University of Minnesota
Aerospace Engineering and Mechanics
Winter 1997 Seminar Series


Exchange of Biogenic Gases at the Air-Ocean Interface



Dr. Wade McGillis

Woods Hole Oceanographic Institute

Abstract

The mechanisms of gas exchange at the air-ocean interface are of considerable importance in estimating fluxes of gas absorbed or released by the ocean. This interfacial gas transfer is very complex. The air and the water are usually in turbulent motion, and the interface between them is irregular, and disturbed by waves, sometimes accompanied by breaking, spray and bubble formation. Thus the transfer involves a wide variety of physical phenomena occurring over a wide range of scales. A major goal is to develop links between the atmospheric wind stress, surface wave field, near-surface flow, surfactant films, and gas transfer. Surfactants have a first-order effect on the gas transfer velocity-wind speed relationship up to moderate wind speeds and the surface mean-square-wave slope offers a very good parameterization of gas transfer velocity. Simultaneous measurements of these parameters are needed to determine mechanisms involving Marangoni viscoelastic damping of waves and near-surface flows.
In this talk, an independent method of estimating the in-situ flux of biogenic gases will will be presented. Recent field evaluation of systems designed to directly measure the flux of CO2 using the eddy correlation method and DMS using the atmospheric profile technique have been performed. During these field tests, flux estimates were combined with measurements of the air-sea concentration difference to determine the transfer coefficients in coastal waters. The success of these field tests indicate that these methods would enable investigations of a number of the physical processes controlling air-sea gas exchange.


Friday, February 21 1997
225 Akerman Hall, 2:30 - 3:30 p.m.


Refreshments served after each seminar in 227 AKERMAN HALL .
Disability accommodations provided upon request.
Contact Leslie Petrus : Secretarial Assistant.

petrus@aem.umn.edu (612) 625-8000.