Holocene climatic variation in southern Alaska — Quantitative estimates of temperature and precipitation, warm intervals, and possible cyclicity

This project seeks to document the range of Holocene climatic variability in southern Alaska based on proxy climate data stored in lake sediment. The research blends paleoecologic and isotopic analyses, glacial-geological studies at proglacial lakes, GIS-based local climatic modeling, and synoptic climatology.  The goal is to apply this complementary suite of approaches to reconstruct past winter precipitation, which in southern Alaska is positively correlated with the strength of the Aleutian low, and past summer temperature, which places recent and projected climatic warming in a long-term context.

The overall research design is to pair a lake optimal for reconstructing summer temperature with a nearby glaciated basin that registers winter precipitation.  Monitoring of local weather and limnological conditions, sampling of lake water, and analysis of modern/recent sediment are being conducted to calibrate the proxies used for paleoclimatic reconstructions.  Summer temperatures will be reconstructed using transfer functions of midge assemblages, and novel techniques for analyzing the isotopic composition of specific organic compounds and diatom opal.  Winter precipitation will be derived using a well-established correlation between summer temperature and winter precipitation at the equilibrium line of glaciers (ELA).  Fluctuations in ELA will be reconstructed by studying the geomorphology of glacier forefields and the physical properties of sediment in proglacial lakes.

Foremost among recent results from southern Alaska is the finding of pronounced centennial-scale cycles throughout the Holocene that match those reported from the North Atlantic region. Cycles imply predictability and therefore may be key to understanding whether natural variations may exacerbate or mitigate anthropogenic warming.  Other sites in southern Alaska are being studied to determine whether these cycles are reproducible, and to understand their possible origin in the climatic system.

View photographs of the 2004 field season

Collaborationg PIs include:

Feng Sheng Hu, University of Illinois

R. Scott Anderson, Northern Arizona University

Al Werner, Mt Holyoke College

Youngsong Huang, Brown University

Other senior collaborators include:

Thomas Brown, Lawrence Livermore National Laboratory

William Manley, University of Colorado

Cary Mock, University of South Carolina

Aldo Shemesh, Weizmann Institute of Science

John Smol, Queens University

Ian Walker, Okanagan University

Postdocs and students include:

Tom Daigle and Kasey Kathen, Northern Arizona University

Gina Clarke and Melisa Farmer, University of Illinois

Billy D'Andrea, Brown University

Erin Dopfel, Mt Holyoke College

This four-year project (2003-2007) is funded by the National Science Foundation.