Earth Institute Contact: Dr. David Ho
Locations: Southern Ocean
In this project, researchers at the Lamont-Doherty Earth Observatory (LDEO) of Columbia University will participate in an international SOLAS (Surface Ocean Lower Atmosphere Study) dual tracer gas exchange study led by a New Zealand scientific team. The study aims at improving our understanding of gas exchange and their dependence on wind speed and other factors in the Southern Ocean, a key region for air-sea exchange of atmospheric CO2. Parameterization of gas transfer velocity (k) with wind speed is not ideal, as there are other factors that contribute to influence k. However, many investigators rely on these parameterizations to derive gas transfer velocities so continuing to improve the parameterization of k versus wind speed (or mean square wave slope) relationships is critical for improving understanding of global biogeochemical budgets, including that of CO2. During the experiment, the LDEO team will contribute the 3He data (ca. 300 measurements) to a dual tracer experiment (3He/SF6) that will provide spatially and temporally averaged k over a period of ca. 20 days and a region of ca. 250 km2. For this experiment, a mixture of 3He and SF6 will be injected into the surface mixed layer at 46.67 'S, 178.5 'E, and the resulting tracer patch will be surveyed for ca. 20 days. k can be derived from the rate of decrease in the 3He/SF6 ratio close to the center of the patch. Depending on the wind regime during the experiment, the team should be able to obtain 4 to 8 estimates of k over a range of wind speeds between ca. 2 and 14 m s-1. These data will be used to test how well gas exchange parameterizations, derived from global ocean 14C inventories and supported by results from dual tracer gas exchange experiments conducted in coastal and shelf area, can be extrapolated to higher southern latitudes. The dual tracer results will be complemented by short time scale, small spatial scale measurements of k that are based on micrometeorological measurements (eddy correlation of CO2, and relaxed eddy accumulation measurements of CO2 and DMS). In addition to the dual tracer measurements, the team will perform Ne, N2, O2 and Ar measurements (in collaboration with colleagues at the University of Rhode Island and Princeton University) to understand better the role of bubbles in gas exchange at high wind speeds. Taken together, these data should improve our knowledge of k in the data-sparse regions in the Southern Ocean and significantly contribute to closing a critical gap in our knowledge of air-sea gas fluxes, thereby addressing a key element of the SOLAS science plan.
Cross Cutting Themes:
University of Rhode Island
National Science Foundation