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The Bølling-Allerød interstadial (14.7-12.9 kyr BP), during the last deglaciation, was characterized by rapid retreat of ice sheets and significant sea level rise (Meltwater Pulse 1A, MWP-1A; 14.7-14.3 kyr BP). Yet, the response of the terrestrial cryosphere during this period of abrupt climate change remains elusive. Here we present a multi-proxy analysis of a sediment record from the upper slope of the Svalbard continental margin that encompasses the last 30 kyr. We show that the Last Glacial Maximum was characterised by the deposition of bedrock material locally sourced by the Barents Sea Ice Sheet. Instead, during MWP-1A permafrost-derived material rich in biospheric carbon became the dominant source of sediments despite the lack of any direct connection with permafrost deposits. Our results suggest massive erosion of Yedoma permafrost deposits during abrupt sea level rise followed by long-range sea ice transport within the Transpolar Drift towards the Arctic Ocean gateway. Overall, we show how permafrost is susceptible to large-scale remobilization in a scenario of rapid warming and sea level rise.

Understanding calving processes and their controls is of importance for reducing uncertainty in sea level rise estimates. The impact of tidal fluctuations and frontal melt on calving patterns has been researched through both modelling and observational studies but remains uncertain and may vary from glacier to glacier. In this study, we isolate various different impacts of tidal fluctuations on a glacier terminus to understand their influence on the timing of calving events in a model of Kronebreen, Svalbard, for the duration of 1 month. In addition, we impose a simplified frontal melt parameterisation onto the calving front in order to allow for an undercut to develop over the course of the simulations. We find that calving events show a tidal signal when there is a small or no undercut, but, after a critical point, undercut-driven calving becomes dominant and drowns out the tidal signal. However, the relationship is complex, and large calving events show a tidal signal even with a large modelled undercut. The modelled undercut sizes are then compared to observational profiles, showing that undercuts of up to ca. 25 m are plausible but with a more complex geometry being evident in observations than that captured in the model. These findings highlight the complex interactions occurring at the calving front of Kronebreen and suggest further observational data and modelling work is needed to fully understand the hierarchy of controls on calving.

Glaciers are an important component of the cryosphere and are key indicators of climate change. Observations of temporal changes in glacier extent are essential for understanding the impacts of climate change, but these observations are not widely available in many parts of the world. Research indicates that climate change has had a significant impact on glacier recession, particularly in the Arctic, where glacier meltwater is an important contributor to global sea-level rise. Therefore, it is important to accurately quantify glacier recession within this sensitive region. In this study, we mapped 480 glaciers in Russian Arctic, Novaya Zemlya, using object-based image analysis (OBIA) applied to multispectral Landsat satellite imagery in Google Earth Engine (GEE) to quantify the area changes between 1986-89 to 2019-21. Our results confirm that in 1986-89, the total glacierized area was 22958.98 km2 and by 2019-21 there was an 5.56% reduction in glacier area to 21680.63 km2. Comparison between manually corrected glacier outlines taken from the Randolph Glacier Inventory (RGI) and the mapped glacier outlines derived using the OBIA method shows there is a 90.26% similarity between both datasets. This confirms that OBIA, combined with the GEE platform, is a promising method for accurately mapping glaciers, reduces the time required for manual correction, and can be applied in other glacierized regions for rapid assessment of glacier change.

While climate model simulations provide valuable insight into potential future Arctic sea-ice scenarios, marine geological archives offer key information on how sea ice responded to substantial climatic warming in the past, particularly during periods characterized by warmer-than-present conditions. The HTM (Holocene Thermal Maximum), ~10.0-6.0 cal ka BP, was expressed in warmer air and ocean temperatures across the globe. Although a result of orbitally-forced summer insolation, the HTM constitutes a valuable parallel to the greenhouse-gas-driven setting of a current (and near-future) warmer world. At higher latitudes in the Northern hemisphere, the HTM has been proposed as an interval of reduced sea ice and increased Atlantic water inflow, similar to a projected future warmer Arctic Ocean. Two sediment archives elucidate the early Holocene HTM evolution of high Arctic seasonal sea ice in the northern Barents Sea (>80°N), a key area for Atlantic-Arctic Ocean water interaction in a hotspot of current climate warming. HBI (highly-branched) biomarkers (IP25, IPSO25, HBI III, HBI IV) unequivocally demonstrate the persistence of spring seasonal sea-ice as high as 55% between 11.7 and 9.1 cal ka BP. Concomitant high δ18O in benthic foraminifera and elevated phytoplankton biomarker (HBI III, HBI IV) concentrations indicate the influence of warm Atlantic-derived bottom water and peak bioproductivity, respectively. Our results highlight the nuanced and complex cryospheric response to climate warming, showing High Arctic sea ice persisting in a setting of warmer-than-present spring and summer conditions under a concomitant increased inflow of subsurface Atlantic Water. This raises important questions about the fate of Arctic sea ice, oceanography, and ecosystems (including commercially important fisheries) in an increasingly warmer climate driven by anthropogenic factors.

