Search

Loess and paleosols are valuable terrestrial archives of past climate change in arid and semiarid Asia, yet most of the available records are located in central Asia and China, with only few records from western Asia. Here we report on a loess-paleosol sequence retrieved from the Gorgan Plain Southeast of the Caspian Sea that extends back to ca. 27,000 years ago. By combining palynological and micromorphological data with granulometry and magnetic properties in different horizons, we infer past changes in soil formation and vegetation composition, and the related climatic conditions. In order to set up a more reliable chronological framework, we applied luminescence and radiocarbon dating. Our results suggest a dry and cold glacial period characterized by steppe vegetation and loess deposition until about 24,000 years ago. Climate conditions during the Last Glacial Maximum (19–23,000 years ago) were relatively wet followed by a drying trend towards the end of the deglaciation. Our record suggests a relatively wet early Holocene but remains inconclusive for the late Holocene due to concurrent anthropogenic impact. We argue that changes in wintertime temperature and precipitation have been decisive in shaping the vegetation and soil formation in our study area during the Holocene, whereas changes in the position of the westerlies together with sea-level fluctuations of the Caspian Sea controlled the regional climate during the last glacial period. [ABSTRACT FROM AUTHOR]

The New Guinea Highlands were among the first areas where agricultural societies developed about 9 kya. Even today, the highest human population densities can be found in the tropical highlands, those are the most important shelters for societies in this seriously malaria-affected equatorial area. In this study, the distribution and altitudinal patterns of Plasmodium vivax and Plasmodium falciparum malaria, as well as the potential generation numbers and the annual season lengths of the extrinsic transmission periods of the parasites were modelled for the Last Glacial Maximum, the Mid-Holocene Period, 1960–1990 and 2061–2080 in the Papua New Guinea Highland provinces. It was found that areas influenced by Plasmodium vivax malaria have always been larger than the endemic regions of Plasmodium falciparum. After the Last Glacial Period, the extension of the malaria-free areas decreased dramatically. It could trigger the development of agriculture in the highlands in the early Holocene due to the increasing population concentration in malaria-free areas. These malaria-free regions could be stable in the rest part of the Holocene, which could explain the high human genetic and cultural diversity of the New Guinea Highlands. Future models predict the disruption of this stability and the notable decrease of the malaria-free areas in the highlands, especially in the case of Plasmodium vivax malaria, but the upward move in the Plasmodium falciparum -endemic regions also seems to be notable. These changes can negatively affect the demographic stability and cultural complexity of the traditional highlander communities in Papua New Guinea. [ABSTRACT FROM AUTHOR]

Atmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions. [Display omitted] • 74 new 10Be dates constrain the age of glaciation and periglaciation in the Limarí Andes. • Glaciers expanded between 24.2 ± 0.4–18.6 ± 0.2 ka in correspondence with the LGM. • Deglaciation with steady ice retreat and thinning was completed by 17.6 ± 0.2 ka. • LGM debris-covered glaciers left a moraine niche for subsequent rock glacier development. • Ice-rich permafrost reworked LGM moraine deposits between 15.5 ± 0.3–13.6 ± 0.3 ka. [ABSTRACT FROM AUTHOR]

• The Irrawaddy River and Ganges-Brahmaputra rivers are the main sediment sources of the northern Ninetyeast Ridge over the last 50 kyr. • Millennial-scale periodic changes of weathering and terrigenous input are revealed during the last glacial period. • Shift of depositional center from Bengal Fan to the continental shelf is controlled by sea level changes. The Ninetyeast Ridge is situated within the world's largest sediment "source-sink" system, which extends from the Tibetan Plateau to the Bay of Bengal (BoB). Modest and stable sedimentation rate makes it a suitable region for studying long-term land-sea interaction. Recent research has primarily focused on the northern Bengal Fan, leaving limited knowledge about sedimentary processes on the distant Ninetyeast Ridge. This study aims to address this gap by investigating sediment transport pattern and its response to climatic and environmental changes since the last glacial period, using the gravity core (CJ04–50) selected from the northern Ninetyeast Ridge. The provenance discrimination based on δEu-(Gd/Yb) N revealed that the Irrawaddy (Irr) River, along with the Ganges-Brahmaputra (G-B) Rivers, represented the primary sources of the study area. Quantitative analysis equations indicated that the contribution of the G-B Rivers decreased from the last glacial period (22%) to the Holocene period (16%), while that of the Irr River increased (from 78% to 84%). Chemical index of alteration (CIA*) values, and terrigenous input proxy indicators (Ti/Ca, Rb/Sr) were used to indicate the changes of weathering and terrigenous input over the past 50 kyr. During the last glacial period, CIA*, Ti/Ca and Rb/Sr revealed significantly millennial-scale periodic changes, including the distinct declining trend during the Last Glacial Maximum (LGM) and Heinrich 2–4 (H2-H4) periods, followed by recovery trend during subsequent warm periods. During these cold periods of LGM and H2–H4, weakened Indian monsoon condition, reduced precipitation, cold climate, and expanding ice sheets, adversely affected physical erosion and chemical weathering in the source area, and the reduced river runoff impeded sediment transport. Conversely, these environmental factors reversed during relatively warm periods. Since the Holocene, CIA*, Ti/Ca and Rb/Sr declined, which was contrast to the climate change, and the sea level changes became the dominant factor. The rapidly rising sea level submerged the main terrigenous input channel (the Swatch of No Ground) of the G-B Rivers, made the depositional center shift from the Bengal Fan to the continental shelf, causing the decline of terrigenous input and lower CIA* values. [ABSTRACT FROM AUTHOR]

