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Both natural and anthropogenic forces can play a substantial role in the demographic history and current structure of a wildlife population. Species with strict habitat requirements are especially susceptible to these impacts. Mountain goats (Oreamnos americanus) in Alaska are of particular interest in this regard due to their influence on alpine ecosystems, importance to human cultures, and enigmatic history in some areas. Here, we used genetic tools to examine the population structure and demographic history of mountain goats in Alaska. We genotyped 816 mountain goats at 18 microsatellites, identified the number of genetically distinct subpopulations, and assessed their genetic diversity. We used Bayesian methods to investigate demographic history relative to the known geologic and human history of Alaska, and we simulated human-mediated translocation events onto islands to address the hypothesis that Baranof Island harbored an extant population prior to an early 20th-century introduction. We showed that Alaska has 4 genetically distinct subpopulations of mountain goats. The main demographic split between Southcentral and Southeast Alaska occurred following the retreat of ice after the Last Glacial Maximum. Simulations of translocation events largely aligned with expected genetic diversity patterns of current subpopulations except for Baranof Island which showed greater diversity than the simulation, consistent with the hypothesis of an endemic population prior to the translocation. This study highlights the value of considering both natural and anthropogenic forces when assessing the biogeographic history of a species and provides new insights about the complex demographic history and biogeography of mountain goats in Alaska. [ABSTRACT FROM AUTHOR]

As part of a larger project identifying and directly radiocarbon dating Late Pleistocene megafaunal remains in British Columbia (B.C.), Canada, we have confirmed the identity of many newly identified mammoth (Mammuthus sp.) specimens (n = 32) from Vancouver Island in Southwestern B.C. We undertook radiocarbon dating on all specimens and were able to obtain dates (due to preservation) on 16 of these remains, including redating a previously dated mammoth using newer radiocarbon extraction methods. The mammoth dates span a wide range, from >47 500 to 18 000 radiocarbon years B.P. (uncalibrated). These later new dates support other lines of evidence for portions of Vancouver Island remaining ice-free until well into the Fraser Glaciation. [ABSTRACT FROM AUTHOR]

A cross-valley beach terrace in Iladalen, in the south-east of the island of Barentsøya, Svalbard, is interpreted as having been built by long-shore sediment transport and deposition, with its maximum height at about 88 m a.s.l., marking the marine limit at deglaciation. A whale vertebra—most probably from a bowhead whale (Balaena mysticetus)—was found embedded in the upper part of the littoral sediments at a height of ca. 80 m a.s.l., that is, about 8 m below the marine limit at deglaciation The bone is dated to 10 762 ± 137 cal yr BP, just a few hundred years after the generally accepted deglaciation of the coastal parts of Barentsøya, about 11 000 years ago. The vertebra’s age and altitudinal position fit well with the relative sea-level curve constructed for the north-eastern tip of the island of Edgeøya, some 29 km east–south-east of Iladalen.

Today, relatively warm Circumpolar Deep Water is melting Thwaites Glacier at the base of its ice shelf and at the grounding zone, contributing to significant ice retreat. Accelerating ice loss has been observed since the 1970s; however, it is unclear when this phase of significant melting initiated. We analyzed the marine sedimentary record to reconstruct Thwaites Glacier's history from the early Holocene to present. Marine geophysical surveys were carried out along the floating ice-shelf margin to identify core locations from various geomorphic settings. We use sedimentological data and physical properties to define sedimentary facies at seven core sites. Glaciomarine sediment deposits reveal that the grounded ice in the Amundsen Sea Embayment had already retreated to within ~45 km of the modern grounding zone prior to ca. 9,400 y ago. Sediments deposited within the past 100+ y record abrupt changes in environmental conditions. On seafloor highs, these shifts document ice-shelf thinning initiating at least as early as the 1940s. Sediments recovered from deep basins reflect a transition from ice proximal to slightly more distal conditions, suggesting ongoing grounding-zone retreat since the 1950s. The timing of ice-shelf unpinning from the seafloor for Thwaites Glacier coincides with similar records from neighboring Pine Island Glacier. Our work provides robust new evidence that glacier retreat in the Amundsen Sea was initiated in the mid-twentieth century, likely associated with climate variability. [ABSTRACT FROM AUTHOR]

ABSTRACTThe majority of the Northwest Territories of mainland Canada was covered by the Laurentide Ice Sheet during the Last Glacial Maximum. The increasing coverage of high resolution remotely sensed data provides new opportunities to map the glacial geomorphology and study the glacial history of this remote location. Here we present a comprehensive map of glacial landforms within the northern Interior Plains and adjacent areas of the Canadian Shield, comprising around 6% of the Laurentide Ice Sheet bed. Twelve landform types were mapped from the high resolution ArcticDEM: ice flow parallel lineations, subglacial ribs, crevasse-squeeze ridges, major and minor moraine crests, hummocky terrain complexes and ridges, shear margin moraines, major, minor and lateral and submarginal meltwater channels, esker ridges and complexes, glaciofluvial complexes, perched deltas, raised shorelines and aeolian dunes. Together, these landforms provide a record of the highly dynamic behaviour of the northwest sector of the Laurentide Ice Sheet.

Anthropogenic stressors have altered the hydromorphological characteristics of rivers worldwide. Environmental guiding principles are essential for planning sustainable river restoration measures. The alpine river Biya, located in the Russian Altai mountains, originates from Lake Teletskoye and joins the Katun near Biysk, forming the Ob. The Biya represents a hydromorphological reference system in anthropogenically ‘least-disturbed’ condition. The presented study aimed to assess the river’s undisturbed morphology in relationship with the geological history of three different river stretches based on an adapted landscape reading approach using remote sensing information (ASTER GDEM v3). The established widths of the active channel, active floodplain and morphological floodplain as well as the longitudinal section were used to explain the differences between upper, middle, and lower Biya. The results confirm differences in the geological origins between the upper Biya, which has previously been described as the least developed and narrowest, and the other two stretches based on the analyses of morphological parameters. Morphological floodplain width could best explain the differences between upper (0-86 km), middle (86-196 km), and lower Biya (196-301 km). The study further showed a clear relationship between the variations in river patterns and adjacent topographic structures (valley confinements, tributary interactions), highlighting that any assessment of river morphology must consider the wider surroundings of a river stretch. The presented morphological observations and analyses of the Biya show that easily obtainable parameters can detect differences in the morphological history of river stretches within the same catchment, supporting process understanding.

