Abstract

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.

Highlights

  • Ice phenology describes the seasonal cycle of lake ice cover and encompasses freeze-up and breakup periods and ice cover duration (Duguay et al, 2015a)

  • 12 North American lakes (GBL, Great Slave Lake (GSL), Smallwood Lake, Nettiling Lake, Dubawnt Lake, Amadjuak Lake, Wollaston Lake, Baker Lake, Kasba Lake, Lesser Slave Lake, and Peter Pond Lake in Canada and Red Lake in USA) that experience annual breakup and freeze-up events were selected for lake-wide intercomparisons between the Lake Ice Phenology (LIP) metrics derived from this study and alternative lake ice products from the Interactive Multisensor Snow and Ice Mapping System (IMS) (Helfrich et al, 2007; http://www.natice.noaa.gov/ims/) and the Canadian Ice Service (CIS) (Howell et al, 2009)

  • The lake ice status derived from the LIP and Global Lake and River Ice Phenology Database (GLRIPD) records are plotted for the selected large lake validation sites (Fig. 2), including Lake Superior (a), Lake Oulujarvi (b), Lake Haukivesi (c), and Lake Paijanne (d), along with the daily ascending AMSR-E/2 Tb retrievals

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Summary

Introduction

Ice phenology describes the seasonal cycle of lake ice cover and encompasses freeze-up and breakup periods and ice cover duration (Duguay et al, 2015a). Freeze-up corresponds to the time period between the beginning of ice formation and the formation of a complete sheet of ice; breakup involves the time period between the onset of spring melt and the complete disappearance of ice from the lake surface (Kang et al, 2012). These ice phenology variables are key metrics sensitive to weather and climate conditions and influence lake– atmosphere interactions and hydrological and ecological processes in high-latitude and high-altitude regions (Duguay et al, 2006, 2012, 2015a; Mishra et al, 2011). The extent and duration of lake ice affect human activities, including hydroelectric power generation, navigation

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