The East Antarctic Ice Sheet (EAIS) is the largest glacial system in the world, and the evolution history of the EAIS strongly affects global climate change. As one of the most extensive ice-free areas in coastal East Antarctica, the Larsemann Hills represent an important site for understanding the glacial evolution of East Antarctica. Generally, the last exposure process in the Larsemann Hills was considered to occur in the last glacial period. However, the initial time of the last exposure process in the Larsemann Hills remains unclear. This study presents the 10Be exposure ages of eight bedrock samples with glacial striae, which means that the original uneroded surfaces are preserved, from the Larsemann Hills and neighboring areas. The 10Be exposure ages ranging from 70.7 ± 4.7 to 13.5 ± 1.2 ka indicate that the Larsemann Hills have become ice-free since MIS4. The 10Be exposure ages with the characteristics of zonal distribution in the E–W direction and ages generally change from north to south, which reveals the combination of glacial retreat and topography differences. The activity of the ice sheet in the Larsemann Hills did not respond to the Last Glacial Maximum (LGM). In contrast, the deglaciation in the Larsemann Hills occurred as a diachronous process during the global last glacial periods, which began long before the LGM and lasted after the LGM. According to the exposure ages in the Larsemann Hills and the distance from the edge of the ice sheet, the average glacial retreat rate since MIS4 has been 71.57 m/ka. [ABSTRACT FROM AUTHOR]

• Detailed chronology revealed that Maerkang loess appeared at least ∼ 60 ka ago. • Dust flux history since MIS 3 in the TP was reconstructed. • High dust accumulation rates occurred in the Last Glacial Maximum. • Rapid climate events on the TP were linked to the North Atlantic climatic system. The Tibetan Plateau (TP) is extremely sensitive to climate change. However, climate variability during the last glaciation in the TP is not well-understood. The widely distributed loess deposits on the eastern TP serve as a significant archive for retrieving past climate changes and aeolian dust dynamics. Through detailed quartz optically stimulated luminescence and radiocarbon dating and the analysis of environmental proxies, we have established a reliable chronology of the Maerkang loess sequence in the eastern TP and reconstructed well-constrained histories of dust activities and environmental variation. Our results demonstrate that the accumulation of aeolian loess in this region occurred at least 60 thousand years ago. The dust mass accumulation rate (MAR) varied highly in the last glacial period, with high MARs in the Last Glacial Maximum and relatively low MARs in marine isotope stage (MIS) 3. Humid conditions occurred in MIS 3 (approximately 50–32 ka) due to the intensified Indian summer monsoon. The rapid climate variations of the Maerkang loess might be correlated to the Dansgaard–Oeschger cycles and the Heinrich events, which implies the significant impact of the North Atlantic climatic system on the TP. Our findings provide new evidence for a better understanding of the history of environmental variations since MIS 3 in the eastern TP. [ABSTRACT FROM AUTHOR]

Abstract Proxy data from pollen and mollusc indicator species, periglacial phenomena, changes in geometry of mountain palaeoglaciers and based on selected lithological and geomorphological features enabled reconstruction of the Late Pleistocene climate characteristics in Poland and adjacent areas. Climate during the Eemian was generally stable but with a distinct west-east gradient in summer. Strong influence of the Atlantic air masses moving to the east resulted in the annual precipitation over 600 mm. Climate instability in the late Eemian as well as during stadials and interstadials of the Early Weichselian was expressed by progressive cooling and increasing temperature difference between winters and summers, reflecting stronger continentalism towards the west, accompanied by decreased precipitation. Periglacial frost crackings and polygonal patterns indicated occurrence of permafrost in Poland already at about 49 ka BP and its occurrence until the termination of the last glaciation. These periglacial structures have developed at mean annual temperatures from −9 to −4 °C, with winter extremes up to about −25 °C. Mean summer temperature reached likely around 10 °C as suggested by palaeobotanic record. Palaeoglaciological studies of mountain glaciers across Europe allowed inferring their activity and sensitivity to climatic fluctuations during the Late Weichselian. The Weichselian of central Europe was controlled mostly by the southerly and easterly circulation dominated by climate cyclones and anticyclones, respectively. An inflow of air masses from the west was significantly limited and concentrated mainly within the so-called periglacial corridor between the Scandinavian ice sheet and the Alps. Such circulation pattern determined serious reduction of precipitation during the Last Glacial Maximum that reached 60% in relation to modern conditions. The following Late Pleistocene cold phases (Oldest and Younger Dryas) were slightly warmer and wetter with increasing contribution of the westerlies that were strongly dependent on progressing shrinkage of the Northern Hemisphere ice sheets. [ABSTRACT FROM AUTHOR]

We measured meteoric 10 Be variation throughout a marine sediment core from the Larsen B embayment (LBE) of the Antarctic Peninsula, and collected in situ 10 Be and 14 C exposure ages on terrestrial glacial deposits from the northern and southern margins of the LBE. We use these data to reconstruct Last Glacial Maximum (LGM) to present deglaciation and ice shelf change in the LBE. Core sedimentary facies and meteoric 10 Be data show a monotonic progression from subglacial deposits to sub-ice-shelf deposits to open-marine conditions, indicating that its collapse in 2002 was unprecedented since the LGM. Exposure-age data from the southern LBE indicate 40 m of ice surface lowering between 14 and 6 ka, then little change between 6 ka and the 2002 collapse. Exposure-age data from the northern LBE show a bimodal distribution in which clusters of apparent exposure ages in the ranges 4.9–5.1 ka and 1.0–2.0 ka coexist near 50 m elevation. Based on these results, other published terrestrial and marine deglaciation ages, and a compilation of sea bed imagery, we suggest a north-to-south progression of deglaciation in the northeast Antarctic Peninsula in response to Holocene atmospheric and oceanic warming. We argue that local topography and ice configuration inherited from the LGM, in addition to climate change, are important in controlling the deglaciation history in this region. [ABSTRACT FROM AUTHOR]

