Firn meltwater retention on the Greenland Ice Sheet: a model comparison

摘要: Runoff has recently become the main source of mass loss from Greenland Ice Sheet and is an important contributor to global sea level rise. Linking runoff surface meltwater production complex, as can be retained within firn by refreezing or perennial liquid water storage. To constrain these uncertainties, outputs two offline snow/firn models different complexity (IMAU-FDM SNOWPACK) are compared assess sensitivity retention model formulation (e.g., densification, irreducible content, vertical resolution). Results indicate that differences largest in areas where aquifers form, i.e., particularly along south-eastern margin ice sheet. The IMAU-FDM simulates higher densification rates for such climatic conditions prescribes a lower content than SNOWPACK. As result, predicts substantially amounts SNOWPACK performs better this area, confirmed both density profiles cores radar-inferred observations. Refreezing integrated over entire sheet averaged period 1960 - 2014 216 Gt a-1 (IMAU-FDM) 242 (SNOWPACK), which 41% 46% total input (snowmelt rainfall). mean areal extents 2010 simulated 55,700 km2 90,200 (SNOWPACK). Discrepancies between modeled observations emphasize importance processes currently not accounted most models, heterogeneous percolation, ponding on impermeable layers, lateral (sub-)surface flow, issue ill-constrained at base aquifers.