MONITORING LAKE ICE SEASONS IN SOUTHWEST ALASKA WITH MODIS IMAGES Page Spencer, Chief of Natural Resources Lake Clark National Park and Preserve 240 W 5th Ave Anchorage, Alaska 99501
[email protected] Amy E. Miller, Ecologist National Park Service, Southwest Alaska Network 240 W 5th Ave Anchorage, Alaska 99501
[email protected] Bradley Reed. Associate Program Coordinator U.S. Geological Survey (USGS) Reston, VA 20191
[email protected] Michael Budde, Geographer USGS Center for Earth Resources Observation and Science (EROS) Sioux Falls, SD 57198
[email protected] ABSTRACT Impacts of global climate change are expected to result in greater variation in the seasonality of snowpack, lake ice, and vegetation dynamics in southwest Alaska. All have wide-reaching physical and biological ecosystem effects in the region. We used Moderate Resolution Imaging Spectroradiometer (MODIS) Rapidfire browse images, snow cover extent, and vegetation index products for interpreting interannual variation in the duration and extent of snowpack, lake ice, and vegetation dynamics for southwest Alaska. The approach integrates multiple seasonal metrics across large ecological regions. The general annual pattern of the lake ice season in southwest Alaska begins as water cools when fall storms sweep in from the North Pacific. Ice forms on high altitude or small lakes by Oct/Nov, with larger lakes usually freezing over by Dec/Jan. Warm mid-winter storms often hit the study area, bringing wind, rain and melting temperatures that result in several inches of water on the ice or partial break-up of the ice pack. The return of cold, still Arctic high pressure refreezes the lakes until spring break-up in April and May.