A general theme of much of our research is to use physical modeling and mathematical methods to address societally relevant problems. We use a variety of models ranging from idealized mathematical representations of physical climate phenomena that can be developed and analyzed with pencil and paper to comprehensive climate models that are run on massive computer clusters. Our work also draws on analysis of observations. A selection of specific research themes are briefly described below. See our publications for a more detailed picture of our research.

Sea ice

Arctic sea ice is one of the components of the climate system that has changed most rapidly during recent decades, and it is projected to continue to change rapidly during the coming century. One of the goals of our research is to develop physical theories to explain how the global sea ice cover interacts with other components of the climate system and how it responds to climate changes. Such theories can provide a framework for interpreting the observed sea ice retreat and constraining the widely differing future sea ice projections from current state-of-the-art climate models. Related areas of our research include investigating the possibility of bifurcation thresholds during sea ice retreat ("tipping points"), uncertainty in satellite-derived sea ice observations, and other topics.


Last Glacial Maximum, which occurred approximately 21,000 years ago, provides a relatively recent example of a markedly different climate. Some of our research aims to build understanding of the modern climate and future climate changes by investigating physical mechanisms for differences in the climate system at the Last Glacial Maximum compared with today. Additionally, the transition from the Last Glacial Maximum to modern conditions was interrupted by a 1500-year cold period known as the Younger Dryas, which is one of the most dramatic incidents of past abrupt climate change reconstructed from paleoclimate proxy records. We have worked on understanding the mechanism that caused this cold period, and we proposed a theory involving interactions between ice sheets, the atmospheric hydrological cycle, ocean heat transport, and sea ice. Our other paleoclimate research has investigated a range of phenomena, including massive iceberg discharge events during the last glacial period ("Heinrich Events"), the Late Ordovician glaciation 450 million years ago and accompanying mass extinction, the global glaciation hypothesized to have occurred 650 million years ago ("Snowball Earth"), and the response of atmospheric circulation to past changes in incident solar radiation associated with variations in earth's orbit.


The calving of icebergs into the polar oceans from Antarctic and Greenland glaciers has increased during recent decades. Projections suggest that this will continue to increase during the coming century, perhaps dramatically. Icebergs can play an important role in the climate system by releasing freshwater into the upper ocean, which influences ocean circulation through its effect on seawater density. We have recently worked on developing and analyzing physical models, as well as observations, in order to build understanding of the drift and decay of icebergs and their role in the modern climate system, as well as their role in paleoclimate phenomena and projected future climates.

Atmosphere-ocean dynamics

Our research also involves other aspects of atmosphere-ocean dynamics, including El Niño, tropical monsoons, and other topics.


Although our research does not directly involve field work, there have been occasional opportunites to take part in research in the field (here are some photos), and students and postdocs in the group have carried out field work with other faculty members.