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

• Main Authors: J. Du, J. S. Kimball, C. Duguay, Y. Kim, J. D. Watts
• Format: Article
• Language: English
• Published: Copernicus Publications 2017-01-01
• Series: The Cryosphere
• Online Access: http://www.the-cryosphere.net/11/47/2017/tc-11-47-2017.pdf

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 (<i>T</i>_b) 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 <i>t</i> 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 (<i>R</i>) with alternative ice phenology records from the Interactive Multisensor Snow and Ice Mapping System (<i>R</i> = 0.84 for water clear of ice (WCI) dates; <i>R</i> = 0.41 for complete freeze over (CFO) dates) and Canadian Ice Service (<i>R</i> = 0.86 for WCI dates; <i>R</i> = 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 (<i>p</i>  &lt;  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.