Abstract
Understanding the response of the Antarctic ice sheets during the rapid climatic change that accompanied the last deglaciation has implications for establishing the susceptibility of these regions to future 21st Century warming. A unique diatom δ18O record derived from a high-resolution deglacial seasonally laminated core section off the west Antarctic Peninsula (WAP) is presented here. By extracting and analysing single species samples from individual laminae, season-specific isotope records were separately generated to show changes in glacial discharge to the coastal margin during spring and summer months. As well as documenting significant intra-annual seasonal variability during the deglaciation, with increased discharge occurring in summer relative to spring, further intra-seasonal variations are apparent between individual taxa linked to the environment that individual diatom species live in. Whilst deglacial δ18O are typically lower than those for the Holocene, indicating glacial discharge to the core site peaked at this time, inter-annual and inter-seasonal alternations in excess of 3‰ suggest significant variability in the magnitude of these inputs. These deglacial variations in glacial discharge are considerably greater than those seen in the modern day water column and would have altered both the supply of oceanic warmth to the WAP as well as regional marine/atmospheric interactions. In constraining changes in glacial discharge over the last deglaciation, the records provide a future framework for investigating links between annually resolved records of glacial dynamics and ocean/climate variability along the WAP.
Highlights
The East and West Antarctic Ice Sheets (EAIS/WAIS), accounting for 90% of the world's freshwater, play a major role in regulating the global climate system (Mayewski et al, 2009)
Such considerations are further complicated by temporal changes in the isotopic composition of glacial discharge, the relatively short timeframe, c. 500 years, analysed in this study suggests that these issues may be negligible over the documented interval
The construction of single-taxon and season-specific δ O 18 diatom records from the deglacial laminated interval at Palmer Deep (ODP Site 1098A), west Antarctic Peninsula (WAP), highlights the considerable potential that exists in using diatom isotope measurements to document atmospheric-terrestrial-marine interactions in sediments which do not contain biogenic/endogenic carbonates
Summary
The East and West Antarctic Ice Sheets (EAIS/WAIS), accounting for 90% of the world's freshwater, play a major role in regulating the global climate system (Mayewski et al, 2009). 3oC increase in surface air temperature since 1950, the most of anywhere in the Southern Hemisphere (Vaughan et al 2003; Turner et al, 2005; Thomas et al, 2009) Accompanying this increase in air temperatures are increases in summer sea surface temperature (SST) (Meredith and King, 2005) and the duration of the annual melting period (Torinesi et al, 2003; Vaughan, 2006). With critical thresholds for increased ice sheet/shelf breakup including summer air temperatures >−1.5oC (Scambos et al, 2004) and mean annual temperatures >−9oC (Morris and Vaughan, 2003), changes in air temperature and SST (Shepherd et al, 2003) can be related to the trend of increasing glacier retreat and basal melting of the ice-sheet across the WAP since the 1940s (Cook et al, 2005; Pritchard et al 2012) together with the recent collapse of the Larsen A and B ice shelves (Doake et al, 1998; Rignot et al, 2004)
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