**Author details**

*Antarctica - A Key to Global Change*

by 123 ± 44 Gt year<sup>−</sup><sup>1</sup>

twentieth century.

time scales [12, 19].

**Acknowledgements**

these recently observed changes in context.

[42].

ing and cooling trends have occurred in recent centuries [19].

evidence of warming surface temperatures, increased glacial melt and mass loss [68] and reduced sea ice in the neighboring Bellingshausen Sea [62]. However, the observational period is short. A small number of meteorological observations span the past 50 years but the records are sparse and often dominated by local conditions. Here we have demonstrated the important role that ice cores have played in placing

Ice core stable water isotope records have demonstrated that the reported warming from stations in the northern AP since the 1950s is not just a local phenomenon, but part of a statistically significant 100-year regional warming trend [7, 31]. However, the ice core records also provide evidence that larger, more abrupt warm-

Ice core snow accumulation records represent mass gains to the ice sheet, a vital component of the total Antarctic mass balance. The observed ice melt in the AP since the 1990s [63] represents a mass loss, while the ice core records provide evidence of significant mass gain during the twentieth century [7, 11, 19]. Ice cores have provided evidence that SMB for the whole of Antarctica has increased since 1800, with the largest contribution (~75%) from the AP, where SMB has increased

The increase in surface temperature and SMB has been linked to changes in sea ice and atmospheric circulation. The observational records demonstrate a shift to the positive phase of the SAM since the 1957s that has increased the strength of the Southern Hemisphere westerly winds, deepened sea level pressures in the Amundsen Sea (ASL) and reduced sea ice in the Bellingshausen Sea. These later changes have also been attributed to the increased strength of ENSO, particularly since the 1990, with evidence interplay between these two modes is responsible for the acceleration in surface temperature and SMB in the late

The ice core records capture the influence of large-scale modes of climate variability over centennial time scales. They reveal that changes in SMB are sensitive to changes in the strength and phase of SAM, but that the relationship with ENSO is not temporally stable. However, the observed tropical teleconnection between climate on the AP and surface pressure and sea surface temperatures in the tropical pacific that are not related to ENSO [60], is consistent on centennial

The observational records suggest that the interplay between modes of variability can have a considerable impact on climate of the AP [58]. Indeed, since the 1990s both SAM and ENSO have been in their positive phase, allowing for an amplification of the tropical teleconnection. In the ice core records the late twentieth century is characterized by a period of increased inter-annual variability and exceptionally high values in SMB [42] and sea ice [63–65], both of which are modulated by the variability in ASL (driven by SAM and ENSO). The combination of climate parameters and atmospheric circulation captured by the ice cores from the AP suggest that this recent coupling of SAM and ENSO is unprecedented in the past 300 years [12].

This work was funded by the British Antarctic Survey, part of the Natural Environment Research Council (NERC) and UK Research and Innovation (UKRI).

D. Tetzner is funded on a CONICYT-Chile Cambridge scholarship.

**86**

Elizabeth R. Thomas\* and Dieter R. Tetzner British Antarctic Survey, Cambridge, UK

\*Address all correspondence to: lith@bas.ac.uk

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
