Snow precipitation at four ice core sites in East Antarctica: provenance, seasonality and blocking factors

Abstract

Snow precipitation is the primary mass input to the Antarctic ice sheet and is one of the most direct climatic indicators, with important implications for paleoclimatic reconstruction from ice cores. Provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites (Dome C, Law Dome, Talos Dome, and Taylor Dome) in East Antarctica were analysed with air mass back trajectories calculated using the Lagrangian model and the mean composite data for precipitation, geopotential height and wind speed field data from the European Centre for Medium Range Weather Forecast from 1980 to 2001. On an annual basis, back trajectories showed that the Atlantic-Indian and Ross-Pacific Oceans were the main provenances of precipitation in Wilkes Land (80%) and Victoria Land (40%), respectively, whereas the greatest influence of the ice sheet was on the interior near the Vostok site (80%) and in the Southwest Ross Sea (50%), an effect that decreased towards the coast and along the Antarctic slope. Victoria Land received snowfall atypically with respect to other Antarctica areas in terms of pathway (eastern instead of western), seasonality (summer instead of winter) and velocity (old air age). Geopotential height patterns at 500 hPa at low ([10 days) and high (2-6 days) frequencies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the Tasman Sea-Eastern Indian Ocean at higher latitudes (60-70°S) than normal. This could be considered part of an atmospheric blocking event, with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low-frequency positive anomalies.

Deglaciation records of <sup>17</sup>O-excess in East Antarctica: reliable reconstruction of oceanic normalized relative humidity from coastal sites

“…The different levels of 17 O-excess between Vostok, EDC and TD at EH are consistent with unequal modern RH n of the OSR, as expected from our current understanding of 17 O-excess in polar regions. The lower 17 O-excess for TD, compared to the one at EDC, reflects the influence of OSR from higher latitudes and therefore higher RH n (Appendix B; Sodemann and Stohl, 2009;Scarchilli et al, 2010). We explain the unequal evolution of 17 O-excess for Vostok, EDC and TD respectively, with a different glacial/interglacial change in RH n at their respective OSRs.…”

“…Indeed, the Lagrangian moisture source diagnostics revealed stronger influences of the Pacific and Atlantic sectors for Vostok, compared to EDC, where moisture is mainly coming from the western Indian Ocean sector ( Fig. 4; Appendix B; Sodemann and Scarchilli et al, 2010;Werner et al, 2001). TD shows a completely different pattern, with moisture sources shifted towards the Pacific sector of the Southern Ocean compared to Vostok and EDC (Fig.…”

Regional Antarctic snow accumulation over the past 1000 years

“…Accumulation in northern Victoria Land, where the coast faces north, comes primarily from storms in the Indian Ocean (Scarchilli et al, 2011), with the origin of air masses similar to that of adjacent Wilkes Land. However, the Transantarctic Mountains block flow to southern Victoria Land so that this region is influenced by storms that cross the Ross Sea (Sodeman and Stohl, 2009).…”

Spatial and temporal variability of snow chemical composition and accumulation rate at Talos Dome site (East Antarctica)

“…The TALDICE ice core revealed that the Talos Dome site is very sensitive to the climatic variations occurring at regional-to-global scale over the last climate cycle . Particular attention was paid to changes in marine and atmospheric circulation and marine productivity in the Ross Sea and Adelie Land sectors (Scarchilli et al, 2011). Its relatively large accumulation rate (with respect to other ice core sites located on the Antarctic Plateau) enables an accurate dating of the core, particularly during the Holocene (the last 11.5 kyear) and the last climatic transition .…”