Unattended Measurements of High Latitude Air-sea CO2 Exchange by Eddy Covariance

High winds, biological productivity, and variable sea ice cover of high latitude oceans present opportunities as well as challenges for measuring and understanding processes controlling air-sea gas exchange. We designed and deployed a ruggedized closed-path eddy covariance system for unattended direct measurements of air-sea CO2 flux on the Research Vessel Icebreaker (RVIB) Nathaniel B. Palmer. Piston velocity was calculated by combining EC CO2 flux data with data from an underway dpCO2 system (courtesy of Taro Takahashi, Columbia University). The flux system was at sea for 344 days (8 cruises) from January 2013 to May 2014, and ship tracks spanned 12S-78S latitude. Four cruises (195 days) were selected for final analysis based on abs(dpCO2) greater than 40 ppm, stable system operation, and a variety of ice and open water conditions. Continuous images of the surface were collected and processed using the approach of Callaghan and White (2009) to quantify whitecap fraction. The ability of a modified version of this method for retrieving ice cover fraction was tested. These data are being used to examine relationships between piston velocity, wind speed, whitecaps, and ice cover.