The subglacial environment and its characteristics are of primary importance for the behaviour and the stability of ice sheets; however, the mechanisms that take place beneath ice sheets still need to be accurately quantified. Here we present the results of a multi-proxy, biogeochemical analysis carried out on a marine sediment core (HH11-09GC) from the northern Svalbard continental slope, encompassing the last 30 ka. During Termination I, our results suggest a persistent polynya-like environment with significant input of terrigenous organic matter. Indeed, the amount of land-derived material during this period is comparable to that found in the immediate proximity of the major Siberian river mouths during modern times. Alkenone fingerprint suggests that the origin of the terrigenous material could be related to an as yet unidentified freshwater body located in the White Sea/Pechora Basin region, at the margin of the Svalbard Barents Sea Ice Sheet; therefore, the environmental conditions at the base of the ice sheet were suitable for the existence of a large subglacial water drainage. According to our data, this drainage network was able to carry huge amounts of water and sediments beneath the ice sheet and, subsequently, discharge them thousands of kilometres away from their origin. This could represent the first evidence of a pervasive, highly connected subglacial drainage network in the Barents Sea region. Our results may shed new insights on the magnitude of subglacial drainage systems, and thus have important implications with regards to ice sheet modelling.

The Nordic Seas are the primary location where the warm waters of the North Atlantic Current densify to form North Atlantic Deep Water, which plays a key part in the modern Atlantic Meridional Overturning Circulation. The formation of dense water in the Nordic Seas and Arctic Ocean and resulting ocean circulation changes were probably driven by and contributed to the regional and global climate of the last glacial maximum (LGM). Here we map the source and degree of mixing of deep water in the Nordic Seas and through the Arctic Gateway (Yermak Plateau) over the past 35 thousand years using neodymium isotopes (εNd) measured on authigenic phases in deep-sea sediments with a high spatial and temporal resolution. We find that a large-scale reorganization of deep-water formation in the Nordic Seas took place between the LGM (23–18 thousand years ago) and the rapid climate shift that accompanied the subsequent deglaciation (18–10 thousand years ago). We show that homogeneous εNd signatures across a wide range of sites support LGM deep-water formation in the Nordic Seas. In contrast, during the deglaciation, disparate and spatially variable εNd values are observed leading to the conclusion that deep-water formation may have been reduced during this time.

Detailed geomorphological mapping was carried out in the terrestrial and submarine forefields of Protektor-, Harriet- and Kjerulfbreen in Trygghamna, western Svalbard, based on high-resolution aerial images and bathymetric data. The mapping reveals that crevasse-squeeze ridges (CSRs) are only observed on land in the forefield of the surge-type Harriet- and Kjerulfbreen, and recessional moraines are only formed at the sea floor in relation to the retreat of these two glaciers. Different factors affect the preservation potential and formation of landforms between the two environments that could explain the absence of CSRs in the submarine environment and the terrestrial forefield of Protektorbreen. The landform assemblage in Trygghamna does not comply well with existing surge-type glacier landsystem models. We present a conceptual landsystem model for surge-type glaciers with combined terrestrial and marine margins, based on the geomorphological archive from Trygghamna. The contrast between the landform assemblages demonstrates how differences in the thermal regime result in different glacier behavior between the warm-based submarine margins and the inactive cold-based terrestrial margin. This study emphasizes the importance of integrating data from both archives to reconstruct past glacier behavior and understand the effect of different glacial dynamics and environments on the preservation potential of sediments and landforms.

In Arctic alpine regions, glacio-lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice-contact lakes into i ...

Methane is the most widespread volatile hydrocarbon and one of the most potent greenhouse gases. Marine sediments form the largest methane reservoir, from where large quantities of methane from gas-saturated sediments are released into the sea water and into the shallow shelf seas, through the water column almost unaltered into the atmosphere. Craters on the sea floor known as pockmarks are often related to seepage of methane-rich fluids originating either from shallow (microbial) or deep (thermogenic) sources. This paper presents the geochemical characteristics of migrating hydrocarbon gas from selected pockmarks and surrounding seabed in Isfjorden and Mohnbukta in western and eastern Spitsbergen, respectively. Collected gas samples, including wet gas fraction, were analyzed for methane concentration and methane carbon stable isotope ratio. Mixtures of microbial and thermogenic methane, together with higher homologies were found in the pockmarks as well as in the adjacent undisturbed seafloor, suggesting that the seepage activity in both areas is currently on the same level. Although the methane concentration profiles and methane stable carbon isotope ratios in Isfjorden and Mohnbukta show signs of biological oxidation and elevated concentrations of ethane/propane indicate input from deeper thermogenic sources. The gas composition and methane carbon stable isotope ratio from Isfjorden and Mohnbukta areas show similar trends, most likely due to originating in the same Mesozoic organic-rich marine mudstone.

The last glacial maximum (LGM) and post-glacial Quaternary history of Forlandsundet, the strait between western Spitsbergen and Prins Karls Forland, are enigmatic. Previous terrestrial field studies report contradicting evidence for an ice sheet either overriding the entire strait or completely absent during the LGM. Here, we present a multi-proxy investigation of marine sediments, high-resolution bathymetric data and aerial imagery from Forlandsundet. We reveal glacial till present at 15 cal. ka BP and geomorphological landforms characteristic to an inter-ice-stream glaciated margin. This new evidence implies that the Forlandsundet region was fully glaciated during the LGM. This glaciation was followed by a stepwise retreat of glacial ice during the Bolling–Allerod (14.7–12.7 cal. ka BP) and Younger Dryas (12.7–11.7 cal. ka BP). The Holocene record from the marine sediments is incomplete, with a hiatus from approximately 11.8 to 7.4 cal. ka BP, interpreted as an erosive event. By the mid-Holocene (7.4 cal. ka BP), more temperate, Atlantic conditions based on the benthic foraminiferal assemblages prevailed, and are followed by gradual cooling into the late Holocene (

