Ann Dieffenbacher-Krall
Climate Change Institute
112 Sawyer Environmental Sciences
University of Maine
Orono, ME     04469-5764

207-581-2956 Ph/Voicemail

Ann_Dieffenbacher at umit.maine.edu

My primary research interests involve the use of paleoecology to reconstruct vegetation prehistory, temperature, and precipitation for the purpose of tracking climate change and ecological responses to both climate and human activities. I have a strong interest in conservation and the use of long-term ecological and climate studies to inform land and water resource management plans. My research has included developing the use of plant macrofossils and carbonate as lake-level proxies and calibrating chironomids as temperature indicators. I have participated in paleoecological research projects on sites in Maine, Florida, Scotland, New Zealand, and Chile. Current projects include those items listed in the following section.

I plan to expand my research area to include carbonate lakes from southern and western New England, and New York state, to broaden the geographic region for which finely resolved, well-dated records of water balance are available.

Determining patterns of abrupt climate change during the Late Glacial-Interglacial Transition (LGIT) in the Southern Hemisphere The origin of Southern Hemisphere millennial-scale climate events during the Last Glacial-Interglacial Transition (LGIT) remains a central issue of paleoclimate studies. The specific details of an out-of-phase relationship could support either Northern Hemisphere forcing or a Southern Hemisphere driver for thermohaline switches. Detailed chronologies of southern deglacial events outside of Antarctica can help clarify the relationship between the hemispheres and hence the coupling mechanisms.

My colleagues and I are developing a continuous, isotopically dated, paleo-chironomid and pollen record of deglacial climate fluctuations from sediment of a lake located in the climatically sensitive eastern margin of the Southern Alps, New Zealand. Paleochironomid analysis utilizes our newly developed chironomid-temperature transfer function for the Southern Alps of New Zealand. Working with scientists from Maine, New Zealand, Argentina, and Chile, we are seeking to expand the current research to includes sites in South America.

Records of Holocene water balance of the Northeastern United States Paleoecological evidence from midwestern and northeastern lakes indicates continuously changing lake levels across the eastern half of North America during the Holocene. However, key features of these records, notably a mid-Holocene dry period, vary across the region indicating time-transgressive water balance changes. By developing refined chronologies of water balance changes across the region, patterns of major air mass influence on precipitation should emerge.

As research progresses, I am advancing understanding of lake-level proxies, particularly plant macrofossils and carbonate. I have determined that carbonate is a valid, inexpensive, and rapid method for qualitative reconstruction of lake levels for small, closed-basin, northeastern lakes in regions of carbonaceous bedrock. By using a multi-proxy, multi-core methodology, I can quantify changes in lake depth, surface area, and volume, and depth of groundwater table, and thus, available water resources. Northern Maine lake levels appear to change in concert with North Atlantic summer sea-surface temperatures suggesting the North Atlantic Oscillation as the predominant influence on northeastern water balance.