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Persistent inflow of warm water onto the central Amundsen shelf

Nature Geoscience volume 5, pages 876–880 (2012)Cite this article

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Abstract

The West Antarctic Ice Sheet contains enough ice to raise global sea level by several metres and, because it is grounded mainly below sea level, it is sensitive to ocean warming1. Accelerated thinning of glaciers that discharge into the Amundsen Sea over the past decades2,3,4 has been proposed to be related to the presence of warmer waters beneath the ice shelves4,5,6. Three deep troughs crosscut the continental shelf of the Amundsen Sea, forming passages through which warm ocean waters can access the ice shelves, but oceanographic data has been limited. Here we present direct measurements from an ocean mooring and ship transect of the temperatures, salinities and velocities from one of these troughs in the central Amundsen Sea during the year 2010. The data show persistent inflow towards the ice shelf of relatively warm and salty water at the bottom of the trough throughout the year, and outflow of colder water above. Superposed on this background flow are barotropic current fluctuations that do not contribute significantly to the overall transport. In contrast to numerical models7,8, which show seasonal inflow changes in response to regional winds, we find that warm water is supplied to the Central Amundsen Shelf without strong seasonal variability.

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Figure 1: Bathymetric map of the Amundsen Sea region.
Figure 2: CTD data from transects in 2008 and 2010, and from the mooring.
Figure 3: Low-pass filtered mooring time series.
Figure 4: Velocities and heat fluxes based on mooring data.

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Acknowledgements

Oden Southern Ocean 2008/2009, 2009/2010, and 2010/2011 cruises were supported by the National Science Foundation (NSF), Swedish Polar Research Secretariat, and the Swedish Research Council (SRC). Support for mooring construction was grant KAW2007.0107 from the K&A Wallenberg Foundation. L.A., A.K.W., G.B., and B.L. were supported by the SRC (through grants 824-2008-6439, 2010-19172-73868-33, and 621-2008-2689), and A.H.O. by the NSF (under grant ANT-0839005). We are indebted to M. Jakobsson for making mooring deployment possible and to C. Wiederwohl for assisting on board the Oden 2009/2010 cruise. We are also grateful to the captains, crews, and technical personnel on board IB Oden, whose enthusiasm and skills made everything run smoothly.

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Authors and Affiliations

  1. Department of Earth Sciences, University of Gothenburg, Box 460, 405 30 Göteborg, Sweden

    L. Arneborg, A. K. Wåhlin, G. Björk & B. Liljebladh

  2. Department of Oceanography, Texas A&M University, College Station, Texas 77843, USA

    A. H. Orsi

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  1. L. Arneborg
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  2. A. K. Wåhlin
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  3. G. Björk
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  4. B. Liljebladh
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  5. A. H. Orsi
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Contributions

All authors discussed the results, commented upon and edited the manuscript. All authors were responsible for planning and executing parts of the field program. L.A. led the analysis, development of the paper, and integration of the results. A.K.W. and L.A. first discussed the results and wrote the first draft. Figure 1 was prepared by A.K.W.

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Correspondence to L. Arneborg.

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Arneborg, L., Wåhlin, A., Björk, G. et al. Persistent inflow of warm water onto the central Amundsen shelf. Nature Geosci 5, 876–880 (2012). https://doi.org/10.1038/ngeo1644

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