| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | July 19, 2017 |
| Latest Amendment Date: | July 19, 2017 |
| Award Number: | 1736504 |
| 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, 2017 |
| End Date: | August 31, 2020 (Estimated) |
| Total Intended Award Amount: | $324,629.00 |
| Total Awarded Amount to Date: | $324,629.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1013 NE 40th Street Seattle WA US 98105-6698 |
| 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): | PHYSICAL OCEANOGRAPHY |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
This project is a proof of concept for a remote sensing method to determine the amount of wave energy lost due to wave breaking, by observing the thermal signatures in the infrared imagery of the breaking wave and the foam it produces. When waves break, energy is dissipated and momentum is transferred from waves to surface currents. These processes are critically important both in the open ocean and in the surf zone. Quantifying the energy dissipation due to wave breaking is directly relevant to wave prediction models used for operational sea-state forecasting and the impact of storms on coastal regions. Bubbles generated by breaking waves are the primary mechanism for gas transfer at moderate to high wind speed. Bubbles also contribute to marine aerosol formation through spray droplets produced when bubbles in foam burst at the surface. Foam generated by wave breaking has increased reflectivity of solar radiation that can affect the Earth?s albedo. Foam also has increased microwave emissivity, which impacts space borne radiometer measurements of wind speed. Success in this proof of concept will open a new research direction with implications for momentum, gas, and heat across the air-water interface and global remote sensing applications. The project will contribute to the training of a postdoctoral fellow who will participate in all aspects of the work and involve two undergraduates in the summer experiments. The undergraduates will participate via the Washington Space Grant Summer Undergraduate Research Program (SURP), through which the PI has mentored students in the past. The PI will request students from an underrepresented group, which the program emphasizes. The project will also enhance research infrastructure by making a recently acquired wind-wave facility fully operational.
The long-term goal of this research team is to develop and utilize a remote sensing technique to infer energy dissipation due to wave breaking by exploiting the unique thermal signature of cooling residual foam left behind by the breaking process. The approach is based on the original idea that the time from when breaking begins to when the residual foam starts to cool can be used as a proxy for the bubble plume decay time, which in turn can be used to parameterize the energy dissipated by an individual breaking wave. The resulting ability to remotely quantify energy dissipation due to wave breaking will provide a new and transformative tool for investigating and understanding the air-sea interaction processes driven by wave breaking in the open ocean and the surf zone. A critical requirement to exploit the cooling signature of foam to quantify breaking is that the onset of cooling is not affected by the natural variability surfactants. The scope of this project is limited to determining the effect of surfactants on cooling foam as a necessary proof of concept to developing this new and promising idea. Success in this first step could lead to a more complete investigation, which exploits the cooling of whitecap foam to quantify wave breaking dissipation.
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.
Quantifying energy dissipation due to wave breaking remains an essential but elusive goal for studying
and modeling air-sea fluxes of heat, gas, and momentum. Breaking waves cause mixing and are important for redistributing heat, transporting gases between
the air and the water, and generating currents. Bubbles from breaking waves eventually rise and stay
at the surface where they can be visually seen as foam. Scientists have found that the time it takes for
the foam to disappear is related to the strength of the breaking waves. However, natural chemicals in
the seawater can cause the bubbles to disappear more slowly, increasing the time they are seen at the
surface. We present a new method to estimate when the bubble plume has decayed based on the foam
temperature. We generate breaking waves in a laboratory and use an infrared camera to measure the
temperature of the foam and find that the foam cools when bubbles stop rising. We varied the strength
of the breaking waves and measured the cooling time for the foam to show that larger, stronger
breaking waves cause a longer time before the foam begins to cool. When we added chemicals to
increase the time foam stays at the surface, the cooling time remains about the same, even though the
foam is still seen at the surface for a longer time.
Last Modified: 12/28/2020
Modified by: Andrew T Jessup
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