saharan Platform during the Early Carboniferous, glacio-eustasy is the most-likely explanation for the origin of the observed scale of sea-level fluctuations, pointing at the onset of incipient Late Paleozoic glaciation during the earliest Visean. This is compatible with published evidence of Visean glacial deposits in Southern Sahara and South America, further inland on the Gondwanan margins. Ice sheet retreat is probably the mechanism responsible for contribution of the large volume of coarse continental clastics that initially fill the valleys exclusively with fluvial facies, preserved by the followed rapid transgression associated with ice melt.In line with paleotemperature reconstruction, our study indicate that the Late Paleozoic Ice Age has started prior to what is generally depicted in the literature. The location of the study area, on a stable passive margin, provides confidence in the mechanism controlling the incision, and the results provide improved resolution that offers an insight into the scale and frequency of glacial cycles in the Visean. [ABSTRACT FROM AUTHOR]

Glacial cirque landforms are the result of glacier erosion on mountain ridges and they are repeatedly activated on every glaciation. Cirque distribution is largely determined by climatic patterns during periods of glacier initiation, whilst their dimensions are largely determined by glacial erosion over tens of thousands of years (continued in successive glacial cycles), which is likely maximised during the onset and termination of periods of glaciation (Barr and Spagnolo 2015). Glacial cirque morphometry has been widely used in revealing glaciation climatic patterns (Barr et al. 2017).In this contribution, the ACME GIS toolbox for ArcGIS (Spagnolo et al. 2017) was used to calculate glacial cirque morphometry in manually mapped glacial cirques N and NW of the Iberian Peninsula. Given that several mountain areas in N and NW of Iberian Peninsula are below the regional Late Quaternary ELA, only areas were Quaternary glaciation has been identified and described were used. A total of 445 cirques were mapped. A 5 m. pixelsize national DEM provided the surface data. The amount of cirque population makes us confident enough to dismiss the influence of topography, lithology or geological structure on the statistically relevant results.Results show an unsurprising NW-SE cirque floor altitude increase pattern, which is concomitant to Quaternary ELA distribution. Cirque orientation shows a N-NE preference, which we interpret as temperature-driven, confirming that glaciation was marginal during a long period of the Quaternary. Cirque depth and shape shows larger, deeper and rounder cirques located in mountain ranges well above the ELA, where cirques have been active for longer. Glacial cirque morphometry has proved to be valuable as palaeoenvironmental tool only if a large population of cirques is considered. The study area for this contribution -the entire Cantabrian Range- and the amount of cirques mapped, can be seen as a minimum thresholds for achieving reliable conclusions. Therefore, only through the use of automatic calculation methods, these studies can be performed in a cost-effective way. I would like to stress the possibilities that ACME has for morphometric analysis on glacial and non-glacial landforms, such as cirques, drumlin, esker, landslides or meanders. Also, I would like to point to automatic or semi-automatic mapping tools as the way forward in the geomorphological mapping research field. [ABSTRACT FROM AUTHOR]

As the biggest submarine fan in the world, the Bangal fan receives huge amounts of terrestrial materials from adjacent coastal areas, which record abundant information of environmental evolution and sedimentary system change. Based on data of Sr-Nd isotopes and clay minerals in the sediments of a gravity core BoB-56 in the central Bay of Bengal, sediment provenance and sedimentary process responding to sea level and Indian Monsoon change was studied. The results show that clay minerals and Sr-Nd isotopes compositions are obviously different during Holocene and the last glacial period. The content of smectite has increased significantly since Holocene, while illite content has decreased. The Nd isotope shows a more negative composition during Holocene than that during the last glacial period, and Sr isotope shows lower values during Holocene with a short increase at the end of Holocene. The sea level mainly controls the sedimentary pattern through the transfer of deposition centers (located in the Bengal Fan during lower sea level stand, and in the shelf and delta during the Holocene higher sea level stand), while Indian Monsoon mainly plays an important role in sediment generation, transport and circulation by controlling the production of erosion materials, precipitation, runoff and monsoon surface current. Indian summer monsoon intensity has increased significantly during Holocene, which strengthens the southwest monsoon current, thus more of the Indian Peninsula material is transported to the study area, while the contribution from Indo-Burman Ridge and Irrawaddy River material transported by the northeast monsoon current has decreased. This study was supported by the NSFC-Shandong Joint Fund for Marine Science Research Centers (U1606401) and International Cooperation Project of Global Change and Ocean-Atmosphere Interaction (GASI-GEOGE-03) [ABSTRACT FROM AUTHOR]

We present a geomorphological assessment of the extent and dynamics of glaciation in the Wicklow Mountains, Ireland, during the Last Glacial Interglacial Transition (LGIT; ~ 20 – 11 ka BP). Previous research has established the existence of a local ice cap, confluent with regional ice at the Last Glacial Maximum (LGM; ~ 25 ka BP). However, there has been little consideration of ice retreat in response to climate amelioration during the LGIT. Here, we investigate ice dynamics during and after the transition from an ice cap to topographically restricted mountain glaciation. The geomorphological record indicates that initial ice cap recession was characterised by rapid retreat and large-scale disintegration, with ice masses only stabilising once topographically constrained within valleys. Following fragmentation of the LGM ice cap, three distinct landsystems were established in the Wicklow Mountains: (1) the large north-eastern sector of the region hosted a mountain icefield with multiple outlet glaciers; (2) a small plateau icefield existed in the central sector, with several outlet glaciers; and (3) several individual valley glaciers persisted in the south-western sector. Each of these landsystems document sustained retreat and subsequent stabilisation during the LGIT, prior to the Younger Dryas. Two-dimensional reconstructions of ice dynamics indicate variations in recession patterns throughout the region. Based on our ice margin reconstructions and the limited published dates for the region, we suggest that following the retreat of regional ice after the LGM, the local ice cap was relatively stable until the start of the LGIT (~20 ka BP). After this, ice experienced sustained thinning and ice margin retreat until ~ 17 ka BP. By this point, ice was topographically restricted and the three aforementioned landsystems established. A period of ice margin stabilisation occurred before further persistent retreat until ~ 15 ka BP, by which time ice had retreated into the upper reaches of valleys. It is likely that the plateau icefield and most of the mountain icefield had disappeared by ~15 ka BP, when the outlet glaciers of both landsystems had detached from their central accumulation areas and experienced sustained retreat. Following this, some small cirque glaciers experienced minor readvance before ice recession continued. The geomorphological record indicates that it is likely that glacial ice disappeared in the Wicklow Mountains during this period but was re-established, in a small number of cirques, during the Younger Dryas. [ABSTRACT FROM AUTHOR]