Pollen data recovered from the sedimentary record of western Amazonia is still inadequate to fully address climate changes over the Last Glaciation in this region. The present work focuses vegetation dynamics from an area of southwestern Amazonia during the past 42,000 cal yr B.P. based on the integration of previous and new pollen data. Sediment cores were sampled from two sites covered by tropical rainforest in fluvial terraces of the Madeira River, a major southern Amazonian tributary. The results indicated a significant proportion of cold-adapted Andean tree species, represented by Alnus (0–20%), Hedyosmum (1–15%), Podocarpus (0–5%), Illex (1–11%) and Weinmannia (0–1%) at least between > 43,163–42,018 cal yr B.P. and 10,394–10,240 cal yr B.P. During the Holocene, only pollen representative of herbs and modern Amazonian vegetation persisted. The new pollen record confirmed previous documented results that vegetation communities presently restricted to Andean areas at altitudes higher than 2000–3000 m, occupied this region of the Amazonian lowlands close to the onset and probably also during the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

It is generally assumed that during the global Last Glacial Maximum (gLGM, i.e. 18–24 ka BP) dry climatic conditions in NE Russia inhibited the growth of large ice caps and restricted glaciers to mountain ranges. However, recent evidence has been found to suggest that glacial summers in NE Russia were as warm as at present while glaciers were more extensive than today. As a result, we hypothesize that precipitation must have been relatively high in order to compensate for the high summer temperatures and the resulting glacial ablation. We estimate precipitation abundance by mass balance calculations for the palaeo-glaciers on Kamchatka and in the Kankaren Range using a degree-day-modelling (DDM) approach, and find that precipitation during the gLGM was likely comparable to, or even exceeded, the modern average. We suggest that stronger than present southerly winds over the Northwest Pacific may have accounted for the abundant precipitation. The DDM-results imply that summer temperature, rather than aridity, limited glacier extent in the southern Pacific Sector of NE Russia during the gLGM. [ABSTRACT FROM AUTHOR]

Milankovitch orbital parameters control cycles of insolation, a primary pacer of long term changes in climate, but exactly how insolation signals are transmitted around the globe in the climate system is unclear. In order to address the fundamental questions of when and how ice age climates begin and end, how fast glaciers retreated during the last deglaciation, and how glaciers behaved before anthropogenic influence, we need robust glacial chronologies. The timing of local glacial maxima beyond the last glacial cycle, however, has remained largely unconstrained due to moraine degradation over time, limiting our ability to fully explore these questions. By developing a detailed geomorphic surficial map and targeting relatively tall, ridge-top boulders, we have constructed a new, precise 10Be chronology of glacial maxima of the Ñirehuao glacier lobe (45°S) for the last two glacial cycles. We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia, which formed a major set of moraines by at least 153 ± 5.1 ka, with a stillstand or smaller readvance by 137 ± 4.2 ka, corresponding to the two coldest and dustiest periods of MIS 6 in Antarctica. The next largest advance occurred at 23.6 ± 0.9 ka, at the end of peak Southern Hemisphere MIS 2 cooling. Retreat of the glacier commenced by ∼18.5 cal ka BP when lakes in a tributary valley just to the southwest became ice-free. Overall we find that advances of the Ñirehuao glacier lobe occur when winter sea ice around Antarctica is expansive and both obliquity and eccentricity are at their minima. • We present a new, detailed geomorphic map and 10Be chronology of the Ñirehuao glacier lobe for the last two glacial cycles • We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia • The Ñirehuao glacier lobe formed a major set of moraines by 153±5.1 ka with a stillstand or smaller readvance by 137±4.2 ka • The MIS 2 glacial maximum occurred at 23.6±0.9 ka and subsequent retreat of the glacier commenced by ∼18.5 cal ka BP • Overall, advances occurred when winter sea ice around Antarctica was expansive and obliquity and eccentricity were at minima [ABSTRACT FROM AUTHOR]

Globally, research aiming to reveal the unique biogeochemical processes and gas hydrate potential in methane seep areas is well established. Furthermore, methane seeps discovered in the South China Sea (SCS) have been widely studied and have achieved significant results. Herein, by systematically analyzing sedimentary samples from the Shenhu area, SCS, we discovered a methane seep that was once active during the last glacial period, particularly the Last Glacial Maximum (LGM) period, and fixed at the seafloor for ∼10 ka. This discovery was achieved by integrating the features of the glauconite within the foraminifera chamber, different morphologies of pyrites, and unique framboid goethites (pyrite pseudomorphs). In addition, this study accounted for the high chromium-reducible sulfur content and extremely negative δ34S values (from −50.78 to −46.92%) between 121 and 231 cmbsf, the Mo content and its correlation with total sulfur (TS) and total organic carbon (TOC), the TS/TOC ratios of sediments, the results of AMS 14C dating, and the results of planktonic foraminifera analysis in the case of carbon and oxygen isotopes. Glauconite, which is usually considered a product associated with transgressive deposits and condensed sections, is widely found in warm climatic intervals. However, these intervals are generally associated with methane emission events. Thus, our results demonstrate another mechanism for the formation of glauconite in methane seeps during the LGM. Furthermore, the existence of framboid goethites implies that this methane seep has been subsiding since the end of the LGM and that few pyrites that formed previously were reoxidized. Notably, this study is the first to report a systematic investigation of methane seep activity during the last glacial period by the indication of authigenic minerals, such as glauconite and framboid goethite, in the SCS. Overall, our results show a direct relationship between methane seep activity and climatic variation. • The diverse morphologies of pyrites indicate various formative environments. • The glauconite records the changed redox condition near the seafloor surface. • The occurrence of Fe (hydrogen) oxide indicates the methane seeps is inactive at present. • All the mineralogical and geochemical characteristics reveal a subsided methane seep. [ABSTRACT FROM AUTHOR]

Abstract: Recent studies of the Last Glacial period Indo-Australian summer monsoon (IASM) have revealed links to both northern and southern hemisphere high latitude climate as well as to regional ocean conditions. Particular interest has been paid to the monsoon response to Heinrich events, with variability explained by meridional shifts in positioning of the intertropical convergence zone (ITCZ), but this model has not been adequately tested. In addition, the shorter-lived Dansgaard/Oeschger (D/O) events have not been detected (beyond D/O-1, the Bølling/Allerød) in land-based records from the Indo-Pacific, despite their prominent expression in stalagmites from southern Asia, raising questions about the sensitivity of the IASM to these events. Here we present a Southern Hemisphere stalagmite oxygen isotopic time series from Ball Gown Cave (BGC), tropical northern Australia, located on the margins of the modern austral summer ITCZ, that spans 40–31 and 27–8 ka. Elevated IASM rainfall coincides with Heinrich stadials and the Younger Dryas, while decreased rainfall characterizes D/O interstadials, a response that is anti-phased with sites spanning the Indo-Pacific Warm Pool and with Chinese records of the East Asian summer monsoon. The BGC time series thus reveals a precipitation dipole consistent with a southward (northward) migration of the ITCZ during periods of high northern latitude cooling (warming) as the primary driver of millennial-scale IASM variability during the Last Glacial period. Our record indicates a strengthening of the IASM after the Younger Dryas period, likely as a result of rising sea level and sea surface temperatures, breaking the link with the high latitudes. [Copyright &y& Elsevier]

Abstract: Several lines of evidence have previously been used to suggest that ice retreat after the last glacial maximum (LGM) resulted in regionally-increased levels of volcanic activity. It has been proposed that this increase in volcanism was globally significant, forming a substantial component of the post-glacial rise in atmospheric CO2, and thereby contributing to climatic warming. However, as yet there has been no detailed investigation of activity in glaciated volcanic arcs following the LGM. Arc volcanism accounts for 90% of present-day subaerial volcanic eruptions. It is therefore important to constrain the impact of deglaciation on arc volcanoes, to understand fully the nature and magnitude of global-scale relationships between volcanism and glaciation. The first part of this paper examines the post-glacial explosive eruption history of the Andean southern volcanic zone (SVZ), a typical arc system, with additional data from the Kamchatka and Cascade arcs. In all cases, eruption rates in the early post-glacial period do not exceed those at later times at a statistically significant level. In part, the recognition and quantification of what may be small (i.e. less than a factor of two) increases in eruption rate is hindered by the size of our datasets. These datasets are limited to eruptions larger than 0.1km3, because deviations from power-law magnitude–frequency relationships indicate strong relative under-sampling at smaller eruption volumes. In the southern SVZ, where ice unloading was greatest, eruption frequency in the early post-glacial period is approximately twice that of the mid post-glacial period (although frequency increases again in the late post-glacial). A comparable pattern occurs in Kamchatka, but is not observed in the Cascade arc. The early post-glacial period also coincides with a small number of very large explosive eruptions from the most active volcanoes in the southern and central SVZ, consistent with enhanced ponding of magma during glaciation and release upon deglaciation. In comparison to non-arc settings, evidence of post-glacial increases in rates of arc volcanism is weak, and there is no need to invoke significantly increased melt production upon ice unloading, as occurred in areas such as Iceland. Non-arc volcanoes may therefore account for a relatively higher proportion of global volcanic emissions in the early post-glacial period than is suggested by the relative contributions of arc and non-arc settings at the present day. The second part of this paper critically examines global eruption records, in an effort to constrain global-scale changes in volcanic output since the LGM. Accurate interpretation of these records relies on correcting both temporal and spatial variability in eruption recording. In particular, very low recording rates, which also vary spatially by over two orders of magnitude, prevent precise, and possibly even accurate, quantitative analysis. For example, if we assume record completeness for the past century, the number of known eruptions (volcanic explosivity index≥2) from some low-latitude regions, such as Indonesia, is approximately 1 in 20,000 (0.005%) for the period 5–20ka. There is a need for more regional-scale studies of past volcanism in such regions, where current data are extremely sparse. We attempt to correct for recording biases, and suggest a maximum two-fold (but potentially much less) increase in global eruption rates, relative to the present day, between 13 and 7ka. Although volcanism may have been an important source of CO2 in the early Holocene, it is unlikely to have been a dominant control on changes in atmospheric CO2 after the LGM. [Copyright &y& Elsevier]

Abstract: Exposure dating of abraded bedrock surfaces below glacial trimlines in the Pięciu Stawów Polskich/Roztoki Valley, using cosmogenic 36Cl, has been applied to determine the deglaciation chronology in the study area. Nineteen rock samples yielded ages between 21.5 and 9.5ka. The spatial distribution of ages provides evidence of progressive downwasting of glaciers within the study area. Dates of exposure indicate that the onset of ice volume decrease occurred no later than 21.5ka. This provides evidence that the local maximum glaciation occurred in accordance with the global Last Glacial Maximum (LGM). The first period of deglaciation in the study area was completed around 18ka. Further significant loss of ice volume is confirmed between 15 and 13ka. The spatial distribution of chronological data within the Pięciu Stawów Polskich Valley indicates post-LGM readvances of glaciers around 17ka and 12ka. Using the glacier modelling and paleoclimate proxies from the study area, the early Late Glacial glacier had been stable with a 9–10°C decrease in temperature and 30–50% lower precipitation in relation to modern conditions. The subsequent advance took place with temperatures 6–7°C lower and 10–30% less precipitation. The timing of the readvances is nearly synchronous with Late Glacial advances in the European Alps, Southern Carpathians and Anatolian peninsula. This suggests synchronicity of major climatic fluctuations across Central Europe and the northern margin of the Mediterranean Basin. [Copyright &y& Elsevier]

Abstract: Reconstructing the paleoglaciation of the Tibetan Plateau is critical to understanding linkages between regional climate changes and global climate changes, and here we focus on the glacial history of the Shaluli Shan, an area of the southeastern Tibetan Plateau that receives much of its precipitation from monsoon flow. Based on field investigation, geomorphological mapping, and 10Be exposure dating of moraines, we identify glacial deposits from the Late Glacial, with minimum ages at 13.0 ± 1.2 –17.1 ± 1.6 ka, global Last Glacial Maximum (gLGM) at 21.6 ± 2.0 ka, and pre-gLGM at 102.3 ± 10.0–183.6 ± 17.0 ka. These ages are consistent with and significantly extend the known range from most prior chronological work using terrestrial cosmogenic nuclides in this area, and include a set of dates for the Kuzhaori moraine that raise questions about prior chronologies based on the electron spin resonance technique. Ice caps about 4000 km2 in size covered the Haizishan Plateau and the Xinlong Plateau during the global LGM, with large glaciers extending far down outlet valleys. The presence of ice cap glaciation, here, contrasts strongly to glaciation elsewhere in the Shaluli Shan and more central regions of the Tibetan Plateau where ice expansion remained constricted to valleys. This work provides important insights into the paleoclimate pattern and monsoon evolution of the Tibetan Plateau over past glacial cycles and indicates that the Shaluli Shan has a glacial chronology more consistent with the Northern Hemisphere paleo-ice sheets than other areas of the Tibetan Plateau. [Copyright &y& Elsevier]

Abstract: We summarize 121 14C and in-situ cosmogenic (10Be and 36Cl) ages that constrain fluctuations of the Irish Ice Sheet (IIS) since the Last Glacial Maximum (LGM) that can be linked to abrupt climate changes in the North Atlantic region. These data provide a robust means to date ice-sheet fluctuations because similar-age events can be identified from widely spaced sites, they are constrained by stratigraphy, and they can be related to large changes in the configuration of a dynamic ice sheet. The following events are recognized. (1) AMS 14C ages and 10Be and 36Cl ages as well as offshore data suggest that the last maximum advance of the IIS occurred between ∼27 and 23 cal ka. (2) Deglaciation began on the western continental shelf and in the Irish Sea Basin at ∼23 cal ka. Dated sites from around Ireland constrain subsequent widespread retreat of ice-sheet margins from the shelf onto Irish coastlines during the Cooley Point Interstadial ≥20 cal ka. AMS 14C ages suggest that the Cooley Point Interstadial continued until ≤18.2 cal ka B.P. During this interstadial, retreat of the ice-sheet margin into the northern Irish Sea Basin indicates that the IIS may have lost up to two-thirds of its mass. (3) Dated sites from northwestern and eastern Ireland indicate that the Cooley Point Interstadial was terminated by ice readvance during the Clogher Head Stadial at ∼18.2 cal ka. (4) The Linns Interstadial was a brief interval (≥17.0–≥16.5 cal ka) of ice recession following the Clogher Head Stadial that is identified from raised marine sediments in eastern and northern Ireland and cosmogenic ages elsewhere in Ireland. (5) The IIS subsequently readvanced during the Killard Point Stadial, reaching its maximum extent ∼16.5 cal ka, indicating that the readvance began sometime earlier. (6) Widespread retreat of the IIS began by ∼15.5 cal ka during the Rough Island Interstadial. (6) Readvance of cirque glaciers in western Ireland occurred during the Younger-Dryas equivalent Nahanagan Stadial. [Copyright &y& Elsevier]

[Display omitted] • Millennial-scale climate variability in the Bay of Bengal is reconstructed by TEX 86. • Warming trend during millennial-scale cold events is revealed in the northern Indian Ocean. • Atmospheric CO 2 force SST change during the millennial-scale cold events over the past 40 kyr. To better understand the process of hydrographic and temperature changes in the Indian Ocean, we present Glycerol dialkyl glycerol tetraether data on core BoB-56 from the Bay of Bengal to reconstruct the sea surface temperature (SST) variability during the last glaciation. The results indicate that the TEX 86 -derived SST ranged from 22.00 to 28.30 °C with several fluctuations since 40 ka BP and that the evolution pattern matched well with the marine isotope stage (MIS). During MIS 3, the SST kept around 24.60 °C with some small amplitudes. The SST showed more significant fluctuations during MIS 2 and increased gradually with a ~3 °C cooling during the Last Glacial Maximum (LGM). After the Younger Dryas (YD) stage, Holocene SST values exhibited miniscule variations. During the last glaciation climate variability process, the cold signals of the YD and Heinrich events were recorded well in our core SST series, revealing a regional response to global climate changes. The warming trend during these millennial-scale cold events in the northern Indian Ocean was also identified, and SST increased in the range of 2 °C. A comparison of SST records and atmospheric CO 2 concentration shows that the warming process during the YD, LGM, and Heinrich (1–4) events matched the gradual increase in atmospheric CO 2 concentration in the northern Indian Ocean. Hence, this study implies millennial-scale hydroclimate change linked with atmospheric CO 2 forcing that could improve our knowledge of the role of atmospheric CO 2 in triggering abrupt Indian Ocean climate changes. [ABSTRACT FROM AUTHOR]

Changes of marine paleoproductivity could reflect the history of marine biogenic cycle process, and exploring the evolution and mechanism of marine productivity are important for understanding the global biogenic factor cycle and its roles in past, present and future climate change. Based on the analysis of biogenic silica (BSi) in core ADM-159 and core BoB-56 from the northeastern Indian Ocean, high-resolution curves of paleoproductivity evolution were obtained. The results show that the BSi contents in these two core sediments are less than 1.8%, mainly affected by the low supply of silica skeleton and the high dissolution and dilution of terrigenous materials. Distinct fluctuations in BSi contents could still be reflected, and their relative values were controlled by chemical weathering processes and terrigenous material supply. The power spectrum analysis of BSi content shows reliable periodicities of 5.86 kyr, 1.95 kyr, 1.35 kyr and 1.09 kyr, suggesting that millennial-scale BSi value might be affected by solar activity. Based on the BSi mass accumulation rates (MAR), lower paleoproductivity during the glacial period and higher level during the Holocene were revealed in our records, which matched well with the global climate changes. Temperatures controlled by low latitude insolation changes could influence the nutrient substance supply, further promote productivity variations at the glacial–interglacial scale. Some millennial events, such as the Heinrich stadial 1 (HS1) and Younger Dryas (YD) periods, showed relatively low paleoproductivity, while the Bølling/Allerød (B/A) period and the middle Holocene showed higher paleoproductivity. These millennial paleoproductivity fluctuations may be due to the changes of nutrient supply caused by Indian summer monsoon (ISM). In addition, the BSi MAR of core ADM-159 and core BoB-56 are well correlated with the isotopic compositions of Greenland ice core and Chinese speleothem, providing robust evidence for the link between northeastern Indian Ocean paleoproductivity and global climate change. • paleoproductivity variability since LGM was reconstructed by BSi in the northeastern Indian Ocean. • BSi content were controlled by supply of silica skeleton, dissolution and dilution of terrigenous materials. • Indian summer monsoon have been proved linked with tropic Indian Ocean paleoproductivity. [ABSTRACT FROM AUTHOR]

Geomorphic reconstructions of the East Antarctic Ice Sheet history across Antarctica suggest diachronous and varying retreat patterns with changing climate. However, little is known of how terrestrial environments responded to these climate changes because the continental ice sheet covered most Antarctic coastal oases during the Last Glacial Maximum (LGM), eliminating terrestrial records. In this study, the environmental history spanning the last 25,400 years was reconstructed using geochronology, lithology, rock magnetism and geochemistry to understand the effect of glacial–deglacial climate variations on surface processes and Mochou Lake ecology. During the last glacial period (25.4 to 18.8 cal. kyr BP), intensified winds and the freeze-thaw action of ice actively weathered the high elevation western catchment that was a dominant sediment source to the lake. The glacial environmental conditions induced a persistent perennial lake ice-cover resulting in anoxia, low sedimentation, primary production and weak brackish conditions. Progressively, as deglacial conditions augmented around 18.8 cal. kyr BP, increased catchment meltwater flow enhanced sediment transport and also transformed the lake into a freshwater basin, although perennial ice-cover still prevailed. Further, the biotic development of the lake began later in the Mid-Holocene as compared to other lakes in the region, wherein the seasonal lake ice cycle and/or ice moat developed. Weak chemical weathering and pedogenesis also commenced in the catchment in response to the warming climate trend. This delayed response to the Holocene warming was possibly due to the local cooling effect of the Dälk Glacier's discharge that also led to sea-ice persistence in the Prydz Bay. This study also provides further evidence that parts of the Larsemann Hills remained free of erosive grounded ice during the LGM and subsequent deglaciation. The Mirror Peninsula, specifically, escaped ice overriding despite being enclosed by the Dälk Glacier, Lake Nella ice lobe and Amery Ice Shelf. [Display omitted] • A multi-proxy record of glacial-deglacial environment change from lake sediments. • The regional weathering changes are due to geomorphic and atmospheric factors. • Variations in lake ice cover across warming phases limited biogenic productivity. [ABSTRACT FROM AUTHOR]

The bathyal Ocean Drilling Program Site 765 at 5725 m water depth, offshore northwest Australia at 16°S is directly under the influence of the Australian monsoon during the Austral summer and is the recipient of continental dust during the Austral winter. It is downstream of the Indonesian Throughflow, which is a major arm of the global thermohaline circulation. As such it is ideally situated to record the climate and oceanic consequences of Quaternary climate variability. Despite being over 400 km from northwest Australia, palynomorphs (pollen and spores) are relatively common in this section, sourced via aeolian (during the dry winter) and benthic transportation processes and sediment plumes (during the summer monsoon). Detailed palynological analyses of this flora in the upper part of this core reveals intermittent snap shots of environmental and climate change over the last 300 kyrs. Interglacial stages are interpreted to be characterised by palynomorph-rich turbidite and calcareous ooze deposition whereas palynomorph-poor slowly accumulating siliceous oozes (deposited below the Calcium Carbonate Compensation Depth) are present during glacials. The dominance of Poaceae sourced from the Australian mainland in interglacial periods suggests that vegetation during these periods was similar to today. Interglacial palynofloral assemblages suggest a more intense wet season (Australian monsoon) with higher rainfall that allowed more active erosion and deposition onto the shelf. The presence of Indonesian sourced pollen and fern spore taxa, as well as warm water dinoflagellate species suggest enhanced Leeuwin Current and monsoonal intensity during interglacials times. The youngest part of the core is dominated by siliceous ooze, likely deposited during the Last Glacial Maximum and the early Holocene. The lack of calcareous ooze near the top of the core is likely caused by Holocene to Recent erosive processes or core disturbance. The presence of common charcoal in all samples over the last 300 kyrs shows that fire was a constant feature of the landscape in northwest Australia prior to human occupation of the region 65,000 years ago. • Palynomorphs in bathyal ODP Site 765 record 300kys of Quaternary climate variability. • Fossil palynomorphs are sourced via dry season aeolian or monsoonal sediment plumes. • Interglacials are turbidites/calcareous oozes whereas glacials are siliceous oozes. • Poaceae from Australia dominated interglacials due to an enhanced Australian Monsoon. • Common charcoal shows fire was a constant landscape feature prior to human occupation 65,000kyrs. [ABSTRACT FROM AUTHOR]

