Observations of Modified Warm Deep Water beneath Ronne Ice Shelf, Antarctica, from an Autonomous Underwater Vehicle

Davis, Peter E. D., Jenkins, Adrian, Nicholls, Keith W., Dutrieux, Pierre, Schröder, Michael, Janout, Markus A., Hellmer, Hartmut H., Templeton, Rob and McPhail, Stephen (2022) Observations of Modified Warm Deep Water beneath Ronne Ice Shelf, Antarctica, from an Autonomous Underwater Vehicle. Journal of Geophysical Research: Oceans, 127 (11). e2022JC019103. ISSN 2169-9275

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Official URL: https://doi.org/10.1029/2022jc019103

Abstract

Filchner-Ronne Ice Shelf (FRIS) is the world’s largest ice shelf by volume. It helps regulate Antarctica’s contribution to global sea level rise, and water mass transformations within the sub-ice-shelf cavity produce globally important dense water masses. Rates of ice shelf basal melting are relatively low, however, as the production of cold (-1.9°C) and dense High Salinity Shelf Water over the Weddell Sea continental shelf isolates the ice shelf from large-scale inflow of warm water. Nevertheless, a narrow inflow of relatively warm (-1.4°C) Modified Warm Deep Water (MWDW) that hugs the western flank of Berkner Bank is observed to reach Ronne Ice Front, although the processes governing its circulation and fate remain uncertain. Here we present the first observations taken within the ice shelf cavity along this warm water inflow using the Autosub Long Range autonomous underwater vehicle. We observe a core of MWDW with a south-westward velocity of 4 cm s-1 that reaches at least 18 km into the sub-ice cavity. The hydrographic properties are spatially heterogeneous, giving rise to temporal variability that is driven by tidal advection. The highest rates of turbulent dissipation are associated with the warmest MWDW, with the vertical eddy diffusivity reaching 10-4 m2 s-1 where the water column is fully turbulent. Mixing efficiency is close to the canonical value of 0.2. Modelling studies suggest MWDW may become the dominant water mass beneath FRIS in our changing climate, providing strong motivation to understand more fully the dynamics of this MWDW inflow.

Item Type: Article
Additional Information: Funding information: Autosub Long Range beneath Filchner-Ronne Ice Shelf was funded by the UK Natural Environment Research Council Large Grant “Ice shelves in a warming world: Filchner Ice Shelf system, Antarctica” (Grant Number NE/L013770/1). This study uses data provided by the Alfred Wegener Institute Helmholtz-Centre for Polar- and Marine Research in Bremerhaven (Grant Number AWI-PS111_01). The authors thank Captain Schwarze and the crew of RV Polarstern for the support during PS111.
Uncontrolled Keywords: Autosub Long Range, Ice shelves, Antarctica
Subjects: F800 Physical and Terrestrial Geographical and Environmental Sciences
Department: Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User: Rachel Branson
Date Deposited: 03 Nov 2022 16:07
Last Modified: 28 Nov 2022 09:30
URI: https://nrl.northumbria.ac.uk/id/eprint/50529

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