The Earth's topography is shaped by tectonic and climatic conditions which influence surface processes via rock uplift, erosion, and deposition. Although early numerical and analogue models provide the theoretical background of the role of erosion on the tectonic evolution of a mountain belt, evidences of feedbacks rather than circumstantial coincidences between topography, climate, and tectonics are challenging to observe in field studies. Here, we use the Central Andes (18-36°S) as a natural laboratory to study possible interactions between these processes. We start by modelling the exhumation rate history in the Central Andes for the last 80 Ma by inverting low-temperature thermochronometric ages compiled from literature (699 ages) and new data (240 ages). The modeled exhumation rates are then compared to the deformation and climatic histories derived from regional sedimentary deposits. Our findings show that before 22 Ma, exhumation rates north of 32°S are lower than 0.15 km/Ma. This is consistent with low shortening rates and low topography in this region. Pulses with slightly higher rates occur only locally in distinct zones in the Western Cordillera. These are probably controlled by regional fault activities during the first major orogenic phase in the Eocene. Exhumation in the Eastern Cordillera started around 26 Ma and subsequently affected the Interandean (~18 Ma) and the Subandean zones (~12 Ma), most likely reflecting the migration of the deformation front to the east. Exhumation rates in these zones increase during the Miocene from ca. 0.15 to 0.3 km/Ma, probably due to the combination of growing topography, higher shortening rates, and intensified precipitation along the eastern deformation front linked to the uplift of the Eastern Cordillera. South of 32°S, exhumation rates in the Principal Cordillera increase from 0.15 km/Ma at 12 Ma to more than 1.2 km/Ma since 2 Ma. This recent increase in erosion is associated with increased precipitation and glaciation, and a feedback with isostatic rock-uplift and active tectonics. Our study shows that the respective influences of climate and deformation on exhumation cannot be decoupled in the northern Central Andes, whereas in the southern part exhumation rates are largely influenced by Pleistocene glacial erosion and intensified precipitation. Furthermore, late Miocene exhumation rates of the semi-arid to arid eastern Andean slope north of 32°S and the Principal Cordillera south of 32°S are similar, although shortening rates are significantly higher in the north than in the south. This highlights the importance of climate on exhumation in active mountain belts. [ABSTRACT FROM AUTHOR]

The Amburnex Valley (Western Swiss Jura) was occupied by a glacial paleolake linked to the retreat of a Würm local ice sheet, which evolved later in well-developed peatland. This humid zone ecosystem is particularly vulnerable to current climate change. The endemism of the Saxifraga hirculus, a flower present at least since the Holocene, is of significant ecological interest. During the Late Glacial period, this peatland was a glacial lake characterized by a significant accumulation of lacustrine sediment deposits.Using a multiproxy approach, this project aims to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediments and peatbog deposits since the last 13'000 years, and to investigate if major volcanic episodes have been recorded throughout this period.High resolution analyses have been performed at cm-scale on a 7 m-thick sedimentary core. Starting with a morainic deposit from the Würm period, this core shows three meters of lacustrine deposits overlain by four meters of peatland deposits. A multiproxy approach based on palynological analyses, grain-size analyses, mineralogical analyses (XRD) and geochemical analyses (TOC, Nitrogen, Phosphorus and Mercury contents; major and trace elements; organic carbon isotopes) have been used to characterise the hydrological and climatic fluctuations, the trophic level and the origin of organic matter in order to reconstruct the paleoenvironmental and paleoclimatic evolution in this area. Mercury anomalies recorded in the sediment can be a robust tracer of volcanic activity in absence of tephra layers. The latter are indeed not always well preserved in sediments due to mineralogical transformation, Hg anomalies could therefore be a reliable tool to characterise atmospheric volcanism fallouts such as the Laacher See Tephra event (Eifel, Germany), the Icelandic tephra (Iceland), the Italian Volcanic Province tephra (Italy) and the Puy de la Nugère tephra (Massif Central, France). [ABSTRACT FROM AUTHOR]

The last glacial period was punctuated by episodes of warm and humid climate. These rapid climate instabilities, called Dansgaard/Oeschger (D/O) events, lasted between a few hundred and a few thousand years. The triggering mechanism of these events is still not comprehensively decoded and various hypotheses are debated including oscillations of the Atlantic Meridional Overturning Circulation driven by changes in the freshwater budget, changes in the elevation of the Laurentide ice-sheet and its effect on wind stress and sea-ice cover, as well as ocean–sea ice interactions internal to the Nordic Seas. Morever, two time periods during the last glacial show a distinctive reduction or even an absence of D/Os (~70 to 60 ka and ~26 to 16 ka). Those periods concur with minimum sea-level and are important constraints to test hypotheses for the D/O triggering mechanism as not all of them can explain this absence of D/O cyclicity. Knowledge about D/O cyclicity could be improved by extending the investigations to the penultimate glacial. However, existing records cover only parts of the interval between ~200 and 130 ka or are located far from the D/O event core location and may have missed some events. Especially marine records, which would be ideally located in the North Atlantic to detect D/O events, are often limited with respect to their age control during this period. Here, we present a new, replicated and precisely dated speleothem record from the northern rim of the European Alps covering the penultimate glacial. This area has previously proven to be highly sensitive to rapid millennial-scale climate variations. Between ~202 and ~133 ka before present our new Alpine speleothem record reveals a similar number of D/O events as compared to the last glacial period. D/O events were notably absent during three ~8 ka-long intervals, which coincided with sea-level low-stands during the penultimate glacial. Hence, our results strongly support findings from the last glacial that D/O-events were precluded during intervals when the Northern Hemisphere ice sheets reached their maximum extent. [ABSTRACT FROM AUTHOR]

The sections of Greenland and Antarctic ice cores covering last glacial period have previously been synchronized primarily by their common records of gas concentrations and cosmogenic isotopes. Here, we apply annual layer counting and matching of volcanic peak patterns to synchronize the onsets and terminations of Greenland Interstadials (GI) in Marine Isotope Stage 3 (MIS3, 25-60 ka). Based on the identification of more than 50 significant bipolar volcanic events throughout MIS3, most abrupt climate events can be synchronized between the two Hemispheres at decadal precision. Layer counting has been performed in the Greenland NGRIP and the Antarctic EDML ice cores using high-resolution records of chemical impurities, dust, and visual grey scale intensity. The time scales obtained from layer counting are not always in agreement with existing ice core chronologies. Volcanic peak patterns have been identified in all available acidity records from the Greenland GRIP, GISP2, NGRIP, and NEEM and the Antarctic EDML (Atlantic sector), EDC (East Antarctic plateau), and WDC (West Antarctica) ice cores. The obtained volcanic synchronizations within Greenland and within Antarctica are in agreement with existing volcanic synchronizations. The bipolar volcanic synchronization is supported by cosmogenic record patterns at several of the major GI onsets and it is in accord with the cosmogenic synchronization at around the geomagnetic Laschamp event (41 ka). The bipolar volcanic synchronization is offset from the NGRIP-WDC methane synchronization by up to 150 years, generally pushing the Antarctic record towards older ages at the GI onsets. The general Antarctic response to a GI onset is a direct warming at the EDC and WDC sites that peaks within a century and a less significant cooling at the EDML site, possibly attributed to a northward shift of the southern hemisphere westerly winds. This pattern is however not consistent among all GI onsets and in particular the weaker GI events show deviating Antarctic response patterns. Several of the sharp Greenland climate transitions in MIS3 are associated with periods of strong volcanism suggesting that volcanism may work as a trigger of abrupt climate change. Other abrupt transitions are not associated with volcanism and many strong volcanic events do not show a response in the climate records. Overall, the bipolar volcanic synchronization gives strong support for the suggested bipolar seesaw mechanism. [ABSTRACT FROM AUTHOR]

