The marginal ice zone (MIZ) is one of the most important and dynamic features in the Arctic. The PIs will conduct an integrated analysis of how delivery of sea ice to the MIZ changed in the past and what changes might be in store in the future. Using a sea ice dynamic model forced with contemporaneous atmospheric fields and including tracers, they will track the origin and transport pathways of sea ice, and the focused release of material from ice melting in the MIZ. They will then extend this analysis back into the past, to examine changes during the Holocene, and into the future, using the Intergovernmental Panel on Climate Change climate change scenarios. They will investigate mixing of ice from different source areas into the Arctic interior; and assess how interannual and seasonal variability in ice from different source regions has influenced, and may influence in the future, redistribution and delivery of freshwater, sediments and biological material.
Intellectual Merit This research integrates models with existing data into a new framework, that of an ice conveyor which transports material across the Arctic basin and releases it in the environmentally sensitive MIZ. Through this project the PIs will examine: . How has the distribution, origin, and age of ice delivered to various MIZ regions changed over time, and during critical seasons, i.e. the spring bloom? . How have changes in ice drift influenced the delivery of freshwater, sediments, and biological material? How are these changes related to observed changes in atmospheric, oceanic, sedimentologic, and ecologic conditions? . How have changes varied regionally and with respect to water depth? For example, when does maximum ice melt - and therefore material release - occur over deep waters of central Fram Strait vs. over the shallow Greenland Shelf in western Fram Strait? . What changes in the distribution, origin, age, and MIZ flux of ice might we expect in the future? What might be the impact of these changes?
Intellectual Merit The marginal ice zone in the Arctic Ocean is where the ocean is partially, but not fully, covered by ice. At the end of winter, the marginal ice zone is along the coast, at the southern edge of the Arctic. Then, as the summer warms up, the marginal ice zone moves north, leaving an area of open water in its wake. This boundary zone between open water and ice is one of the most dynamic regions of the Arctic, both for its dramatic seasonal range and because of its extreme sensitivity to temperature trends: warming of the Arctic moves the marginal ice zone further north. This project focused on the changing location and timing of the marginal ice zone’s seasonal northward migration, changes in the origin of sea ice transported to these regions, and on some of the potential impacts of changes that are projected by climate models over the next several decades. Sea ice has long been known to be formed in one part of the marginal ice zone, travel thousands of kilometers, and melt in another. The Siberian sector, for example, is an ice "factory", while the area north of Canada and Greenland is an ice "warehouse." And the prevailing winds move ice, and anything attached to it, from one region to the other. Using ice velocity data derived from satellite imagery, we have been able to estimate the origin and amount of sea ice being moved between marginal ice zone regions, and to quantify changes in this long-range transport. Model results confirm and project these trends over the next several decades. Specifically, over the grant period from 2006-2010 our analyses expanded understanding of the potential for rapid sea ice retreat, the potential duration of summer ice free conditions over this century, the increased exchange of Arctic sea ice among the various shelf seas, and the transport and release of ice-transported material under past, present and future conditions. Broader impacts This research has helped to understand the Arctic system, and has implications for many other fields. Results from this research have been integrated into Barnard College, Columbia University, and McGill University courses, as well as the research projects and theses of several undergraduate and Master’s level students. It has informed an analysis of historical expeditions, and has been presented in a wide variety of public venues ranging from the American Museum of Natural History, to radio broadcasts, newspapers and magazines, and Internet news sites. It has led to partnerships with other scientists and policy analysts to explore the ecological and policy implications of these shifting ice patterns. Findings from the analysis of trajectories from potential pollutant sources contribute to identifying, managing and protecting crucial Arctic marine habitats. For example, there is a scientific consensus that future summer sea ice will be most persistent adjacent to the northern coasts of Greenland and the Canadian Arctic Archipelago where the oldest and thickest ice is now occurs. Using satellite images, we tracked the trajectories of ice in this region to determine its origin and melt locations. We show that both locally formed and transported sea ice is projected to maintain a summer sea ice cover in this region far into the 21st century, raising the possibility of it forming a natural refugium for ice-dependent species. Our results have led to a discussion of a "last Arctic sea ice refuge."