Significance Extensive release of methane from sediments of the world’s largest continental shelf, the East Siberian Arctic Ocean (ESAO), is one of the few Earth system processes that can cause a net transfer of carbon from land/ocean to the atmosphere and thus amplify global warming on the timescale of this century. An important gap in our current knowledge concerns the contributions of different subsea pools to the observed methane releases. This knowledge is a prerequisite to robust predictions on how these releases will develop in the future. Triple-isotope–based fingerprinting of the origin of the highly elevated ESAO methane levels points to a limited contribution from shallow microbial sources and instead a dominating contribution from a deep thermogenic pool., The East Siberian Arctic Shelf holds large amounts of inundated carbon and methane (CH4). Holocene warming by overlying seawater, recently fortified by anthropogenic warming, has caused thawing of the underlying subsea permafrost. Despite extensive observations of elevated seawater CH4 in the past decades, relative contributions from different subsea compartments such as early diagenesis, subsea permafrost, methane hydrates, and underlying thermogenic/ free gas to these methane releases remain elusive. Dissolved methane concentrations observed in the Laptev Sea ranged from 3 to 1,500 nM (median 151 nM; oversaturation by ∼3,800%). Methane stable isotopic composition showed strong vertical and horizontal gradients with source signatures for two seepage areas of δ13C-CH4 = (−42.6 ± 0.5)/(−55.0 ± 0.5) ‰ and δD-CH4 = (−136.8 ± 8.0)/(−158.1 ± 5.5) ‰, suggesting a thermogenic/natural gas source. Increasingly enriched δ13C-CH4 and δD-CH4 at distance from the seeps indicated methane oxidation. The Δ14C-CH4 signal was strongly depleted (i.e., old) near the seeps (−993 ± 19/−1050 ± 89‰). Hence, all three isotope systems are consistent with methane release from an old, deep, and likely thermogenic pool to the outer Laptev Sea. This knowledge of what subsea sources are contributing to the observed methane release is a prerequisite to predictions on how these emissions will increase over coming decades and centuries.

Climate change is causing a structural change in Arctic ecosystems, decreasing the effectiveness that the polar regions have in cooling water masses, with inevitable repercussions on the climate and with an impact on marine biodiversity. The Svalbard islands under study are an area greatly influenced by Atlantic waters. This area is undergoing changes that are modifying the composition and distribution of the species present. The aim of this work is to provide a method for the classification of acoustic patterns acquired in the Kongsfjorden, Svalbard, Arctic Circle using multibeam technology. Therefore the general objective is the implementation of a methodology useful for identifying the acoustically reflective 3D patterns in the water column near the Kronebreen glacier. For each pattern identified, characteristic morphological and energetic quantities were extracted. All the information that describes each of the patterns has been divided into more or less homogeneous groupings by means of a K-means partitioning algorithm. The results obtained from clustering suggest that the most correct interpretation is that which divides the data set into 3 distinct clusters, relating to schools of fish. The presence of 3 different schools of fish does not allow us to state that they are 3 different species. The method developed and implemented in this work is a good method for discriminating the patterns present in the water column, obtained from multibeam data, in restricted contexts similar to those of the study area.

Large amounts of methane are trapped as natural gas hydrate (NGH) in the sediments of the Arctic. Unlike NGH provinces offshore west of Svalbard (Vestnesa Ridge), NGH potential in Svalbard’s fjords and near-shore environment is poorly constrained. In this study we modelled the NGH stability zone (GHSZ) to determine the NGH formation potential within the fjords of Svalbard. We applied a nearest neighbour interpolation method to dynamically derive statistical bottom-water temperature (BWT) trends from available CTD data. The BWT trends along with available geothermal gradient data constrained Svalbard-wide sub-bottom thermobaric models suitable for GHSZ modelling in the near subsurface. Analyses of source rock and fluid seepage data in Isfjorden, including 15 newly identified acoustic gas flares, indicate an active petroleum system with fluid migration reaching the seafloor with significant contributions of higher-order hydrocarbons to the gas feed. A GHSZ is predicted for most fjords at mean BWT conditions and 95:5 methane:ethane gas compositions. Suitable conditions for pure methane NGH formation are only met in the deepest parts of Isfjorden, Hinlopenstretet, Kross- and Kongsfjorden, and Rijpfjorden. Temporal constraints implemented along the well-defined Isfjorden transect indicated a notable negative response to water column warming. The predicted GHSZ across Svalbard’s fjords is likely to disappear over the next few decades.

The cryospheric response to climatic warming responsible for recent Arctic sea ice decline can be elucidated using marine geological archives which offer an important long-term perspective. The Holocene Thermal Maximum, between 10 and 6 thousand years ago, provides an opportunity to investigate sea ice during a warmer-than-present interval. Here we use organic biomarkers and benthic foraminiferal stable isotope data from two sediment cores in the northernmost Barents Sea (>80 °N) to reconstruct seasonal sea ice between 11.7 and 9.1 thousand years ago. We identify the continued persistence of sea-ice biomarkers which suggest spring sea ice concentrations as high as 55%. During the same period, high foraminiferal oxygen stable isotopes and elevated phytoplankton biomarker concentrations indicate the influence of warm Atlantic-derived bottom water and peak biological productivity, respectively. We conclude that seasonal sea ice persisted in the northern Barents Sea during the Holocene Thermal Maximum, despite warmer-than-present conditions and Atlantic Water inflow. The northern Barents Sea contained seasonal sea ice between 11.7 and 9.1 thousand years ago, even during the warmer-than-present Holocene Thermal Maximum and despite warm Atlantic Water inflow, according to biomarker and benthic foraminiferal stable isotope records.

