Unravelling Seasonal Changes in Arctic Ice Cap Surface Conditions through Multi-Satellite Synthesis

Satellite remote sensing is the primary way to monitor seasonal as well as long-term changes across broad portions of the Arctic. Subject to certain conditions (e.g., illumination), these data are collected continuously with known spatiotemporal coverage and resolution. And when supplemented with ground-based in situ calibration/validation measurements, satellite measurements can be used to infer some of the critical geophysical properties (e.g., surface elevation change, surface melting, etc.) that underpin our ability to project long-term ice sheet and ice cap evolution to in the future.

 This workflow however relies on the assumption that how the actual in situ conditions affect and manifest within the satellite measurements is constant or predictable through time and space. Put another way, that the in situ measurements used in calibration and validation are 1) representative of all transient (e.g., seasonal and/or multi-annual) conditions, or 2) that we can reliably modify/correct our satellite data interpretations to account for these changes. Recent work on the Greenland Ice Sheet has started to show that this assumption may be violated during periods of extreme warming; where warming may impact the satellite measurements in one way in one region (e.g., as an increase in radar altimetry echo strength), but in a different way in another (e.g., a fall in radar altimetry echo strength). Without a fuller understanding of how melting is affecting the ice sheet near-surface, these differences directly complicate the recovery of temporally comparable long-term satellite records.

 As an alternative to costly in situ calibration/validation campaigns, in this study we investigate the transient changes in the surface conditions of Arctic ice caps (i.e., Flade Isblink in Greenland, Austfonna in Svalbard and Vatnajökull in Iceland) via their impact on multiple satellite datasets. Small Arctic ice caps are useful in this regard as they often experience more variable climate forcings than remote interior portions of the Greenland Ice Sheet and therefore stronger seasonal patterns. Specifically, we are interested in developing a consistent model for how seasonal melt alters the near-surface of these ice caps by integrating Copernicus Sentinel-2 (optical), ESA CryoSat-2 (Ku-band radar altimetry), ISRO/CNES SARAL/AltiKa (Ka-band radar altimetry), Copernicus Sentinel-1 (C-band SAR), ESA SMOS (L-band passive microwave), and JAXA AMSR-2/E (multi-frequency passive microwave) satellite datasets. Our interpretation of these satellite datasets are supplemented with in situ measurements where available.