CO2 Gas Exchange and Ocean Acidification Studies in the Coastal Gulf of Maine

The University of New Hampshire is studying CO2 gas exchange, ocean acidification, air-sea dynamics, and associated biological processes in the western Gulf of Maine. Three buoys and shipboard cruises have provided data to support these studies. The first, a CO2 monitoring buoy, is deployed jointly with NOAA’s Pacific Marine Environmental Laboratory and has been moored in 70 m of water northeast of the Isles of Shoals off the Maine coast during the last 4 years. The second, Jeffrey’s Ledge Moored Observatory, is a development mooring testing new techniques and is deployed east of Gloucester, MA near our third platform, a dedicated 2D wave measurement buoy. The Jeffrey’s Ledge mooring is testing the direct measurement of the wind stress from a discus buoy using a 3-D sonic anemometer along with a motion package to remove buoy motion effects. A fast-rate atmospheric CO2 sensor is mounted next to the anemometer to evaluate the potential for direct covariance gas flux measurements. Both discus buoys have additional meteorological and oceanographic sensors to provide key supporting measurements and to augment our regional ocean observing system. Long-term data from the CO2 buoy have helped to quantify the seasonal air-sea flux cycle of CO2 in the Gulf of Maine, and this buoy site is now the central node for near-term Carbon cycle process control experiments and longer term ocean acidification monitoring in this region. Jeffrey’s Ledge buoy momentum flux estimation results indicate reasonable first-order buoy motion corrections, likely flow disturbance leading to a non-zero mean vertical velocity, and possible artifacts due to large azimuthal rotations of the buoy. All aspects are under study. The paired sonic anemometer and open-path CO2 sensor package shows promise for long-term measurements using solar power. Ten minute resolution vertical water column oxygen profiles from this mooring show phytoplankton bloom signatures and permit robust net community production estimates in summer and fall 2009. Finally, all three buoys are providing information on mooring response, platform survival/servicing, sensor biofouling, and low-power data system and telemetry issues in the Gulf of Maine region