Evolution of a supercooled Ice Shelf Water plume with an act

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TitleEvolution of a supercooled Ice Shelf Water plume with an actively growing subice platelet matrixAbstractWe use new observations in Western McMurdo Sound, combined with longitudinal hydrographic transects of the sound, to identify a northward-flowing Ice Shelf Water (ISW) plume exiting the cavity of the McMurdo-Ross Ice Shelf. We estimate the plumeÅ› net northward transport at 0.4~±0.1 Sv, carving out a corridor approximately 35 km wide aligned with the Victoria Land Coast. Basal topography of the McMurdo Ice Shelf is such that the plume is delivered to the surface without mixing with overlying warmer water, and is therefore able to remain below the surface freezing temperature at the point of observation beneath first-year ice. Thus, the upper ocean was supercooled, by up to 50 mK at the surface, due to pressure relief from recent rapid ascent of the steep basal slope. The 70 m thick supercooled layer supports the growth and maintenance of a thick, semirigid, and porous matrix of platelet ice, which is trapped by buoyancy at the ice-ocean interface. Continued growth of individual platelets in supercooled water creates significant brine rejection at the top of the water column which resulted in convection over the upper 200 m thick, homogeneous layer. By examining the diffusive nature of the intermediate water between layers of ISW and High Salinity Shelf Water, we conclude that the ISW plume must have originated beneath the Ross Ice Shelf and demonstrate that it is likely to expand eastward across McMurdo Sound with the progression of winter. Key Points An ISW plume is identified exiting the RIS cavity via Western McMurdo Sound Recent pressure relief gives rise to significant supercooling of the ISW plume A growing platelet matrix causes density instability at the ice-ocean interface Copyright 2014. American Geophysical Union. All Rights Reserved.AcknowledgementsThe authors would like to thank Ross Vennell, Inga Smith, Andy Mahoney, Craig Stewart, Greg Leonard, Ken Hughes, and two anonymous reviewers for valuable comments on previous versions of this manuscript. David Dempsey, Brett Grant, and Scott Base staff were instrumental in data collection during the 2007 field season. This work was funded throughan Otago University postgraduate scholarship, an Air New Zealand Post Doctoral Fellowship and with NIWA core funding under the National Climate Centre Research Climate Systems Programme. Logistical support was provided by Antarctica New Zealand.

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1st AuthorRobinson, N.AuthorRobinson, N.Williams, M.Stevens, C.Langhorne, P.Haskell, T.Year2014JournalJournal of Geophysical Research: OceansVolume119Number6Pages3425-3446DOI10.1002/2013JC009399URLhttps://www.scopus.com/inward/recor.....c17f104b0c427616d8583cbd5KeywordsPlateletsSupercoolingSurface topography, AntarcticaISW plumeMcMurdo soundsPlatelet icesRoss ice shelvesSupercooled water, Ice, rank5Author KeywordsAntarcticaISW plumeMcMurdo Soundplatelet iceRoss Ice Shelfsupercooled waterProgrammeK131 - Sea Ice and Southern Ocean Processes

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TypeArticleCitationRobinson, N., Williams, M., Stevens, C., Langhorne, P. and Haskell, T. (2014). Evolution of a supercooled Ice Shelf Water plume with an actively growing subice platelet matrix. Journal of Geophysical Research: Oceans, 119(6): 3425-3446 IdentifierRobinson2014Relevancerank5

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1st Author

Robinson, N.

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Programme

K131 - Sea Ice and Southern Ocean Processes