The Northeast Greenland Ice Stream (NEGIS) is the largest ice stream of the Greenland Ice Sheet (GrIS). Its area has been suffering a significant ice mass loss during the last decade, partly due to rising oceanic temperatures in the subpolar North Atlantic, which increase submarine basal melting and enhance mass discharge. This behavior demonstrates the high sensitivity of this region to oceanic changes. In parallel, a recent study suggests that the NEGIS grounding line was about 300 km behind its glacial maximum location for 15 ka during Marine Isotopic Stage (MIS) 3, despite the background glacial conditions. This retreat has been explained through a combination of atmospheric and external forcings but a modelling approach to the problem is pending. Here we study the sensitivity of the NEGIS to the oceanic forcing during the Last Glacial Period (LGP) using a three-dimensional hybrid ice-sheet-shelf model, dotated of a submarine melt parameterisation that transform oceanic temperature changes into melting at the grounding line. Our results suggest that a sufficiently high oceanic forcing could account for a NEGIS ice-margin retreat of several tens of km, potentially explaining the recently proposed NEGIS grounding-line retreat during MIS-3. [ABSTRACT FROM AUTHOR]

High-latitude trough mouth fans are high-resolution paleoclimate and ice-sheet monitors, and allow a continuous reconstruction of climate and sedimentary processes active during glacial-interglacial cycles. The North Sea Fan is located on the northern North Sea margin and is built-up by c. 40,000 km3 of sediments dominated by the erosional products of the Norwegian Channel Ice Stream. The aims of this contribution are (i) to characterize the sediments deposited in the North Sea Fan, and (ii) to do a three-dimensional reconstruction of the processes involved into the formation of the North Sea Fan. We use 16,000 km2 of high-resolution processed 3D seismic data collected in 2017 and 2018 from the proximal North Sea Fan. These data allow us to image the shallow subsurface in a resolution of 8 m vertically and 20 m horizontally. Fifteen horizons have been picked with an in-line spacing of 150 m, followed by gridding, horizon attribute extraction, sediment volume calculations, and seismic geomorphological interpretation. Our results show that six sediment packages containing stacked glacigenic debris flows (GDFs) have been deposited at the upper slope of the North Sea Fan. The GDF package related to the last glaciation has a thickness of up to 400 m and is characterized by a homogenous seismic facies intercalated by five continuous high-amplitude reflections, which separate the package into six sub-units. The structure maps of these reflections show multiple sharp, SE-NW-oriented channels with well-developed levees and densely-spaced pockmarks. The GDF deposits have been removed from the upper slope by four megaslides, which are identified as deformed sequences bound by smooth lower and irregular upper surfaces. Negative-amplitude, continuous reflections at the base of the megaslides fade out uphill of the slide headwalls. The topography shaped by these megaslides is infilled by glacimarine deposits identified as low-amplitude, continuous reflections. Continuous reflections with mounded geometries, interpreted as contourites, characterize the deepest part of the fan. The GDF packages show that the Norwegian Channel Ice Stream reached the shelf edge during six marine isotope stages, and that the ice stream oscillated six times during the last glaciation. The up to 400 m thick GDF package related to the last glaciation has been deposited within 4 kyr, which correlates to a sedimentation rate of up to 100 m/kyr, and a sediment flux of 1500 km3/kyr for the study area. Channels identified at multiple levels within the GDF package indicate that the sediment delivery from the Norwegian Channel Ice Stream to the slope was continuous and did not occur in pulses of several decades. Channel-fed levees and debris lobes characterize the paleo-seafloor between the channels. The circular depressions, interpreted as pockmarks, indicate fluid escape events in some intra-channel areas during the deposition of the GDFs. Negative, high-amplitude reflections below the GDFs and megaslides indicate gas-charged sandy bases and show a strong correlation between pre-conditioned glacimarine glide planes and megaslide occurrence. Contourites at the base of the fan indicate different oceanic processes dominating the early Quaternary deposition. [ABSTRACT FROM AUTHOR]

The Mid Pleistocene Transition (MPT) was a global climatic event that occurred between 1250 and 700 thousand years (ky) ago. This period was characterized by a drastic change in the deep thermohaline circulation during the glacial periods that resulted in more intense and longer lasting glacial periods (changing from 40ky to 100ky cycles) and cooler sea-surface temperatures (SST). It is believed that the MPT may have been influenced by ocean-atmosphere system changes directly linked to an increased ice volume. A consensus point is that there was a pCO2 reduction which in turn reduced the atmosphere's temperature, causing the expansion of continental ice sheets. In the North Atlantic, high-resolution records documenting the MPT's impact are still limited. The present study's objective is therefore to characterize surface-water variations at the mid-latitude southern Portuguese margin during the MPT. We are generating planktonic foraminifera faunal and related SST data for Integrated Ocean Drilling Program (IODP) Site U1387, retrieved from the Faro Drift in the Gulf of Cadiz, for the MPT interval from Marine Isotope Stage (MIS) 20 to MIS 26 at a temporal resolution of about 500 y. Nowadays, this site is dominantly influenced by subtropical surface waters. Frist results for the interval from MIS 20 to MIS 23 indicate highly variable SSTs off southern Portugal. Warmest summer SST between 23-25ºC are recorded during interglacial MIS 21 when the fauna is dominated by tropical-subtropical species. During interglacial MIS 23, SST reached only 21ºC with warm periods being interrupted by abrupt cooling events with minimum SST of 10ºC. Glacial MIS 22 has three phases starting and ending with extreme cold events separated by an interstadial period of 14ky duration, during which SST increased up to 21ºC. During the first extreme cold event SST stayed below 10ºC for nearly 5ky. The impact of the second cold event was more extreme with SST dropping below 5ºC for 4ky. The transition from this cold event to MIS 21 interglacial conditions occurred within 1ky. Contrary to MIS 22, MIS 20 was a relative warm glacial period with SST dropping down to 9ºC only during the terminal event at the MIS 20/19 transition. So, the Site U1387 SST record reveals dominantly subtropical gyre influence interrupted by incursions of subpolar waters when the North Atlantic's subarctic front moved to southernmost position during the MPT. [ABSTRACT FROM AUTHOR]

