| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | July 9, 2014 |
| Latest Amendment Date: | July 25, 2016 |
| Award Number: | 1434886 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Henrietta Edmonds
hedmonds@nsf.gov (703)292-7427 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | January 1, 2015 |
| End Date: | December 31, 2018 (Estimated) |
| Total Intended Award Amount: | $454,947.00 |
| Total Awarded Amount to Date: | $454,947.00 |
| Funds Obligated to Date: |
FY 2015 = $201,148.00 FY 2016 = $208,970.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
2221 UNIVERSITY AVE SE STE 100 MINNEAPOLIS MN US 55414-3074 (612)624-5599 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
100 Union Street SE Minneapolis MN US 55455-0141 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Chemical Oceanography |
| Primary Program Source: |
01001516DB NSF RESEARCH & RELATED ACTIVIT 01001617DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
In support of the 2015 U.S.GEOTRACES Arctic expedition, this project will focus on the fate and distributions of naturally-occurring radioisotopes in the Arctic Ocean. Such information is useful for understanding why other chemical substances, both natural and man-made, occur where they do in the ocean. Like other national initiatives involved in the International GEOTRACES Program, the goals of this U.S. Arctic expedition are to identify processes and quantify fluxes that control the distributions of key trace elements and isotopes (TEI) in the ocean, and to establish the sensitivity of these distributions to changing environmental conditions. Working at sea alongside a multi-institutional team of ocean trace element experts, investigators on this project will define regions of unusually high rates of TEI removal, anticipated to be located near basin margins and near the sea floor. By combining their measurements of naturally-occurring thorium and protactinium with TEI data collected by other participating investigators, they expect to be able to translate these rates into information that can be applied to other TEIs. Like most other participating investigators, this group will include graduate students as part of the research team and will participate in a variety of public educational outreach activities for Alaskan communities.
This study will undertake measurements of the dissolved and particulate concentrations of 230Th and 231Pa, two isotopes designated as key or critical to the success of the GEOTRACES program. Additionally the team will measure dissolved and particulate 232Th concentrations and analyze a limited number of aerosol samples, aerosol leachates, sea ice, melt pond water and surface sediments for these radionuclides. The work plan will be broken down into five tasks geared to: (1) determine the rates of boundary scavenging of 231Pa and 230Th associated with the particle-rich waters near the southern margin of the Canada Basin; (2) determine the rates of bottom scavenging of 231Pa and 230Th associated with nepheloid layers that are prevalent in the Arctic Ocean; (3) assess the contribution to scavenging in the Canada basin by MnO2-coated particles, formed during early diagenesis in organic-rich sediments surrounding the Arctic Ocean; (4) determine the rate of supply of lithogenic 232Th from margin sediments using information derived from 230Th; and (5) determine the rate of supply of lithogenic 232Th from sea ice, including the aerosols and ice-rafted sediments that they transport, by the combined study of 232Th and 230Th. The proposed work fulfills core scientific objectives defined in the U.S. GEOTRACES Arctic Implementation Plan.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
This project is part of a major initiative to study the chemistry of the world's oceans as a means of understanding how the oceans work. This project focused on the Arctic Ocean and on understanding the processes that affect the concentrations of exceedingly rare forms of the elements thorium and protactinium. The particular forms of these elements have the unique characteristic that they are produced everywhere within the ocean at the same rate (from trace amounts of uranium naturally present throughout the oceans). Therefore, by measuring the concentrations of these elements in ocean waters and the particles contained within ocean water, we are able to ascertain processes within the ocean, which remove elements or redistribute elements within the ocean.
In order to understand these processes, we analyzed hundreds of samples of Arctic Ocean water and of particles filtered from Arctic Ocean water. We collected these samples at different sites around the Arctic and at different depths. Indeed, not only did we analyze these many samples, but we developed new techniques to analyze different sized particles filtered from seawater.
With this data in hand, we proceeded to assess the processes that resulted in the pattern of concentrations that we observed. We were able to assess processes such as the removal of trace metals near submarine hot springs and near the portions of the ocean close to the continents. The former is important as it relates to the cycling of iron in the oceans and the latter is important as it relates to the cycling of carbon in the oceans. Both are ultimately related to carbon dioxide in the atmosphere and to the climate of the earth.
Last Modified: 05/01/2019
Modified by: R. Lawrence Edwards
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