Climatic signals from 76 shallow firn cores in Dronning Maud Land, East Antarctica

S Altnau,E Schlosser,E Isaksson,D Divine

doi:10.5194/tc-9-925-2015

Abstract

Abstract. The spatial and temporal distribution of surface mass balance (SMB) and δ18O were investigated in the first comprehensive study of a set of 76 firn cores retrieved by various expeditions during the past 3 decades in Dronning Maud Land, East Antarctica. The large number of cores was used to calculate stacked records of SMB and δ18O, which considerably increased the signal-to-noise ratio compared to earlier studies and facilitated the detection of climatic signals. Considerable differences between cores from the interior plateau and the coastal cores were found. The δ18O of both the plateau and the ice shelf cores exhibit a slight positive trend over the second half of the 20th century. In the corresponding period, the SMB has a negative trend in the ice shelf cores, but increases on the plateau. Comparison with meteorological data from Neumayer Station revealed that for the ice shelf regions, atmospheric dynamic effects are more important than thermodynamics while on the plateau; the temporal variations of SMB and δ18O occur mostly in parallel, and thus can be explained by thermodynamic effects. The Southern Annular Mode (SAM) has exhibited a positive trend since the mid-1960s, which is assumed to lead to a cooling of East Antarctica. This is not confirmed by the firn core data in our data set. Changes in the atmospheric circulation that result in a changed seasonal distribution of precipitation/accumulation could partly explain the observed features in the ice shelf cores.

Highlights

In the ongoing discussion about climate change, the climate of the polar regions is one of the foci of attention
In contrast to other studies, which state that the relationship between altitude and stable isotopes in precipitation depends on the altitude range because of differences in moisture transport (e.g. Masson-Delmotte et al, 2008), in our study we find that the same linear relationship holds for the entire range of altitudes covered by the cores
76 shallow firn cores from Dronning Maud Land (DML) were analysed in order to assess the spatial and temporal variability of water stable isotope ratios (δ18O) and surface mass balance (SMB)

Summary

Introduction

In the ongoing discussion about climate change, the climate of the polar regions is one of the foci of attention. Whereas the enhanced warming that models predict for the polar regions is obvious in the Arctic (Stocker et al, 2013), Antarctica behaves differently. An increase in sea ice extent is observed (Parkinson and Cavalieri, 2012) and the expected warming combined with a corresponding increase in precipitation and increased surface mass balance is still not observed over the entire Antarctic continent. For East Antarctica, no general warming and increase in precipitation is found in surface observational data (Turner et al, 2005; Monaghan et al, 2006, 2008). This is important because an increase in precipitation, and increased surface mass balance (SMB), might mitigate sea level rise

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