Air-sea exchange is responsible for the buoyancy loss that causes mode waters to form. Specifically, determination of transformation requires accurate estimates of the sensible, latent, and radiative heat fluxes to compute the net heat flux. The net heat flux is then combined with estimates of the net freshwater flux to compute the buoyancy flux. Finally, the variation of the buoyancy flux integrated across isopycnals at the ocean surface is required to compute transformation rates. Obtaining accurate air-sea heat and freshwater fluxes and precise estimates of their gradients are crucial if we are to better understand and model the formation of EDW and evolution of upper ocean structure in the EDW formation region. However, there are large uncertainties in air-sea fluxes obtained from climatological data, atmospheric models, or remotely sensed such as those used to produce Fig.1. Errors in these fields stem from sparse sampling in a region of strong spatial gradients in the ocean, inaccuracies in atmospheric boundary layer properties and structure, especially during cold air outbreaks, and from the choice of flux algorithms. In CLIMODE for the first time we will accurately quantify the magnitude of the fluxes, their temporal and spatial variability, and their role in EDW formation. This requires long time series, spatial sampling (both remote and in situ), numerical modeling, and efforts to improve the parameterization of air-sea exchanges in bulk aerodynamic formulae.
Therefore to reduce these errors and provide accurate estimates of the transformation and formation rates in the EDW region we intend to: