Quaternary stratigraphy, geochronology, and paleoclimatology.
Present research: Quaternary stratigraphy and dating methods; amino acid geochronology and cosmogenic exposure dating; and glacial history of the Arctic, focusing on glacial chronology and ice-sheet dynamics using direct field evidence and quantitative estimates of the timing and magnitude of warm times in the Arctic. I also have research interests in monsoons on Quaternary time scales and the causes of megafauna extinctions.
My primary scholarly interests focus on gaining an improved understanding of how the physical earth system operates. Toward this end, I am specifically interested in using the Quaternary as a means to reconstruct the coupled ocean/atmospheric/ice climate system. By reconstructing past environmental changes it is possible to get a better understanding of the rates and magnitude of natural climate variability and the various feedback mechanisms in the global climate system. I am also interested in the role of humans in the modification of landscapes and ecosystem on Quaternary timescales.
- Elected Fellow , Geological Society of America, 1986
- Easterbrook Distinguished Scientist Award , Quaternary Geology and Geomorphology Division, Geological Society of America, 2005
- Elected Foreign Member, Norwegian Academy of Science and Letters, 2008
- Elected Fellow , American Geophysical Union, 2009