Publisher's version (útgefin grein), We synthesize the current understanding of glacier activity on Svalbard from the end of the Late Pleistocene (12,000 yrs. before present) to the end of the Little Ice Age (c. 1920 AD). Our glacier history is derived from the SVALHOLA database, the first compilation of Holocene geochronology for Svalbard and the surrounding waters, including over 1,800 radiocarbon, terrestrial cosmogenic nuclide and optically stimulated luminescence ages. Data have been categorized by geological setting, uniformly (re-)calibrated, quality assessed and ultimately used to constrain glacier fluctuations (deglaciation, ice free conditions, glacier re-advances and ice marginal positions). We advance existing knowledge by mapping the extent and distribution of ice-cover during the Holocene glacial maximum and the glacial minimum, as well as present retreat rates (and percentages) within Early Holocene fjord-systems. Throughout the Holocene, Svalbard glaciers have responded to a varying combination of climatic, environmental and dynamic driving factors which influence both the extent and behavior of ice margins. We discuss the complexities of glacier systems and their dynamics in response to changes in climate. This review provides a holistic state of the art of Holocene glaciers on Svalbard, suitable for orienting future works which address gaps in our current knowledge., Fianancial support has been provided by the Svalbard Environmental Protection Fund (16/35; to WRF), the Carlsberg Foundation (CF14-0756 to AS), The University Center in Svalbard (UNIS) (research grant to ÓI), and Arctic Research and Studies funded by the Ministries for Foreign Affairs of Norway and Iceland (2017-ARS-79772 to AS & WRF). We are grateful for extensive support from the UNIS Library (Berit Jakobsen and Catherine Fjeldstad). Constructive comments from and discussions with Skafti Brynjólfsson, Kelly Hogan, Anna L.C. Hughes, Sofia Kjellman, Nicolaj K. Larsen and Anne Sofie Søndergaard have improved this manuscript. We are also thankful for anonymous reviews as well as constructive comments from Managing Editor, Professor Negri.

Bathymetry (seafloor depth), is a critical parameter providing the geospatial context for a multitude of marine scientific studies. Since 1997, the International Bathymetric Chart of the Arctic Ocean (IBCAO) has been the authoritative source of bathymetry for the Arctic Ocean. IBCAO has merged its efforts with the Nippon Foundation-GEBCO-Seabed 2030 Project, with the goal of mapping all of the oceans by 2030. Here we present the latest version (IBCAO Ver. 4.0), with more than twice the resolution (200 × 200 m versus 500 × 500 m) and with individual depth soundings constraining three times more area of the Arctic Ocean (∼19.8% versus 6.7%), than the previous IBCAO Ver. 3.0 released in 2012. Modern multibeam bathymetry comprises ∼14.3% in Ver. 4.0 compared to ∼5.4% in Ver. 3.0. Thus, the new IBCAO Ver. 4.0 has substantially more seafloor morphological information that offers new insights into a range of submarine features and processes; for example, the improved portrayal of Greenland fjords better serves predictive modelling of the fate of the Greenland Ice Sheet., Measurement(s)depthTechnology Type(s)digital curationFactor Type(s)geographic locationSample Characteristic - Environmentocean floorSample Characteristic - LocationArctic Ocean Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12369314

The Barents Sea Ice Sheet was part of an interconnected complex of ice sheets, collectively referred to as the Eurasian Ice Sheet, which covered north-westernmost Europe, Russia and the Barents Sea during the Last Glacial Maximum (around 21 ky BP). Due to common geological features, the Barents Sea component of this ice complex is seen as a paleo-analogue for the present-day West Antarctic Ice Sheet. Investigating key processes driving the last deglaciation of the Barents Sea Ice Sheet represents an important tool to interpret recent observations in Antarctica over the multi-millennial temporal scale of glaciological changes. We present results from a perturbed physics ensemble of ice sheet model simulations of the last deglaciation of the Barents Sea Ice Sheet, forced with transient atmospheric and oceanic conditions derived from AOGCM simulations. The ensemble of transient simulations is evaluated against the data-based DATED-1 reconstruction to construct minimum, maximum and average deglaciation scenarios. Despite a large model/data mismatch at the western and eastern ice sheet margins, the simulated and DATED-1 deglaciation scenarios agree well on the timing of the deglaciation of the central and northern Barents Sea. We find that the simulated deglaciation of the Barents Sea Ice Sheet is primarily driven by the oceanic forcing, with prescribed eustatic sea level rise amplifying the ice sheet sensitivity to sub-shelf melting over relatively short intervals. Our results highlight that the sub-shelf melting has a very strong control on the simulated grounding-line flux, showing that a slow, gradual ocean warming trend is capable of triggering sustained grounded ice discharge over multi-millennial timescales, even without taking into account marine ice sheet or ice cliff instability.

Vaigattbogen is located in northern Svalbard. The area is currently affected by several tidewater glaciers. This study uses multibeam-, sub-bottom acoustic data, and four sediment cores to reconstruct the Late Weichselian and Holocene glacial history in Vaigattbogen. During the last glacial, ice flowed northwards through Vaigattbogen and fed into the Hinlopen Strait Ice Stream. Streamlined bedforms indicate relatively fast ice flow and their increasing elongation ratios towards the north suggest increasing flow velocities. De Geer moraines in the shallower parts of Vaigattbogen imply that multiple halts and/or re-advances interrupted the ice retreat in these areas. A sediment core suggests that the north basin deglaciated prior to 9.1 cal. ka BP. In the south basin, two large moraine ridges and networks of crevasse-squeeze ridges suggest that at least two surge-type advances occurred during the Holocene. The Hinlopenbreen glacier surged in the early 1970s and deposited the inner (R.2) of the two large moraine ridges. Radiocarbon ages from a sediment core recovered from the crest of the outer (R.1) ridge yield a basal age of 2.6 cal. ka BP. However, the core did not sample subglacial diamict and the age of the ridge could be anything between 2.6 cal. ka BP and early Holocene. The R.1 ridge formed prior to the Little Ice Age (LIA), implying that more than one tidewater glacier has experienced a pre-LIA surge on the east coast of Spitsbergen, suggesting that surging during the Holocene was a regional phenomenon. The R.1 ridge is double-crested with small crevasse-squeeze ridges between the crests suggesting that more than one surge-type advance occurred during the Holocene reaching approximately the same location. Data from eastern Svalbard indicate differences in surge-landform assemblages suggesting that different mechanisms could have governed surge-cycles throughout the Holocene.

