Collaborative Research: Testing the Orbital Theory of Ice Ages Through Analysis of Glacial Deposits and Numerical Modeling
DESCRIPTION: This research project will examine the timing and causes of ice ages in the Southern Hemisphere and how these observed climate changes compare with those found in the Northern Hemisphere. A major question in the earth-system sciences has been ascertaining what drives different sections of Earth to switch in and out of ice age climates. This is an outstanding question that remains unresolved. The traditional Milankovitch or orbital "ice-age theory" proposes that the intensity of summer insolation received in the Northern Hemisphere paces ice ages across Earth. Measurements of the intensity of summer insolation in the Northern and Southern hemispheres have been found to be out of phase, however. If glaciers expand and retreat in similar ways around Earth at the same time, other driving mechanisms therefore must be involved, such as greenhouse gasses or a global impact of the largest ice sheets that covered the land in the Northern Hemisphere. A problem is that in the Southern Hemisphere, there is insufficient information regarding when the last cold glacial period started, how long it lasted, and when it ended. Without this information, scientists are ill-equipped to assess how well Southern Hemisphere glacial climates correspond to possible driving forces, such as changes in (orbital) solar insolation intensity, Northern Hemisphere ice sheets, and atmospheric carbon dioxide. They also are unable to assess the underlying causes of ice-age climates and to refine the Milankovitch theory. This project will focus on the collection and analyses of materials that help document how glaciers in southern South America have changed over time. The investigators will employ state-of-the-art techniques in dating glacier landforms and glacial-climate modeling. The dated paleogeography of glaciers will provide boundary conditions for experiments using models developed by the researchers and others to assess the roles and responses associated with possible climate parameters, such as temperature and precipitation ranges that are needed for an ice sheet to grow and retreat over the southern Andes. This project will provide deeper understanding of the nature and causes of ice age climates and related natural environmental processes as well as their spatial and temporal differences around the globe. The project also will provide enhanced information about natural climate states, such as the climate during the last ice age that can be used as test beds for general circulation models that simulate future change. The project will provide opportunities to enhance international research collaborations between scientists in the U.S. and Chile. Education and training opportunities will be provided for undergraduate students, and educational outreach will be pursued through collaborative relationships with the American Museum of Natural History and New York City schools.