GasEx-III Experiment: Processes of Gas Exchange in the Southern Ocean

Collaborators: Michael DeGrandpre (University of Montana)
James B. Edson (University of Connecticut)
Christopher W. Fairall (NOAA)
Wade B. McGillis (LDEO)
Christopher L. Sabine (PMEL)

This project is a collaborative field effort to investigate the processes that drive air-sea CO2 exchange in the Southern Ocean. To conduct these investigations, W. McGillis (LDEO), J. Edson (University of Connecticut, Avery Poi6nt), and C. Zappa (LDEO) Iceberg Photo will directly measure the CO2 flux and measure the surface ocean wave field that controls the air-sea CO2 flux. These will include estimates of the surface fluxes GasExIII boat of momentum, latent and sensible heat, atmospheric forcing using meteorological approaches, surface ocean waves, and wavebreaking. In collaboration with C. Sabine (PMEL) and M. DeGrandpre (University of Montana), we will provide other measurements characterizin9g the oceanic velocity, thermal structure, bubbles, and interfacial mixing processes. These observations, and supporting measurements, will allow us to examine the dependence of CO2 exchange on atmospheric forcing, surface waves, turbulence, and stratification in the Southern Ocean, a region having limited understanding of processes controlling the air-sea carbon cycle.

Our main objective is to investigate the exchange of CO2 between the ocean and atmosphere at moderate to high wind speeds where the CO2 flux may be significantly enhanced by wave breaking. For example, the GasEx-98 study suggested a cubic relationship between wind speed GasExIII Map and gas transfer velocities above 12 m/s. However, the scarcity of data created very large error bars and uncertainty in this relationship. The Southern Ocean GasExIII Mapis an ideal site to test this hypothesis where persistent high winds and storms are prevalent. The Southern Ocean and other mid to high-latitude regions represent the primary oceanic sink of atmospheric CO2 over the global ocean. Therefore, an accurate parameterization of the CO2 flux in these regions is of critical importance for accurate estimates of the global carbon budget, climate model forecasts, and ultimately predictions of climate change. Therefore, the overall goal of the GasEx process studies will be to determine the dependence of gas exchange on easily measured atmospheric and/or oceanic variables and derive parameterizations applicable to all regions of the ocean. For more information on the Southern Ocean GasEx experiment, be sure to check out the Southern Ocean GasEx Homepage and the GasEx III Blog site.