No abstract

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

Subglacial hydrology modulates how ice sheets flow, respond to climate, and deliver meltwater, sediment and nutrients to proglacial and marine environments. Here, we investigate the development of subglacial lakes and drainage networks beneath the Fennoscandian and Barents Sea ice sheets over the Late Weichselian. Utilizing an established coupled climate/ice flow model, we calculate highresolution, spatio-temporal changes in subglacial hydraulic potential from ice sheet build-up (~37 ka BP) to complete deglaciation (~10 ka BP). Our analysis predicts up to 3,500 potential subglacial lakes, the largest of which was 658 km 2 , and over 70% of which had surface areas <10 km 2 , comparable with subglacial lake-size distributions beneath the Antarctic Ice Sheet. Asynchronous evolution of the Fennoscandian Ice Sheet into the flatter relief of northeast Europe affected patterns of subglacial drainage, with up to 100 km 3 more water impounded within subglacial lakes during ice build-up compared to retreat. Furthermore, we observe frequent fill/drain cycles within clusters of subglacial lakes at the onset zones and margins of ice streams that would have affected their dynamics. Our results resonate with mapping of large subglacial channel networks indicative of highdischarge meltwater drainage through the Gulf of Bothnia and central Barents Sea. By tracking the migration of meltwater drainage outlets during deglaciation, we constrain locations most susceptible to focussed discharge, including the western continental shelf-break where subglacial sediment delivery led to the development of major trough-mouth fans. Maps of hydraulic potential minima that persist throughout the Late Weichselian reveal potential sites for preserved subglacial lake sediments, thereby defining useful targets for further field-investigation.

Processes occurring at the grounding zone of marine terminating ice streams are crucial to marginal stability, influencing ice discharge over the grounding‐line, and thereby regulating ice‐sheet mass balance. We present new marine geophysical data sets over a ~30×40 km area from a former ice‐stream grounding zone in Storfjordrenna, a large cross‐shelf trough in the western Barents Sea, south of Svalbard. Mapped ice‐marginal landforms on the outer shelf include a large accumulation of grounding‐zone deposits and a diverse population of iceberg ploughmarks. Published minimum ages of deglaciation in this region indicate that the deposits relate to the deglaciation of the Late Weichselian Storfjordrenna Ice Stream, a major outlet of the Barents Sea–Svalbard Ice Sheet. Sea‐floor geomorphology records initial ice‐stream retreat from the continental shelf break, and subsequent stabilization of the ice margin in outer‐Storfjordrenna. Clustering of distinct iceberg ploughmark sets suggests locally diverse controls on iceberg calving, producing multi‐keeled, tabular icebergs at the southern sector of the former ice margin, and deep‐drafted, single‐keeled icebergs in the northern sector. Retreat of the palaeo‐ice stream from the continental shelf break was characterized by ice‐margin break‐up via large calving events, evidenced by intensive iceberg scouring on the outer shelf. The retreating ice margin stabilized in outer‐Storfjordrenna, where the southern tip of Spitsbergen and underlying bedrock ridges provide lateral and basal pinning points. Ice‐proximal fans on the western flank of the grounding‐zone deposits document subglacial meltwater conduit and meltwater plume activity at the ice margin during deglaciation. Along the length of the former ice margin, key environmental parameters probably impacted ice‐margin stability and grounding‐zone deposition, and should be taken into consideration when reconstructing recent changes or predicting future changes to the margins of modern ice streams.