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Knowledge of microparticle geometry is essential for accurate calculation of ice core volume-related dust metrics (mass, flux, and particle size distributions) and subsequent paleoclimate interpretations, yet particle shape data remain sparse in Antarctica. Here we present 41 discrete particle shape measurements, volume calculations, and calibrated continuous particle time series spanning 50–16 ka from the South Pole Ice Core (SPC14) to assess particle shape characteristics and variability. We used FlowCAM, a dynamic particle imaging instrument, to measure aspect ratios (width divided by length) of microparticles. We then compared those results to Coulter counter measurements on the same set of samples as well as high-resolution laser-based (Abakus) data collected from SPC14 during continuous flow analysis. The 41 discrete samples were collected during three periods of millennial-scale climate variability: Heinrich Stadial 1 (18–16 ka , n=6 ; ∼250 years per sample), the Last Glacial Maximum (LGM) (27–18 ka , n=19 ; ∼460 years per sample), and during both Heinrich Stadial 4 (42–36 ka , n=8 ; ∼620 years per sample) and Heinrich Stadial 5 (50–46 ka , n=8 ; ∼440 years per sample). Using FlowCAM measurements, we calculated different particle size distributions (PSDs) for spherical and ellipsoidal volume estimates. Our calculated volumes were then compared to published Abakus calibration techniques. We found that Abakus-derived PSDs calculated assuming ellipsoidal, rather than spherical, particle shapes provide a more accurate representation of PSDs measured by Coulter counter, reducing Abakus to Coulter counter flux and mass ratios from 1.82 (spherical assumption) to 0.79 and 1.20 (ellipsoidal assumptions; 1 being a perfect match). Coarser particles (>5.0 µm diameter) show greater variation in measured aspect ratios than finer particles (<5.0 µm). While fine particle volumes can be accurately estimated using the spherical assumption, applying the same assumption to coarse particles has a large effect on inferred particle volumes. Temporally, coarse and fine particle aspect ratios do not significantly change within or among the three time periods (p value >0.05), suggesting that long-range transport of dust is likely dominated by clay minerals and other elongated minerals. [ABSTRACT FROM AUTHOR]

The timing of the first appearance of animals is of crucial importance for understanding the evolution of life on Earth. Although the fossil record places the earliest metazoans at 572–602 Ma, molecular clock studies suggest a far earlier origination, as far back as ~850 Ma. The difference in these dates would place the rise of animal life into a time period punctuated by multiple colossal, potentially global, glacial events. Although the two schools of thought debate the limitations of each other's methods, little time has been dedicated to how animal life might have survived if it did arise before or during these global glacial periods. The history of recent polar biota shows that organisms have found ways of persisting on and around the ice of the Antarctic continent throughout the Last Glacial Maximum (33–14 Ka), with some endemic species present before the breakup of Gondwana (180–23 Ma). Here we discuss the survival strategies and habitats of modern polar marine organisms in environments analogous to those that could have existed during Neoproterozoic glaciations. We discuss how, despite the apparent harshness of many ice covered, sub‐zero, Antarctic marine habitats, animal life thrives on, in and under the ice. Ice dominated systems and processes make some local environments more habitable through water circulation, oxygenation, terrigenous nutrient input and novel habitats. We consider how the physical conditions of Neoproterozoic glaciations would likely have dramatically impacted conditions for potential life in the shallows and erased any possible fossil evidence from the continental shelves. The recent glacial cycle has driven the evolution of Antarctica's unique fauna by acting as a "diversity pump," and the same could be true for the late Proterozoic and the evolution of animal life on Earth, and the existence of life elsewhere in the universe on icy worlds or moons. [ABSTRACT FROM AUTHOR]

