Deep ocean circulation and uranium-series radionuclides in arctic ocean sediments

The National Science Foundation Division of Polar Programs awarded The Trustees of Columbia University in the City of New York $256,690 on January 15, 2027, through the Polar Programs project grant to analyze deep-sea sediment cores from the Arctic Ocean for uranium-series radionuclides and evidence of deep ocean circulation patterns.

The project will examine sediment cores collected from Lomonosov Ridge, Northwind Ridge, Canada Basin, Nansen Basin, and the Fram Strait, along with selected Arctic periphery locations, using inductively coupled plasma mass spectrometry to measure uranium, thorium, and protactinium isotopes. The analysis will assess radionuclide inventories and the Arctic budget while exploring changes in lateral transport and the cycling of relatively insoluble elements through Arctic seawater, into deep-sea sediments, and southward through the Fram Strait. The work will provide research and training opportunities at multiple levels and includes a partnership with science educators to host a workshop for middle and high school teachers to increase public awareness of the Arctic.

Performance occurs at Palisades, Orangetown, New York, with a period of performance ending December 31, 2028. The assistance type is a project grant.

Abstract

The arctic ocean remains one of the least explored realms on earth, despite the increasing awareness of its importance and ongoing changes. This project is designed to increase our understanding of the cycling of relatively insoluble elements in seawater through the arctic and either into the underlying deep-sea sediments or south through the fram strait into the nordic seas and possibly beyond. The element uranium is easily dissolved in the ocean, and decays predictably to thorium, which is essentially insoluble, and protactinium, which is only slightly soluble. This contrasting behavior of highly soluble uranium and its less soluble long-lived radioactive decay ?daughters? Provides a wide array of insights into global ocean processes including biological productivity, atmospheric dust deposition and the movement of deep currents, yet has been far less utilized in the arctic. In this study, an array of deep-sea sediment cores from within and around the arctic ocean will be analyzed for evidence of the transport and burial of thorium and protactinium, with a particular focus on the variability of deep ocean currents through time. The project will provide research opportunities and student training at multiple levels. In partnership with a team of science educators, the researchers will also host a workshop for middle and high school science teachers to increase public awareness of the arctic. Deep-sea sediment cores from lomonosov ridge, northwind ridge, canada basin, nansen basin and the fram strait, along with selected locations around the periphery of the arctic ocean will be analyzed for uranium, thorium and protactinium isotopes using bulk sediment digestion and inductively coupled plasma mass spectrometry (ICP-MS). The data will be examined to assess the inventories and arctic budget of the radionuclides, and to explore evidence of changes in the preferential lateral transport of protactinium out of the basin through the fram strait by deep ocean currents since the last ICE age. These results will be used to test the hypotheses that the seawater production and deep-sea sedimentary burial of thorium are in balance in the arctic, as in the global ocean, and that there has been a persistent deficit in the burial of protactinium due to its transport out of the arctic by deep ocean currents. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.