National Aeronautics and Space Administration

National Climate Assessment

NASA National Climate Assessment (NCA) Activities

NASA Indicators Solicitation Proposals

Development and Testing of Potential Indicators for the National Climate Assessment

Lead PI and Center: Harry Stern, University of Washington, Seattle
Title: The Timing of Arctic Sea Ice Advance and Retreat as an Indicator of Ice-Dependent Marine Mammal Habitat

The Arctic is widely recognized as the front line of climate change.  The Arctic sea-ice cover is shrinking and thinning, with total disappearance of summer sea ice projected to occur in a matter of decades.  These changes are already impacting ice-dependent marine mammals, which depend on the sea-ice cover as an integral part of their existence.

We propose to use daily sea-ice concentration data (generated by the NASA Team algorithm from satellite passive microwave instruments) to develop and test potential indicators of changes in Arctic marine mammal habitat based on the timing of sea-ice retreat in spring and advance in fall.  The steps of the method are: (1) Define a region. (2) Calculate the daily sea-ice area (km2) in the region (1979-present). (3) Select a sea-ice area threshold (km2) roughly halfway between the summer minimum and winter maximum over a baseline period. (4) Pick off the date each spring when the sea-ice area drops below the threshold, and the date each fall when the sea-ice area rises above the threshold.  The result is two time series for each region: the date of spring transition each year, and the date of fall transition each year.  The spring and fall sea-ice transition dates derived in this manner go back in time more than 30 years.  We will focus on regions that are biologically important to Arctic marine mammals such as the North Water polynya, narwhal summering and wintering grounds in Baffin Bay, walrus habitat in the Chukchi and Bering seas, key polar bear habitat, and shallow continental shelf regions.

As part of developing our timing indicators, we will conduct two ecological case studies, one involving the migration of beluga whales from the north coast of Alaska to the Bering Sea in fall, and one involving the dates when polar bears in Baffin Bay arrive on land in the spring and return to the sea ice in the fall.
We will use output from several Global Climate Models (GCMs) that participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5), in preparation for the IPCC Fifth Assessment Report, to compute our sea-ice indicators and assess the future impact on Arctic marine mammals over the next several decades.
Our sea-ice timing indicators will be useful to many groups of people, such as wildlife managers, indigenous hunters, shipping companies, fishermen, cruise-ship operators, oil and gas exploration companies, sea-ice researchers, and marine mammal biologists.  We will make our indicators broadly available.  The indicators possess all the proposed qualities of physical indicators set forth in a recent National Climate Assessment report, and the sea-ice data on which the indicators are based are certain to be available long into the future.  The data products we produce will be archived at the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC).

The involvement of a graduate student in this project meets NASA's objective of increasing the pool of "assessment-capable" early career scientists, and the project builds on our current and previous NASA-funded work.