Evaluation of a coupled climate ice sheet model over the Greenland ice sheet and sensitivity to atmospheric, snow and ice sheet parameters

Charlotte Lang,Ruza Ivanovic,Jonathan Gregory,Sam Sherriff-Tadano,Robin S Smith,Lauren Gregoire,Victoria Lee,Niall Gandy

doi:10.5194/egusphere-egu22-11929

Abstract

&lt;p&gt;As part of a project working to improve coupled climate-ice sheet modelling of the response of ice sheets to changes in climate across different periods since the Last Glacial Maximum, we present simulations of the modern Greenland climate and ice sheet using the FAMOUS-BISICLES model.&lt;/p&gt;&lt;p&gt;FAMOUS-BISICLES, a variant of FAMOUS-ice (Smith et al., 2021a), is a low resolution (7.5&amp;#176;X5&amp;#176;) global climate model that is two-way coupled to a higher resolution (minimum grid spacing of 1.2 km) adaptive mesh ice sheet model, BISICLES. It uses a system of elevation classes to downscale the lower resolution atmospheric variables onto the ice sheet grid and calculates surface mass balance using a multilayer snow model. FAMOUS-ice is computationally affordable enough to simulate the millennial evolution of the coupled climate-ice sheet system, and has been shown to simulate Greenland well in previous work using the Glimmer shallow ice model (Gregory et al., 2020).&lt;/p&gt;&lt;p&gt;The ice sheet volume and area are sensitive to a number of parametrisations related to atmospheric and snow surface processes and ice sheet dynamics. Based on that, we designed a perturbed parameters ensemble using a Latin Hypercube sampling technique and ran simulations with climate forcings appropriate for the late 20&lt;sup&gt;th&lt;/sup&gt; century. The ice sheet area and volume are most correlated to parameters that set the snow/firn albedo while the relationship is less simple for parameters related to clouds and precipitation.&lt;/p&gt;&lt;p&gt;We compare FAMOUS-ice SMB and coupled behaviour against the more sophisticated, higher resolution, CMIP6-class UKESM-ice coupled climate ice sheet model for a late 20&lt;sup&gt;th&lt;/sup&gt; century simulation as well as an abrupt 4XCO&lt;sub&gt;2&lt;/sub&gt; experiment.&lt;/p&gt;&lt;p&gt;Our simulations produce a large range of climate and ice sheet behaviours, including a stable control state for the modern Greenland, and we have been able to highlight the sensitivity of the system to other sets of parameters and future changes in climate.&lt;/p&gt;

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