LAKE LEVEL CHANGE IN LARGE LAKE SYSTEMS: IMPLICATIONS FOR INTERPRETING RECORDS OF SALMON HISTORY IN THE LAKE CLARK/ILIAMNA REGION, ALASKA

Dave Hopkins inspired generations of students and researchers to study the paleo- ecology, geography, and climate of Beringia. His interdisciplinary approach and broad scope of interest led him, and many others, to pursue collaborative research efforts that typically broke down both disciplinary and political boundaries. Today many projects continue to unravel the history of Beringia, many of which maintain the spirit of interdisciplinary and international cooperation fostered by the lifelong efforts and example of Dave Hopkins.

Current research in Lake Clark National Park and other Southwest Alaskan parks combines landscape history, paleoecology, salmon history, and geoarcheology in an effort to understand the formation of the present ecosystem and its vulnerability to climatic or other change. Studies of landscape changes such as timing of deglaciation, lake level history, and change in drainage patterns compliment ongoing studies on the archeology and salmon ecology of these lake systems. Records of changing salmon abundance over millennia have been obtained from marine derived 15N istotopes in lake sediments (Finney 2002). While regional climate trends, and changes in ocean productivity likely influence salmon return to nursery lakes, it is also important to determine other factors such as geologic and hydrologic barriers. Lake level histories around Lake Clark and other large southwest Alaska lakes can been determined using sediment cores obtained from kettle ponds located within the paleoshorelines of the larger lakes. These small lakes act as ‘isolation basins’ recording the change from large, glacial fed lake to small isolated pond as the lake level drops below its threshold. Studies to date show that Lake Clark gradually dropped at least 25 meters between deglaciation and the mid Holocene. A similar history is expected from Lake Illiamna, Naknek Lake, and others on the northern Alaska Peninsula. Extensive radiocarbon dating combined with excellent tephra stratigraphy will allow us to determine the timing, rate, and synchronicity of lake level changes within connected lake systems as well as over the large area encompassed by Southwest Alaska parks. These detailed histories will allow us to determine the potential cause of lake level change (e.g. isostasy, climate, tectonics).