Localized rapid warming of West Antarctic subsurface waters by remote winds

Abstract

The highest rates of Antarctic glacial ice mass loss are occurring to the west of the Antarctica Peninsula in regions where warming of subsurface continental shelf waters is also largest. However, the physical mechanisms responsible for this warming remain unknown. Here we show how localized changes in coastal winds off East Antarctica can produce significant subsurface temperature anomalies (>2 °C) around much of the continent. We demonstrate how coastal-trapped barotropic Kelvin waves communicate the wind disturbance around the Antarctic coastline. The warming is focused on the western flank of the Antarctic Peninsula because the circulation induced by the coastal-trapped waves is intensified by the steep continental slope there, and because of the presence of pre-existing warm subsurface water offshore. The adjustment to the coastal-trapped waves shoals the subsurface isotherms and brings warm deep water upwards onto the continental shelf and closer to the coast. This result demonstrates the vulnerability of the West Antarctic region to a changing climate.

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Figure 1: Annual mean model response to East Antarctic poleward intensifying winds.
Figure 2: Antarctic Peninsula shelf response to East Antarctic poleward intensifying winds.
Figure 3: Hovmöller and time-series plots of Antarctic coastal ocean response to East Antarctic poleward intensifying wind forcing.
Figure 4: Across-shelf transects of western side of peninsula response to East Antarctic wind perturbation.
Figure 5: Schematic of the warming response of West Antarctic Peninsula waters to East Antarctic wind perturbation.

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Acknowledgements

This research was undertaken on the National Computational Infrastructure (NCI) in Canberra, Australia, which is supported by the Australian Commonwealth Government. Thanks to S. Ramsden and the NCI Vizlab for helping with the schematic in Fig. 5. Thanks to NOAA/GFDL for helping with model developments. Thanks to N. Jourdain for providing Supplementary Fig. 1 and helpful comments. Thanks to E. Bergkamp for investigating baroclinic modes in idealized simulations and to O. Saenko, J. Le Sommer, A. Stewart, J. Fyke, R. Hallberg, C. Dufour, G. Marques and P. Goddard for helpful comments. P.S. was supported by an Australian Research Council (ARC) DECRA Fellowship DE150100223, A.M.H. by an ARC Future Fellowship FT120100842 and M.H.E. by an ARC Laureate Fellowship FL100100214 and R.M.H. by an ARC Discovery Project DP150101331.

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P.S. conceived the study, conducted the global ocean modelling and wrote the initial draft of the paper. R.M.H. performed the single-layer, shallow-water modelling. P.S. and R.M.H. analysed the model data. All authors contributed to interpreting the results, discussion of the associated dynamics, and refinement of the paper.

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Correspondence to Paul Spence.

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Spence, P., Holmes, R., Hogg, A. et al. Localized rapid warming of West Antarctic subsurface waters by remote winds. Nature Clim Change 7, 595–603 (2017). https://doi.org/10.1038/nclimate3335

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