The Larsemann Hills, near Prydz Bay is a key region to understand past glacial dynamics in East Antarctica. However, multi-proxy dating constraints for this area indicate an uncertain chronology for deglaciation history during the Last Glacial Period (LGP). In this paper, we report two 26Al exposure ages and eighteen 10Be exposure ages for bedrock samples to better understand past glacial histories. The minimum exposure ages range from 82.84 ± 4.67 ka to 15.1 ± 1.95 ka corresponding to Marine Isotope Stages (MIS) 5–2, and fourteen of these samples date from before the global Last Glacial Maximum (c. 19–26.5 ka). Analysis of 10Be and 26Al concentrations implies a complex deglaciation history, and surface lowering of bedrock may have caused systematic age underestimation. Further comparisons between two adjacent regions in the Mirror Peninsula reveal two major deglaciations involving the Lambert Glacier / Amery Ice Shelf System dated at 61.78 ka to 82.84 ka and 21.98 ka to 49.5 ka during the LGP. • We present new evidence for studying glacial history of Larsemann Hills, Antarctica. • Cosmogenic nuclides 10Be and 26Al dating method is applied for better analysis. • Two major deglaciation events occurred regionally within MIS 2–3 and MIS 4–5. • The exposure age and elevation show a highly significant positive correlation. • Multi-proxy and adjacent evidence are summarized and compared with this study. [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]

An accurate reconstruction of the Antarctic Ice Sheet is essential in order to develop an understanding of ice-sheet responses to global climate changes. However, the erosive nature of ice-sheet expansion and the difficulty of accessing much of Antarctica make it challenging to obtain field-based evidence of ice-sheet and sea-level changes before the Last Glacial Maximum. Limited sedimentary records from Lützow-Holm and Prydz Bays in East Antarctica demonstrate that the sea level during Marine Isotope Stage 3 was close to the present level despite the global sea-level drop lower than -40 m. We demonstrate glacial isostatic adjustment modeling with refined Antarctic Ice Sheet loading histories. Our experiments reveal that the Indian Ocean sector of the Antarctic Ice Sheet would have been required to experience excess ice loads before the Last Glacial Maximum in order to explain the observed sea-level highstands during Marine Isotope Stage 3. As such, we suggest that the Antarctic Ice Sheet partly reached its maximum thickness before the global Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The East Antarctic Ice Sheet (EAIS) is the largest glacial system in the world, and the evolution history of the EAIS strongly affects global climate change. As one of the most extensive ice-free areas in coastal East Antarctica, the Larsemann Hills represent an important site for understanding the glacial evolution of East Antarctica. Generally, the last exposure process in the Larsemann Hills was considered to occur in the last glacial period. However, the initial time of the last exposure process in the Larsemann Hills remains unclear. This study presents the 10Be exposure ages of eight bedrock samples with glacial striae, which means that the original uneroded surfaces are preserved, from the Larsemann Hills and neighboring areas. The 10Be exposure ages ranging from 70.7 ± 4.7 to 13.5 ± 1.2 ka indicate that the Larsemann Hills have become ice-free since MIS4. The 10Be exposure ages with the characteristics of zonal distribution in the E–W direction and ages generally change from north to south, which reveals the combination of glacial retreat and topography differences. The activity of the ice sheet in the Larsemann Hills did not respond to the Last Glacial Maximum (LGM). In contrast, the deglaciation in the Larsemann Hills occurred as a diachronous process during the global last glacial periods, which began long before the LGM and lasted after the LGM. According to the exposure ages in the Larsemann Hills and the distance from the edge of the ice sheet, the average glacial retreat rate since MIS4 has been 71.57 m/ka. [ABSTRACT FROM AUTHOR]

Environmental conditions were particularly severe during the Last Glacial Maximum, altering the distribution of the Southern Hemisphere biota, particularly at higher latitudes. The copepod Boeckella poppei is the only macroscopic continental invertebrate species known to be distributed today across the three main biogeographic regions in Antarctica as well as in southern South America. Signy Island (South Orkney Islands) is a unique location for the study of Antarctic freshwater ecosystems due to its location and geographic isolation; it contains 17 lakes in several low altitude catchments. We conducted phylogeographic and demographic analyses using the cox1 gene on 84 individuals of B. poppei from seven lakes across Signy Island. We recorded low levels of genetic diversity and a strong genetic differentiation signal between the eastern and western valleys within the island. Phylogeographic structure and demographic inference analyses suggested at least one asymmetrical dispersal event from west to east. Demographic inference detected a strong signal of population growth during the deglaciation process, which may have followed either (1) a strong genetic bottleneck due to a reduction in population size during the last glacial period, or (2) a founder effect associated with postglacial recolonization of Signy Island from elsewhere. The genetic architecture of this island's populations of B. poppei shows that historical events, rather than continuous dispersal events, likely played a major role in the species' current distribution. Finally, our study considers possible mechanisms for dispersal and colonization success of the most dominant species in the Antarctic freshwater community. [ABSTRACT FROM AUTHOR]

