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Changes to sea ice thickness distribution due to Ice Shelf Water

Presented by: 
Pat Langhorne University of Otago
Wednesday 13th September 2017 - 11:45 to 12:30
INI Seminar Room 1
Co-authors: Inga Smith, Greg Leonard, Andrew Pauling, Pat Wongpan, David Dempsey, Ken Hughes, Craig Purdie, Eamon Frazer (University of Otago), Mike Williams, Natalie Robinson, Craig Stevens (NIWA), Alena Malyarenko, Stefan Jendersie (NIWA & University of Otago), Wolfgang Rack, Gemma Brett, Dan Price (University of Canterbury), Christian Haas (Alfred Wegener Institute), Cecilia Bitz (University of Washington), Andy Mahoney (Geophysical Institute) and Tim Haskell (Callaghan Innovation Ltd) 

Satellite observations show that the winter maximum sea ice extent around Antarctica has been increasing slowly over the past three decades, a behaviour superficially at odds with “global warming”.  One hypothesis is that an increase in freshwater input from the base of ice shelves has influenced sea ice extent. This process can drive seawater temperatures below the surface freezing point. Ice crystals then persist in the supercooled water and add to the mass of the coastal sea ice cover. The crystals may form a porous, friable layer, called the sub-ice platelet layer, which can be several metres thick beneath the two-metres of sea ice. Consequently platelet ice formation not only causes sea ice to be thicker, but it also alters the hydrostatic relationship between sea ice elevation and thickness, influencing satellite altimeter determination of sea ice thickness.  

Here we describe ice shelf–sea ice interaction at a range of scales from parameterization in an Earth System Model, to the sub-metre detail of winter ice-ocean relationships. On a regional scale we have focused on a location affected by an ISW outflow at the surface. Regional ocean modeling and satellite altimeter observations provide context for airborne sea ice thickness surveys using electromagnetic (EM) induction sounding. These regional surveys have been supported over smaller geographic areas by detailed on-ice sea ice and snow thickness measurements, by on-ice EM induction transects of sea ice thickness, and by under-ice oceanographic observations that track the heat deficit and mixing in the upper ocean at selected sites.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons