Articles | Volume 11, issue 1
Research article
12 Jan 2017
Research article |  | 12 Jan 2017

Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015

Jinyang Du, John S. Kimball, Claude Duguay, Youngwook Kim, and Jennifer D. Watts

Abstract. A new automated method enabling consistent satellite assessment of seasonal lake ice phenology at 5 km resolution was developed for all lake pixels (water coverage  ≥  90 %) in the Northern Hemisphere using 36.5 GHz H-polarized brightness temperature (Tb) observations from the Advanced Microwave Scanning Radiometer for EOS and Advanced Microwave Scanning Radiometer 2 (AMSR-E/2) sensors. The lake phenology metrics include seasonal timing and duration of annual ice cover. A moving t test (MTT) algorithm allows for automated lake ice retrievals with daily temporal fidelity and 5 km resolution gridding. The resulting ice phenology record shows strong agreement with available ground-based observations from the Global Lake and River Ice Phenology Database (95.4 % temporal agreement) and favorable correlations (R) with alternative ice phenology records from the Interactive Multisensor Snow and Ice Mapping System (R = 0.84 for water clear of ice (WCI) dates; R = 0.41 for complete freeze over (CFO) dates) and Canadian Ice Service (R = 0.86 for WCI dates; R = 0.69 for CFO dates). Analysis of the resulting 12-year (2002–2015) AMSR-E/2 ice record indicates increasingly shorter ice cover duration for 43 out of 71 (60.6 %) Northern Hemisphere lakes examined, with significant (p  <  0.05) regional trends toward earlier ice melting for only five lakes. Higher-latitude lakes reveal more widespread and larger trends toward shorter ice cover duration than lower-latitude lakes, consistent with enhanced polar warming. This study documents a new satellite-based approach for rapid assessment and regional monitoring of seasonal ice cover changes over large lakes, with resulting accuracy suitable for global change studies.

Short summary
A new automated method for microwave satellite assessment of lake ice conditions at 5 km resolution was developed for lakes in the Northern Hemisphere. The resulting ice record shows strong agreement with ground observations and alternative ice records. Higher latitude lakes reveal more widespread and larger trends toward shorter ice cover duration than lower latitude lakes. The new approach allows for rapid monitoring of lake ice cover changes, with accuracy suitable for global change studies.