The changes in isotope composition and accumulation of snow at Vostok station, East Antarctica, over the past 200 years

Abstract

High-resolution records of isotope composition (dD) and accumulation of snow have been obtained from 10-12 m deep snow pits dug in the vicinity of Vostok station during the 1979/80 and 1999/2000 Antarctic field seasons. We employ meteorological, balloon-sounding and snow-stake data to interpret the isotope record in terms of past temperature changes. Our reconstruction suggests that snow accumulation rate and the near-surface air temperature at Vostok have varied during the past 200 years between 15 and 30 kg m -2 a -1 , and between -56 and -558C, respectively, with a slight general tendency to increase from the past to the present. Both parameters reveal a 50 year periodicity that correlates with the Pacific Decadal Oscillation index, implying a climatic teleconnection between central Antarctica and the tropical Pacific.

A promising location in Patagonia for paleoclimate and paleoenvironmental reconstructions revealed by a shallow firn core from Monte San Valentín (Northern Patagonia Icefield, Chile)

“…[50] (1) Atmospheric temperature reanalyses are averaged over a too large grid and do not represent the local surface temperature on the San Valentín summit area at interannual timescales [Garreaud et al, 2008], (2) the isotopic composition does not account for temperature under a certain time resolution as it has been shown for Antarctica [Ekaykin et al, 2002[Ekaykin et al, , 2004, (3) the isotopic composition of the firn is also related to other climate parameters as precipitation, moisture source changes (atmospheric circulation) or regional tropospheric temperature due to the high elevation location of the site, (4) as mentioned in section 2.4, because of wind erosion, part of the annual snow layer could be missing for specific years, leading to a seasonal bias when comparing the isotopic composition year-to-year (''summer'' snow for one year could be compared to ''winter'' snow for another year). This last assumption, although not fully supported by calcium measurement (section 2.5), is interesting.…”

Comment on Zwally and others (2015)-Mass gains of the Antarctic ice sheet exceed losses

“…The stake farm observations at Vostok, extended to the 40 a period, 1970-2010, yield a mean surface density of 0.335 g cm −3 and a (densification-corrected) snow build-up rate of 67.8 mm a −1 (Ekaykin and Lipenkov, 2010). If preference is given to this instrumental (in situ) result instead of the long-term mean accumulation rate from snow pits and shallow cores (Ekaykin and others, 2004), the surface height change implied by the GPS observations around Vostok station (Richter and others, 2008) amounts to 67.8 mm a −1 -62.1 mm a −1 = +5.7 ± 5.2 mm a −1 . Accumulation rates and density values that, together with the GPS observed vertical particle velocity of −62.1 mm a −1 , yield surface height change rates of +14.2 mm a −1 or even +61.2 mm a −1 as proposed by Zwally and others (2015) are very much incompatible with the results of decades of high-quality glaciological fieldwork at Vostok.…”

“…A pragmatic approach to reduce the noise introduced by this spatial variation is to increase the temporal integration interval. For this reason, and considering the significant 50 a period in temporal accumulation variation established in the Vostok station area (Ekaykin and others, 2004), Richter and others (2008) preferred the 200 a mean accumulation rate over that derived from 25 a of stake measurements.…”

“…The density value of 0.33 g cm −3 adopted by Richter andothers (2008, 2014) represents the best estimate for the surface snow layer combining the results from numerous snow pits and measurements in the Vostok accumulation stake farm (Ekaykin and others, 2003;personal communication from Ekaykin, 2007). This value was used to derive the accumulation rate of 22.9 ± 1.8 mm a −1 from the snow buildup observed in the Vostok stake farm in the period 1970-1995(Ekaykin and others, 2004, and there is neither reason nor evidence given by Zwally and others (2015) for why a density of 0.30 g cm −3 is 'a better value' for the Vostok station area. The density variation within the uppermost 20 cm of the stacked snow-pit profile represents random scatter rather than a dependence on depth (Ekaykin and others, 2003; personal communication from Ekaykin, 2007).…”

Atmospheric circulation in the Indian Ocean sector of East Antarctica over the last 200 years according to chemical studies of snow‑firn cover

“…К наи более надёжному индикатору переноса морско го аэрозоля в различные районы Антарктиды относится содержание Na + в антарктическом снеге [1] . Исследование изотопных профилей из района станции Восток позволило рекон струировать изменения температуры возду ха и аккумуляции снега за пределами периода инструментальных наблюдений [2][3][4][5] . В то же время реконструкции атмосферной циркуля ции по данным внутриконтинентальных райо нов Антарктиды крайне редки .…”