• Abrupt mid-Holocene ice sheet thinning in western Weddell Sea Embayment since LGM. • At least 385 m of ice surface lowering revealed by in situ 14C exposure dating. • Glacial-geological data neither preclude nor mandate late Holocene ice thinning. The glacial history of the westernmost Weddell Sea sector of Antarctica since the Last Glacial Maximum is virtually unknown, and yet it has been identified as critical for improving reliability of glacio-isostatic adjustment models that are required to correct satellite-derived estimates of ice sheet mass balance. Better knowledge of the glacial history of this region is also important for validating ice sheet models that are used to predict future contribution of the Antarctic ice sheet to sea level rise. Here we present a new Holocene deglacial chronology from a site on the Lassiter Coast of the Antarctic Peninsula, which is situated in the western Weddell Sea sector. Samples from 12 erratic cobbles and 18 bedrock surfaces from a series of presently-exposed ridges were analysed for cosmogenic 10Be exposure dating, and a smaller suite of 7 bedrock samples for in situ 14C dating. The resulting 10Be ages are predominantly in the range 80–690 ka, whereas bedrock yielded much younger in situ 14C ages, in the range 6.0–7.5 ka for samples collected from 138–385 m above the modern ice surface. From these we infer that the ice sheet experienced a period of abrupt thinning over a short time interval (no more than 2700 years) in the mid-Holocene, resulting in lowering of its surface by at least 250 m. Any late Holocene change in ice sheet thickness — such as re-advance, postulated by several modelling studies — must lie below the present ice sheet surface. The substantial difference in exposure ages derived from 10Be and 14C dating for the same samples additionally implies ubiquitous 10Be inheritance acquired during ice-free periods prior to the last deglaciation, an interpretation that is consistent with our glacial-geomorphological field observations for former cold-based ice cover. The results of this study provide evidence for an episode of abrupt ice sheet surface lowering in the mid-Holocene, similar in rate, timing and magnitude to at least two other locations in Antarctica. [ABSTRACT FROM AUTHOR]

Here we summarize the motivation and issues surrounding the responses of ice sheets and sea level to past climate warming as part of the PALeo constraints on SEA level rise (PALSEA) working group. Papers in this special issue of Quaternary Science Reviews focus on the timescale of glaciations during the late Pliocene, the magnitude of ice-sheet fluctuations and volume leading up to and during the last glacial maximum, the timing and persistence of ice-sheet impacts on deglacial and future relative sea-level change, and relative sea-level change during peak interglacial climate. A more dynamic cryosphere is noted under both late Pliocene and last glacial cycle climate conditions, while relative sea-level changes during the last deglaciation appear to correspond closely with individual ice-sheet deglaciation. Lastly, relative sea-level change during peak interglacial conditions may have fluctuated by as much as a meter, although the sources of such variability (Greenland, Antarctica or elsewhere) remain elusive. [ABSTRACT FROM AUTHOR]

