
NSF Org: |
OPP Office of Polar Programs (OPP) |
Recipient: |
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Initial Amendment Date: | August 31, 2010 |
Latest Amendment Date: | June 6, 2012 |
Award Number: | 1025523 |
Award Instrument: | Standard Grant |
Program Manager: |
William J. Wiseman, Jr.
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
Start Date: | September 1, 2010 |
End Date: | August 31, 2015 (Estimated) |
Total Intended Award Amount: | $921,071.00 |
Total Awarded Amount to Date: | $955,333.00 |
Funds Obligated to Date: |
FY 2012 = $34,262.00 |
History of Investigator: |
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Recipient Sponsored Research Office: |
104 AIRPORT DR STE 2200 CHAPEL HILL NC US 27599-5023 (919)966-3411 |
Sponsor Congressional District: |
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Primary Place of Performance: |
104 AIRPORT DR STE 2200 CHAPEL HILL NC US 27599-5023 |
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): |
ANT Ocean & Atmos Sciences, ARCSS-Arctic System Science, ANS-Arctic Natural Sciences, OPPORTUNITIES FOR RESEARCH CMG, MATHEMATICAL GEOSCIENCES |
Primary Program Source: |
0100XXXXDB 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): | 47.078 |
ABSTRACT
Funds are provided to improve understanding of the fluid dynamics behind marine aggregate settling, in particular investigating the processes by which marine snow, an aggregate of small particles within a mucous-like matrix, accumulates at density transitions and their implications for prolonged residence times in the surface ocean. This will be accomplished through a combination of careful laboratory fluid dynamics experiments and rigorous mathematical hydrodynamic theory in concert with state-of-the-art biogeochemical laboratory measurements. The consequences of these prolonged residence times will be assessed by biogeochemical measurements of the rates of microbial activity, and conversion of particulate organic carbon to dissolved organic carbon and CO2. A synthesis of the biological and physical components will be achieved by combined experiments that directly measure organic matter transformation during settling through a stratified seawater column, linking the physical and biological timescales under conditions representative of the ocean. The results of this work should inform development of improved models of carbon sequestration in the deep ocean, an essential process in the global carbon cycle. The project will contribute to the scientific workforce by supporting an early career faculty member, as well as the continued training of a post-doctoral associate, two graduate students, and four undergraduate students.
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.
Through this funding, we have documented experimentally and theoretically the role which sharp stratification plays in slowing the vertical transport of carbon in the ocean, either from bottom to top, as in the case of a deepwater oil spills or seeps, or from top to bottom, as in the case of phytoplankton -- ``marine snow" -- converting dissolved carbon dioxide into solid sinking carbon. The physical mechanisms for subsurface trapping of carbon was identified to be a combination of two effects: First, ambient fluid dragged by moving carbon, in the form of oil droplets or phytoplankton by-products called ``marine snow", alters the buoyancy of particulates and leads to trapping at location where the ambient density changes. This prevents the carbon from moving through layers of different density. For instance, marine snow from upper, lighter ocean waters can become trapped going through more dense, lower layer ocean waters. Second, the diffusion of salt or other stratifying agents into the carbon particulate is often the mechanism for increasing the particulate density, and hence determines how long carbon will reside at intermediate, sublayers in the ocean. We have also shown that this trapped marine snow leads to an intense amount of biological activity in the form of bacteria feeding off the phytoplankton by-products. This results in biological hot spots at different depths in the water column. The intellectual merit of our proposal has been in demonstrating how these combined effects of trapping, diffusion and enhanced bio-activity can severely limit the ocean’s ability to absorb carbon, a process central to the Earth Carbon cycle. Lastly, our work with turbulent buoyant jets has developed a predictive framework for determining where trapped subsurface oil plumes may be found in general oceanic conditions. The broader impacts of our proposal have resulted in training many trainees (undergraduates, graduates, and postdocs) in fluid dynamics.
Last Modified: 03/21/2016
Modified by: Richard M Mclaughlin
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