Download - Microbreaking Waves on the Open Ocean What they are Why they are interesting How we are trying to learn more Damon Turney PhD Seminar, May 23, 2003

Microbreaking Waves on the Open Ocean

• What they are

• Why they are interesting

• How we are trying to learn more

Damon TurneyPhD Seminar, May 23, 2003

What are Microbreaking Waves?

• Microbreaking waves are on the order of 1 meter in length, and 0.1 meters tall. They are different from other small waves in that they actually “break”.

Photo credit: University of Florida

What are Microbreaking Waves?

• Microbreaking waves are formed by interaction with the wind.

Photo credit: Navy Meteorology and Oceanography Home Page

Why are Microbreaking Waves Interesting?

• Microbreaking waves, and turbulence production in general, probably play an important role in any gas-liquid exchange process where they exist.

Credit: Donnelan and Wanninkhof, Gas Transfer at Water Surfaces, 2002


Credit: Donnelan and Wanninkhof, Gas Transfer at Water Surfaces, 2002


• Carbon cycling between the atmosphere and ocean is an example of the relevance to environmental science.

Photo Credit: Australian Greenhouse Office http://www.greenhouse.gov.au/science/faq/index.html

http://www.greenhouse.gov.au/science/faq/index.html





• Microbreaking waves increase and modify the mixing of the top ~10 centimeters of the ocean.

Credits: Leifer, Piorek, Smith and Banerjee, unpublished. Period of Burst, s

0 1 2

Gen

eration

Rate, m

-2s-1s

-1

4

2

0

Lower windspeeds

Higher windspeeds

Credits: Leifer, Piorek, Smith and Banerjee, unpublished.


•Microbreaking waves might be the dominant surface mode on the open ocean, since the anually averaged wind speed is ~7 m/s. Since microbreakers are hard to distinguish, this statements is only a hypothesis.

•White-caps are only beginning to form at this wind speed.

•Much of the ocean experiences wind speeds which do not produce white-caps.


Photo Credit: NASA Winds Measurements from NSCAT http://winds.jpl.nasa.gov/index.html

http://winds.jpl.nasa.gov/index.html







• Increased mixing in the top ~10 centimeters of the open ocean will affect oxygen transport, carbon dioxide transport, nitrogen transport, etc…

• But we still have much uncertainty about how these small waves, and other small waves, affect mixing. Our empirical measurements of gas transport have a debilitating scatter.


• For Example: Subtropical Mode Water near Bermuda has been found to store large amounts of dissolved CO2 as a result of seasonal/decadal mixing layer oscillations. People believe this storage is dictated by interfacial gas transfer rates. Thus, uncertainties of ~400% could be “annoying”.


How we are Trying to Learn More

• High speed digital photographs of the mixing process in a lab, with controllable conditions.

• Gas transport measurements in a lab, with controllable conditions.

• Observations on the Santa Barbara Channel, maybe.


0 m/s wind: mean is 5.5e-6 +/- 5.4e-6 m/s1.5 m/s wind: mean is 1.1e-5 +/- 8.8e-6 m/s3.7 m/s wind: mean is 2.2e-5 +/- 9.2e-6m/s

kw =depth/( Ca/H-C)*( dC/dt + Um* dC/dx)


1.5 m/s wind: mean k is 1.0e-5 +/- 8.0e-6 m/s3.7 m/s wind: mean k is 4.7e-5 +/- 8.4e-6 m/s

Other Processes I’m Interested In

• Fluids in general.

• Lab experiments which give limnologists the better ability to model nutrient cycling.

• Understanding rivers or ocean with perturbed nutrient cycles. Relation of gas transport – or any fluid transport process -to environmental quality.

• Ok, questions and lunch.

Download - Microbreaking Waves on the Open Ocean What they are Why they are interesting How we are trying to learn more Damon Turney PhD Seminar, May 23, 2003

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