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Considerable uncertainty surrounds the extent and timing of the advance and retreat of the Greenland Ice Sheet (GIS) on the continental shelf bordering Baffin Bay during the last glacial cycle. Here we use marine geophysical and geological data to show that fast-flowing ice sheet outlets, including the ancestral Jakobshavn Isbræ, expanded several hundred kilometers to the shelf edge during the last glaciation ca. 20 ka. Retreat of these outlets was asynchronous. Initial retreat from the shelf edge was underway by 14,880 calibrated (cal) yr B.P. in Uummannaq trough. Radiocarbon dates from the adjacent Disko trough and adjoining trough-mouth fan imply later deglaciation of Jakobshavn Isbræ, and, significantly, an extensive readvance and rapid retreat of this outlet during the Younger Dryas stadial (YD). This is notable because it is the first evidence of a major advance of the GIS during the YD on the West Greenland shelf, although the short duration suggests that it may have been out of phase with YD temperatures. [ABSTRACT FROM AUTHOR]

The Antarctic Peninsula is one of the three fastest warming regions on Earth. Here we review Holocene proxy records of marine and terrestrial palaeoclimate in the region, and discuss possible forcing mechanisms underlying past change, with a specific focus on past warm periods. Our aim is to critically evaluate the mechanisms by which palaeoclimate changes might have occurred, in order to provide a longer-term context for assessing the drivers of recent warming. Two warm events are well recorded in the Holocene palaeoclimate record, namely the early Holocene warm period, and the 'Mid Holocene Hypsithermal' (MHH), whereas there are fewer proxy data for the 'Mediaeval Warm Period' (MWP) and the 'Recent Rapid Regional' (RRR) warming. We show that the early Holocene warm period and MHH might be explained by relatively abrupt shifts in position of the Southern Westerlies, superimposed on slower solar insolation changes. A key finding of our synthesis is that the marine and terrestrial records in the AP appear to show markedly different behaviour during the MHH. This might be partly explained by contrasts in the seasonal insolation forcing between these records. Circumpolar Deep Water (CDW) has been implicated in several of the prominent changes through the Holocene but there are still differences in interpretation of the proxy record that make its influence difficult to assess. Further work is required to investigate contrasts between marine and terrestrial proxy records, east-west contrasts in palaeoclimate, the history of CDW, to retrieve a long onshore high resolution record of the Holocene, and determine the role of sea ice in driving or modulating palaeoclimate change, along with further efforts to study the proxy record of the RRR and the MWP. [ABSTRACT FROM AUTHOR]

Morphology and sedimentation on the Pine Island Bay continental margin, eastern Amundsen Sea, is investigated using swath bathymetry, parametric subbottom profiler (TOPAS) records, and sediment cores. A major cross-shelf trough extends to the continental shelf edge at 114°W, through which fast-flowing ice drained the West Antarctic Ice Sheet under full-glacial conditions. The slope adjacent to the trough mouth is 4°, whereas to the east and west it is steeper. A bulge in bathymetric contours beyond and east of the trough mouth indicates some slope progradation. Elsewhere, seismic-reflection profiles indicate major shelf aggradation and minor slope progradation. Networks of gullies and channels dominate the slope adjacent to Pine Island Bay. In front of the trough mouth, gullies at the shelf edge and uppermost slope connect directly with channels that continue to the continental rise. Other gullies connect indirectly with channels further downslope. TOPAS records indicate that gully-channel systems acted as conduits for coarse-grained sediment transfer. Cores comprise turbidites representing channel deposits and diamicton facies deposited by debris flows. Sandy turbidites interbedded with hemipelagic muds occur on the rise and abyssal plain. The West Antarctic Ice Sheet extended to the shelf edge during full glacials, delivering water-saturated till and turbid water directly to the continental slope along a line source. Gully-channel systems are probably a product of sediment gravity flows derived from the release of water-saturated till and turbid water along the ice-sheet margin, perhaps augmented subsequently by downslope flow of dense cold and saline water associated with sea-ice production during the Holocene. The gully-channel systems enable sediment to bypass the continental slope. Spatial variations in gully-channel system morphology along the Amundsen Sea continental slope are probably linked to differences in sediment gravity flow processes and the rate and composition of sediment delivered to the shelf edge from the ice sheet. Cored sediments on the slope and abyssal plain record the widespread presence of turbidite sands, indicating that downslope transfer of glacier-derived sediments has taken place. This supports our interpretation that submarine channels are derived from, and are conduits for, mass wasting. Submarine channels on the upper slope continue into the abyssal plain as far north as 67°S. They are separated by sediment drifts and sediment waves resulting from the interaction between downslope turbidity current processes and along-slope bottom currents. Similar deep-sea sedimentary processes operate along much of West Antarctica and the western side of the Antarctic Peninsula. [ABSTRACT FROM AUTHOR]

The pattern of late Weichselian (ca. 20 ka) ice fl ow in the northern Barents Sea is not well known, due mainly to a lack of marine data east of Svalbard. Several years with little summer sea ice have allowed acquisition of swath-bathymetric imagery of well-preserved subglacial landforms characterizing late Weichselian ice-fl ow directions over ∼150,000 km2 of the northwestern Barents Sea. We show that a major ice dome was located on easternmost Spitsbergen or southern Hinlopen Strait, at least 500 km west of its previously inferred position in the northern Barents Sea. This dome controlled the regional fl ow pattern; ice fl owed eastward around Kong Karls Land into Franz Victoria Trough and north through Hinlopen Strait. An ice dome west of Kong Karls Land is required to explain the observed ice-fl ow pattern, but does not preclude an additional ice dome to the southeast. Discrepancies with earlier ice-sheet reconstructions reflect the lack of previous seafl oor observations, with evidence limited mainly to past ice loading and postglacial rebound. The new pattern of ice-fl ow directions shows predominantly eastward rather than northward flow, with Franz Victoria Trough a major drainage pathway with a full-glacial balance fl ux of >40 km3 yr-1. [ABSTRACT FROM AUTHOR]