Ian Willis will work with Mike Willis to study water production, ponding, and refreezing in Greenland and Antarctic ice shelves, which have important implications for ice sheet/shelf mass balance, runoff, ice dynamics, and ultimately sea level change. The first aim of his proposal is to amass a large, remotely-sensed data set which will be used to quantify spatial and temporal patterns of surface and subsurface water extents across the firn zone of the GrIS (Greenland Ice Sheet) and across several AISs (Antarctic Ice Shelves). The recent advent of Google Earth Engine will help considerably with this task. The second aim of his proposal is to work towards incorporating the horizontal advection of water and its storage, refreezing, and draining in snow/firn aquifers, on both the GrIS and AISs, into a numerical modelling framework. Such a model will help to better make sense of recent observations made on the GrIS and AISs, increase understanding of important hydrological processes operating on those ice masses, and ultimately enhance the ability to predict their future behavior.