Start Date/Time: Tuesday, August 14, 2012, 12:30 PM
Location: OSB 425
APL Special Seminar
Cecilia Peralta Ferriz, School of Oceanography and Applied Physics Laboratory, University of Washington
Ph.D. Dissertation Defense
Dr. James Morison, Committee Chair
Over the last few decades, the Arctic Ocean has experienced drastic changes including increased temperature, changes in freshwater distribution and decreased sea ice extent and thickness. These changes, which potentially affect global climate, are intimately linked to changes in the Arctic Ocean circulation. Thus, understanding Arctic Ocean circulation patterns is fundamental to monitoring and predicting the fate of the Arctic System. Since 2002, NASA's Gravity Recovery and Climate Experiment (GRACE) has provided continuous measurements of the time-varying gravity field of the Arctic Ocean. The gravitational variations represent mass variations, or the time-varying ocean bottom pressure(OBP) field. OBP are the sum of the mass change due to the sea surface height change and the integrated density variations through the water column.
In this dissertation, in situ and GRACE measurements of OBP anomalies, complemented by information from ocean models, are used to investigate the relative contribution of sea surface height change and density variations on the Arctic OBP field. The dynamics associated with the observed OBP changes are investigated. Major findings include the identification of three primary temporal-spatial modes of OBP variability at monthly to inter-annual timescales with the following characteristics:
- Mode 1 is a wintertime basin-coherent Arctic mass change forced by southerly winds through Bering and Fram Straits.
- Mode 2 reveals mass change along the Siberian shelves, driven by surface Ekman dynamics and associated with the Arctic Oscillation.
- Mode 3 reveals a mass drop in the 'Western' Arctic shelves forced by the strengthening of the anticyclonic Beaufort Gyre, and wintertime along-shore westerly winds that increase OBP in the Barents Sea.
This work integrates the character of the Arctic mass changes at different timescales.