Latest insights from paleo-climatic research (Luetscher et al. 2015) and glacier modelling (Seguinot et al. 2018) suggest that ice build-up during the Last Glacial Maximum may not have been uniform across the European Alps. Favoured by predominant precipitation patterns and a steep topographic gradient, paleo-glaciers on the southern side of the Alps are believed to have reached their maximum extent earlier than glaciers that drained north. While reliable glacial chronologies based on radiocarbon and exposure dates are available for several of the major Italian amphitheatres, the LGM glaciation of the central part of the southern European Alps is a clear lack of knowledge. The latter's connection to the major Alpine ice domes makes understanding the Ticino/Toce glaciers behaviour especially critical. The present study aims on filling this gap of understanding with detailed mapping of the Toce/Ticino glacier combined with cosmogenic nuclide dating. A total of thirty rock samples for surface exposure dating has been collected from erratics deposited on the western shore of Lago Maggiore by the Ticino/Toce glacier. Preliminary Beryllium-10 results support an LGM extent larger than recently proposed (Bini et al. 2009). Next to LGM ages, the present data set together with field evidence also suggests a glacier re-advance following the LGM that ended with rapid down wasting of the glacier. ReferencesBini et al. 2009, Federal Office of Topography, Swisstopo.Luetscher et al. 2015, Nature Communications 7433. Seguinot et al. 2018, Cryosphere 12, 3265-3285. [ABSTRACT FROM AUTHOR]

Repeated glacier advances affected the Swiss Plateau during the Quaternary. Deeply carved valleys, where the bedrock surface is located far below the current drainage level, are a prominent feature on the Swiss Plateau. How and when the glaciers lead to the formation of so-called overdeepenings is still a matter of debate.Different studies show that overdeepenings in the Bern area contain thick and widespread lacustrine deposits of pre-Eemian age (Preusser & Schlüchter, 2004; Preusser et al., 2005). A coherent geological model of this complex setting is missing. Likely, glaciers carved into pre-existing overdeepening fills and repeatedly dug large troughs. Furthermore, access to the sedimentary record is limited. Outcrops containing sediments of the last glaciation are scarce and isolated. Access to older sediments is almost entirely limited to excavations and drillings.Nevertheless, the overdeepenings served as local sedimentary traps while and after they were covered by ice during different glaciations. Hence, these troughs are prone to preserve a coherent sediment succession of a glaciation cycle in an ideal case, and they are therefore worth studying.In this study, we attempt to resolve the local stratigraphic framework of pre-Eemian lacustrine deposits in the Bern area. In February 2019, we will conduct a ca. 200 m deep scientific drilling in order to link it to existing investigations aided by publicly available drill log data. We will study the lithofacies and use relative and absolute dating methods (palynology, luminescence dating, U-Th dating) to determine the development of a lake throughout a pre-Eemian glacial cycle. Preliminary OSL results of the lacustrine sediments yield a minimum age of 220 ka. This study will provide new insights into the timing, extent and impact of this glaciation as well as its climatic conditions.ReferencesPreusser, F., Drescher-Schneider, R., Fiebig, M., Schlüchter, C., 2005. Re-interpretation of the Meikirch pollen record, Swiss Alpine Foreland, and implications for Middle Pleistocene chronostratigraphy. J. Quat. Sci. 20, 607–620Preusser, F., Schlüchter, C., 2004. Dates from an important early Late Pleistocene ice advance in the Aare valley, Switzerland. Eclogae Geol. Helv. 97, 245–253 [ABSTRACT FROM AUTHOR]

Reconstruction of denudation rates through time is an important task to quantify andunderstand the impact of climate on landscape evolution. Cosmogenic nuclides have beenwidely used to infer denudation rates at the watershed scale from both present day sedimentsand past stratigraphic records. Here, we analyze the in situ 10Be cosmogenic concentrationin sediments of two long-piston cores that were collected offshore the Var River(Western Mediterranean Sea), precisely along the Var sedimentary ridge. Thesesedimentary archives have been well dated at a high resolution and analyzed forsediment provenance (Bonneau et al., 2017-EPSL) thus providing a unique record toreconstruct the denudation history of the Var catchment in the Southern French Alps overthe last 70 ka. This period covers the majority of the last glacial period and theassociated Dansgaard-Oeschger events, the last glacial maximum (LGM, 26-19 ka) andthe subsequent deglaciation (19-11 ka), and the Holocene, with all these eventsbeing precisely defined in the studied cores. Therefore, this setting offers the rareopportunity to study the impact of rapid climate fluctuations on denudation ratesin a mountainous glaciated catchment over a time scale that is not impacted bytectonics. We present 21 10Be paleo concentrations ranging from 1.24±0.51 x 104 atoms/gquartz to5.99±1.90 x 104 atoms/gquartz. The 10Be paleo concentrations overall are very similar topresent day 10Be concentrations (average of 4.20±0.67 x 104 atoms/gquartz at thewatershed&#x2019;s outlet in 2016, or a denudation rate of 0.20 ±0.03 mm/year). This suggestssimilar paleo denudation rates between today, the 0-17 ka period and the 27-70 kaperiod. Only the LGM shows a clear change in 10Be concentrations with much lowerconcentrations (average of 1.68±0.48 x 104 atoms/gquartz) suggesting high denudation ratesduring this period of maximum glacial extent in the French Alps. These results suggest that climatic settings have a limited impact on overall denudationrates and that glaciers in the Mediterranean Alps either weren&#x2019;t strong agents of erosionduring the MIS 3 (70-25 ka) or were smaller than previously thought. These results alsosuggest that only strong climatic fluctuations (such as the LGM) can induce meaningfulchanges in denudation rates. [ABSTRACT FROM AUTHOR]

Recent studies suggest that the eastern end of the Alps may have experienced almost one kilometer of surface uplift at post-Miocene times. In order to improve our understanding of the extent and magnitude of this not very well-constrained surface uplift event, we map planation surfaces in the Fischbach Alps of eastern Austria. In this region, elevations range from about 1800 m in the north to 350 m at the orogen-basin transition zone in the south. The Fischbach Alps remained ice-free during the glacial periods and thus offer the opportunity to interpret mapped planation surfaces in terms of pre-Pleistocene relict landscapes.Combining geomorphic mapping in the field and morphometric analysis, we identify several planation surfaces, which we correlate to established reference-surfaces in other parts of the Styrian block. In particular, we recognize planation surfaces at about 150 - 200 m (correlating with the Stadelberg/Zahrerberg-Level) and 25 - 80 m (correlating with the Niedere- and Mittlere Terassengruppe) above the current base-level of the Feistritz river. At higher elevations, we recognize relict landscapes that correlate with the Teichalm (Hubenhalt-Level). The results of our mapping extend our knowledge about surface uplift in the Plio-Pleistocene period further to the east and suggest that the Fischbach Alps experienced a southward tilting of the Styrian block during this time. Some peculiar changes in the drainage direction of the Feistritz along the (Anger-Piregg)-fault point towards tectonic unrest in the area during the Pliocene. [ABSTRACT FROM AUTHOR]

We presented benthic foraminiferal δ18O and δ13C records of Ocean Drilling Program (ODP)Site 807 (3∘36′N, 156∘37′E, 2804m) in the western equatorial Pacific in 3.5-0 Ma by 1345paired isotopic measurements, with a time resolution of 2.6 Kyr. The most significant event inbenthic δ18O is a gradual increase of nearly 1.2‰ in 3.3-2.5 Ma (Tiedemann et al., 1994;Shackleton et al., 1995; Tian et al., 2002; Tian et al., 2006), which indicates the late Plioceneonset of the Northern Hemisphere Glaciation (NHG). Based on the benthic δ18O record ofODP Site 807 and other records from the Atlantic, the Eastern Pacific, the Indian Ocean andSouthern Oceans, we tentatively discussed the response of benthic foraminiferal δ18O to thelate Pliocene onset of the NHG. We carried out linear regression analyses on thebenthic foraminiferal δ18O to investigate the amplitude of the variability of δ18Owithin the period between Marine Isotope Stages M2 and G6 (∼3.3-2.7 Ma). Thedeep water sites in the North Atlantic (DSDP (Deep Sea Drilling Program) Site607(41∘00′N, 32∘58′W, 3427m), and ODP Site 659(18∘05′N, 21∘02′W, 3070m)) andthe Southern Ocean (ODP Site 704(46∘53′S, 7∘25′E, 2532m)) display the mostsignificant increase in δ18O, while those in the western equatorial Pacific (ODP Site 807)and the Indian Ocean (ODP Site 758(5∘23′N, 90∘21′E, 2925m)) exhibit moderateincrease in δ18O. ODP Site 982(57∘31′N, 15∘53′W, 1145m) in the North Atlanticintermediate water also exhibits relatively small increase in benthic foraminiferal δ18O.Both the sea surface temperature and bottom water temperature of ODP Site 982show an increasing trend from 3.3 Ma to 2.7 Ma. The basin-to-basin difference inthe responses of the benthic foraminiferal δ18O to the late Pliocene onset of theNHG probably reflect the status of the global Thermohaline Circulation (THC). Wespeculate that the production of the North Atlantic Deep Water (NADW) mightbecame sluggish during this period, indicating a weakened Thermohaline Circulation. [ABSTRACT FROM AUTHOR]

Mars' present climate is extremely cold and arid. Until recently, it was widely thought that debris-covered glaciers in Mars' mid-latitudes have been pervasively cold-based since their formation 10s–100s Myr ago. However, we recently discovered eskers associated with ~110–150 Myr old glaciers in the Phlegra Montes [1] and NW Tempe Terra [2] regions of Mars' northern mid-latitudes. Eskers are sinuous ridges comprising sediments deposited in glacial meltwater conduits. Therefore, eskers associated with existing mid-latitude glaciers on Mars indicate that localised wet-based glaciation did occur during Mars' most recent geological period. Eskers are important tools for reconstructing the nature, extent, and dynamics of wet-based glaciation on Earth, and have similar potential for Mars.We used 1–2 m/pixel resolution digital elevation models derived from 25–50 cm/pixel High Resolution Imaging Science Experiment stereo-pair images to measure the planform and 3D morphometries of the Phlegra Montes and NW Tempe Terra eskers, and compare them with the morphometries of Quaternary-aged eskers in Canada [3] and SW Finland [4]. We found that the Martian eskers have remarkably similar lengths, sinuosities and heights to terrestrial eskers, but that the Martian eskers are typically wider and have lower side slopes. Large width-height ratios of the Martian eskers are consistent with our previous measurements of ancient (~3.5 Ga) eskers close to Mars' south pole [5], and may arise from differences in either: esker degradation state, or fundamental glacio-hydrological controls on esker formation between Mars and Earth. Portions of the two Martian eskers with comparable crest morphologies (e.g., sharp- or round-crested) have similar width-height relationships, suggesting that glacio-hydrological processes may exert controls upon the observed relationships between esker morphology and morphometry.Our morphometric analyses also reveal that the Martian esker in NW Tempe Terra has a 'stacked' morphology: the crest of a wide, round-crested underlying ridge is superposed by a narrow, sharp- to multi-crested ridge. Based on morpho-sedimentary relationships observed along terrestrial eskers [6], we interpret this transition to represent waning sediment supply and meltwater discharge towards the end of the esker-forming drainage episode(s). Direct sedimentary insights into Martian eskers are not yet possible so we emphasise that such inferences should be rigorously grounded in observations of analogous landforms on Earth.This work was funded by STFC grant ST/N50421X/1.References: [1] Gallagher, C., and Balme, M.R., (2015), Earth. Planet. Sci. Lett. 431, 96-109, [2] Butcher, F.E.G., et al. (2017), J. Geophys. Res. Planets. 122(12), 2445-2468, [3] Storrar, R.D., et al. (2014) Quat. Sci. Rev. 105, 1-25, [4] Storrar, R.D., and Jones, A., Unpublished, [5] Butcher, F.E.G., et al. (2016), Icarus 275, 65-84, [6] Burke, M.J., et al. (2010) Geol. Soc. Am. Bull. 122, 1637-1645. [ABSTRACT FROM AUTHOR]

As the largest reservoir of carbon actively exchanging with the atmosphere on glacial-interglacial timescales, the deep ocean has been identified as the likely location of carbon dioxide sequestration during Pleistocene glaciations. Not only is the total magnitude of ocean carbon storage important, but examining individual watermass carbon storage also has the potential to shed light on attendant changes in ocean circulation and biogeochemical processes. Thus, spatially resolved reconstructions of respired carbon storage are critical for improving our understanding of glacial-interglacial climate change and the feedbacks and mechanisms responsible for amplifying insolation forcing.Because of the stoichiometric relationship between respiratory carbon storage and dissolved oxygen concentrations, proxy data reflecting watermass oxygenation are of value in addressing questions about glacial carbon storage. Significant amounts of new data have resulted from the recent application of novel and classic proxies for watermass oxygen concentrations including aU, Δδ13C, δ15N, and I/Ca. Unfortunately, these new records continue to foster conflicting interpretations about the watermass(es) containing the respired carbon.Here, we critically evaluate the relative strengths and limitations of existing deep water oxygen proxies and use our findings to reconcile data about the watermasses associated with respiratory carbon storage over the past glacial cycle. We combine new aU and Δδ13C data from the eastern and southeastern Pacific with previously published results to propose a picture of glacial carbon storage and Pacific watermass structure that is internally consistent. We also use our proxy evaluation to suggest best practices for future proxy reconstructions and their interpretation. [ABSTRACT FROM AUTHOR]

