| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | August 19, 2014 |
| Latest Amendment Date: | August 19, 2014 |
| Award Number: | 1433170 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Baris Uz
bmuz@nsf.gov (703)292-4557 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | September 1, 2014 |
| End Date: | August 31, 2018 (Estimated) |
| Total Intended Award Amount: | $394,862.00 |
| Total Awarded Amount to Date: | $394,862.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
266 WOODS HOLE RD WOODS HOLE MA US 02543-1535 (508)289-3542 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
266 Woods Hole Road Woods Hole MA US 02543-1535 |
| 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): | OCE-Ocean Sciences Research |
| Primary Program Source: |
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| 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
Freshwater flowing out of the Arctic and from Greenland ice melt has the potential to modulate or even shut down deep convection in the sub-polar North Atlantic. The processes that control this exchange, and how they depend on external factors such as wind and outflow from the Arctic, are not well known and are not well resolved in basin-scale and climate models. Better understanding of the freshwater budget on the shelf, and how these waters get into the deep ocean interior, is essential to improve climate models and understand how the ocean will respond to a changing climate. The dynamically-based diagnostics planned in this project using a hierarchy of numerical ocean circulation models will also inform on mechanisms, locations, and times of exchange in other sensitive areas, such as the east coast of Labrador. Findings from the project will be used in undergraduate and graduate classes. Undergraduate students supported by the Woods Hole Oceanographic Institution Summer Student Fellowship program and assisted by graduate students will gain research experience. Material from the project will also be used in a textbook on ocean circulation. A graduate student will be trained in physical oceanography, geophysical fluid dynamics, and ocean modeling at Johns Hopkins University.
The exchange of freshwater between the east Greenland shelf and the interior of the sub-polar North Atlantic and Nordic Seas is a key element in the maintenance and variability of the Atlantic Meridional Overturning Circulation (AMOC) and its sensitivity to changes in atmospheric forcing and freshwater outflow from the Arctic Ocean. A realistic, very high resolution, regional model of the east Greenland shelf and adjacent deep ocean will be combined with idealized, process oriented models and in-situ observations to identify the strength, mechanisms, and sensitivity of this exchange. Processes likely important for this cross-shelf exchange include: surface and bottom Ekman layers; nonlinear eddy fluxes; local and remote wind-forcing; and wind-driven sea ice. The exchange will be diagnosed in a series of realistic model runs. Experiments will be designed with the idealized model to isolate the relevant processes for further study and understanding, and comparisons will be made with in-situ mooring and hydrographic observations and remotely sensed sea ice data. The main goal of the project is to reach a basic understanding of what controls the flux of freshwater from the shelf to the basin interior and how it depends on external forcing (wind, outflow from the Arctic, Greenland runoff) and environmental conditions such as bottom bathymetry and the ambient stratification.
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.
The overarching theme of this research was to better understand where and how high-latitude, low salinity waters are transported from the shelves to the ocean interior. This is important because these waters can disrupt deep convection in the ocean and the exchange of heat between the ocean and atmosphere, which has implications for both weather and climate. Several mechanisms were considered, including: wind-jets that eminate from fjords along the east coast of Greenland, nonlinear advection through Barrow Canyon in the Chukchi Sea, and wind-driven transport in the near-surface Ekman layer. It was found that the dominant pathway by which waters of Pacific origin enter the interior of the Canada Basin in the Arctic Ocean is through advection in a very strong, narrow current down Barrow Canyon (Figure 1). Along the east coast of Greenland, narrow wind jets that are forced through fjords by passing weather systems are an effective means to force low salinity water across the shelf and into the Greeland Sea, and also at the same time draw higher salinity and warmer waters of Atlantic origin into the deep fjords. This is important because these warmer waters are thought to enhance melting of some Greenland glaciers. Other results relate patterns of precipitation and winds over the subpolar North Atlantic to decadal variations of transports across the Greenland-Scotland ridge, and the influence of surface winds on mixing of low salinity waters on the shelf and the transport of waters from the shelf to the basin interior. The approach combined numerical models of the ocean, direct ocean observations, and theory. The combination of these three approaches allows for not only an assessment of how important these mechanisms are in the specific region of interest, but also how important they might be in future climate scenarios or in other regions of the World Ocean. The Intellectual Merit of the work lies in this development of a general understanding of these exchange mechanisms and how they depend on both environmental parameters (such as latitude, bottom depth, ocean temperature and salinity) and external forcing (such as wind strength and direction, seaice cover). The Broader Impacts of this work include the training of graduate students in physical oceanography, climate, and numerical methods, as well as providing guidence on which processes need to be included in climate models in order to accurately represent the transport of freshwater in the climate system.
Last Modified: 11/05/2018
Modified by: Michael A Spall
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