The majority of the Northwest Territories of mainland Canada was covered by the Laurentide Ice Sheet during the Last Glacial Maximum. The increasing coverage of high resolution remotely sensed data provides new opportunities to map the glacial geomorphology and study the glacial history of this remote location. Here we present a comprehensive map of glacial landforms within the northern Interior Plains and adjacent areas of the Canadian Shield, comprising around 6% of the Laurentide Ice Sheet bed. Twelve landform types were mapped from the high resolution ArcticDEM: ice flow parallel lineations, subglacial ribs, crevasse-squeeze ridges, major and minor moraine crests, hummocky terrain complexes and ridges, shear margin moraines, major, minor and lateral and submarginal meltwater channels, esker ridges and complexes, glaciofluvial complexes, perched deltas, raised shorelines and aeolian dunes. Together, these landforms provide a record of the highly dynamic behaviour of the northwest sector of the Laurentide Ice Sheet. [ABSTRACT FROM AUTHOR]

Sulphate (SO 4 ), predominantly derived from sulphur (S)-bearing glacial sediments distributed widely across the Canadian Interior Plains, contributes to high groundwater salinity and can be detrimental to riparian and dry-land ecosystems, agricultural production, and water use. While previous researchers investigated SO 4 distribution and dynamics in shallow groundwater at local scales (<1500 km 2 ), we examine SO 4 occurrence in groundwater at larger scales, and to depths of ~150 m, considering variations in geology, glacial history, climate, and geochemical and hydrogeological settings in the Canadian province of Alberta. Sulphate concentrations in groundwater vary considerably, with 15 % of 139,130 samples above the 500 mg/L Canadian drinking water aesthetic objective. Analysis of δ 34 S SO4 and δ 18 O SO4 from 179 wells throughout Alberta shows SO 4 is dominantly derived from oxidation of S-bearing material. At this large scale, marine shale bedrock subcrops, glacial ice flow directions, and climate control SO 4 distribution. Groundwater contains less SO 4 (<200 mg/L) in western Alberta compared to the east due to a lack of S-bearing bedrock, higher groundwater recharge rates, thinner glacial sediments, and increased groundwater circulation. Focusing on a region in south-central Alberta (Red Deer area), hydrogeological characteristics relating to SO 4 formation, recharge, permeability, hydraulic gradient, and travel time are included in a principal component analysis to identify six groundwater groups at varying stages of evolution and SO 4 concentrations depending on their hydrogeological setting. Low SO 4 concentrations are associated with areas of high recharge, where SO 4 has been leached from the sediments, or with more evolved bedrock groundwater where SO 4 has been reduced or was recharged in pre-glacial times. High SO 4 concentrations are found in areas of lower recharge and permeability, where flushing occurs more slowly. Combining the Red Deer area and province-wide analyses, we identify seven regions across Alberta with characteristic distribution and controls on SO 4 occurrence in shallow groundwater., (Copyright © 2024. Published by Elsevier B.V.)

The glaciated island of South Georgia in the sub-Antarctic is a key area for climate reconstructions, because it is positioned in the Southern Ocean amidst the core belt of the Southern Westerlies and the main fronts of the Antarctic Circumpolar Current. This makes it particularly susceptible to changes in local, regional, but also Southern Hemisphere-wide climate conditions. Marine-geological records recovered from its continental shelf therefore offer unique potential to constrain how ice masses in this part of the Southern Ocean responded to Quaternary climate change, but despite this, little glacial-geomorphological and sedimentological research has been done offshore South Georgia. Here, we present a new suite of glacial landforms, identified from high-resolution bathymetry data, supplemented with acoustic facies from sub-bottom profiles, in order to reconstruct the pre-Holocene glacial history of the King Haakon Trough System on the southwestern South Georgia continental shelf. Our data show numerous landforms common for phases of ice advance and retreat, which are interpreted to document the confluence of two major trunk glaciers during peak glaciation. Progressively elongated linear bedforms imply accelerated ice flow and/or softer sediment substrate towards the shelf edge and suggest that the South Georgia Ice Cap experienced streaming ice and behaved similarly to other palaeo-ice sheets. A grounding-zone wedge close to the shelf edge marks the position of maximum ice extent during a peak glaciation, while clusters of recessional moraines and three large morainal banks indicate repeated phases of staggered retreat. Multiple extensive ice advances are indicated by stacked till sequences within the sub-bottom profiles of the mid- and outer shelf. The second-to-last till generation appears to be slightly more extensive than the most recent glacial till, and could suggest that South Georgia may have had a similar glacial evolution to other sub-Antarctic islands. This paper complements two studies focusing on the Holocene depositional environments and their associated sedimentary processes in the same trough system, in an effort to elucidate an important part of the Quaternary evolution of South Georgia's marine environment. • King Haakon Trough System formed over the course of several glaciations. • Glacial landforms on the modern seafloor show evidence of fast advance and staggered retreat. • Ice stream draining South Georgia Ice Cap during LLGM configured as ice-cliff margin. • Stacked till sequences attest to multiple ice advances to the shelf edge. [ABSTRACT FROM AUTHOR]