The Late Paleozoic Ice Age (LPIA) spans the latest Devonian through Late Permian, withglaciations recorded across Gondwana. Reconstructing the timing and extent of theglaciations depends on the availability of precise and accurate age control in order tocorrelate near and far-field glaciogenic sediments across basins and continents. We presentsingle zircon U-Pb CA-TIMS ages from a suite of volcaniclastic strata intercalated with nearand far-field glaciogenic deposits of latest Carboniferous to Early Permian age in the Paraná,Karoo and Kalahari basins in southern Brazil and Africa, respectively. The zircon ageinventory of individual volcanic layers is in many cases complex due to the occurrence ofinheritance and xenocrysts as well as, in some cases, the effects of Pb loss despitethe application of aggressive chemical abrasion prior to analysis, making the datainterpretation challenging. These complexities where unrecognized in previous studies asresult of lower resolution geochronological techniques and resulted in compromisedreconstructions. The new U-Pb zircon ages seem to suggest that the final demise of LPIA ice in theParaná, Karoo and Kalahari basins is diachronous and at least in part, related to latitudinalposition. Individual deglaciation events in each basin are in sync across these basinssuggesting an additional driver, and there is emerging evidence that changes in the extentand the synchronous nature of deglaciation in these areas mimic fluctuations inatmospheric pCO2. Current efforts are aimed at integrating our findings with records fromboth low and high latitude sedimentary archives in order to test our hypothesis of agreenhouse gas forced glaciation with the goal of refining the underlying mechanismsthat drive the LPIA. Deglaciation sequences in the Paraná, Karoo and Kalaharibasins can now be reconstructed with a resolution as low as ca 200 ka, higher orderfluctuations down to the few ka level are still difficult to reconstruct and require thedetailed study of cyclic sedimentary sequences in combination with high-resolutiongeochronology. [ABSTRACT FROM AUTHOR]

Earth system science, the study of our planet as an integrated set of subsystems that drive planetary function, is a modern approach to understanding rapidly evolving issues such as climate change, ecosystem stress, and environmental degradation. That is, the Earth system approach offers a holistic perspective of how our planet functions under a spectrum of external and internal forcings that is not obtained by more traditional disciplinary studies. An Earth system approach is transferable to the geologic past, i.e., the deep time, made possible by the advent of high precision radioisotope dating of volcanics intercalated with sedimentary deposits and the potential for astronomically calibrating broad intervals of the geologic time scale. The application of Earth System (climate) Models and process-based ecosystem models to deep time studies and the ability to build high-fidelity proxy time series with resolutions as high as seasonal- to millenial-scale further facilitate Earth systems studies in deep-time.In this talk, I use our collective research, focused on the late Paleozoic Earth system, to illustrate this approach. The ubiquitous presence of cyclothems, the fundamental stratigraphic unit for the late Carboniferous through early Permian (340 to 275 Ma), throughout paleotropical successions coupled with single-zircon U-Pb CA-TIMS ages has documented eccentricity scale cyclicity and the potential for orbital tuning of stratigraphic and stable and radiogenic proxy records. We use thispaleotropical chronostratigraphic framework to reconstruct onlap-offlap history, to build terrestrial and marine proxy records, and to better understand spatial and temporal variability in paleo-surface seawater composition and climate conditions. Integrated morphologic and isotopic study of well-preserved fossil plants permits evaluation of vegetation climate feedbacks and development of multi-proxy atmospheric pCO2 and O2:CO2 trends. Our efforts to obtain high-precision and accurate U-Pb ages for volaniclastic strata from mid- to high-latitude Gondwanan successions (Paganzo, Paraná, Karoo, Kalahari basins) enables correlation between glaciogenic successions in Southern Hemisphere Gondwana as well as into the paleotropics. These studies provide a new view of the glaciation history of southern Gondwana and new constraints on ice initiation and stability thresholds. Interactive data-model comparisons permit contextural interpretations and reveal counterintuitive process relationships.These findings for Earth's penultimate icehouse, in the context of other recent studies, have important implications for better understanding the 'sources and sinks' for atmospheric pCO2 through time and regional climate responses to global forcings under different boundary conditions. They further address the challenges of reconstructing meaningful 'global' surface temperatures and seawater composition from epicontinental-dominated records. Lastly, these findings document the ability of vegetation to physiologically force regional climate and strongly perturb surface hydrology with potential for global-scale impact. On a process-scale, such findings are transferable to other time periods of Earth history, including potentially Earth's future, despite very different time scales of perturbation and boundary conditions. [ABSTRACT FROM AUTHOR]

The high-altitudinal plateaus of Jotunheimen in central South Norway, the mountain region home of Norway's highest summits, create a unique and diverse natural environment. The specific gross morphology of Jotunheimen facilitates the occurrence of a variety of periglacial landforms ranging considerably in both dimension and age. The regional distribution of permafrost is one of the major controlling factors for the altitudinal distribution of these periglacial landforms. The largest individual features of patterned ground, undisputed the regionally most dominant periglacial landforms, are situated on terrain currently underlain by permafrost. They visually appear to be quite relict, despite the occurrence of permafrost, and the exact timing of their formation remains unknown. This example points to additional factors significantly influencing the periglacial landform assemblage, like topography, ground moisture availability, and the local deglaciation history. The lack of a regional overview regarding periglacial landforms in Jotunheimen exacerbates the need for a profound investigation of their altitudinal zonation and potential causal links to climate, permafrost, (de-)glaciation, and other factors.The compilation of a regional overview based on aerial imagery and a literature review aims, therefore, to reveal further insight into the controlling factors for and mechanisms of periglacial landform development in Jotunheimen. This shall be achieved by creating an altitudinal zonation for periglacial features and highlighting causal links between their spatial/altitudinal distribution and possible influencing factors. In an outlook to future studies this attempt may also provide more detailed information on the regional basal properties of the former Scandinavian ice sheet, the regional/local deglaciation patterns for the Jotunheimen region, and about the exact chronology of formation of the periglacial landforms studied. [ABSTRACT FROM AUTHOR]

About one-third of the current anthropogenic carbon dioxide (CO2) emissions are absorbed by the terrestrial biosphere. The uncertainty as to how this uptake might respond to projected future climate change can be constrained by knowledge of its behavior during glacial-interglacial cycles. Previous investigations of the vegetation and land carbon storage during the glacial period suggested a reduction of forests, productivity and biomass. Nevertheless, an evaluation based on a historical warm period is needed to better understand the implications for the future, and to understand the roles of temperature, moisture and CO2 concentration (pCO2) in the climate transition, which are currently still poorly understood. Consistent with paleo-vegetation and carbon cycle-related reconstructions, here we show the vegetation migration and terrestrial carbon variation in both past cold and warm climates, simulated by the Dynamic Global Vegetation Model LPJ-GUESS. We find that the vegetation extent is mainly determined by temperature anomalies, especially in a cold climate, while precipitation forcing is limited on a regional scale to shape vegetation patterns. The pCO2 change controls the global carbon balance with higher pCO2 linking to higher vegetation coverage, an enhanced terrestrial carbon sink and increased terrestrial carbon storage. Our results indicate a coherent transfer of carbon from ocean and permafrost/peat to biosphere and atmosphere from cold to warm climate scenarios. We further highlight the importance of expansion of the terrestrial ecosystem carbon stock in slowing atmospheric pCO2 growth. [ABSTRACT FROM AUTHOR]

