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Future climate and sea-level projections depend sensitively on the response of the Antarctic Ice Sheet to ocean-driven melting and the resulting freshwater fluxes into the Southern Ocean. Incursion of Circumpolar Deep Water (CDW) across the Antarctic continental shelf, and into cavities beneath ice shelves, is increasingly recognised as a crucial heat source for ice shelf melt. Quantifying past changes in the temperature of CDW is therefore of great benefit for modelling ice sheet response to past warm climates, for validating paleoclimate models, and for putting recent and projected changes in CDW temperature into context. Here we synthesise the few available bottom water temperature reconstructions representative of CDW and its principal source water mass (North Atlantic Deep Water) over the past 800 kyr. Estimated CDW temperature anomalies consistently reached ca. −2 °C during glacial periods, warming to +0.1 to +0.5 °C during the strongest interglacials (marine isotope stages MIS 11, 9, 5, and 1). The temperature anomaly in MIS 7 was comparatively cooler at ca. −0.6 °C. Despite high variance amongst a small number of records, and poor (4 kyr) temporal resolution, we find persistent and close relationships between our estimated CDW temperature and Southern Ocean sea-surface temperature, Antarctic surface air temperature, and global ocean temperature reconstructions at glacial cycle time scales. Given the important role that CDW plays in connecting the world's three main ocean basins, and in driving Antarctic Ice Sheet mass loss, additional temperature reconstructions targeting CDW are urgently needed to increase temporal resolution and to decrease uncertainty in past CDW temperatures – whether for use as a boundary condition, model validation or in their own right. [ABSTRACT FROM AUTHOR]

The Transantarctic Mountains are an important corridor between the East Antarctic Ice Sheet and the Western Ross Sea, where most current ice streams and outlet glaciers arise. We investigated Ricker Hills, the largest exposed mountainous region between Southern Victoria Land and Terra Nova Bay, and dated the glacial landforms using in-situ cosmogenic-nuclide 10Be surface exposure dating to reconstruct the paleo-glacial dynamics. The surface of the Hollingsworth glacier lowered since the middle of Marine Isotope Stage (MIS) 2 (22.1 ka); therefore, the Last Glacial Maximum (LGM) occurred before that period. Cosmogenic, geomorphic, and climatic records constrained the glacial surface slope to be between 5.4° and 6.8°. The ice was 270–320 m thicker at the LGM (MIS 2) than presently but did not override the top surface of the Benson Knob. Moreover, previous glacial periods such as the local LGM (MIS 4) or Penultimate Glacial Maximum (MIS 6) maintained thicker ice than the LGM (MIS 2). The Ross Ice Shelf opening during the mid-Holocene (∼6 ka) caused the rapid collapse of the terminal outlet glaciers and supplied notable snow accumulation upstream, which stagnated lowering. The greatest lowering and retreat occurred during the late Holocene (2.3 ∼ 0.8 ka), when elephant seal colonies thrived in the Ross Embayment. [ABSTRACT FROM AUTHOR]

High-resolution seismic data from the Sabrina Coast continental shelf, East Antarctica, elucidate the Cenozoic evolution of the East Antarctic Ice Sheet. Detailed seismic stratigraphic and facies analysis reveal the Paleogene to earliest Pliocene glacial evolution of the Aurora Basin catchment, including at least 12 glacial expansions across the shelf indicated by erosional surfaces and chaotic acoustic character of strata. Differences in facies composition and seismic architecture reveal several periods of ice-free conditions succeeded by glacial expansions across the shelf. A deep (~100 m), undulating erosional surface suggests the initial appearance of grounded ice on the shelf. Following the initial ice expansion, the region experienced an interval of open-marine to ice-distal conditions, marked by an up to 200-m-thick sequence of stratified sediments. At least three stacked erosional surfaces reveal major cross-shelf glacial expansions of regional glaciers characterized by deep (up to ~120 m) channel systems associated with extensive subglacial meltwater. The seismic character of the sediments below the latest Miocene to earliest Pliocene regional unconformity indicates intervals of glacial retreat interrupted by advances of temperate, meltwater-rich glacial ice from the Aurora Basin catchment. Our results document the Paleogene to late Miocene glacial history of this climatically sensitive region of East Antarctica and provide an important paleoenvironmental context for future scientific drilling to constrain the regional climate and timing of Cenozoic glacial variability. [ABSTRACT FROM AUTHOR]