The Quaternary is well known for being a period of the geological record that saw significant and alternating climatic fluctuations. Here, we concentrate on the last 94 millennia that saw Australia and its surrounding seas undergo significant environmental changes. Importantly also it is during that this period of time includes the arrival and settlement of humans in Australia. Following on from Marine Isotopic Stage 4 (MIS4) that saw, over the period of 71-59 ka BP, a significant eustatic sea level drop (∼100 m), low sea-surface temperatures as well as glacial conditions on land, Australia experienced wet conditions again, but eventually progressively entered into a glacial phase. By then, humans had arrived on this large continent and later the megafauna progressively became extinct. This paper describes in detail the climate over this period, based principally on the high-resolution record of two marine sediment cores located offshore of the southern Australian margin, and that are then compared with known events on land as well as other deep-sea cores. Particular emphasis is placed on the period that spans the Last Glacial Maximum (LGM), the extent of which thus far had been poorly defined in the Australian region. Emphasis is placed on the period from 34 to 14 ka to demonstrate that (1) the LGM, defined here as the period 24 to 18 ka, was not always extremely dry and cold, and (2) that people were able to live in inland Australia as water existed in places, despite generally cold conditions. We also show using a series of ten maps - at 2 ka intervals over the 34-14 ka period - the waxing and waning of oceanic fronts such as the Subtropical and Subantarctic Fronts, link sea-surface temperatures (SST) with periods of glacial expansion in the Australian Alps and Tasmania, as well as the South Island of New Zealand, and the extent of the Leeuwin Current down to south of Australia. Aeolian dust was transported at sea over the main core site from ∼26 to 18 ka period, pointing to arid conditions in Australia, but this period was punctuated by two significant reductions in dust transport to both core sites, coinciding with a retreat of the Subantarctic Front away from the Australian southern coastline, and slight SST shifts for a few centuries at ∼24 and 22-21 ka BP. At the peak of the cold phase, from 23 to 18.4 ka, summer SST were of the order of 9 °C below that experienced during the middle of the Holocene at about 6 ka BP. A similar temperature drop was also experienced offshore the northwestern corner of Western Australia. Periglacial activity dates for the Australian mainland and Tasmania pool around ∼22 ka. On either side of the 24 ka event, the chain of lakes in the Willandra Lakes retained water and human activity was registered in the area. Elsewhere in Australia, water was present to sustain human populations during the cold and dry times. It is postulated here that northern Australia was at times quite wet, especially during MIS4. The cessation of the LGM is set on 18.4 ka from offshore southern Australia as confirmed for the deep-sea cores by several proxies, and more likely at 18 ka inland. Finally, we document that it took two millennia for "glacial" conditions to end in the Australian region as registered in our deep-sea core records, well after the lowest global sea level ∼20.6 and 20 ka, respectively, started to rise. There is also evidence of another very cold period determined on the Australian mainland, Tasmania and the South Island of New Zealand centred around 27 ka, after which time warmer conditions occurred before the start of the LGM. This is matched with our deep-sea records with very cold conditions and changes in oceanographic conditions. • 2 deep-sea cores provide information on the waxing and waning of oceanic fronts south of Australia. • The Last Glacial Maximum for the Australian region spans 24-18 ka. • 10 maps detail conditions in the Australian region spaning the period 34–14 ka. • Environmental conditions for MIS2 & MIS4 are compared in great detail in the cores. • Australia was arid and cold during the LGM but there was water to support human occupation. [ABSTRACT FROM AUTHOR]

We have developed a density-based method for determining porewater salinity that can be performed shipboard on small volume samples with greater efficiency and precision than the currently available shore-based chloride titration technique. This approach is based on a recently developed water column method that determines salinity at the precision of a conductivity measurement through density measurements and the seawater thermodynamic equation of state. Diagenesis causes deviations in porewater composition from standard seawater values, affecting the density salinity relationship, that we correct for through precise measurements of each ion's concentration before converting measured density to chloride concentration. We account for the diffusive change in porewater chloride that occurs over time independent of diagenesis by optimizing diffusion modeled, sea-level determined bottom water chloride as a function of time to measured modern porewater and converting the best fit to salinity. We applied our density method to porewater samples extracted from adjacent long cores collected from the deep western North Atlantic, determining Last Glacial Maximum (LGM) bottom water paleosalinity in a region critical to understanding deep water mass distribution. High uncertainty is associated with current LGM bottom water salinity characterizations and their implications for LGM overturning circulation and climate. Density was determined to a precision of 2.3 × 10−6 g/mL, which translates to a relative uncertainty of 0.03% for LGM salinity. We compare the high precision chloride concentration profiles determined using our method to profiles determined from chloride titrations of parallel samples. Salinity change at our site between the pre-industrial and LGM is 3.07 ± 0.03 % and 3.65 ± 0.06 % when determined from density and 2.96 ± 0.12 % and 1.96 ± 0.21 % when determined from titrated Cl− for the two co-located cores analyzed. This is consistent with nearby deep Atlantic paleosalinity data (Adkins et al., 2002) and global sea-level-change determined salinity change (Clark and Mix, 2002). By comparing these uncertainties we demonstrate that porewater salinity can be determined to a higher precision and with increased reproducibility through our density protocol compared to titration-determined salinity. Application of our shipboard method at further locations will increase the resolution, precision, and accuracy of available LGM bottom water salinity reconstruction, improving the characterization of glacial deep water masses and overturning circulation. • Shipboard density-based method for determining porewater salinity • Last Glacial Maximum paleosalinity of deep western North Atlantic • Higher precision and increased reproducibility data compared to chloride titration • Can improve characterization of glacial deep water mass and overturning circulation [ABSTRACT FROM AUTHOR]