Aim of the research: In general, marine terraces are covered by later non-marine deposits and difficult to obtain former shoreline using disturbed terrace surfaces. Precise determination of the former shoreline could be obtained from geological analysis of marine terrace deposits. Numbers of tight drilling have done to establish new method for terrace analysis.Study area and geology: Japan Sea side margin of the Shakotan Peninsula and the southern region, Hokkaido, Japan. MIS5e Marine Terrace deposits which are mainly composed of well sorted shore sand and gravels associated with volcanic ash, Toya (erupted about 115,000 years ago) in the upper most part of the deposits. The terrace deposits (1 to 4m) are covered by thick talus deposits (5 to 30m) formed by periglacial process.Method of terrace analysis: 7 sections across the MIS5e Terrace were selected. 4 to 8 tight drilling in individual sections, total numbers of 32(total length 456m) drilling have done. Buried wave-cut bench and sea cliff are reconstructed by distribution of the terrace deposits and the precise site of former shoreline was obtained.Results: Obtained altitudes of the former shoreline from the 7 sections are about the same 25m. Our research proofed that the MIS5e terrace surface is not inclined in the study area and the previous study was misinterpreted by the cover of talus deposits. In some areas, we were recognized three peat layers from drilling cores. The deposition rate obtained from the depth of some peat layer and the 14C dating value is approximately 0.3mm / yr. Events in the last glacial period were recorded. [ABSTRACT FROM AUTHOR]

Improved understanding of the dynamics, extent and palaeogeography of retreating ice sheets can be accomplished by combining ice sheet modelling with the wealth of evidence they leave behind. Large volumes of constraining data exist and numerical models which can simulate entire glaciations are readily available. However, attempts to directly compare and connect empirically-based reconstructions with model-based simulations have been surprisingly rare, perhaps due to the complexity of combining the two fields and the abundance of approaches that could be taken. Here, we focus on a new method of directing ice sheet model simulations to match empirically reconstructed ice extents through time. Empirical evidence recording the behaviour of the last British-Irish Ice Sheet has been enhanced by the BRITICE-CHRONO consortium of researchers. This has been a six-year project to constrain the timing of retreat by a systematic dating programme focused on the marine-to-terrestrial transition. From two research cruises (18,000 km of geophysical data and 377 vibro- and piston cores), along with numerous investigations of stratigraphic sections on land we collected samples for dating from 914 sites from which 639 new geochronometric ages have been derived (336 radiocarbon, 156 luminescence and 157 cosmogenic). Organised into eight key transects from the shelf break to tens of kilometers onshore the pattern and pace of retreat has been compiled into an ice sheet wide reconstruction of ice extent at one thousand year times steps. We then used numerical models either forced or nudged to comply with these ice extents to yield simulations of ice sheet change thereby incorporating ice sheet physics, grounding lines, ice shelves, ice streams, and glacio isostatic adjustment and sea level. This empirically-constrained model simulation of the last British-Irish Ice Sheet will be presented. [ABSTRACT FROM AUTHOR]

During the Quaternary, the deglaciations are associated with large changes of atmospheric CO2 concentration with a difference of up to 100 ppm between the glacial and the interglacial periods. A complete and quantitative explanation for these CO2 increases in atmospheric CO2 concentration is still an open question since several fluxes contribute to the variations of atmospheric CO2. Biological productivity is often invoked as one of the processes involved in the changes of atmospheric CO2, and understanding its impact over deglaciations is key. While marine and continental proxies have been used to reconstruct the past variations of productivity at a regional scale, measurements of Δ17O of O2 (ln(δ17O+1) - 0,516 ln(δ18O+1)) in ice core has revealed to be a good indicator for inferring the past variation of global biospheric oxygen fluxes. We focus here on the special case of Termination V and the influence of the flux associated with biospheric productivity.Of the last 9 deglaciations, Termination V displays a unique feature. This deglaciation occurs during a minimum in eccentricity and follows a strong glacial period (MIS 12) preceding the long and warm MIS 11 interglacial period. It is the first termination clearly associated with the 100 ka glacial – interglacial periodicity after the MPT.Here we present the first record of the variation of the global biospheric productivity reconstructed from the triple isotopic composition of atmospheric oxygen (Δ17O of O2) measured in the bubbles of 50 samples of EDC ice core (Antarctica) over Termination V, i.e. from 444,1 to 405,7 ka. Compared to the previous records of Δ17O of O2 on the last 400 ka (Blunier et al., 2012), results show that Termination V is the only termination on which we can observe a different trend between CO2 and Δ17O of O2, the decrease of Δ17O of O2 during the Termination and the beginning of MIS 11 being twice longer than the increase in CO2. This shift reflects an increase in global oxygen biospheric productivity up to 20 % higher compared the other interglacial periods hence confirming the specificity of Termination V and MIS 11.We then confront this result to other long series linked to terrestrial and marine productivities for a perspective on the link between CO2 concentration and productivity over Termination V compared to the 4 younger Terminations. [ABSTRACT FROM AUTHOR]

Geomorphological mapping is a well-established method in glacial research, supplyingcrucial data for a wide range of process-oriented studies and palaeoglaciologicalreconstructions. In the latter case, it provides the essential geomorphological basis forestablishing glacial chronologies. Recent decades have seen significant developments inremote sensing and Geographical Information Systems (GIS), with a plethora of high-qualityremotely-sensed datasets now available for glacial geomorphological mapping. Mostrecently, the emergence of unmanned aerial vehicle (UAV) technology has allowedsub-decimetre-scale imagery to be obtained. Given the increasing abundance of mappingmethods available, approaches are needed to assimilate glacial-geomorphological dataeffectively. Here, we provide an idealised framework for mapping the "legacy"(geomorphological imprints) of mountain glaciations, synthesised from a broader review ofmapping approaches across a range of glacial environments (Chandler et al., 2018). Thisframework emphasises the importance of using multiple mapping approaches, which shouldideally include considerable field mapping. We also offer general recommendations for bestpractice that will aid accuracy assessment, comparison, and integration of geomorphologicaldata. Our approach and recommendations should help ensure robust interpretations of glaciallandforms and overall glacier systems, which is crucial to using the geomorphologicalimprints of mountain glaciations for subsequent palaeoglaciological and palaeoclimaticreconstructions. Reference: Chandler BMP. et al. 2018. Glacial geomorphological mapping: A review ofapproaches and frameworks for best practice. Earth-Science Reviews 185(C): 806–846. [ABSTRACT FROM AUTHOR]