The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming.

The study of glacial landforms is important for understanding past subglacial processes and dynamics. The Nordenskioldbreen forefield hosts numerous streamlined landforms resulting from a late Holocene glacier advance. Here, we present a geomorphological map constructed from remotely sensed imagery of both the marine and terrestrial environments. Sixteen drumlin bedforms have been identified in the mapped forefield – ten terrestrial and six submarine. A sedimentological investigation of drumlins in the Nordenskioldbreen forefield shows that they are composed of pre-existing sediments draped by a thin layer of till which formed during the most recent advance of the glacier. Analysis of recent (2008–2012), high-resolution aerial imagery of all the glacier forelands in Svalbard suggests drumlin features are widespread. Here, we have identified 49 previously undocumented terrestrial glacier forefields, where subglacially streamlined landforms occur within the margins of the late Holocene glacier exten...

Ice stream configuration and sedimentary processes in Albertini Trough, north of Nordaustlandet, were studied using multibeam bathymetry, seismic reflection and sub-bottom profiles together with sediment gravity cores. Progradational sediment packages in the outer Albertini Trough suggest that streaming ice reached the shelf edge multiple times during the last c. 2.6 Ma. S–N-oriented glacial lineations imply that the Last Glacial Maximum (LGM) ice flow reached Albertini Trough mouth, and likely sourced from Duvefjorden and Albertinibukta. The ice flows from these two areas were separated on the inner shelf until they merged north of Karl XII Island, suggesting a geologic control on the ice flows. The scarceness of landforms characteristic of grounded ice margin retreat in the outermost Albertini Trough suggests a locally floating ice tongue. The presence of iceberg ploughmarks on the outer shelf suggests that the ice margin mainly disintegrated through calving. Push moraines and De Geer moraines superimposed on terminal moraines and a grounding zone wedge with superimposed SSW–NNE-oriented glacial lineations indicate a stepwise retreat of the ice margin with at least three readvances during deglaciation. Grounding line stabilization in the outer Albertini Trough is partly attributed to southwards shallowing and narrowing trough geometry. However, a southwards change in the orientation of glacial lineations from S–N to SSW–NNE suggests that the ice flow from Duvefjorden became more dominant in Albertini Trough during deglaciation. Spacing between the De Geer moraines generally increases southwards in Albertini Trough, implying an increased retreat rate during deglaciation. Three acoustic units were distinguished in the chirp data and correlated with till, glacimarine and marine deposits, respectively. Two sediment cores west of Albertini Trough consist of subglacial diamicton at the base with a sharp transition to homogenous marine mud above. The diamicton–mud transition in the cores was 14C-dated to 15.3 and 14.0 ka, implying increased retreat rate of the ice sheet margin during deglaciation across the continental shelf. The increased retreat rate is attributed to rapid sea level rise. Well-preserved listric fault scarps in the Albertini Trough mouth indicate relatively recent formation. The locally downfaulted bedrock beneath the glacial–interglacial sediments at the trough mouth probably contributed to the formation of thick and unstable sediment succession, which resulted in the faulting.

Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam-bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Konigsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well-preserved geometric networks of ridges, interpreted as crevasse-squeeze ridges inshore of the moraines. The arrangement of crevasse-squeeze ridges suggests that both landform sets were produced during surge-type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast-rich mud unit. This unit represents pre-surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15-01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge-type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

Fast-flowing outlet glaciers currently drain the Greenland Ice Sheet (GIS), delivering ice, meltwater and debris to the fjords around Greenland. Although such glaciers strongly affect the ice sheet's mass balance, their glacimarine processes and associated products are still poorly understood. This study provides a detailed analysis of lithological and geophysical data from Disko Bay and the Vaigat Strait in central West Greenland. Disko Bay is strongly influenced by Jakobshavn Isbrae, Greenland's fastest-flowing glacier, which currently drains ∼7% of the ice sheet. Streamlined glacial landforms record the former flow of an expanded Jakobshavn Isbrae and adjacent GIS outlets through Disko Bay and the Vaigat Strait towards the continental shelf. Thirteen vibrocores contain a complex set of lithofacies including diamict, stratified mud, interbedded mud and sand, and bioturbated mud deposited by (1) suspension settling from meltwater plumes and the water column, (2) sediment gravity flows, and (3) iceberg rafting and ploughing. The importance of meltwater-related processes to glacimarine sedimentation in West Greenland fjords and bays is emphasised by the abundance of mud preserved in the cores. Radiocarbon dates constrain the position of the ice margin during deglaciation, and suggest that Jakobshavn Isbrae had retreated into central Disko Bay before 10.6 cal ka BP and to beyond Isfjeldsbanken by 7.6–7.1 cal ka BP. Sediment accumulation rates were up to 1.7 cm a−1 for ice-proximal glacimarine mud, and ∼0.007–0.05 cm a−1 for overlying distal sediments. In addition to elucidating the deglacial retreat history of Jakobshavn Isbrae, our findings show that the glacimarine sedimentary processes in West Greenland are similar to those in East Greenland, and that variability in such processes is more a function of time and glacier proximity than of geographic location and associated climatic regime.

