Understanding the low frequency dynamics of the throughflow from the Pacific to the Arctic
The Bering Strait is a narrow ocean gap between Alaska and Russia and is the only ocean pathway between the Pacific and the Arctic. In the past, ocean transport through this region may have played a key role in climate fluctuations. In the future, disappearing Arctic ice may make the Bering Strait the Pacific gateway to an Arctic ship route between the Pacific and Atlantic. Lying at the southern end of the Bering Strait is the Bering Sea, a shallow continental shelf hosting some of the most valuable fisheries in the U.S. and huge populations of marine wildlife. Although winds on average blow southward through the Strait, the average flow of ocean currents is northward, carrying nutrients, heat, and fresh water into the Arctic. Previous work suggests that a pressure head at the southern end of the Strait drives flow to the north against the southward wind, and evidence suggests that this pressure head has increased by about 70% since 2001. The origin of year-to-year and longer-term variability of this pressure head is unknown. This project will combine existing data on sea surface height, coastal sea level, theory, and modeling to understand changes in the pressure head and the basic dynamics of the Bering Sea continental shelf. A graduate student will be supported. The Bering Strait connects the Pacific and Arctic Oceans, and serves as a conduit of nutrients, heat, and fresh water. Therefore, understanding the factors influencing that connection will help predict current and future regional ocean conditions. Analysis of satellite altimetry, coastal sea level, theory, and a model will be used to: determine the origin and dynamics of the low-frequency pressure head that drives flow through the Bering Strait into the Arctic; understand the origin and basic dynamics of the interannual sea level and flow on the wide Bering Sea shelf; and determine the low-frequency variability of volume, heat, and fresh water flux of the Alaskan Coastal Current. A wealth of along-track satellite altimeter data available from TOPEX/Poseidon and Jason1,2,3 (TPJ123) will be used to address the question of what drives the Bering Sea pressure head. Preliminary analysis suggests that a major contributor to the low-frequency Bering Strait pressure head originates on the Gulf of Alaska continental shelf. This contribution is communicated along the Gulf of Alaska coastal wave guide, through Unimak Pass in the Aleutian Arc, onto the shallow Bering Sea shelf wave guide, and then through the Bering Strait. A second factor is the interannual and lower frequency signal generated on the Bering Sea shelf.