Its submarine base and exposure to warm shelf waters makes the West Antarctic Ice Sheet (WAIS) highly vulnerable to climatic and oceanographic changes. Modelling infers that the WAIS has likely had a very dynamic history throughout the Neogene to the present. A complete collapse of the WAIS would result in a global sea level rise of 3.3 to 4.3 m, yet there is large uncertainty on predicting its future behavior and its role in sea level rise. Geological data on the past behavior of the WAIS are relatively sparsely and unequally distributed, in particular records of time intervals with climatic conditions similar to those expected for the near and distant future. Reconstructions and quantifications of partial or complete WAIS collapses in the past are therefore urgently needed for constraining and testing ice sheet models that aim to project future WAIS behavior.JOIDES Resolution departed from Punta Arenas in mid-January 2019 for IODP Expedition 379 to drill sites on the continental shelf and rise of the Amundsen Sea Embayment (ASE), where records are expected to represent dynamical advance and retreat processes of the central part of the WAIS. This embayment is of particular significance for studying WAIS dynamics as this sector currently experiences the largest ice mass loss in Antarctica, driven by ocean heat transport to the cavities of the main outlet glaciers. The plan was to drill a series of sites on the shelf where seismic data reveal seaward-dipping sedimentary sequences that span from the preglacial depositional phase to the most recent glacial periods. Deep-water sites on the continental rise were selected for recovering continuous records of glacially transported sediments and detailed archives of climatic and oceanographic changes throughout glacial–interglacial cycles.In this presentation, we will provide on-hand information of the recently completed drilling operation in a notoriously ice-infested environment as well as first preliminary drilling results with regard to our objectives of reconstructing the onset of glaciation in the greenhouse to icehouse transition, processes of dynamic ice sheet behavior during the Neogene and Quaternary, and ocean conditions associated with the glacial cycles. [ABSTRACT FROM AUTHOR]

The climate instability (millennial-scale rapid climatic oscillations) during the last glacial period has been a hot issue in Quaternary paleoclimate cycle, however, the driving mechanism and involved areas are still unclear. Previous reports mainly came from Green ice cores, North Atlantic deep-sea sediments and loess, stalagmites, lake records in the East Asian monsoon area, however, evidences from the Asian interior arid regions are scarce. Central Asia is distant from oceanic moisture sources and the climate is dominated by the Westerlies and the Subtropical High. Late Pleistocene loess sediments sporadically distributed at the pediments, terraces and basins provide us an opportunity to verify the existence of millennial-scale climatic fluctuations in Central Asia and understand the relations between high-low latitude climate. During the last decades, we have carried lots of loess investigations in Central Asian mainly around the Tienshan Mountains including Xinjiang in China, Kazakhstan, Kyrgyzstan and Tajikistan. In this paper, we report the preliminary results of loess investigations, and divide the loess distribution in Central Asia into three zones, which correspond to different hydrothermal combination conditions; and coupled with previous literatures, we review the progress of paleoclimate study of loess especially chronology in Central Asia, analyze problems of the last glacial climate events in Central Asia, and discusses its process and mechanism. Up to now, paleoclimatic proxies like grain size, mineralogy and geochemistry confirmed that that there are indeed millennial-scale rapid oscillations during the last glacial period in Central Asia, but they are inconsistent in age and variability. These rapid changes may be related to the following aspects: (a) contraction and expansion of the ice sheet in the high latitudes region of North Atlantic, (b) changes in the intensity and extent of the Siberian high pressure which further lead to the variance in wind dynamics, (c) and the north-south migration of the mid-latitude westerlies. The solar radiation is not the main driving factor for the rapid changes in Central Asia. [ABSTRACT FROM AUTHOR]

A number of near-field (glacial, proglacial, and glacimarine) records of glacial activity in the late Paleozoic constrain the onset of the main phase of glaciation to the late Mississippian (Viséan-Serpukhovian). These events postdate some more isolated occurrences of glacially-influenced deposits in the late Devonian and early Carboniferous. The main onset is, nonetheless, not precisely constrained because of apparent differences in age among widely separated outcrop areas. This suggests that glacial onset was not globally synchronized and/or is inadequately constrained in absolute time. The near-field record holds the advantage that it is a direct reflection of glacial activity, but the disadvantage that such records are notoriously stratigraphically incomplete. On the other hand, far-field records from the paleo-tropical realm preserve the record of an indirect response to glaciation in the form of eustatic sea-level fluctuations, but are more likely to be a complete, time-averaged, global signal. Herein, we review the stratigraphic record of several late Mississippian successions in North America and northwest Europe, all of which show an upward transition from a noncyclic or cryptic stratigraphic stacking pattern to a strongly cyclic motif ("cyclothems") through the late Mississippian. Among these successions are the Big Snowy Group of Montana, Manning Canyon and Doughnut Formations of Utah and Colorado, Windsor and Mabou Groups of Atlantic Canada, Clare Group of western Ireland, and Strathclyde and Clackmannan Groups of eastern Scotland. Cyclothems are m to tens of m thick intervals showing alternation between offshore marine and exposed, nonmarine deposits, and are interpreted as a record of sediment accumulation on low-gradient paleotropical shelves with low rates of sediment supply that were subjected to repeated, large-magnitude sea-level excursions. The transition to a strongly cyclothemic motif is a consistently recognizable change in these successions, and seems to have taken place at about 330-332 Ma (straddling the Viséan-Serpukhovian boundary). This change significantly predates both major, global excursions in carbon and oxygen stable isotope values, and the Mississippian-Pennsylvanian unconformity, and is considered a more reliable indicator of the onset of widespread glaciation. [ABSTRACT FROM AUTHOR]

Increased knowledge about anthropogenic climate change has raised growing concerns about its potential catastrophic impacts on both ecosystems and human societies. Yet, several studies on damages induced on the economy by unmitigated global warming have proposed a much less worrying image of the future, with only a few points decrease in the world GDP per capita by the end of the century, even for high levels of warming. Here we consider two different empirically estimated damage functions, linking GDP growth or GDP level to temperature, and apply them to a global cooling of -4°C in 2100, corresponding to a return to glacial conditions. We show that the alleged impact on average GDP per capita is comprised between -1.8% and +36%.These results are then compared to the living conditions on the planet during the last glacial maximum. The modeled impacts on the world GDP appear clearly unrealistic given the magnitude of climate and environmental changes recorded for that period. We therefore conclude that, if such damage functions cannot reasonably be trusted for a cooling outside their calibration range, nor should they be considered as plausible for the future climate projection under massive greenhouse gas emissions. [ABSTRACT FROM AUTHOR]