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SUMMARY:Quantifying spatio-temporal boundary condition uncertainty for the
  deglaciation - James Salter (University of Exeter)
DTSTART:20180308T160000Z
DTEND:20180308T164500Z
UID:TALK102247@talks.cam.ac.uk
CONTACT:INI IT
DESCRIPTION:Ice sheet models are currently unable to reproduce the retreat
  of the North American ice sheet through the last deglaciation\, due to th
 e large uncertainty in the boundary conditions. To successfully calibrate 
 such a model\, it is important to vary both the input parameters and the b
 oundary conditions. These boundary conditions are derived from global clim
 ate model simulations\, and hence the biases from the output of these mode
 ls are carried through to the ice sheet output\, restricting the range of 
 ice sheet output that is possible. Due to the expense of running global cl
 imate models for the required 21\,000 years\, there are only a small numbe
 r of such runs available\; hence it is difficult to quantify the boundary 
 condition uncertainty.  We develop a methodology for generating a range of
  plausible boundary conditions\, using a low-dimensional basis representat
 ion for the spatio-temporal input required. We derive this basis by combin
 ing key patterns\, extracted from a small climate model ensemble of runs t
 hrough the deglaciation\, with sparse spatio-temporal observations. Varyin
 g the coefficients for the chosen basis vectors and ice sheet parameters s
 imultaneously\, we run ensembles of the ice sheet model. By emulating the 
 ice sheet output\, we history match iteratively and rule out combinations 
 of the ice sheet parameters and boundary condition coefficients that lead 
 to implausible deglaciations\, reducing the uncertainty due to the boundar
 y conditions.
LOCATION:Seminar Room 1\, Newton Institute
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