• Comparative phylogeographic study of a plant community within the Payunia District in the Patagonia Province. • Role of past environmental, climatic, volcanic, and species-specific factors on geographic genetic patterns. • Shared phylogeographic trends, but modulated by species autecological traits. • Quaternary volcanism rather than climatic oscillations explain the evolutionary history of this plant community. • Trait-based approach suggests the role of autecological traits modulating the species responses to environmental changes. Shared genetic patterns within a community of ecologically distinct species may reflect the role of past geoclimatic events imprinting species evolutionary history. Although Pleistocene glaciations are the most important processes evoked as drivers of these shared patterns, in some regions Quaternary volcanic activity should also be considered as a potential process shaping genetic diversity distribution. Additionally, phenotypic attributes related to dispersal and persistence may affect the time and manner in which species respond to geoclimatic changes. We performed a comparative phylogeographical study within a plant community of the South American Arid Diagonal to assess whether genetic patterns are better explained by climatic changes or volcanisms, taking into account the possible influence of life form and dispersal syndromes of the focal species. Chloroplast intergenic spacers were sequenced for five plant species. Genealogy, divergence time estimates, demographic and range expansion analyses were performed. Approximate Bayesian computation was used to test plausible shared phylogeographic scenarios. Climatically stable areas during the last glacial period were inferred with distribution modeling. Results showed that most species were split into northern and southern lineages separated by a phylogeographic break at around 37.5 °S, with the northern populations being genetically less diverse, inhabiting both climatically stable and unstable areas, but being severely affected by intense Plio-Pleistocene magmatic activity; the southern populations, less influenced by volcanism, appeared to be genetically more diverse and occupied climatically stable areas through time. Most recent range expansions and effective population size increases occurred after most of the volcanic episodes, before and during the Last Glacial Maximum. All species shared the same geographic origin of the detected spatial expansion. Overall, our results suggest a preponderant effect of Quaternary volcanism rather than climatic oscillations on the evolutionary history of this xerophytic community. Additionally, we found evidence that autecological traits would have modulated the community historical responses. [ABSTRACT FROM AUTHOR]

• We present a modeled scenario on the evolution of glaciation over the Himalayan-Tibetan orogen for the past 20 ka. • Summer temperature dominates the overall evolution of glaciation, with precipitation modulating the extent and change rate. • The timing and extent of glaciation varies greatly across the orogen. The evolution of past glaciations over the Himalayan-Tibetan orogen and their links with climate change remain elusive, partially owing to the immense scale of the orogen preventing the investigation of all areas. Numerical modeling aids in filling the gaps, verifying the geologic observations, and exploring forcing factors. Based on a transient climate-ice sheet simulation for the past 20 kyr, we demonstrate that the maximum extent of glaciation over the Himalayan-Tibetan orogen occurs around the last glacial maximum (LGM; defined here at ∼20 ka), with expanded ice caps and extensive valley glaciers and being equivalent to a fourfold/sixfold expansion of today's glacier area/volume. The glacier extent shrinks rapidly after the LGM and reaches the minimum around ∼8–7 ka, followed by a slight long-term advancing trend afterwards. Our results suggest a dominant role of summer temperature in controlling the overall trend of glacier response, with precipitation generally modulating the regional extent of glaciation. However, the timing and extent of glaciation in the simulations varies across the Himalayan-Tibetan orogen on millennial timescale, especially between the monsoon-influenced southern and westerly-influenced western parts, further confirming previous speculations based on glacial geologic records. Despite the uncertainties in the simulations and the discrepancy in glaciation between the simulations and the glacial geologic evidence (e.g., 10Be ages), our results provide additional clues on the relationship between climatic change and glacier response. In addition, the modeling aids in advancing our knowledge of the paleoglaciological history of the Himalayan-Tibetan orogen. [ABSTRACT FROM AUTHOR]

Eolian sediments, an important paleoenvironmental archive, are widespread in the Yarlung Tsangpo River (YTR) valley of the southern Tibetan Plateau (TP), but their chronology and spatial-temporal differentiation are poorly understood. And it is not clear whether eolian accumulation is controlled by global climate changes, or local paleoenvironment, or both. In this study, we applied quartz OSL dating to 30 eolian sediment samples (sandy loess and eolian sand) from eight profiles in the YTR catchment. Our new dates were combined with 72 previously published eolian sediment ages (OSL/TL and 14C) for the YTR catchment to analyze the response of eolian accumulation to paleoenvironmental changes. The overall dataset has eolian accumulation spanning the period from the Last Interglacial through to the Little Ice Age, ranging from 84.6 ± 8.7 ka BP (possibly as old as 118 ± 11 ka BP) to 0.4 ± 0.1 ka BP, with most occurring since the Late Glacial Period (15 ka BP), which suggests that the preservation of eolian deposits is controlled by geologic recirculation. Probability density function distributions (PDFs) of eolian ages from different parts of the YTR catchment show different age clusters, suggesting that factors controlling eolian accumulation vary across the catchment, so that spatial-temporal disparities are inherent in the system. To investigate the effect of regional and global paleoclimate since the Last Glacial Maximum (LGM) on eolian deposition processes in the YTR, we compared the PDF of ages from the combined dataset with a range of paleoclimate proxies. The PDF shows significant fluctuations since the LGM, including the Younger Dryas cold event. There is no consistent eolian sediment response to changes of the 30°N summer insolation, Asian Summer Monsoon, and westerlies. Phases of strong eolian sediment accumulation in the YTR basin do not show a simple correspondence with the classical global climate curve, suggesting that eolian processes in the alpine valley environment may be modified by local responses to these changes. • Ages of eolian deposits in the Yarlung Tsangpo River (YTR) catchment are compared. • Most of the ages are since 15 ka BP, ranging from 0.4±0.1 to 118±11 ka BP. • Spatial-temporal disparities of eolian accumulation in the YTR are pointed out. • A relation between eolian accumulation and paleoenvironment is provided. [ABSTRACT FROM AUTHOR]