The Quaternary history of the Arctic Ocean reflects pronounced periodic changes in marine and glacial environments. This variability is an important component of the Arctic paleoclimatic system. For more insight, we use isotopic measurements on the detrital (Nd-Sr-Pb) and authigenic (Nd) phases of the Quaternary sediments from the central Arctic Ocean. We analyze core ICE4 from ∼3 km water depth off the Lomonosov Ridge. This core was previously studied for other sedimentary proxies (Dong et al., 2022). The analyzed record is estimated to cover major Late Pleistocene Weichselian/Wisconsinian glaciations occurring over the last ∼100–200 ka. Our results provide new evidence that glacially-derived waters from the glaciated margins reached the bottom of the deep Arctic basins. We infer that these waters were delivered to the deep basins by hyperpycnal flows originating from subglacial outbursts accompanying overflow meltwater and iceberg discharge during glacial/deglacial events. Voluminous outbursts during the older, presumed Early/Middle Weichselian glaciation, ca. 115-35 ka, are traced to the West Siberian margin impacted by the Eurasian Ice Sheet. Similar sedimentary layers are found in longer records from the central Arctic Ocean at older stratigraphic intervals. Sediments constrained to the Last Glacial Maximum have less pronounced glacigenic inputs with a stronger Laurentide Ice Sheet signature. The circulation patterns were likely dependent on the interplay of the timing and extent of the Laurentide and Eurasian ice sheets. • Late Pleistocene sediment record from Eurasia Basin, Arctic Ocean. • Isotope proxies in the detrital (Nd, Sr, Pb) and authigenic (Nd) phases. • Eurasian Ice Sheet waters transported to deep basins via hyperpycnal flows. • Less glacigenic inputs with a stronger Laurentide signature during LGM. [ABSTRACT FROM AUTHOR]

Cyclic climatic and glacial fluctuations of the Late Quaternary produced a dynamic biogeographic history for high latitudes. To refine our understanding of this history in northwestern North America, we explored geographic structure in a wide-ranging carnivore, the wolverine (Gulo gulo). We examined genetic variation in populations across mainland Alaska, coastal Southeast Alaska, and mainland western Canada using nuclear microsatellite genotypes and sequence data from the mitochondrial DNA (mtDNA) control region and Cytochrome b (Cytb) gene. Data from maternally inherited mtDNA reflect stable populations in Northwest Alaska, suggesting the region harbored wolverine populations since at least the Last Glacial Maximum (LGM; 21 Kya), consistent with their persistence in the fossil record of Beringia. Populations in Southeast Alaska are characterized by minimal divergence, with no genetic signature of long-term refugial persistence (consistent with the lack of pre-Holocene fossil records there). The Kenai Peninsula population exhibits mixed signatures depending on marker type: mtDNA data indicate stability (i.e. historical persistence) and include a private haplotype, whereas biparentally inherited microsatellites exhibit relatively low variation and a lack of private alleles consistent with a more recent Holocene colonization of the peninsula. Our genetic work is largely consistent with the early 20th century taxonomic hypothesis that wolverines on the Kenai Peninsula belong to a distinct subspecies. Our finding of significant genetic differentiation of wolverines inhabiting the Kenai Peninsula, coupled with the peninsula's burgeoning human population and the wolverine's known sensitivity to anthropogenic impacts, provides valuable foundational data that can be used to inform conservation and management prescriptions for wolverines inhabiting these landscapes. [ABSTRACT FROM AUTHOR]

Since the Last Glacial Maximum ∼20,000 years ago, the Antarctic Ice Sheet has undergone extensive changes, resulting in a much smaller present‐day configuration. Improving our understanding of basic physical processes that played important roles during that retreat is critical to providing more robust model projections of future retreat and sea‐level rise. Here, a limited‐area nested ice sheet model was applied to the last deglacial retreat of the West Antarctic Ice Sheet in the Amundsen Sea Embayment (ASE), at 5 km resolution. The ice sheet response to climate and sea‐level forcing was examined at two sites along the flowlines of Pine Island Glacier and Pope Glacier, close to the Hudson Mountains and Mount Murphy respectively, and the simulated responses compared with ice sheet thinning histories derived from glacial‐geological data. The sensitivity of results to selected model parameters was also assessed. The model simulations predict a broadly similar response to ocean forcing in both the central and eastern ASE, with an initial rapid phase of thinning followed by a slower phase to the modern configuration. Although there is a mismatch of up to 5,000 years between the timing of simulated and observed thinning, the modeling suggests that the upstream geological records of ice surface elevation change reflect a response to retreat near the grounding line. The model‐data mismatch could potentially be improved by accounting for regional variations in mantle viscosity, sea‐surface heights and basal sliding properties across the continental shelf. Plain Language Summary: During the last glacial period approximately 20,000 years ago, the West Antarctic Ice Sheet was much larger than today. Since then, it has undergone extensive changes such as retreat and thinning of its glaciers, and currently dominates the contribution to global sea‐level rise from Antarctica. Glacial‐geological studies undertaken in two mountain ranges in the region (the Hudson Mountains and Mt Murphy, close to Pine Island Glacier and Pope Glacier) provided records of the magnitude and speed of those changes. Here we compare those records with model simulations that predict response of the ice sheet to different forcing mechanisms (climate and sea‐level) over the past 20,000 years. We find that the model predicts a similar response to forcing at both study sites, with initially fast thinning followed by a slower phase as the ice sheet shrinks to its modern shape and size. The similarity in behavior at both sites may be due to similar ocean forcing mechanisms affecting both glaciers. When we compare the model simulations with geological records of ice sheet change, we find a mismatch of up to 5,000 years. Improving how ice‐Earth interactions are represented in the model could potentially resolve this mismatch. Key Points: A nested ice sheet model was applied to the last deglacial retreat in the Amundsen Sea sector, Antarctica. Model outputs were compared with ice thinning historySimilar response to forcing across Amundsen Sea Embayment, possibly resulting from similar (ocean) forcing mechanisms in early HoloceneImproved representation of regionally varying Earth‒ice‒sea‐level interactions may resolve model‐data mismatch in timing of ice thinning [ABSTRACT FROM AUTHOR]

Ice ages constitute a significant part of Earth's climate history with the first signs of widespread ice sheets occurring at about 2.4 billion years ago. In 2004, a nearly 450 metres thick accumulation of seafloor sediments on the submarine Lomonosov Ridge in central Arctic Ocean was drilled by the international Arctic Coring Expedition (ACEX). This geological archive has provided insights into the long-term history of the Arctic Ocean back to 56 million years. The first signs of extensive sea ice along the Arctic coasts appear 47.5 million years ago (Ma), while evidence for the type of pack ice we have today that survives more than one season occurs first 15-13 Ma. The Earth's climate changed mode at about 2.6 Ma. Cold periods, characterized by large ice sheets covering the Northern Hemisphere, were intervened by warmer periods with climates more similar of today. These glacial-interglacial cycles were largely controlled by changes in solar insolation resulting from cyclical variations in Earth's orbit around the Sun. In this article, I tell the personal story of how we mapped the Lomonosov Ridge and found evidence supporting a controversial hypothesis of the existence of kilometre-thick floating ice shelves in the Arctic Ocean during past glaciations. [ABSTRACT FROM AUTHOR]

