Biases in the air-sea flux of CO2 resulting from ocean surface temperature gradients
McGillis, Wade R.
Jessup, Andrew T.
DeGrandpre, Michael D.
Hare, Jeffrey E.
Edson, James B.
MetadataShow full item record
The difference in the fugacities of CO2 across the diffusive sublayer at the ocean surface is the driving force behind the air-sea flux of CO2. Bulk seawater fugacity is normally measured several meters below the surface, while the fugacity at the water surface, assumed to be in equilibrium with the atmosphere, is measured several meters above the surface. Implied in these measurements is that the fugacity values are the same as those across the diffusive boundary layer. However, temperature gradients exist at the interface due to molecular transfer processes, resulting in a cool surface temperature, known as the skin effect. A warm layer from solar radiation can also result in a heterogeneous temperature profile within the upper few meters of the ocean. Here we describe measurements carried out during a 14-day study in the equatorial Pacific Ocean (GasEx-2001) aimed at estimating the gradients of CO2 near the surface and resulting flux anomalies. The fugacity measurements were corrected for temperature effects using data from the ship's thermosalinograph, a high-resolution profiler (SkinDeEP), an infrared radiometer (CIRIMS), and several point measurements at different depths on various platforms. Results from SkinDeEP show that the largest cool skin and warm layer biases occur at low winds, with maximum biases of −4% and +4%, respectively. Time series ship data show an average CO2 flux cool skin retardation of about 2%. Ship and drifter data show significant CO2 flux enhancement due to the warm layer, with maximums occurring in the afternoon. Temperature measurements were compared to predictions based on available cool skin parameterizations to predict the skin-bulk temperature difference, along with a warm layer model.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C08S08, doi:10.1029/2003JC001800.
Showing items related by title, author, creator and subject.
Evaluation of the National Oceanic and Atmospheric Administration/Coupled-Ocean Atmospheric Response Experiment (NOAA/COARE) air-sea gas transfer parameterization using GasEx data Hare, Jeffrey E.; Fairall, Christopher W.; McGillis, Wade R.; Edson, James B.; Ward, Brian; Wanninkhof, Rik (American Geophysical Union, 2004-07-16)During the two recent GasEx field experiments, direct covariance measurements of air-sea carbon dioxide fluxes were obtained over the open ocean. Concurrently, the National Oceanic and Atmospheric Administration/Coupled-Ocean ...
Gerbi, Gregory P.; Trowbridge, John H.; Edson, James B.; Plueddemann, Albert J.; Terray, Eugene A.; Fredericks, Janet J. (American Meteorological Society, 2008-05)This study makes direct measurements of turbulent fluxes in the mixed layer in order to close heat and momentum budgets across the air–sea interface and to assess the ability of rigid-boundary turbulence models to predict ...
Plueddemann, Albert J.; Galbraith, Nancy R.; Ostrom, William M.; Tupper, George H.; Handy, Robert E.; Dunn, James M. (Woods Hole Oceanographic Institution, 2001-07)A surface mooring outfitted for meteorological and oceanographic measurement was deployed near 14°50'N, 51°00'W in the northwest tropical Atlantic on 30 March 2001. This was the initial deployment of the Northwest Tropical ...