Abstract
Abstract. Three shallow firn cores were retrieved in the austral summers of 2011/12 and 2013/14 on the ice rises Kupol Ciolkovskogo (KC), Kupol Moskovskij (KM), and Blåskimen Island (BI), all part of Fimbul Ice Shelf (FIS) in western Dronning Maud Land (DML), Antarctica. The cores were dated back to 1958 (KC), 1995 (KM), and 1996 (BI) by annual layer counting using high-resolution oxygen isotope (δ18O) data, and by identifying volcanic horizons using non-sea-salt sulfate (nssSO42−) data. The water stable isotope records show that the atmospheric signature of the annual snow accumulation cycle is well preserved in the firn column, especially at KM and BI. We are able to determine the annual surface mass balance (SMB), as well as the mean SMB values between identified volcanic horizons. Average SMB at the KM and BI sites (0.68 and 0.70 mw. e. yr−1) was higher than at the KC site (0.24 mw. e. yr−1), and there was greater temporal variability as well. Trends in the SMB and δ18O records from the KC core over the period of 1958–2012 agree well with other previously investigated cores in the area, thus the KC site could be considered the most representative of the climate of the region. Cores from KM and BI appear to be more affected by local meteorological conditions and surface topography. Our results suggest that the ice rises are suitable sites for the retrieval of longer firn and ice cores, but that BI has the best preserved seasonal cycles of the three records and is thus the most optimal site for high-resolution studies of temporal variability of the climate signal. Deuterium excess data suggest a possible effect of seasonal moisture transport changes on the annual isotopic signal. In agreement with previous studies, large-scale atmospheric circulation patterns most likely provide the dominant influence on water stable isotope ratios preserved at the core sites.
Highlights
The Antarctic ice sheet plays a major role in the global climate system; despite much recent attention, there are still many unresolved issues around both its mass balance and recent climate history, in East Antarctica (IPCC, 2013)
Interpretation of satellite data is complicated by the fact that most of the region is close to balance: even when combining several different methods, corrections for isostatic rebound and changes in firn density, relatively poorly known quantities in East Antarctica, can alter the overall mass-balance estimate from positive to negative (i.e. Shepherd et al, 2012; Zwally et al, 2015), the results presented in the latter study are debated (Scambos and Shuman, 2016)
Three shallow firn cores were retrieved at Fimbul Ice Shelf (FIS) (Fig. 1, Table 1) in January 2012 (KC) and January 2014 (KM and Blåskimen Island (BI)) during field expeditions organised by the Norwegian Polar Institute (NPI)
Summary
The Antarctic ice sheet plays a major role in the global climate system; despite much recent attention, there are still many unresolved issues around both its mass balance and recent climate history, in East Antarctica (IPCC, 2013). Estimating mass balance for the ice sheet from field data is made difficult by the logistical challenges of collecting in situ data, as well as the enormous size of the region. Interpretation of satellite data is complicated by the fact that most of the region is close to balance: even when combining several different methods, corrections for isostatic rebound and changes in firn density, relatively poorly known quantities in East Antarctica, can alter the overall mass-balance estimate from positive to negative (i.e. Shepherd et al, 2012; Zwally et al, 2015), the results presented in the latter study are debated (Scambos and Shuman, 2016). Vega: Surface mass balance and water stable isotopes derived from firn cores
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