Quaternary processes and environmental changes are often difficult to assess in remote subantarctic islands due to high surface erosion rates and overprinting of sedimentary products in locations that can be a challenge to access. We present a set of high-resolution, multichannel seismic lines and complementary multibeam bathymetry collected off the eastern (leeward) side of the subantarctic Auckland Islands, about 465 km south of New Zealand's South Island. These data constrain the erosive and depositional history of the island group, and they reveal an extensive system of sediment-filled valleys that extend offshore to depths that exceed glacial low-stand sea level. Although shallow, marine, U-shaped valleys and moraines are imaged, the rugged offshore geomorphology of the paleovalley floors and the stratigraphy of infill sediments suggests that the valley floors were shaped by submarine fluvial erosion, and subsequently filled by lacustrine, fjord, and fluvial sedimentary processes. [ABSTRACT FROM AUTHOR]

Flies (Diptera) are the dominant animal in the North yet are underrepresented in ecological studies. Our study aimed to examine the diversity patterns of the poorly documented acalyptrate flies across the Canadian North. Our main objective was to determine large- and small-scale drivers of species richness, abundance and community composition of acalyptrate fly assemblages. We collected flies at 12 Canadian sites in three ecoclimatic zones (Northern Boreal, Sub-Arctic and High Arctic), from two habitats (wet and mesic). We tested the effect of climatic variables and habitat on species richness and abundance using a generalized linear mixed-effects model, and on community composition using permutational multivariate analysis of variance. Species turnover between sites and ecoclimatic zones was examined by testing for multivariate homogeneity of group dispersions and visualised using non-metric multidimensional scaling. We identified 3631 acalyptrate flies, belonging to 333 species. Diversity measures and community composition were associated with seasonal and limiting temperature variables, consistent with the latitudinal diversity gradient seen in other animal groups. However, habitat only explained a small portion of the variation in our data, and only for observed species richness and species composition. Turnover patterns showed slight, statistically non-significant variation across zones. The High Arctic ecoclimatic zone was as spatially heterogenous in composition as the Northern Boreal and Sub-Arctic ecoclimatic zones but hinted at complex interplays between geographical and glacial legacies. Our results contradict the historical view of Arctic arthropod diversity as simple and uniform, and may serve as a baseline for future biodiversity monitoring. [ABSTRACT FROM AUTHOR]

The movement of sediment through mountain river networks remains difficult to predict, as processes beyond streamflow and particle size are responsible for the entrainment and transport of bedload sediment. In deglaciated catchments, additional complexity arises from glacial impacts on landscape organization. Research to date indicates that the quantity of sediment stored in the channel is an important component of sediment transport in systems which alternate between supply and transport limited states, but limited long‐term field data exist which can capture storage‐transfer dynamics over a timescale encompassing episodic supply typical of mountain streams. We use a 45‐year dataset with annual and decadal‐scale data on sediment storage, channel morphology, and wood loading to investigate the spatial and temporal organization of storage in Carnation Creek, a previously glaciated 11 km2 catchment on Vancouver Island, British Columbia. Sediment is supplied episodically to the channel, including additions from debris flows in the early 1980s just upstream of the studied channel region. Analyzing the spatial and temporal organization of sediment storage along 3.0 km of channel mainstem reveals a characteristic storage wavelength similar to the annual bedload particle travel distance. Over time, two scales of variation in storage are observed: small‐scale fluctuation of 3–10 years corresponding to local erosional and depositional processes, and larger scale response over 25–35 years related to supply of sediment from hillslopes. Complex relationships between storage and sediment transfer (i.e., annual change in storage) are identified, with decadal‐scale hysteresis present in storage‐transfer relations in sites influenced by hillslope sediment and logjams. We propose a conceptual model linking landscape organization to temporal variability in storage and to storage–export cycles. Collectively, our results reaffirm the importance of storage to sediment transport and channel morphology, and highlight the complexity of storage–transport interactions. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Channel morphology of forested, mountain streams in glaciated landscapes is regulated by a complex suite of processes, and remains difficult to predict. Here, we analyze models of channel geometry against a comprehensive field dataset collected in two previously glaciated basins in Haida Gwaii, B.C., to explore the influence of variable hillslope–channel coupling imposed by the glacial legacy on channel form. Our objective is to better understand the relation between hillslope–channel coupling and stream character within glaciated basins. We find that the glacial legacy on landscape structure is characterized by relatively large spatial variation in hillslope–channel coupling. Spatial differences in coupling influence the frequency and magnitude of coarse sediment and woody material delivery to the channel network. Analyses using a model for channel gradient and multiple models for width and depth show that hillslope–channel coupling and high wood loading induce deviations from standard downstream predictions for all three variables in the study basins. Examination of model residuals using Boosted Regression Trees and nine additional channel variables indicates that ~10 to ~40% of residual variance can be explained by logjam variables, ~15–40% by the degree of hillslope–channel coupling, and 10–20% by proximity to slope failures. These results indicate that channel classification systems incorporating hillslope–channel coupling, and, indirectly, the catchment glacial legacy, may present a more complete understanding of mountain channels. From these results, we propose a conceptual framework which describes the linkages between landscape history, hillslope–channel coupling, and channel form. © 2018 John Wiley & Sons, Ltd. We investigate the influence of glacial history on hillslope‐channel coupling, channel geometry, and morphology in two forested mountain streams in coastal British Columbia. Glaciation of the catchments introduced variable patterns of hillslope–channel coupling, resulting in variability of hillslope sediment and wood input, channel morphology, and channel geometry. We evaluate observed channel geometry against models predicting width, depth, and slope, and results of statistically analyzing model residuals indicate that substantial variability can be explained by slope failure and logjam variables. [ABSTRACT FROM AUTHOR]