Calculating cosmogenic-nuclide surface-exposure ages is critically dependent on a knowledge of the altitude of the sample site. Changes in altitude have occurred through time as a result of glacial isostatic adjustment (GIA), potentially altering local nuclide production rates and, therefore, surface-exposure ages. Here we assess the impact of GIA on surface-exposure dating by calculating global time-dependent production rates since the Last Glacial Maximum using surface elevations that were corrected and uncorrected for GIA. We find that the magnitude of the GIA effect is spatially and temporally variable. Nuclide production could be reduced by up to 50% in the interior of large ice masses (in North America, Scandinavia and West Antarctica) at times of maximum glacial isostatic depression. Although smaller, the effect is still significant at ice sheet margins, where nuclide production is reduced by >5% and potentially >10%, making exposure ages older in those areas. Away from the ice sheet margins, land surfaces can be isostatically elevated, which can increase nuclide production by >5% and, therefore, make exposure ages younger. Areas that were more recently exposed or that are distal to large ice masses will generally be less affected. Importantly, we find that the effect at the primary 10Be production calibration sites is <1%. Applying a GIA correction to surface-exposure data may help resolve mismatches between some chronologies, but not necessarily in all regions, implying that additional factors may need to be considered. Past atmospheric changes can amplify or reduce the impact of GIA on nuclide production, and the combined effects should be fully accounted for in the future. These time-dependent influences on surface-exposure dating have potentially important implications for interpreting chronologies and for using the data to constrain ice sheet models. • Glacial isostatic adjustment (GIA) can make exposure age estimates older or younger. • Nuclide production can be reduced by up to 50% from isostatic depression. • The GIA effect at the primary 10Be production rate calibration sites is negligible. • Correcting existing exposure datasets can make ages up to ∼2,500 years (15%) older. • Atmospheric changes may amplify or reduce the impact of GIA on exposure ages. [ABSTRACT FROM AUTHOR]

Milankovitch orbital parameters control cycles of insolation, a primary pacer of long term changes in climate, but exactly how insolation signals are transmitted around the globe in the climate system is unclear. In order to address the fundamental questions of when and how ice age climates begin and end, how fast glaciers retreated during the last deglaciation, and how glaciers behaved before anthropogenic influence, we need robust glacial chronologies. The timing of local glacial maxima beyond the last glacial cycle, however, has remained largely unconstrained due to moraine degradation over time, limiting our ability to fully explore these questions. By developing a detailed geomorphic surficial map and targeting relatively tall, ridge-top boulders, we have constructed a new, precise 10Be chronology of glacial maxima of the Ñirehuao glacier lobe (45°S) for the last two glacial cycles. We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia, which formed a major set of moraines by at least 153 ± 5.1 ka, with a stillstand or smaller readvance by 137 ± 4.2 ka, corresponding to the two coldest and dustiest periods of MIS 6 in Antarctica. The next largest advance occurred at 23.6 ± 0.9 ka, at the end of peak Southern Hemisphere MIS 2 cooling. Retreat of the glacier commenced by ∼18.5 cal ka BP when lakes in a tributary valley just to the southwest became ice-free. Overall we find that advances of the Ñirehuao glacier lobe occur when winter sea ice around Antarctica is expansive and both obliquity and eccentricity are at their minima. • We present a new, detailed geomorphic map and 10Be chronology of the Ñirehuao glacier lobe for the last two glacial cycles • We report one of the first directly dated records of a MIS 6 glacier advance in Patagonia • The Ñirehuao glacier lobe formed a major set of moraines by 153±5.1 ka with a stillstand or smaller readvance by 137±4.2 ka • The MIS 2 glacial maximum occurred at 23.6±0.9 ka and subsequent retreat of the glacier commenced by ∼18.5 cal ka BP • Overall, advances occurred when winter sea ice around Antarctica was expansive and obliquity and eccentricity were at minima [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]

In the modern climate, the ocean below 2 km is mainly filled by waters sinking into the abyss around Antarctica and in the North Atlantic. Paleoproxies indicate that waters of North Atlantic origin were instead absent below 2 km at the Last Glacial Maximum, resulting in an expansion of the volume occupied by Antarctic origin waters. In this study we show that this rearrangement of deep water masses is dynamically linked to the expansion of summer sea ice around Antarctica. A simple theory further suggests that these deep waters only came to the surface under sea ice, which insulated them from atmospheric forcing, and were weakly mixed with overlying waters, thus being able to store carbon for long times. This unappreciated link between the expansion of sea ice and the appearance of a voluminous and insulated water mass may help quantify the ocean's role in regulating atmospheric carbon dioxide on glacial-interglacial timescales. Previous studies pointed to many independent changes in ocean physics to account for the observed swings in atmospheric carbon dioxide. Here it is shown that many of these changes are dynamically linked and therefore must co-occur. [ABSTRACT FROM AUTHOR]

