Investigation of the evolution of altimeter-derived sea ice thickness estimates through the summer melt season using a Lagrangian ice motion tracking approach

Sea ice thickness is a key component of the sea ice mass balance, but observations have historically been sparse, both in space and time. In recent years satellite and airborne altimeters have begun providing much better coverage though data acquisition has in some cases been sporadic with observations only one or two months per year (e.g., ICESat and Operation IceBridge). CryoSat-2 now provides routine continuous coverage through the winter months. However, the radar altimeter is not able to retrieve thickness during summer (May through September). This results in a gap during the key summer melt season and a discontinuity in observations. Here we employ a Lagrangrian tracking method to advect parcels of thickness through summer. The tracking method employs buoy displacement, feature matching in remote sensing imagery, and wind forcing to estimate motion, which is then used to advect sea ice parcels at weekly intervals. While melt and thinning cannot be explicitly observed, the method shows the evolution of the spatial distribution of thickness through the summer and when compared to the initial autumn thickness altimeter retrievals can potentially provide a total thickness change during the summer melt season. It also highlights potential inconsistencies between the spring and autumn altimeter-derived thickness fields.