Geographical isolation, habitat quality and habitat size are known as driving factors shaping species communities and richness. We analysed cave-dwelling springtail communities from 187 caves of the Carpathian Mountains and the Dobrogea Region across Romania. These caves differ in size, geographical isolation, habitat heterogeneity and age, and in the surrounding environmental conditions. Based on these data we tested for potential effects of environmental factors on species composition and richness. Despite high species turnover we found that caves which are geographically close to each other, at similar altitudes and with similar climatic conditions tend to have a more similar species composition than expected from random colonization. Particularly important for current species spatial distributions were past (glacial) environmental conditions. We found that co-occurring species are taxonomically more clustered than expected by chance. In turn, species traits, namely dispersal ability and body size and shape, were only of minor influence and did not significantly affect community assembly. These findings are consistent with long-term isolation and cave specific speciation/extinction dynamics. Our study adds to the increasing evidence that isolated habitat islands might maintain a stable although species-poor fauna due to a trade-off between past colonization, speciation and extinction. [ABSTRACT FROM AUTHOR]

Quaternary evolution of high-latitude margins has, to a large degree been shaped by the advance and retreat of ice sheets. Our understanding of these margins and the role of ice sheets is predominantly derived from the polar North Atlantic during the Late Weichselian. This region has formed the basis for conceptual models of how glaciated margins work and evolve through time with particular focus on trough-mouth fans, submarine landslides and channel systems. Here, by reviewing the current state of knowledge of the margins of the Nordic Seas during the Quaternary we provide a new set of models for different types of glaciated margin and their deposits. This is achieved by tracking the growth and decay of the Greenland, Barents Sea and Scandinavian Ice Sheets over the last 2.58 Ma and how these ice sheets have influenced sedimentation along their margins. The reconstructed histories show 1) the completeness of records along each ice sheet margin is highly variable. 2) Climatic deterioration and the adoption of 100 kyr cyclicity has had progressive impacts on each ice sheet and the resulting sedimentation and evolution of its related margin. These reconstructions and records on other margins worldwide enable us to identify first order controls on sediment delivery at ice sheet scales, propose new conceptual models for trough-mouth fans and glaciated margin development. We are also able to show how the relationship between large submarine landslide occurrence and ice sheet histories changes on different types of margin. [ABSTRACT FROM AUTHOR]

The longstanding nomenclature for the species Lycaena mariposa was examined and considered with respect to its ability to compass the observed variation and hypothetical evolutionary adaptation and radiation of this northwestern North American species. Through examination and comparison of long series of specimens from throughout the known range of the species, we discerned consistently recognizable clusters of characteristics across the landscape. We describe nine new subspecies, five of which occur in apparent genetic isolation, two as exceedingly narrow endemics. The other four have large ranges bridging existing named taxa. We discuss the hypothetical biogeographic history of the species, including routes of dispersion, conformity to geomorphologic features and glacial effects, and the basis for isolation and autochthony in L. mariposa, as well as host plants, habitats, and conservation status for each named taxon. [ABSTRACT FROM AUTHOR]

Geomorphic analysis and optically stimulated luminescence (OSL) ages from undated Lake Agassiz beaches and adjacent fluvial sediments on Riding Mountain in Manitoba provide insight into their early history. New OSL ages of 14.5±2.4 and 13.4±0.7 ka on the oldest (Herman to Norcross) beaches of Lake Agassiz near the Canada-U.S. border indicate that the Laurentide Ice Sheet (LIS) retreated from that part of the Agassiz basin by ~14.5 ka. To the north along Riding Mountain, the Herman strandlines are absent, and OSL ages on the oldest beach there average 12.9 ka, which links it to the younger Norcross-Tintah strandlines. In adjacent Riding Mountain, OSL ages and geomorphological relationships of a large abandoned glacial spillway >200 m above the oldest beaches of Lake Agassiz indicate that this channel predates retreat of the LIS and formation of beaches in this part of the Agassiz basin, with ice remaining in this area until after 14.5 ka. OSL ages on the Gimli beach 170 km to the east are >3000 yr older than conventional assignments, suggesting that it formed during the Moorhead low-water phase 12.8–10.6 ka. Luminescence ages support the conclusion that the Campbell beach formed ~10.9 ka near the end of the Moorhead low-water phase. [ABSTRACT FROM PUBLISHER]

The Pamir Mountains in Central Asia are one of the highest mountain systems in the world. Throughout the Quaternary, these mountains have acted as one of the main sources of water to most of Central Asia. The large rivers of Amudaria and Syrdaria also transported large amounts of sediment, which was then reworked into the Karakum and Kyzylkum deserts. Orographic and climatic conditions have caused the widespread formation of glaciers, and the Pamir have experienced several large glaciations. Studying the timing and extent of glaciations in the Pamir helps us to understand the temporal evolution of the High Asia climate. For many decades, geomorphologists and glaciologists have strived to reconstruct glacial chronologies for the Pamir Mountains, but only in the last 20 years has CRN dating of moraines allowed researchers to obtain any quantitative results on the glacial chronology [1]. As part of the THOCA project ("Timing and Ecology of the Human Occupation in Central Asia"), we wish to further improve our knowledge of the climate history of the Pamir and to understand the possible effects of mountain glaciation on the supply and provenance of aeolian dust. To achieve this, luminescence dating has been applied to the glacially dammed lake deposits in the basin of the Panj River, the largest tributary of the Amudaria. Our study area is located on the right bank on the Panj River, on the southern slope of the Ishkashim ridge (southwestern Pamir). Within a small tributary, on the upper part of the slope, a unique series of glacial lacustrine deposits has been preserved. These lacustrine silts are evidence of the blocking of the Panj valley by a large glacier, forming a lake within the tributary arm. Quartz OSL and K-rich feldspar pIRIR50,290 measurements were made on sand-sized grains. Dose recovery ratios are satisfactory for both quartz (n=25) (1.01±0.02) and feldspars (n=25) (1.08±0.4). The average pIRIR290/OSL age ratio is 1.12±0.05, confirming that the quartz OSL signals are very likely sufficiently well bleached. The new luminescence ages indicate that this large glacial event in the Pamir Mountains took place in MIS 6. [ABSTRACT FROM AUTHOR]

