Satellite Microwave remote sensing of contrasting surface water inundation changes within the Arctic–Boreal Region

Surface water inundation in the Arctic–Boreal region is dynamic and strongly influences land-atmosphere water, energy and carbon (CO2, CH4) fluxes, and potential feedbacks to climate change. Here we report on recent (2003–2010) surface inundation patterns across the Arctic–Boreal region (≥ 50°N) and within major permafrost (PF) zones detected using satellite passive microwave remote sensing retrievals of daily fractional open water (Fw) cover from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E). The AMSR-E Fw (25-km resolution) maps reflect strong microwave sensitivity to sub-grid scale open water variability and compare favorably (0.71 ≤ R2 ≤ 0.84) with alternative, static Fw maps derived from finer scale (30-m to 250-m resolution) Landsat, MODIS and SRTM radar (MOD44W) data. The AMSR-E retrievals show dynamic seasonal and annual variability in surface inundation that is unresolved in the static Fw maps. The AMSR-E Fw record also corresponds strongly (0.71 ≤ R ≤ 0.87) with regional wet/dry cycles inferred from basin discharge records. An AMSR-E algorithm sensitivity analysis shows a conservative estimate of Fw retrieval uncertainty (RMSE) within ± 4.1% for effective resolution of regional inundation patterns and seasonal to annual variability. A regional trend analysis of the 8-year AMSR-E record shows no significant Arctic–Boreal region wide Fw trend for the period, and instead reveals contrasting inundation changes within different PF zones. Widespread Fw wetting is detected within continuous (92% of grid cells with significant trend; p < 0.1) and discontinuous (82%) PF zones, while sporadic/isolated PF areas show widespread (71%) Fw drying trends. These results are consistent with previous studies showing evidence of contrasting regional inundation patterns linked to PF degradation and associated changes to surface hydrology under recent climate warming.

► We evaluate surface inundation changes in the Arctic–Boreal region from 2003 to 2010. ► AMSR-E passive microwave analysis effectively captures surface water variability. ► Contrasting inundation changes are observed within the major permafrost (PF) zones. ► Continuous PF shows widespread wetting; drying predominates in more degraded PF.