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SUMMARY:Ocean’s response to the stochastic atmospheric forcing - Shenjie
  Zhou (British Antarctic Survey)
DTSTART:20210210T140000Z
DTEND:20210210T150000Z
UID:TALK156271@talks.cam.ac.uk
CONTACT:Dr Irena Vankova
DESCRIPTION:The ocean is forced by the atmosphere on a range of spatial an
 d temporal scales. In ocean and climate models the resolution of the atmos
 pheric forcing sets a limit on the scales that are represented. For typica
 l climate models this means mesoscale (< 400 km) atmospheric forcing is ab
 sent. Previous studies have demonstrated that mesoscale forcing significan
 tly affects key ocean circulation systems such as the North Atlantic Subpo
 lar gyre and the Atlantic Meridional Overturning Circulation (AMOC). Howev
 er\, the approach of these studies has either been ad hoc or limited in re
 solution. Here we present ocean model simulations with and without realist
 ic mesoscale atmospheric forcing that represents scales down to 10 km. We 
 use a novel stochastic parameterization – based on a cellular automaton 
 algorithm that is common in weather forecasting ensemble prediction system
 s – to represent spatially coherent weather systems over a range of scal
 es\, including down to the smallest resolvable by the ocean grid. The para
 meterization is calibrated spatially and temporally using marine wind obse
 rvations. The addition of mesoscale atmospheric forcing leads to coherent 
 patterns of change in the sea surface temperature and mixed-layer depth. I
 t also leads to non-negligible changes in the volume transport in the Nort
 h Atlantic subtropical gyre (STG) and subpolar gyre (SPG) and in the AMOC.
  A non-systematic basin-scale circulation response to the mesoscale wind p
 erturbation emerges – an in-phase oscillation in northward heat transpor
 t across the gyre boundary\, partly driven by the constantly enhanced STG\
 , correspoding to an oscillatory behaviour in SPG and AMOC indices with a 
 typical time scale of 5-year\, revealing the importance of ocean dynamics 
 in generating non-local ocean response to the stochastic mesoscale atmosph
 eric forcing. Atmospheric convection-permitting regional climate simulatio
 ns predict changes in the intensity and frequency of mesoscale weather sys
 tems this century\, so representing these systems in coupled climate model
 s could bring higher fidelity in future climate projections.
LOCATION:British Antarctic Survey\, Zoom
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