The Laurentide Ice Sheet was a major driver of global sea-level change during the last deglaciation and may have impacted both atmospheric and oceanic circulation. An understanding of past changes in the ice sheet is important for constraining its interaction with other components of the climate system. Here, we present the geologic context and chronology for ice-sheet fluctuations in eastern Maine, adjacent to the North Atlantic Ocean, thought to be a key player in the termination of the last ice age. Retreat of the Laurentide Ice Sheet through coastal Maine first produced a series of lobate grounding-line moraines, followed by deposition of the prominent Pineo Ridge System, which crosscut the earlier moraine set and which is characterized by extensive ice-contact deltas, closely spaced parallel moraines, and association with eskers. Our new 10 Be surface exposure ages indicate that the Pineo Ridge System, which extends for more than 100 km in eastern Maine and Atlantic Canada, dates to ∼15.3 ka, ∼800 years older than recent estimates. Our data are in accord with inboard minimum-limiting radiocarbon ages of terrestrial materials, which indicate deglaciation as early as 15.3 ka, as well as of marine shells that are as old as 15.0 ka. Both the deglaciation that produced the lobate moraines and the short-lived readvance that led to the Pineo Ridge System occurred during Heinrich Stadial 1. Given that faunal and isotopic evidence indicates that the ocean remained cold during deglaciation of coastal Maine, we infer that ice recession was due to rising summer air temperatures that gave way briefly to cooling to allow minor readvance. Glacial deposits north of the Pineo Ridge System display evidence of ice stagnation and downwasting, suggesting rapid ice retreat following deposition of the delta-moraine complex, coincident with the onset of the Bølling. [ABSTRACT FROM AUTHOR]

The expansion of woody shrubs in arctic tundra alters many aspects of high-latitude ecosystems, including carbon cycling and wildlife habitat. Dendroecology, the study of annual growth increments in woody plants, has shown promise in revealing how climate and environmental conditions interact with shrub growth to affect these key ecosystem properties. However, a predictive understanding of how shrub growth response to climate varies across the heterogeneous landscape remains elusive. Here we use individual-based mixed effects modeling to analyze 19 624 annual growth ring measurements in the stems of Salix pulchra (Cham.), a rapidly expanding deciduous shrub. Stem samples were collected at six sites throughout the North Slope of Alaska. Sites spanned four landscapes that varied in time since glaciation and hence in soil properties, such as nutrient availability, that we expected would modulate shrub growth response to climate. Ring growth was remarkably coherent among sites and responded positively to mean June temperature. The strength of this climate response varied slightly among glacial landscapes, but in contrast to expectations, this variability was not systematically correlated with landscape age. Additionally, shrubs at all sites exhibited diminishing marginal growth gains in response to increasing temperatures, indicative of alternative growth limiting mechanisms in particularly warm years, such as temperature-induced moisture limitation. Our results reveal a regionally-coherent and robust shrub growth response to early season growing temperature, with local soil properties contributing only a minor influence on shrub growth. Our conclusions strengthen predictions of changes to wildlife habitat and improve the representation of tundra vegetation dynamics in earth systems models in response to future arctic warming.

Pronounced Quaternary circulation and depositional changes in the Arctic Ocean basins remain poorly understood. We investigate sediment core ARC5-ICE4 (ICE4) in the Eurasian (Amundsen) Basin off the Lomonosov Ridge to reconstruct glacial-interglacial variability in sediment sources and circulation. The ICE4 record features variable lithologies including distinct glacigenic deposits with Ice Rafted Debris (IRD). The sediment age is constrained by a combination of the organic carbon 14C with paleomagnetic data and correlation to earlier developed stratigraphies. The derived sedimentation rates constitute several cm/kyr (6.5 cm/kyr average) consistent with estimates from regional geophysical data. The developed age model covers the time interval from ca. 10 to 75 ka including Late and Middle Weichselian/Wisconsinian glaciations. Respective glacigenic sediments were primarily deposited by pulsed iceberg discharge. The Last Glacial Maximum and deglaciation is expressed in sharp IRD peaks including mineral proxies of the Laurentide Ice Sheet with an apparent millennial-scale variability. The older glacigenic sedimentary unit with abundant IRD of predominantly Siberian provenance was deposited during deglaciation of the Middle Weichselian (MIS 4/3) Eurasian Ice Sheet. These sedimentary differences indicate diverging impacts of the two glaciations on the Arctic Ocean, including ice-sheet sizes/geometries and oceanic circulation. • Continuous 75-ka Arctic Ocean sediment record from Eurasia Basin off Lomonosov Ridge. • New stratigraphic constraints including 14C OC and paleomagnetic inclination data. • Different circum-Arctic ice sheet extent and circulation inferred for MIS 2 and 4. [ABSTRACT FROM AUTHOR]

Glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic, tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata. We review the current state of knowledge on the generation, transfer, and accumulation of glacigenic sediment from land to sea. We draw from geomorphology, marine geology, geochronology, numerical modeling of surface processes and landscape evolution, and experimental and field observations of glacier erosion and deposition, and the interaction of ice with its bed and the ocean boundary. Our primary goal is to examine glacial systems using a holistic source-to-sink approach, with a focus on describing a) how glacial motion produces sediment, b) how the sediments (sink) record the dynamic nature of glacial systems under different climatic (thermal) regimes, c) the challenges in using the sedimentary record to interpret these dynamics in space and time, and d) the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations. The dynamic state of ice, i.e., the ice flux and ice extent, is defined differently between the source and sink communities, reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate. Advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics, and have identified the primary depocenters and key lithofacies of glacial sinks. Sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned, of which there are few examples, rather than from discrete point measures of sediment flux that are subject to sediment transfer biases. Forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental-margin scale, but finer time/space scale ice-dynamic models do not yet recreate observed ice extent or flowpaths. Future source-to-sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production, and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams. [ABSTRACT FROM AUTHOR]

