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Uranium-Series Radionuclide Records of Paleoceanographic and Sedimentary Changes in the Arctic Ocean

Sharon Hoffmann, Ph.D., 2009
Jerry McManus, Advisor

Sedimentary 231Pa and 230Th offer insight into past dynamics of water column and sedimentary processes. I show that a state of balance exists between 230Th production and burial in the Arctic basins, establishing this nuclide’s utility as a paleoceanographic tool. I present the first 230Th-normalized particle fluxes calculated for the central Arctic: vertical particle fluxes were extremely low during the late glacial; rose during the deglaciation due to particle inputs from shelf inundation and increased productivity, and fell again following through the Holocene. Lateral sediment redistribution occurred in the Makarov Basin during the deglaciation and may have been due to destabilization of slope and shelf sediments as sea level rose.
I present the first high-resolution, radiocarbon-dated records of sedimentary 231Pa/230Th from the Arctic. 231Pa was exported from all sites during the late glacial period, with export decreasing during the deglaciation and Holocene. We find no evidence yet for a 231Pa sink related to boundary scavenging on the continental slopes. 231Pa/230Th ratios show a very significant variation by water depth, with strong export of 231Pa at deep sites but little or no export at shallow sites. The Arctic appears similar to other ocean basins in its 231Pa and 230Th dynamics.