Physically Consistent Ice-Sheet--Climate Coupling for the UK Met Office Unified Model and UKESM1

Abstract:

The high spatial resolution and long integration times required to model ice-sheets explicitly within climate models have led to their have generally been treated as a static part of the land surface. Until recently, the climate--ice-sheet studies that existed were based on simplified, non-conserving coupling physics and loosely constrained empirical parameterisations. The next-generation UK Earth System Model (UKESM1), which is being developed jointly between NERC and the UK Met Office, will allow ice-sheets to be modelled as an physically consistent, interactive part of the climate. Surface mass balance will be explicitly calculated in the climate model with a multi-layer snowpack model with snow ageing and explicit refreezing processes, deployed on subgrid tiles representing different orographic heights. This will be coupled to the BISICLES adaptive mesh ice-sheet model, whose floating ice-shelves will also be coupled to the NEMO ocean model to allow explicit representation of the sub-shelf circulation and melt. We report on the development and evaluation of this coupling in a number of versions of the Met Office's Unified Model system across a broad range of resolutions.