Abstract: The Last Glacial Maximum (LGM; ca 23–19 ka BP) extent of grounded ice in the Filchner Trough, a major cross shelf trough extending seaward from the Filchner Ice Shelf in the southern Weddell Sea, has been much debated. Here we present data from the first extensive multibeam swath bathymetry and sub-bottom acoustic profiling surveys in the Filchner Trough that include several parallel survey lines with overlapping swaths. We interpret these new data, combined with published observations and radiocarbon dates from sediment cores, as indicating that the grounding line in the Filchner Trough during the LGM advanced beyond the middle shelf, probably to within 40 km of the shelf break, and possibly reached the shelf break. Three different hypotheses are discussed that could reconcile this interpretation with interpretations, based on ice coring and surface exposure age data, that LGM ice surface elevations in areas draining into the Filchner and Ronne ice shelves were no more than a few hundred metres higher than today: (1) ice plain conditions extended along most of the Filchner Trough; (2) the ice shelf advanced and thickened so that it “touched down” on the continental shelf for a short period; (3) LGM ice drainage pathways in the interior of the Weddell Sea embayment were different from those observed today. [Copyright &y& Elsevier]

Abstract: The marine geological record of the glacial-retreat history of the South Shetland Islands is derived from the integration of seismic data, core lithofacies, radiocarbon ages and geomorphological data from two study areas. On the northern shelf, we present one of the first published multibeam bathymetric images of the seafloor. This new image combined with descriptions of new and existing short sediment cores and high-resolution seismic data from the continental shelf north of King George Island are used to map a grounding zone wedge that marks the minimum seaward extent of the South Shetland Ice Cap during the Last Glacial Maximum. Seismic data, multibeam bathymetry, and sediment cores from Maxwell Bay, on the opposite side of King George Island, are used to provide further spatial constrains on the history of grounding and retreat of the ice cap along the southern margin of the South Shetland Islands. During the Last Glacial Maximum the South Shetland Ice Cap extended onto the outer continental shelf, some 50 km north of its present location. The ice grounded on the shelf in troughs in present water depths of almost 400 m. It had a minimum thickness of ∼570 m and was also grounded in the deepest part of fjords and straits between the islands. To the south, the ice cap extended seaward of the mouths of fjords and straits to the steep northern boundary of the Bransfield Strait. Sediment eroded from the fjords and straits was deposited in prominent fans that extend into the Bransfield Strait and show evidence for an ice shelf that covered the Bransfield Strait during the Last Glacial Maximum. A long drill core (SHALDRIL) in Maxwell Bay and several jumbo piston cores yielded carbonate material used to constrain the timing and spatial extent of glacial retreat within Maxwell Bay. The oldest glacimarine sediments in the fjord date back to ∼14.1 to ∼14.8 ka and suggest an initial deglaciation earlier than most previous studies of the South Shetland Islands. Upper Maxwell Bay was ice free by 9.1 ka and most of Maxwell Bay proper was ice free by 5.9 ka except for the smaller tributary fjords of Maxwell Bay. These smaller tributary fjords were ice free by 1.7 ka, but may have been ice free earlier but reoccupied by a neoglacial advance that ended approximately 1.7 ka. [Copyright &y& Elsevier]

Geomorphic reconstructions of the East Antarctic Ice Sheet history across Antarctica suggest diachronous and varying retreat patterns with changing climate. However, little is known of how terrestrial environments responded to these climate changes because the continental ice sheet covered most Antarctic coastal oases during the Last Glacial Maximum (LGM), eliminating terrestrial records. In this study, the environmental history spanning the last 25,400 years was reconstructed using geochronology, lithology, rock magnetism and geochemistry to understand the effect of glacial–deglacial climate variations on surface processes and Mochou Lake ecology. During the last glacial period (25.4 to 18.8 cal. kyr BP), intensified winds and the freeze-thaw action of ice actively weathered the high elevation western catchment that was a dominant sediment source to the lake. The glacial environmental conditions induced a persistent perennial lake ice-cover resulting in anoxia, low sedimentation, primary production and weak brackish conditions. Progressively, as deglacial conditions augmented around 18.8 cal. kyr BP, increased catchment meltwater flow enhanced sediment transport and also transformed the lake into a freshwater basin, although perennial ice-cover still prevailed. Further, the biotic development of the lake began later in the Mid-Holocene as compared to other lakes in the region, wherein the seasonal lake ice cycle and/or ice moat developed. Weak chemical weathering and pedogenesis also commenced in the catchment in response to the warming climate trend. This delayed response to the Holocene warming was possibly due to the local cooling effect of the Dälk Glacier's discharge that also led to sea-ice persistence in the Prydz Bay. This study also provides further evidence that parts of the Larsemann Hills remained free of erosive grounded ice during the LGM and subsequent deglaciation. The Mirror Peninsula, specifically, escaped ice overriding despite being enclosed by the Dälk Glacier, Lake Nella ice lobe and Amery Ice Shelf. [Display omitted] • A multi-proxy record of glacial-deglacial environment change from lake sediments. • The regional weathering changes are due to geomorphic and atmospheric factors. • Variations in lake ice cover across warming phases limited biogenic productivity. [ABSTRACT FROM AUTHOR]