Understanding the role of fjords in modulating the long-term interaction between ice sheets and glaciers with the surrounding ocean requires the investigation of glacigenic landform and sediment archives. In Svalbard, there is a wealth of data from fjords in west Spitsbergen that constrains the glacial history of this sector of the Svalbard-Barents Sea Ice Sheet (SBIS) since the Last Glacial Maximum (LGM), and the nature and timing of subsequent ice retreat. In contrast, however, very little is known about the glacial history of fjords in east Spitsbergen. This paper combines multibeam swath-bathymetry, sub-bottom profiles, lithological data and radiocarbon dates from Lomfjorden, Svalbard, to provide the first insights into the dynamics of tidewater glaciers and associated glacimarine sedimentary processes in a northeast Spitsbergen fjord. At the LGM, a fast-flowing ice stream drained the SBIS through Lomfjorden, serving as a tributary to a south-north flowing ice stream in Hinlopenstretet. Ice advance is recorded by streamlined bedrock, glacial lineations and drumlins. A radiocarbon date of ∼9.7 ka BP from the outer fjord provides a minimum date for retreat of this ice stream, and suggests that Lomfjorden was ice-free earlier than fjords in west Spitsbergen. Ice retreat occurred in a slow and step-wise manner, indicated by the presence of recessional moraines and De Geer moraines. By 4.5 ka BP the local tidewater glaciers had probably retreated inland of their present positions. The limited extent of glacigenic landform assemblages in front of these glaciers implies that any Holocene re-advances were probably restricted. The principal sedimentary processes during deglaciation were suspension settling from meltwater, causing deposition of weakly stratified, bioturbated mud in ice-distal settings at rates of 0.02–0.08 cm a−1, and gravitational mass flows forming sandy turbidites in ice-proximal areas. Iceberg ploughmarks and ice-rafted debris provide evidence for the presence of large icebergs during deglaciation. Our data suggest an early and extensive deglaciation in east Spitsbergen fjords and show that previous reconstructions of the extent of the SBIS need to be revised as new data emerges from east Spitsbergen. The data confirm that tidewater glaciers from different regions of Spitsbergen behaved differently since the LGM, and that variations in landform-sediment assemblages occur even within geographically adjacent fjords.

Evidence of a dynamic Holocene glacial history is preserved in the terrestrial and marine archives of St. Jonsfjorden, a small fjord-system on the west coast of Spitsbergen, Svalbard. High-resolution, remotely sensed imagery from marine and terrestrial environments was used to construct geomorphological maps that highlight an intricate glacial history of the entire fjord-system. The geomorphology and stratigraphy indicate an early Holocene local glacier advance constrained to the Lateglacial–early Holocene transition. Identification and 14C dating of the thermophilous bivalve mollusc Modiolus modiolus to 10.0±0.12 cal. ka BP suggest a rapid northward migration of the species shortly after deglaciation. Further evidence enhances the understanding of the onset and subsequent climax of the Neoglacial-Little Ice Age in inner St. Jonsfjorden. The present-day terminus of Osbornebreen, the dominating glacier system in St. Jonsfjorden, is located over 8.5 km up-fjord from its Neoglacial maximum extent. Cross-cutting relationships suggest subsequent advances of all the smaller glaciers in the area following the break-up of Osbornebreen. Glacial deposits, landforms and their cross-cutting relationships observed in both terrestrial and marine settings imply a complex and highly dynamic environment through the later part of the Holocene.

New information is presented on the configuration of the northern Barents Sea Ice Sheet (BSIS) during the last glacial and deglaciation (21–11.5 ka). The glacial dynamics of the BSIS that we discuss are based on clay-mineral compositions of subglacial tills and a distinct kaolinite source in the central Barents Sea where previous workers have placed a large, single ice dome for the last glacial BSIS. Our results, which appear to show that subglacial sediments were sourced locally, suggest that the BSIS consisted at least temporarily of multiple domes and may have been more dynamic than previously thought. New radiocarbon dates are presented along with new ice-extent reconstructions for 16.5–15, 14, 13.5 and 11.5 ka. Our reconstructions add information to previous regional and continental-scale efforts in areas east of Svalbard. Ice retreat in the northern Barents Sea progressed as follows. (i) 19–16.5 ka. Major calving led to dynamic thinning in shelf troughs and was accompanied by significant ice-sheet thinning inland as a result of ice drawdown. (ii) 16.5–15 ka. Rapid ice-margin retreat of between 75–100 km occurred, via lift-off and iceberg calving, in Hinlopen and Kvitoya troughs, as well as major retreat (>300 km) in Franz Victoria Trough (FVT) further east. (iii) 15–13.5 ka. Retreat progressed westwards from the FVT towards Svalbard with troughs east of Svalbard (Kvitoya, Olga, and Erik Eriksen) mostly ice-free by 13.5 ka. (iv) 13.5–11.5 ka. Ice retreated gradually towards residual ice masses on Svalbard, Kong Karls Land and possibly Storbanken. Our data require a modification of earlier views of the BSIS because they point toward a more dynamic ice sheet and decay that, once initiated at the shelf break, was dominated by the withdrawal of ice from the FVT that progressed westwards towards the Svalbard archipelago.

