Greenland’s Melting Firn and Ice Sheet Response

forthcoming

TheThe FirnMelt ERC Synergy project focuses on the Greenland Ice Sheet’s reaction to surface melting across its vast firn plateau, currently covering almost 90 % of its surface. Firn is the up to 100 metres thick, porous near-surface layer of compressed snow. Most of Greenland’s firn plateau experienced only occasional melt in the past but ever rising temperatures increase melting and it is uncertain how much of the melt refreezes or runs off. Current state-of-the-art firn models were built on the earlier premise that firn experiences little melt and are fundamentally limited in modelling melting firn. Consequently, we need a paradigm shift to a new generation of models simulating the physics of melting firn. When coupled to ice sheet hydrology and ice dynamics models, these new firn models will enable assessing how a melting firn plateau will impact mass balance, hydrology and dynamics of the ice sheet. The FirnMelt team will tackle this opportunity through (i) large-scale in situ and remote sensing measurements of all types of firn and meltwater discharge, (ii) develop new physical parameterizations of melting firn based on these measurements, (iii) develop a new generation of models able to simulate melting firn and firn meltwater discharge in three dimensions, and (iv) embedding these models into a fully coupled ice-sheet model suite. (v) Eventually, we will calculate how the melting firn plateau will impact the entire ice sheet and its sea level contribution, until the year 2300. To date, no such concerted effort has been undertaken. FirnMelt unites a team of four world-leading PIs whose combined thematic expertise in firn processes, ice-sheet dynamics, remote sensing and numerical modelling makes such an ambitious effort possible. Our research will have profound impact beyond this project, e.g. for assessing the influence of Greenland meltwater on the Atlantic overturning circulation and understanding of the role of firn in Antarctic ice shelves (in)stability.