| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | August 31, 2017 |
| Latest Amendment Date: | August 31, 2017 |
| Award Number: | 1751193 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Barbara Ransom
bransom@nsf.gov (703)292-7792 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | June 6, 2017 |
| End Date: | March 31, 2018 (Estimated) |
| Total Intended Award Amount: | $109,001.00 |
| Total Awarded Amount to Date: | $109,001.00 |
| Funds Obligated to Date: |
FY 2016 = $19,375.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
615 W 131ST ST NEW YORK NY US 10027-7922 (212)854-6851 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NY US 10027-6902 |
| 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): | Marine Geology and Geophysics |
| Primary Program Source: |
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
Supplies of fresh drinking water typically come from aquifers deep below the surface. These aquifer units do not stop at the shoreline, but instead extend offshore for perhaps hundreds of kilometers, carrying freshwater with them. In some cases, it is suspected that isolated bodies of freshwater may exist, emplaced during periods of time when sea level was much lower than it is today. Although the presence of large volumes of freshwater beneath the continental shelf is likely a global phenomenon, estimates of the extent of potential resources vary widely. A recent modeling study suggests that as much as 1300 km3 of fresh water could be trapped off the New England shore. For reference, the city of New York consumes roughly 1.5 km3 per year. As freshwater resources become increasingly stressed, many nations will need to exploit these valuable resources in a manner that does not result in contamination of the freshwater supply. Although we suspect that extensive freshwater exists offshore, our knowledge of where the water can be found is limited to drilling sites where samples have been collected. For example, it has been known for ~40 years that a substantial body of freshwater can be found offshore New Jersey. However, drilling gives only point measurements and is prohibitively expensive when large areas need to be studied. What is missing are tools capable of mapping the subsurface that are sensitive to fresh groundwater and for mapping deposits in new areas where water supplies onshore are scarce.
This research takes advantage of electromagnetic surveying tools that were initially developed by academia, but which have been adopted and expanded by the petroleum industry. These tools measure how well the seafloor can conduct electrical current and, as a result, are sensitive to changes in the salinity of water in the subsurface because fresh water conducts current less than seawater. The electromagnetic methods that will be used in this projet are the only non-invasive means available to detect the presence of fresh-water in the subsurface and to map these layers over length-scales of tens of kilometers. In this research, the project will characterize the spatial distribution of sub-seafloor fresh water beneath the continental shelf of the US Atlantic coast in two locations: off Martha's Vineyard, Massachusetts, and the offshore New Jersey. Broader impacts of the work include providing a proof of concept that electromagnetics can be effectively used to detect freshwater reserves in the offshore marine environment.
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 led to the discovery of a massive submarine aquifer system that spans at least 350 km of the U.S. Atlantic continental shelf. Low salinity groundwater had been previously detected in this region through a scattering of boreholes there were drilled during the last few decades, but the extent of the larger aquifer system had remained unclear due to a lack of observational data. Our findings were made through the first offshore groundwater mapping use of electromagnetic (EM) instrumentation that was originally developed for large-scale oil and gas exploration. The imaged aquifer has a volume that rivals some of the largest onshore aquifer systems. The spatial distribution provided by our study can be used to constrain paleo-hydrologic models of the relative importance of stratigraphy, sea level changes, and ice sheet dynamics for current and paleo freshwater emplacement. Understanding where groundwater is stored is relevant for determining increased ocean salinization during glacial periods. Furthermore, the onshore connectivity of this aquifer may represent a significant, yet widely unaccounted for, nutrient exchange mechanism between the terrestrial and ocean environments that is important for global carbon cycling. It may also influence sub-seafloor ecology and microbiology. Water resources are poised to become a major societal issue over the coming decades and offshore groundwater on the continental shelves may become an important natural resource.
Last Modified: 08/03/2018
Modified by: Kerry W Key
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