Search

Palaeoclimate changes, such as the Medieval Climate Anomaly and the Little Ice Age, are well-defined in the Northern Hemisphere during the past 2000 years. In contrast, these anomalies appear to be either absent, or less well-defined, in high-latitude regions of the Southern Hemisphere. Here, we inferred environmental changes during the past two millennia from proxies in a sediment core from Mago Ike, an East Antarctic lake in Skarvsnes (Lützow Holm Bay). Variations in lake primary production were inferred from fossil pigments, sedimentological and geochemical proxies and combined with absolute diatom counts to infer past diatom productivity and community changes. Three distinct stratigraphic zones were recognized, resulting from a shift from marine to lacustrine conditions with a clear transition zone in between. The presence of open-water marine diatoms indicates a coastal zone seasonally free of sea ice between c. 2120–1500 cal yr bp. Subsequently, the lake became isolated from the ocean due to isostatic uplift. Freshwater conditions were established from c. 1120 cal yr bp onwards after which the proxies are considered highly sensitive to temperature changes. There is no evidence for a Medieval Climate Anomaly, Little Ice Age or twentieth century warming in our lake sediment record suggesting that studies that have imposed Northern Hemisphere climate anomalies onto Southern Hemisphere palaeoclimate records should be treated with caution. [ABSTRACT FROM AUTHOR]

The Antarctic Ice Sheet (AIS) is the largest potential source for future global sea level rise. However, there are widely diverging estimates of its contribution, which emphasizes the need to improve our understanding of the long‐term behavior of the AIS and its impact on the solid Earth. This knowledge gap results from a shortage of records of glacial history, especially for the pre‐Holocene. Marine transgression and recession in the coastal areas of Antarctica are influenced by the mass of the overlying ice, providing crucial information about regional ice sheet dynamics. In this study, we determined a marine transgression from 53 kyr BP onward by diatom assemblages and a δ13C‐C/N biplot for the organic component in a sediment core (MCM2), from the Larsemann Hills in East Antarctica. Relative sea level (RSL) reached a maximum of ~12 m a.p.s.l. (above present sea level) during 38–29 kyr BP. Concurrent with the transgression, the regional crust experienced glacial‐isostatic‐adjustment (GIA)‐induced subsidence from ~75 to ~95 m beneath the present land level, suggesting an expansion trend of the East Antarctic ice sheet (EAIS), which may have outpaced global cooling. After the last deglaciation, the RSL rose to a highstand of ~8–10 m a.p.s.l. at ~8.5–7.1 kyr BP, when the bedrock uplifted to ~20 m below the present level. After 4.0 kyr BP, both regional and global deglaciation ceased, but an effect of ongoing relaxation caused the land to rebound continuously at a uniform rate of ~1.5 m/kyr, which can account for the sustained fall of RSL across Antarctica since mid‐Holocene. Key Points: A marine transgression period was constrained to 53–29 kyr BP at the Larsemann Hills, East AntarcticaWe provide a synthesis of the relative sea level changes and GIA‐induced displacement of the Larsemann Hills in the last 50 kyrThe ongoing relaxation process of GIA account for the sustained fall of the relative sea level since mid‐Holocene [ABSTRACT FROM AUTHOR]

The East Antarctic Ice Sheet has relatively few field data to constrain its past volume and contribution to global sea-level change since the Last Glacial Maximum. We provide new data on deglaciation history and develop new relative sea-level (RSL) curves along an 80 km transect (from Skallen to Skarsvnes, Langhovde and the Ongul Islands) in Lützow Holm Bay, East Antarctica. The geological constraints were compared with output from two Glacial Isostatic Adjustment (GIA) models. The minimum radiocarbon age for regional deglaciation is c. 11,240 cal. yr BP on West Ongul Island with progressively younger deglaciation ages approaching the main regional ice outflow at Shirase Glacier. Marked regional differences in the magnitude and timing of RSL change were observed. More in particular, in Skarvsnes a minimum marine limit of 32.7 m was inferred, which is c. 12.7 m higher than previously published evidence, and at least 15 m higher than that reported in the other three ice-free areas. Current GIA model predictions slightly underestimate the rate of Late Holocene RSL fall at Skallen, Langhovde, and West Ongul, but provide a reasonable fit to the reconstructed minimum marine limit at these sites. GIA model predictions are unable to provide an explanation for the shape of the reconstructed RSL curve at Skarvsnes. We consider a range of possible explanations for the Skarvsnes RSL data and favour an interpretation where the anomalously high marine limit and rate of RSL fall is due to reactivation of a local fault. [ABSTRACT FROM AUTHOR]