Reconstructing the advance and retreat of past ice sheets provides important long-term context for recent change(s) and enables us to better understand ice sheet responses to forcing mechanisms and external boundary conditions that regulate grounding line retreat. This study applies various radiocarbon dating techniques, guided by a detailed sedimentological analyses, to reconstruct the glacial history of Anvers-Hugo Trough (AHT), one of the largest bathymetric troughs on the western Antarctic Peninsula (WAP) shelf. Existing records from AHT indicate that the expanded Antarctic Peninsula Ice Sheet (APIS) advanced to, or close to, the continental shelf edge during the Last Glacial Maximum (LGM; 23-19 cal kyr BP [ = calibrated kiloyears before present]), with deglaciation of the outer shelf after ∼16.3 cal kyr BP. Our new chronological data show that the APIS had retreated to the middle shelf by ∼15.7 cal kyr BP. Over this 600-year interval, two large grounding-zone wedges (GZW) were deposited across the middle (GZW2) and inner shelf (GZW3), suggesting that their formation occurred on centennial rather than millennial timescales. Expanded sequences of sub-ice shelf sediments occur seaward of the inner GZW3, which suggests that the grounding line remained stationary for a prolonged period over the middle shelf. Grounding-line retreat rates indicate faster retreat across the outer to middle shelf compared to retreat across the middle to inner shelf. We suggest that variable retreat rates relate to the broad-scale morphology of the trough, which is characterised by a relatively smooth, retrograde seabed on the outer to middle shelf and rugged morphology with a locally landward shallowing bed and deep basin on the inner shelf. A slowdown in retreat rate could also have been promoted by convergent ice flow over the inner shelf and the availability of pinning points associated with bathymetric highs around Anvers Island and Hugo Island. • The deglacial history of Anvers-Hugo Trough is revealed by marine geological and geophysical data. • Application of multiple 14C dating methods allows reliable dating of ice sheet retreat. • Grounded ice had retreated to the mid-shelf by ∼15.7 cal kyr BP. • Retreat rates are controlled by the broad-scale morphology of the shelf. [ABSTRACT FROM AUTHOR]

Knowledge regarding the response of the East Antarctic Ice Sheet to glacial–interglacial climatic cycles in the late Pleistocene is critical to understanding the global climate system and projections of future sea level rise. Here, we observed notable glacial–interglacial cyclicity in magnetic properties, bulk detrital Sr–Nd isotopes, and Fe/Ti ratios over the previous 530 kyr in three well-dated gravity cores from the continental rise offshore of Prydz Bay (East Antarctica). Our results show that Antarctic continental sources with more Ti-rich magnetite, less radiogenic epsilon neodymium (ε Nd), and higher Fe/Ti ratios were predominant during glacials in comparison with interglacials. Specifically, the ε Nd amplitude through MIS 11–5 differs from that in the remainder of the records, which is also expressed in the magnetic coercivity cycles with subdued patterns. Following source identification on the basis of the detrital Sr–Nd distribution, we recognize two main (rock type) sources and infer two types of ice drainage flow pattern ("flank" and "channelized"), which follow different pathways in the Lambert Glacier–Amery Ice Shelf system (LG-AISS). The first follows an eastern path connecting the Ingrid Christensen Coast (flank), while the second follows a central channel via the LG-AISS (channelized) during MIS 11–5. Regular dynamics on glacial–interglacial timescales, manifested by changes in magnetic coercivity, are closely related to the modeled Antarctic ice volume and ice sheet movement, in which the second channelized pathway during MIS 11–5 corresponds to a 340-kyr-long episode with contiguous warmer-than-present Antarctic interglacials (MIS 11, 9, 7, and 5). Our records thus provide the clearest evidence so far of variable patterns of ice sheet dynamics during the late Pleistocene in the Prydz Bay sector of East Antarctica, which coincided with similar variation of ice drainage during the late Miocene–early Pliocene at around 1.13 Ma (ODP188). Similar ice drainage changes in these two periods imply that major ice flow reconfiguration can be triggered repeatedly by abrupt changes from a stable warm period to a cold one. The presented data not only reveal glacial–interglacial cyclicity in ice sheet advance and retreat in the meridional direction, but also implicate latitudinal adjustment (lateral) within a thin elongated drainage basin of the LG-AISS. • Ti-rich and Ti-poor magnetite dominate glacial and interglacial terrigenous material respectively eroded by ice sheet. • Detrital Sr/Nd show two end members from Archean―paleoproterozoic and Meso-Neoproterozoic outcrops from Prydz Bay sector. • Amplitude changes of ε Nd during MIS 11―MIS 5 produce three-stage shifts in terrigenous sources and ice sheet patterns. • "Channel" and "flank" erosion patterns are postulated respectively for MIS 11―MIS 5 and the remainder the last 530 kyr. • The long period of warmth during MIS 11―MIS 5 might correspond to the long eccentricity controlled Antarctic ice volume. [ABSTRACT FROM AUTHOR]

Reconstructing past ice-sheet surface changes is key to testing and improving ice-sheet models. Data constraining the past behaviour of the East Antarctic Ice Sheet are sparse, limiting our understanding of its response to past, present and future climate change. Here, we report the first cosmogenic multi-nuclide (10Be, 26Al, 36Cl) data from bedrock and erratics on nunataks along the Jutulstraumen and Penck Trough ice streams in western Dronning Maud Land, East Antarctica. Spanning elevations between 741 and 2394 m above sea level, the samples have apparent exposure ages between 2 ka and 5 Ma. The highest-elevation bedrock sample indicates (near-) continuous minimum exposure since the Pliocene, with a low apparent erosion rate of 0.15 ± 0.03 m Ma−1, which is similar to results from eastern Dronning Maud Land. In contrast to studies in eastern Dronning Maud Land, however, our data show clear indications of a thicker-than-present ice sheet within the last glacial cycle, with a thinning of ∼35–120 m during the Holocene (∼2–11 ka). Difficulties in separating suitable amounts of quartz from the often quartz-poor rock-types in the area, and cosmogenic nuclides inherited from exposure prior to the last deglaciation, prevented robust thinning estimates from elevational profiles. Nevertheless, the results clearly demonstrate ice-surface fluctuations of several hundred meters between the current grounding line and the edge of the polar plateau for the last glacial cycle, a constraint that should be considered in future ice-sheet model simulations. • Cosmogenic 26Al, 10Be, and 36Cl constrain past EAIS dynamics in Dronning Maud Land. • EAIS in western DML was at least 100–200 m thicker than present within last 25 ka. • EAIS in western DML was at least 150–300 m thicker within the last glacial cycle. • Ice-sheet thinning ∼35–120 m towards present ice sheet surface during the Holocene. • Short duration of Pleistocene ice covers >200 m above regional ice at Borgmassivet. [ABSTRACT FROM AUTHOR]

• Deglacial history of Pope Glacier reconstructed using surface exposure dating. • 560 m of early Holocene thinning at an average rate of 0.13 ± 0.09/0.04 m yr−1. • Thinning coincides with enhanced upwelling of warm water onto continental shelf. • Reduction in ice shelf buttressing may have triggered widespread glacier thinning. The Amundsen Sea sector of the Antarctic ice sheet presently dominates the contribution from Antarctica to sea level rise. Several large ice streams that currently drain the sector have experienced rapid flow acceleration, grounding line retreat and thinning during the past few decades. However, little is known of their longer-term – millennial-scale – retreat history, despite the reliance of several ice sheet and glacial-isostatic adjustment models on such data for improving sea level prediction from this critical region. This study investigates the timing and extent of surface lowering of one of those ice streams, Pope Glacier, since the Last Glacial Maximum (LGM), using glacial-geological evidence for former ice cover. We present a new deglacial chronology for the glacier, derived from surface exposure dating of glacially-deposited cobbles and ice-scoured bedrock from Mount Murphy and its surrounding peaks. Cosmogenic 10Be exposure ages from 44 erratic cobbles and 5 bedrock samples, and in situ 14C exposure ages from one erratic and 8 bedrock samples are predominantly in the range 5.5-16 ka. Although 10Be inheritance from prior exposure is prevalent in some erratics and probably all bedrock samples, none of the ages pre-date the LGM. From these results we infer that the surface of Pope Glacier lowered by 560 m during the early- to mid-Holocene (9-6 ka), at an average rate of 0.13 ± 0.09/0.04 m yr−1. The lowering coincided with a period of enhanced upwelling of warm Circumpolar Deep Water onto the continental shelf in the region. A reduction in buttressing − facilitated by such upwelling − by an ice shelf that is thought to have spanned the embayment until 10.6 cal kyr BP could have triggered simultaneous early Holocene thinning of Pope Glacier and glaciers elsewhere in the Amundsen Sea Embayment. [ABSTRACT FROM AUTHOR]

During the last glacial cycle, the Antarctic Ice Sheet (AIS) has passed from an interglacial state, warmer than present day (PD), slowly into a glacial state, known as the Last Glacial Maximum (LGM) and then deglaciated on a faster timescale into the Holocene and PD conditions. Although we have proxy data of the size and extent of the ice sheet for the LGM, neither the oceanic temperatures of the Southern Ocean, nor the precipitation fields are well constrained. Also the time evolution of the ice volume during the glacial cycle is not fully clear. It is well assumed that it follows a sawtooth pattern, but from a modelling perspective different combinations of parameters and boundary conditions can give rise to plausible Antarctic configurations. Here we aim to study the uncertainty in AIS evolution resulting from ice-sheet model parameters, as well as the imposed climatic fields used as forcing. For this purpose we use the three-dimensional thermomechanical hybrid ice-sheet-shelf model Yelmo, which treats ice dynamics via the shallow-ce and shallow-shelf approximations, and accounts for basal melt below ice shelves and a subgrid parameterisation for treatment of the grounding line. We will focus on the effect of different climatic fields, such as precipitation and oceanic temperatures, as well as the effect of different enhancement factors and basal drag choices for reproducing consistent Antarctic configurations in the LGM and the PD. Improving our understanding of the effect of different ice-dynamics configurations in various climatic scenarios will help to better understand the past evolution of the AIS and potentially constrain its future evolution as well. [ABSTRACT FROM AUTHOR]