REASSESS · Probing and predicting the dynamical response of the Greenland-Ice-Sheet to surface melt water

Over just three decades, the Greenland Ice Sheet contribution to sea-level rise has grown six-fold. Increased basal slipperiness from increased surface melt was initially proposed as a key mechanism reinforcing ice loss, but a wealth of studies deconstructed this idea, leading the Intergovernmental Panel on Climate Change (IPCC) to conclude that increased surface melt “has not led to sustained increases in glacier flux”. Last year, however, my group re-established meltwater as a primary mechanism driving ice dynamics, albeit in a different manner than previously envisioned. Basal slipperiness is not set by melt rates but by ice-sheet morphology, which drives low slipperiness in steep and fast glaciers that terminate into the ocean, and high slipperiness in gentle and slow glaciers that terminate on land. As a result, a previously unforeseen meltwater-ice dynamics feedback potentially drives a higher than anticipated mass loss as glaciers transition from marine- to land-terminating in the future.In this project, I plan to REASSESS the control of surface meltwater on ice loss from the changed paradigm that glacier morphology rather than melt rates controls its impact. (AIM1) will probe the mechanisms responsible for the morphology control on basal slipperiness by overcoming long-lasting observational challenges through an innovative seismologically- and geodetically-based monitoring scheme exporting recently established proofs of concept for the first time to Greenland.(AIM2) will predict the control of meltwater on ice-sheet evolution from incorporating the new observational insights from AIM1 into a hierarchy of small-scale physical to large-scale parametrized models.With this strategy, we will, for the first time, fully evaluate the dynamical response of the Greenland Ice Sheet to surface meltwater and its impact on sea-level variations under deglaciation as inferred in the past and expected over the coming centuries.