Wahlenbergfjorden is a fjord situated in the western part of Nordaustlandet in northern Svalbard. It leads into the 400 m deep Hinlopen Strait located between Nordaustlandet and Spitsbergen. High-r ...

Observations of subglacial landforms yielding the configuration and dynamics of former ice-flows have for the first time been made in Rijpfjorden and Duvefjorden, Nordaustlandet, Svalbard, using sub-bottom acoustic, swath-bathymetric data and sediment cores. Five acoustic-stratigraphic units were distinguished suggesting the presence of a complete glacial–postglacial succession in the central fjord basins. 14C ages from the sediments indicate that the inner Rijpfjorden and central Duvefjorden were deglaciated before ca. 10.6 cal ka BP and 11.0 cal ka BP, respectively. Maximum sediment thickness in Rijpfjorden and Duvefjorden is 26 m, resulting in sediment accumulation rates of ca. 66 cm ka−1. The landform record suggests that the ice streaming in both fjords was topographically controlled. The considerably deeper basin and higher elongation ratios of the crag-and-tails in Duvefjorden are linked to the faulted bedrock and possibly to somewhat larger ice stream and/or more focused ice-flow compared to that in Rijpfjorden. De Geer moraines suggest slower retreat of a grounded ice margin from shallow areas of Rijpfjorden. In deeper areas of the fjords, the glaciers were probably floating, resulting in the lack of ice-marginal transverse landforms. The ice margin retreat from these areas was probably relatively rapid and dominated by calving.

© 2016 Regents of the University of Colorado. Previous advances and retreats of Blomstrandbreen within the cold period known as the Little Ice Age, between approximately 1400 and 1920, are relatively well documented. The seafloor characteristics associated with these glacier fluctuations, and their importance for the identification of similar surge-type tidewater glaciers, are discussed. We use detailed multibeam-bathymetric data acquired within Nordvågen, the marine area offshore of Blomstrandbreen, to provide a new understanding of the style and pattern of deglaciation around Blomstrandhalvøya since Blomstrandbreen's neoglacial maximum. Glacial landforms on the seafloor of Nordvågen comprise overridden moraines, glacial lineations, terminal moraines, and annual recessional moraines. Crevasse-fill ridges, which are often regarded as a characteristic landform of surging tidewater glaciers, are present on only restricted areas of Nordvågen. Significantly, this study shows that large terminal surge moraines and numerous crevasse-fill ridges may not always be well developed in association with glacier surges, with implications for the identification of surges in the geological record. Using historical observations, aerial photographs, and satellite imagery of Blomstrandbreen, we have correlated former ice-marginal positions with mapped submarine landforms. Three surge events occurred during a pattern of overall retreat, with a spacing of about 50 years between active advance phases; this represents a relatively short quiescent phase for Svalbard glaciers. Average retreat rates of 10-50 m yr-1 are typical of the quiescent phase of the surge cycle, whereas surge advances vary from 200 m to over 725 m.

The Barents Sea is a wide, relatively deep epicontinental sea consisting of shallower banks ( c. 50–100 m depth) separated by broad, flat-bottomed troughs ( c. 200–400 m depth) that radiate out towards its western and northern margins (Fig. 1a). These troughs have been excavated by grounded ice during multiple glaciations through the Plio-Pleistocene (Jakobsson et al. 2014). During the Last Glacial Maximum (LGM) the Barents Sea Ice Sheet (BSIS) extended across the entire northern Barents Sea to the shelf break (Svendsen et al. 2004; Jakobsson et al. 2014). Fast-flowing ice drained the ice sheet through these troughs and produced a suite of seafloor landforms that preserves both a record of former ice-flow patterns and of how the ice sheet retreated during deglaciation (Dowdeswell et al. 2010; Hogan et al. 2010 a ). Fig. 1. Bathymetric images and sub-bottom profiles of landforms in glacial troughs east of Svalbard. Acquisition system Kongsberg EM120. Frequency 12 kHz. Grid-cell size 10–20 m. Acquisition system for profiles Kongsberg TOPAS PS018 parametric sub-bottom profiler (secondary beam frequency 0.5–6 kHz). ( a ) Location of study area (red boxes; map from IBCAO v. 3.0). KT, Kvitoya Trough; OT, Olga Trough; E, eastern Erik Eriksen Trough; W, western Erik Eriksen Trough; KKL, Kong Karls Land; No, Nordaustlandet; FVT, Franz Victoria Trough. ( b ) Glacial lineations (long dashes) overprinted in part by a debris-flow deposit (dotted) in western Erik Eriksen Trough; recessional moraine orientations shown by solid lines. Large black arrow indicates former ice-flow direction. ( c ) Saw-tooth-shaped recessional moraines in Olga Trough. ( d ) Hill–hole pairs and glacial lineations in eastern Olga Trough; same depth scale as (c). ( e ) Streamlined crag-and-tail landforms in Kvitoya Trough. ( f ) Sub-bottom profile over the till sheet and recessional moraines shown in (c). ( g ) Acoustic facies on the upper slope north of Kvitoya Trough. ( h ) Subglacial meltwater channels …

Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2–1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.

