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Ocean access to a cavity beneath Totten Glacier in East Antarctica

Abstract

Totten Glacier, the primary outlet of the Aurora Subglacial Basin, has the largest thinning rate in East Antarctica1,2. Thinning may be driven by enhanced basal melting due to ocean processes3, modulated by polynya activity4,5. Warm modified Circumpolar Deep Water, which has been linked to glacier retreat in West Antarctica6, has been observed in summer and winter on the nearby continental shelf beneath 400 to 500 m of cool Antarctic Surface Water7,8. Here we derive the bathymetry of the sea floor in the region from gravity9 and magnetics10 data as well as ice-thickness measurements11. We identify entrances to the ice-shelf cavity below depths of 400 to 500 m that could allow intrusions of warm water if the vertical structure of inflow is similar to nearby observations. Radar sounding reveals a previously unknown inland trough that connects the main ice-shelf cavity to the ocean. If thinning trends continue, a larger water body over the trough could potentially allow more warm water into the cavity, which may, eventually, lead to destabilization of the low-lying region between Totten Glacier and the similarly deep glacier flowing into the Reynolds Trough. We estimate that at least 3.5 m of eustatic sea level potential drains through Totten Glacier, so coastal processes in this area could have global consequences.

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Figure 1: Satellite imagery, a priori ice-bottom elevation map, and gravity data coverage of the study area.
Figure 2: Shape of the sea floor beneath the Totten Glacier Ice Shelf.
Figure 3: A newly discovered oceanic entryway to Totten Glacier.

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Acknowledgements

This project is the result of the ongoing ICECAP collaboration between the USA, UK and Australia with support from NSF grants PLR-0733025 and PLR-1143843, and CDI-0941678, NASA grants NNG10HPO6C and NNX11AD33G (Operation Ice Bridge and the American Recovery and Reinvestment Act), Australian Antarctic Division projects 3013 and 4077, NERC grant NE/D003733/1, the G. Unger Vetlesen Foundation, the Jackson School of Geosciences, and the Antarctic Climate and Ecosystems Cooperative Research Centre. We thank the captains and crews of Kenn Borek Airlines Ltd, ICECAP project participants, CMG Operations Pty Ltd, and the Geosoft Education Program. We also thank S. Kempf for assistance with radar data processing, as well as A. Leventer, A. Wåhlin, D. Gwyther, K. Soderlund, C. Grima, F. Habbal and S. Zedler for comments on the manuscript. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. This is UTIG contribution 2831.

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J.S.G. performed the gravity inversions, magnetic depth to basement estimates, hydrostatic analysis, applied the bed reflectivity corrections, and wrote the manuscript. D.D.B., D.A.Y. and A.R.A.A. assisted with the potential field interpretations. J.S.G. and T.G.R. performed the initial gravity reduction and J.S.G. levelled the result. J.L.R. estimated the sea level potential for Totten Glacier. B.L. computed the percentage deflection expected for a range of trough widths and commented on what would be detectable using existing ERS data. D.M.S. provided radar technical and interpretation guidance for the discussion of reflectivity and specularity. A.R.A.A. performed the magnetics data reduction. J.L.R., R.C.W. and T.D.v.O. provided the glaciological context for Totten Glacier. J.S.G., D.A.Y., D.D.B., T.D.v.O., J.L.R., M.J.S. and R.C.W. designed the surveys. J.S.G., D.A.Y., T.D.v.O., J.L.R. and R.C.W. collected the data. All authors contributed comments to the interpretation of results and preparation of the final paper.

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Correspondence to J. S. Greenbaum.

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Greenbaum, J., Blankenship, D., Young, D. et al. Ocean access to a cavity beneath Totten Glacier in East Antarctica. Nature Geosci 8, 294–298 (2015). https://doi.org/10.1038/ngeo2388

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