Thermokarst Lake Drainage - Vulnerability to Climate Change and Prediction of Future Lake Habitat Distribution on the North Slope
Lakes of the Arctic Coastal Plain of northern Alaska provide essential habitat for many species of water birds and fish, but are vulnerable to the effects of climate change. The mechanisms of effect include interactions between climate, permafrost, and surface hydrology that are reasonably well understood, but managers need a spatially-explicit model of landscape change to assess the risk of lost habitat value. Mean annual air temperature in Arctic Alaska is projected to increase 7°C by the end of the century. In a zone of deep, continuous permafrost, warming temperatures influence permafrost in ways that both promote and jeopardize the persistence of large lakes. Warming results in accelerated thermal erosion of lake shores and expansion of deep lakes at the expense of adjacent tundra habitats In general, therefore, large deep lakes in the Arctic Coastal Plain and Foothills ecoregions are likely to increase in area. In some landscapes, however, lakes will be susceptible to catastrophic drainage, as lakes are “tapped” by new drainage networks resulting from permafrost degradation. The vulnerability of an individual lake to tapping is dependent on the ice-content of surrounding permafrost and the existence of a topographic gradient. Ongoing remote sensing research by the PIs found numerous thermokarst lakes on the North Slope and the Seward Peninsula that drained during the last 50 years. Drainage rates on the North Slope, in cold continuous permafrost, were found to be 1-2 lakes / year. On the northern Seward Peninsula, a warm continuous permafrost region near the boundary to discontinuous permafrost and a potential analogue for future North Slope conditions, up to 10 lakes / year were draining. These drainage events appear to be connected to surface permafrost thawing, tapping by ocean coastal erosion and river channel migration, lake expansion, human-caused disturbances, and other factors. Thermokarst lake drainage completely changes the habitat character of a site. The Arctic Coastal Plain contains the second-largest lake district in the state, providing essential breeding, molting, and migratory stopover habitat for millions of migratory water birds, including 3 species of loons, and 20 species of large waterfowl (ducks, geese, and swans). Notable among these species are the Yellow-billed Loon, which is currently a candidate for listing under the Endangered Species Act, and Spectacled and Steller’s eiders, both listed as “threatened.” North Slope lakes also provide habitat for a variety of resident and anadromous fish, including least cisco, round whitefish, broad whitefish, lake trout, arctic char, arctic grayling, and ninespine stickleback. Lakes that are connected to stream systems are particularly important, as are deep lakes (> 2 m) that provide overwintering habitat. Understanding the potential for loss of lake habitat is vital to assessing the vulnerability of water birds and fish to range contraction and/or population decline.
- Classify North Slope lakes by their relative susceptibility to drainage via processes related to climate warming and permafrost degradation
- Generate maps identifying potential candidate lakes for drainage during the next 50 years for the Alaska North Slope, using remote sensing data, GIS-based layers of digital elevation models and surface geology, remote sensing-based lake expansion, coastal erosion, and stream channel migration rates.
The study area on the North Slope will be limited to the portion of the National Petroleum Reserve – Alaska (NPR-A).
- Remote sensing of rates of lake expansion, coastal erosion and river channel movement for the past 50 years
- GIS-based analyses and extrapolation of these movement rates for the coming 50 years
- GIS-based assessment of potential drainage pathways resulting from these predicted changes and in relation to land surface elevation
- GIS-based assessment of surface geology and permafrost characteristics as relevant to lake drainage
- Visit of selected sites for ground truthing lake drainage candidates, collecting bathymetric information for water depth and volume estimates, and characterizing lake habitats
- Jones BM, Grosse G, Arp CD (2010): Habitat cycling in coastal lowland thermokarst lake and basin-rich landscapes in northern Alaska. Alaska Bird Conference, Anchorage, AK, November, 2010.
- Jones BM, Grosse G (2011): The role of thermokarst lakes in the mobilization of near-surface soil organic carbon in North American Arctic lowlands. NACP All Investigator Meeting, New Orleans, February 2011.
- Arp C, B. Jones, R. Beck, M. Whitman, J. Derry, M. Lilly, G. Grosse (2010): Variation in snow-water equivalent (SWE) among tundra, lakes, and streams on the Alaska Arctic Coastal Plain: implications for regional SWE estimates, 2010 AWRA Annual Water Resources Conference, Philadelphia, PA.