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The Cryosphere An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/tc-2017-192
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
22 Sep 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal The Cryosphere (TC).
Atmospheric influences on the anomalous 2016 Antarctic sea ice decay
Elisabeth Schlosser1,2, F. Alexander Haumann3, and Marilyn N. Raphael4 1Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
2Austrian Polar Research Institute, Vienna, Austria
3Environmental Physics, Inst. of Biogeochemistry and Pollutant Dynamics, ETH Zürich, Zürich, Switzerland
4Department of Geography, University of California, Los Angeles, California, USA
Abstract. In contrast to the Arctic, where total sea ice extent (SIE) has been decreasing for the last three decades, Antarctic SIE has shown a small, but significant increase during the same time period. However, in 2016, an unusually early onset of the melt season was observed; the maximum Antarctic SIE was already reached as early as August rather than end of September, and was followed by a rapid decrease. The decline of the sea ice area (SIA) started even earlier, namely in July. The decay was particularly strong in November where Antarctic SIE exhibited a negative anomaly (compared to the 1979–2015 average) of approximately 2 Mio. km2, which, combined with reduced Arctic SIE, led to a distinct minimum in global SIE. ECMWF- Interim reanalysis data were used to investigate possible atmospheric influences on the observed phenomena. The early onset of the melt and the rapid decrease in SIA and SIE were associated with atmospheric flow patterns related to a positive ZW3 index, i.e. synoptic situations leading to strong meridional flow. Particularly, in the first third of November northerly flow conditions in the Weddell Sea and the Western Pacific triggered accelerated sea ice decay, which was continued in the following weeks due to positive feed-back effects, leading to the extraordinary low November SIE. In 2016, the monthly mean SAM index reached its second lowest November value since the beginning of the satellite observations. SIE decrease was preconditioned by SIA decrease. A better spatial and temporal coverage of reliable ice thickness data is needed to assess the change in ice mass rather than ice area.

Citation: Schlosser, E., Haumann, F. A., and Raphael, M. N.: Atmospheric influences on the anomalous 2016 Antarctic sea ice decay, The Cryosphere Discuss., https://doi.org/10.5194/tc-2017-192, in review, 2017.
Elisabeth Schlosser et al.
Elisabeth Schlosser et al.
Elisabeth Schlosser et al.

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Short summary
The atmospheric influence on the unusually early and strong decrease in Antarctic sea ice in the Austral spring 2016 was investigated using data from the global forecast model of the European Center for Medium-range Weather Forecasts. Weather situations related to warm, northerly flow conditions in the regions with large negative anomalies in sea ice extent and area were frequent and explain to a large part the observed melting. Additionally, oceanic influences might play a role.
The atmospheric influence on the unusually early and strong decrease in Antarctic sea ice in the...
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