Our understanding of processes relating to the retreat of marine-based ice sheets, such as the West Antarctic Ice Sheet and tidewater-terminating glaciers in Greenland today, is still limited. In particular, the role of ice stream instabilities and oceanographic dynamics in driving their collapse are poorly constrained beyond observational timescales. Over numerous glaciations during the Quaternary, a marine-based ice sheet has waxed and waned over the Barents Sea continental shelf, characterized by a number of ice streams that extended to the shelf edge and subsequently collapsed during periods of climate and ocean warming. Increasing availability of offshore and onshore geophysical data over the last decade has significantly enhanced our knowledge of the pattern and timing of retreat of this Barents Sea ice sheet (BSIS), particularly so from its Late Weichselian maximum extent. We present a review of existing geophysical constraints that detail the dynamic evolution of the BSIS through the last glacial cycle, providing numerical modelers and geophysical workers with a benchmark data set with which to tune ice sheet reconstructions and explore ice sheet sensitivities and drivers of dynamic behavior. Although constraining data are generally spatially sporadic across the Barents and Kara Seas, behaviors such as ice sheet thinning, major ice divide migration, asynchronous and rapid flow switching, and ice stream collapses are all evident. Further investigation into the drivers and mechanisms of such dynamics within this unique paleo-analogue is seen as a key priority for advancing our understanding of marine-based ice sheet deglaciations, both in the deep past and in the short-term future.

The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming.

New swath-bathymetric data from the inner parts of the three Svalbard fjords Ymerbukta, Trygghamna, and Magdalenefjorden reveal the landform assemblages deposited in front of tidewater glaciers in west and northwest Spitsbergen. Overridden moraines in Ymerbukta, a tributary of Isfjorden in central west Spitsbergen, record several re-advances of the Esmarkbreen glacier at the head of the fjord after deglaciation, and glacial lineations formed in seafloor sediments are indicative of fast ice advance during one of these events. A terminal moraine and associated debris lobe mark the maximum ice extent during the Holocene, which, implied by the presence of crevasse-squeeze ridges, is likely related to a surge of Esmarkbreen. Several De Geer moraines provide evidence for subsequent slow and step-wise retreat. In the adjacent Trygghamna and in Magdalenefjorden in northwest Spitsbergen the landforms are similar but the absence of overridden moraines and glacial lineations shows that the glaciers probably only re-advanced once during the Holocene and that ice flow was relatively slow. Terminal moraines and associated debris lobes mark the maximum extent of these advances and formed during the Little Ice Age (LIA). In Magdalenefjorden the relatively small size of the debris lobe suggests that the ice margin was at its maximum position for only a short period of time, or that sediment availability was restricted during the LIA advance. Similar to Esmarkbreen the retreat phase of the glaciers in Trygghamna and Magdalenefjorden was also characterised by periods of still-stand or small re-advances, although the comparatively small number of De Geer moraines in all three fjords shows that these landforms probably formed much less frequently than previously thought. Sub-bottom profiler data, four sediment cores and six radiocarbon dates from Magdalenefjorden further provide information about the Holocene sedimentary environments in a northwest Spitsbergen fjord. The main source of sediment is glacial meltwater entering the fjord from the surrounding coastline, which has led to the accumulation of thick sequences of fine-grained mud. Stratified and laminated muds record glacier-proximal conditions, probably related to a LIA re-advance of Waggonwaybreen around 300 cal a BP, where the interplay of a range of glacimarine processes led to the formation of partially rhythmic couplets of one coarser and one finer layer, accumulated at a rate of around 3 cm a −1. Multiple sandy layers intercalated with the glacimarine mud provide evidence for the occurrence of gravitational mass-flow events like turbidity currents. In ice-distal settings, massive to weakly stratified, occasionally bioturbated mud accumulated at a lower rate of 0.04–0.49 cm a −1. Occasional clasts and diamictic layers show that the depositional environment in Magdalenefjorden is also influenced by sedimentation from icebergs and sea ice, but the ubiquitous glacimarine mud underscores the predominance of meltwater-related sedimentation in the fjord.

The Disko Trough-Mouth Fan (TMF) is a major submarine sediment fan located along the central west Greenland continental margin offshore of Disko Trough. The location of the TMF at the mouth of a prominent cross-shelf trough indicates that it is a product of repeated glacigenic sediment delivery from former fast-flowing outlets of the Greenland Ice Sheet, including an ancestral Jakobshavn Isbrae, which expanded to the shelf edge during successive glacial cycles. This study focuses on the uppermost part of the fan stratigraphy and analyses multibeam swath bathymetry and sub-bottom profiler records, supplemented by a series of vibrocores up to 6 m in length. The swath bathymetry data show that the surface of the fan is prominently gullied and channelled with channels extending downslope from a series of shelf-edge incising gullies. Sub-bottom profiles from across- and down-fan show that the fan sediments are often acoustically stratified. Glacigenic-debris flows (GDFs) were recovered in sediment cores from the uppermost slope but they are absent in cores from elsewhere on the fan. Instead, glacimarine lithofacies in the Disko TMF are dominated by turbidites, hemipelagic sediments and IRD. The gullied and channelled surface of the fan implies erosion at the base of dense, sediment-laden, turbidity currents related to the delivery of meltwater and sediment from an ice sheet grounded at the shelf edge. Such meltwater-related fans have been documented previously on mid-latitude, glacier-influenced margins, but they have rarely been described from high-latitude settings. Although GDFs are often regarded as the building blocks of TMFs, the morphology and sedimentary architecture of the uppermost, Late Quaternary part of the Disko TMF indicates that it represents a clear example of a fan in which sediment delivery is strongly influenced by meltwater. This implies that there is a spectrum of TMFs on glaciated continental margins that reflects the relative dominance of meltwater processes vs. GDFs. It highlights the variability in fan morphology and mechanisms of sediment delivery on high-latitude TMFs and shows that the classic Polar North Atlantic model of GDF dominated fans is but one of a number of styles for such large-scale, high-latitude glacimarine sedimentary depocentres.