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SUMMARY:Impact of surface wave mixing on sea ice and mixed layer depth - S
 tefanie Rynders (University of Southampton)
DTSTART:20170915T092000Z
DTEND:20170915T094000Z
UID:TALK79401@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Co-authors: Yevgeny Aksenov (National Oceanography Centre)\, D
 aniel Feltham (University of Reading)\, George Nurser (National Oceanograp
 hy Centre)\, Gurvan Madec (L&rsquo\;OCEAN Sorbonne Universit&eacute\;s)<br
 ><br>Breaking waves cause mixing of the upper water column and present mix
 ing schemes in ocean models take this into account through surface roughne
 ss. Sea surface roughness can be calculated from significant wave height\,
  which is commonly parameterised from wind speed. We present results from 
 simulations using modelled significant wave height instead\, which account
 s for the presence of sea ice and the effect of swell. The simulations use
  the NEMO ocean model coupled to the CICE sea ice model in a one degree co
 nfiguration\, with wave information from the ECWAM model of the European C
 entre for Medium-Range Weather Forecasts (ECMWF). It is found that in the 
 simulations with modelled wave height mixing is reduced under the ice cove
 r\, since the parameterisation from wind speed overestimates wave height i
 n the ice-covered regions. Decreased mixing decreases vertical heat fluxes
  to and from the sea ice\, which in turn affects sea ice concentration and
  ice thickness. In the Arctic\, ice thicknesses increase overall\, with hi
 gher increases in the Western Arctic and decreases along the Siberian coas
 t. In the Southern Ocean the meridional gradient in ice thickness and conc
 entration is increased. The new mixing parameterisation improves sea ice v
 olumes in the simulation\, especially in the Southern Ocean\, where the mo
 del has difficulty reproducing the winter sea ice volumes. The mixed layer
  depth under sea ice is also improved\, without affecting mixed layer dept
 h in ice-free regions. Wave and sea ice coupling will become more importan
 t in the future\, when wave heights in a large part of the Arctic are expe
 cted to increase due to sea ice retreat and a larger wave fetch. Therefore
 \, wave mixing constitutes a possible positive feedback mechanism for sea 
 ice decline. The research leading to these results has received funding fr
 om the European Union&#39\;s Seventh Framework Programme (FP7/2007-2013) u
 nder grant agreement n&deg\;&nbsp\;607476.
LOCATION:Seminar Room 1\, Newton Institute
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