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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Impact of surface wave mixing on sea ice and mixed
layer depth - Stefanie Rynders (University of Sou
thampton)
DTSTART;TZID=Europe/London:20170915T102000
DTEND;TZID=Europe/London:20170915T104000
UID:TALK79401AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/79401
DESCRIPTION:Co-authors: Yevgeny Aksenov (National Oceanography
Centre)\, Daniel Feltham (University of Reading)\
, George Nurser (National Oceanography Centre)\, G
urvan Madec (L&rsquo\;OCEAN Sorbonne Universit&eac
ute\;s)
Breaking waves cause mixing of the
upper water column and present mixing schemes in o
cean models take this into account through surface
roughness. Sea surface roughness can be calculate
d from significant wave height\, which is commonly
parameterised from wind speed. We present results
from simulations using modelled significant wave
height instead\, which accounts for the presence o
f 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 configuration\, with wav
e information from the ECWAM model of the European
Centre for Medium-Range Weather Forecasts (ECMWF)
. It is found that in the simulations with modelle
d wave height mixing is reduced under the ice cove
r\, since the parameterisation from wind speed ove
restimates wave height in the ice-covered regions.
Decreased mixing decreases vertical heat fluxes t
o and from the sea ice\, which in turn affects sea
ice concentration and ice thickness. In the Arcti
c\, ice thicknesses increase overall\, with higher
increases in the Western Arctic and decreases alo
ng the Siberian coast. In the Southern Ocean the m
eridional gradient in ice thickness and concentrat
ion is increased. The new mixing parameterisation
improves sea ice volumes in the simulation\, espec
ially in the Southern Ocean\, where the model has
difficulty reproducing the winter sea ice volumes.
The mixed layer depth under sea ice is also impro
ved\, without affecting mixed layer depth in ice-f
ree regions. Wave and sea ice coupling will become
more important in the future\, when wave heights
in a large part of the Arctic are expected to incr
ease due to sea ice retreat and a larger wave fetc
h. Therefore\, wave mixing constitutes a possible
positive feedback mechanism for sea ice decline. T
he research leading to these results has received
funding from the European Union'\;s Seventh Fra
mework Programme (FP7/2007-2013) under grant agree
ment n°\; \;607476.
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:INI IT
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