Paleoclimatic constraints from regions at the confluence of major climate systems are particularly important in understanding past climate change. Using geomorphic mapping based on remote sensing and field investigations, combined with in situ cosmogenic 10 Be and 26 Al dating of boulders associated with glacial landforms, we investigate the chronology of past glaciation in the Inylchek and Sary-Dzaz valleys in the eastern Kyrgyz Tian Shan, a tectonically active area with some of the highest peaks in the world outside of the Himalayas. Cosmogenic 10 Be and 26 Al exposure ages of boulders on moraines record up to five glacial advances including: Lateglacial age lateral moraine remnants and meltwater channels in the upper Inylchek Valley; Last Glacial Maximum (LGM, Marine Oxygen Isotope Stage [MIS] 2) moraines in the Sary-Dzaz Valley and in a terminal moraine complex at the west end of the Inylchek Valley, overriding older moraines; an MIS 4 or 5 moraine remnant above the Inylchek terminal moraine complex; and an older high moraine remnant down-valley from the confluence of the Inylchek and Sary-Dzaz valleys. The evidence for glacial extent in this study is consistent with a limited ice expansion hypothesis for Tian Shan glaciation. Published results from the western and central Kyrgyz Tian Shan do not show evidence for significant LGM glacier expansion, which in combination with the results presented here, indicate a spatial variation in glacier records along the Tian Shan. This may reflect either paleoclimatic gradients or the impact of local physiographic conditions on responses to regional climate change, or both. [ABSTRACT FROM AUTHOR]

The Weddell Sea sector is one of the main formation sites for Antarctic Bottom Water and an outlet for about one fifth of Antarctica's continental ice volume. Over the last few decades, studies on glacial–geological records in this sector have provided conflicting reconstructions of changes in ice-sheet extent and ice-sheet thickness since the Last Glacial Maximum (LGM at ca 23–19 calibrated kiloyears before present, cal ka BP). Terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the Weddell Sea, ice-sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding-line advance at the LGM. Other marine geological and geophysical studies concluded that subglacial bedforms mapped on the Weddell Sea continental shelf, subglacial deposits and sediments over-compacted by overriding ice recovered in cores, and the few available radiocarbon ages from marine sediments are consistent with major ice-sheet advance at the LGM. Reflecting the geological interpretations, different ice-sheet models have reconstructed conflicting LGM ice-sheet configurations for the Weddell Sea sector. Consequently, the estimated contributions of ice-sheet build-up in the Weddell Sea sector to the LGM sea-level low-stand of ∼130 m vary considerably. In this paper, we summarise and review the geological records of past ice-sheet margins and past ice-sheet elevations in the Weddell Sea sector. We compile marine and terrestrial chronological data constraining former ice-sheet size, thereby highlighting different levels of certainty, and present two alternative scenarios of the LGM ice-sheet configuration, including time-slice reconstructions for post-LGM grounding-line retreat. Moreover, we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research. The aim of our study is to provide two alternative interpretations of glacial–geological datasets on Antarctic Ice-Sheet History for the Weddell Sea sector, which can be utilised to test and improve numerical ice-sheet models. [ABSTRACT FROM AUTHOR]

Onshore and offshore studies show that an expanded, grounded ice sheet occupied the Ross Sea Embayment during the Last Glacial Maximum (LGM). Results from studies of till provenance and the orientation of geomorphic features on the continental shelf show that more than half of the grounded ice sheet consisted of East Antarctic ice flowing through Transantarctic Mountain (TAM) outlet glaciers; the remainder came from West Antarctica. Terrestrial data indicate little or no thickening in the upper catchment regions in both West and East Antarctica during the LGM. In contrast, evidence from the mouths of the southern and central TAM outlet glaciers indicate surface elevations between 1000 m and 1100 m (above present-day sea level). Farther north along the western margin of the Ross Ice Sheet, surface elevations reached 720 m on Ross Island, and 400 m at Terra Nova Bay. Evidence from Marie Byrd Land at the eastern margin of the ice sheet indicates that the elevation near the present-day grounding line was more than 800 m asl, while at Siple Dome in the central Ross Embayment, the surface elevation was about 950 m asl. Farther north, evidence that the ice sheet was grounded on the middle and the outer continental shelf during the LGM implies that surface elevations had to be at least 100 m above the LGM sea level. The apparent low surface profile and implied low basal shear stress in the central and eastern embayment suggests that although the ice streams may have slowed during the LGM, they remained active. Ice-sheet retreat from the western Ross Embayment during the Holocene is constrained by marine and terrestrial data. Ages from marine sediments suggest that the grounding line had retreated from its LGM outer shelf location only a few tens of kilometer to a location south of Coulman Island by ∼13 ka BP. The ice sheet margin was located in the vicinity of the Drygalski Ice Tongue by ∼11 ka BP, just north of Ross Island by ∼7.8 ka BP, and near Hatherton Glacier by ∼6.8 ka BP. Farther south, 10 Be exposure ages from glacial erratics on nunataks near the mouths of Reedy, Scott and Beardmore Glaciers indicate thinning during the mid to late Holocene, but the grounding line did not reach its present position until 2 to 3 ka BP. Marine dates, which are almost exclusively Acid Insoluble Organic (AIO) dates, are consistently older than those derived from terrestrial data. However, even these ages indicate that the ice sheet experienced significant retreat after ∼13 ka BP. Geomorphic features indicate that during the final stages of ice sheet retreat ice flowing through the TAM remained grounded on the shallow western margin of Ross Sea. The timing of retreat from the central Ross Sea remains unresolved; the simplest reconstruction is to assume that the grounding line here started to retreat from the continental shelf more or less in step with the retreat from the western and eastern sectors. An alternative hypothesis, which relies on the validity of radiocarbon ages from marine sediments, is that grounded ice had retreated from the outer continental shelf prior to the LGM. More reliable ages from marine sediments in the central Ross Embayment are needed to test and validate this hypothesis. [ABSTRACT FROM AUTHOR]

Abstract: While there are numerous hypotheses concerning glacial–interglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere's late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the present state-of-the-art knowledge gained from field work and chronological studies, and with a specific focus on ice-sheet extent and environmental conditions during the Last Glacial Maximum (LGM). The maximum Quaternary extension of ice sheets is discussed and compared to LGM. We bring together recent results from the circum-Arctic continental margins and the deep central basin; extent of ice sheets and ice streams bordering the Arctic Ocean as well as evidence for ice shelves extending into the central deep basin. Discrepancies between new results and published LGM ice-sheet reconstructions in the high Arctic are highlighted and outstanding questions are identified. Finally, we address the ability to simulate the Arctic Ocean ice sheet complexes and their dynamics, including ice streams and ice shelves, using presently available ice-sheet models. Our review shows that while we are able to firmly reject some of the earlier hypotheses formulated to describe Arctic Ocean glacial conditions, we still lack information from key areas to compile the holistic Arctic Ocean glacial history. [Copyright &y& Elsevier]

We invesfigated connecfions between the natural and the cultural history of the Flathead Indian Reservation through the integrafion of geoscience, tradifional tribal knowledge, and oral narratives for the purpose of improving Earth Science educafion in the tribal community. The project served as an avenue for the incorporafion of indigenous knowledge into science curricula by providing parallel perspecfives for the same landscapes while considering compatibilifies between Western science and Nafive knowledge. We developed educational resources through coUaborafions with local school communities, tribal elders, and culfiiral experts who approved the materials for general disfiibufion. Parficipants idenfified mulfiple localities throughout the reservafion that served as field sites crifical to understanding geoscience concepts, tribal scientific knowledge, and oral histories. One such place (the Big Draw Valley west of Flathead Lake) figures prominently in both geoscience and indigenous accounts of the evolufion of the land. Compafible perspecfives of local landscape formation are indicated by similarifies between the interconnected Earth Science and Native narratives. Indigenous knowledge reveals potenfial locafions for addifional scienfific research that could prompt a reconsiderafion of current geoscience theories regarding the glacial history of the region. Preliminary research suggests that culturally congruent instruction using the Flathead Geoscience Educafion Project materials was effective in supporfing increased American Indian shident achievement in geosciences on the reservafion. We believe that curricular materials similar to those produced during this project can also be developed for and successfully used in other tribal communifies. [ABSTRACT FROM AUTHOR]

Abstract: We present multibeam swath bathymetric surveys of the major fjords surrounding the sub-Antarctic island of South Georgia to characterise the glacial geomorphology and to identify the relative timings and extent of past glacial advance and retreat. Bathymetry data revealed a range of glacial features including terminal, retreat and truncated moraines, deep (distal) outer and shallow (proximal) inner basins and cross shelf troughs. These provide evidence of glacial advance and retreat through several glacial cycles. A near consistent pattern of large scale submarine geomorphological features was observed in the different fjords suggesting a similar response of margins of the island ice cap to past climate forcing. A relative chronology based on the relationships between the submarine features with their radiocarbon and cosmogenic isotope dated terrestrial counterparts suggests that widely observed inner basin moraines date from the last major glacial advance or Last Glacial Maximum, while deep basin moraines may date from an earlier (pre-LGM) more extensive glaciation, which we speculate corresponds to MIS6. On the sides of the deep basins a series of truncated moraines show ice advance positions from preceding glacial periods. The cross shelf troughs, and mid-trough moraines are interpreted as the product of much more extensive glaciations that predate the fjord geomorphology mapped here, thus possibly older than MIS6. This hypothesis would suggest that South Georgia followed a glacial history similar to that of central Patagonia (46°S) where a series of Pleistocene glaciations (of MIS 20 and younger) extended beyond LGM limits, with the most extensive glacial advance occurring at c. 1.1 Ma. [Copyright &y& Elsevier]

Abstract: This work presents the results of morpho-stratigraphic analyses carried out on more than 180 buried tunnel valleys imaged in the central North Sea using 3D seismic data at a variety of resolutions. The buried tunnel valleys form complex networks of multiple cross-cutting generations. In the northern part of the study area, cross-cutting relationships within higher resolution 3D seismic data are used to extrapolate seven generations of tunnel valleys over an area of 14,400 km2. Three generations of cross-cutting tunnel valleys are also observed within higher resolution 3D seismic data in the southern part of the study area. Detailed morphological measurements of individual tunnel valleys reveal average widths between 300 m and 3000 m, lengths in the region of tens of kilometres, and relatively straight and simple planform geometries. The majority of the tunnel valleys display undulating basal profiles which provide evidence for the uphill movement of water over distances greater than 10 km and indicate formation by meltwater under pressure. Tunnel valley geometries vary between generations and defy a simple link between formation process and end form. Detailed orientation measurements for the tunnel valley generations reveal an overall NE–SW trend in the northern part of the study area, and a NW–SE directionality in the south. When considered in light of palaeoglaciological models for the British and Scandinavian ice sheets during the Pleistocene, tunnel valley orientation and distribution are consistent with the majority of tunnel valley generations forming perpendicular to a retreating British ice sheet. Changes in orientations between generations (in both northern and southern study areas) provide evidence for changes in the dynamics of the British and Scandinavian ice sheets between subsequent glaciations of the central North Sea. [Copyright &y& Elsevier]

Abstract: The history of research on the Late Quaternary Svalbard–Barents Sea ice sheet mirrors the developments of ideas and the shifts of paradigms in glacial theory over the past 150 years. Since the onset of scientific research there in the early 19th Century, Svalbard has been a natural laboratory where ideas and concepts have been tested, and played an important (but rarely acknowledged) role in the break-through of the Ice Age theory in the 1870''s. The history of how the scientific perception of the Svalbard–Barents sea ice sheet developed in the mid-20th Century also tells a story of how a combination of fairly scattered and often contradictory observational data, and through both deductive and inductive reasoning, could outline a major ice sheet that had left but few tangible fingerprints. Since the 1980''s, with increased terrestrial stratigraphical data, ever more marine geological evidence and better chronological control of glacial events, our perception of the Svalbard–Barents Sea ice sheet has changed. The first reconstructions depicted it as a static, concentric, single-domed ice sheet, with ice flowing from an ice divide over the central northern Barents Sea that expanded and declined in response to large-scale, Late Quaternary climate fluctuations, and which was more or less in tune with other major Northern Hemisphere ice sheets. We now increasingly perceive it as a very dynamic, multidomed ice sheet, controlled by climate fluctuations, relative sea-level change, as well as subglacial topography, substrate properties and basal temperature. In this respect, the Svalbard–Barents Sea ice sheet will increasingly hold the key for understanding the dynamics and processes of how marine-based ice sheets build-up and decay. [Copyright &y& Elsevier]