The increased flux of soluble iron (Fe) to the Fe-deficient Southern Ocean by atmospheric dust is considered to have stimulated the net primary production and carbon export, thus promoting atmospheric CO2 drawdown during glacial periods. Yet, little is known about the sources and transport pathways of Southern Hemisphere dust during the Last Glacial Maximum (LGM). Here we show that Central South America (~24‒32°S) contributed up to ~80% of the dust deposition in the South Pacific Subantarctic Zone via efficient circum-Antarctic dust transport during the LGM, whereas the Antarctic Zone was dominated by dust from Australia. This pattern is in contrast to the modern/Holocene pattern, when South Pacific dust fluxes are thought to be primarily supported by Australian sources. Our findings reveal that in the glacial Southern Ocean, Fe fertilization critically relies on the dynamic interaction of changes in dust-Fe sources in Central South America with the circumpolar westerly wind system. Dust deposition brings iron that fuels ocean productivity, a connection impacting climate over geological time. Here the authors use sediment cores to show that in contrast to dynamics today, during the last glacial maximum westerly winds shuttled dust from Australia and South America around Antarctica and into the South Pacific. [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]

The Jangbogo Hills are erratic-covered landforms consisting of a series of benches that are parallel to the length of Campbell Glacier, northern Victoria Land, Antarctica. We sampled 41 erratic cobbles from six benches to reveal the exposure times of glacier erratics using in situ 10Be and 26Al. The erratics from the upper three benches yield exposure ages older than Marine Isotope Stage (MIS) 4, with most exposed since MIS 5. However, the lower three benches exhibit tight clusters of exposure ages that range from MIS 3 to the Holocene. Campbell Glacier underwent rapid downwasting during MIS 5, centered at 98.3 ka from its maximum position at the penultimate glacial maximum (PGM). This downwasting continued throughout the last glacial period, with a potential minor stagnation around a bench (∼90 m asl) between 35.4 and 17.0 ka. Our cosmogenic nuclides surface exposure dating results highlight three important points concerning the glacial history of Terra Nova Bay since the penultimate glacial maximum (PGM) in northern Victoria Land, Antarctica: 1) Campbell Glacier was thicker at the PGM than at the global last glacial maximum (LGM); 2) the local LGM occurred during MIS 4; and 3) the extent of Campbell Glacier during the global LGM (90 m) was much smaller than previously assumed (300–400 m). Hence, the previous view that the local LGM (MIS 4) in Victoria Land, Antarctica was synchronous with the global LGM (MIS 2) should be treated with caution. • >500 m lower ice surface in Terra Nova Bay at the last glacial maximum compared with the penultimate glacial maximum. • Local LGM occurred at MIS 4 or 3, before 37 ka. • Campbell Glacier has undergone downwasting since MIS 3, with a possible minor MIS 2 stagnation. • Glacier expansion was stagnated during the global last glacial maximum which is consistent with other areas in Victoria Land. • Campbell Glacier has thinned by > 300 m since MIS 5. [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]

The author discusses the existence of life on the Antarctic continent. Topics include existence of remnant species in the extreme ice cover of Last Glacial Maximum during the Pleistocene epoch, geothermal hypothesis stating hat some life in Antarctica survived glaciation as a result of thermal refugia, and quantitative data needed to connect geography to the geophysics of thermal propagation.