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The marine-based Barents Sea Ice Sheet covered the polar continental shelf north of Norway and western Russia during the Last Glacial Maximum. Initial ice sheet retreat along the western margin is well established, while the retreat pattern in the interior parts of the ice sheet remains poorly known. Here we present new geological data from the central Barents Sea, including the formerly disputed zone. The results are based on analysis of several marine geophysical datasets, including geomorphological mapping of multibeam swath bathymetry data and analysis of seismic and acoustic stratigraphy. The new results provide insights into the configuration and dynamics of the ice sheet during its retreat across the central Barents Sea. In particular they show clear changes in the location of the main ice divides and domes, with ice flow becoming gradually more topographically controlled as deglaciation progressed. Major troughs were characterised by episodic retreat and reoccurring cycles of fast and slow ice flow, sometimes leading to stagnation and ice shelf formation. Meanwhile, adjacent bank areas were covered by comparatively slowly retreating ice, although evidence of streaming ice is also seen locally. Highlights (for review)

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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 origin of two acoustic sediment units has been studied based on lithological facies, chronology and benthic stable isotope values as well as on foraminifera and clay mineral assemblages in six marine sediment cores from Kveithola, a small trough west of Spitsbergenbanken on the western Barents Sea margin. We have identified four time slices with characteristic sedimentary environments. Before c. 14.2 cal. ka, rhythmically laminated muds indicate extensive sea ice cover in the area. From c. 13.9 to 14.2 cal. ka, muds rich in ice‐rafted debris were deposited during the disintegration of grounded ice on Spitsbergenbanken. From c. 10.3 to 13.1 cal. ka, sediments with heterogeneous lithologies suggest a shifting influence of suspension settling and iceberg rafting, probably derived from a decaying Barents Sea Ice Sheet in the inner‐fjord and land areas to the north of Kveithola. Holocene deposition was episodic and characterized by the deposition of calcareous sands and shell debris, indicative of strong bottom currents. We speculate that a marked erosional boundary at c. 8.2 cal. ka may have been caused by the Storegga tsunami. Whilst deposition was sparse during the Holocene, Kveithola acted as a sediment trap during the preceding deglaciation. Investigation of the deglacial sediments provides unprecedented details on the dynamics and timing of glacial retreat from Spitsbergenbanken.

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Abstract. Continental shelf sediments are places of both rapid organic carbon turnover and accumulation, while at the same time increasingly subjected to human-induced disturbances. Recent research suggests that shelf sediments might have a role to play as a natural climate solution, e.g. by storing organic carbon if left undisturbed from anthropogenic activity. However, we have an incomplete understanding about the centres of organic carbon accumulation and storage on continental shelves. To better constrain the rate of accumulation and the mass of organic carbon that is stored in sediments, we developed and applied a spatial modelling framework that allows us to estimate those quantities from sparse observations and predictor variables known or suspected to influence the spatial patterns of these parameters. This paper presents spatial distribution patterns of organic carbon densities and accumulation rates in the North Sea and Skagerrak. We found that organic carbon stocks and accumulation rates are highest in the Norwegian Trough, while large parts of the North Sea are characterised by low stocks and zero net accumulation. The total stock of organic carbon that is stored in the upper 0.1 m of sediments amounted to 230.5 ± 134.5 Tg C, of which approximately 26 % is stored in the Norwegian Trough. Rates of organic carbon accumulation in the Norwegian Trough are comparable with those reported from nearby fjords. We provide baseline datasets that could be used in marine management, e.g. for the establishment of “carbon protection zones”. Additionally, we highlight the complex nature of continental shelves with zones of rapid carbon cycling and accumulation juxtaposed, which will require further detailed and spatially explicit analyses to constrain sedimentary organic carbon stocks and accumulation rates globally.

10The Barents Sea Ice Sheet (BSIS) is a good palaeo-analogue for the present day West Antarctic 11 Ice Sheet. Both were marine-based ice sheets, particularly vulnerable to ocean warming and 12 sea-level rise. Understanding the BSIS ice dynamics and patterns of retreat since the Last 13 Glacial Maximum (LGM) is useful in developing our knowledge of spatial and temporal 14 variations during marine-based ice sheet retreat. While the western margins of the Barents Sea 15 have been extensively studied, few studies have focused on the central regions, which hosted 16 key ice stream tributaries and major ice domes and divides. Presenting a new high-resolution 17 (5 m) bathymetric dataset, this glacial geomorphological study focuses on the Sentralbankrenna 18 palaeo-glacial system in the central Barents Sea. A large number of grounding zone wedges, 19 mega-scale glacial lineations and areas with tunnel valleys and palaeo-subglacial basins were 20 identified. These form the basis for a six-stage reconstruction of ice stream retreat through 21 deglaciation since the LGM. In reconstructing the retreat of the Sentralbankrenna Ice Stream, 22 we document the rapid but highly spatially variable pattern of retreat of a marine-based ice 23 sheet margin. The presence of several tunnel valleys and interconnected palaeo-subglacial basin 24 systems indicates an abundance of meltwater, likely to have been stored and released through 25 several discharge events, significantly influencing the ice stream margin dynamics. This study 26 provides insight into the behaviour and dynamics of ice during the late stages of the BSIS 27 deglaciation within the central Barents Sea, increasing our understanding of grounding line 28 processes. 29 30 31 2