Aircraft-based observations of air-sea fluxes during the Greenland Flow Distortion (GFD) experiment

An aircraft-based field campaign, the Greenland Flow Distortion experiment, was based out of Keflavík, Iceland, in February and March 2007. The 12 mission were primarily over open ocean conditions over the Denmark Strait and the Irminger and Iceland Seas. In situ observations of high impact weather phenomena found in this region and their associated air-sea fluxes were made. These fluxes can be of great importance as it has been suggested that processes in the Irminger Sea may be important for the overturning of the thermohaline circulation.

In total five low-level flights were flown, measuring turbulent wind, temperature and humidity. The air-sea fluxes were estimated using the eddy covariance method for flux runs of 2 minutes (approximately 12 km) at typical altitudes of 30-40 m above the sea surface. In total there were 131 flux runs, 121 over open water, the remainder over sea ice or the marginal ice zone. Strict quality control procedures have been applied, resulting in a total of 112 runs over open water for wind stress and sensible heat fluxes and 106 for latent heat fluxes.

The mean 10-m neutral wind speed of the flux runs varies from 5 to 25 m ^-1 with 80% of the runs in the range 14-19 m s^-1. The measured wind stress over open water has a range of 0.1-1.6 N m^-2. The sensible and latent heat fluxes over open water vary between 50 and 300 W m^-2. The mean exchange coefficients for the interval 15-18 m s^-1 are C_DN = 2.1 x 10^-3, C_HN = 1.7 x 10^-3 and C_EN = 1.6 x 10^-3. These coefficients are somewhat higher than most previous studies have suggested, although they are within the range presented for the few high wind speed data sets that are available.