Surface energy, CO2 fluxes and sea ice

Abstract

This paper reviews the current state of observation, parameterization and evaluation of surface air-sea energy and gas fluxes, and sea ice, for the purposes of monitoring and predicting the state of the global ocean. The last 10 years have been marked by the development of more accurate parameterizations of turbulent fluxes, in particular COARE-3. A seamless approach to surface flux observing systems is also being developed ranging from highly accurate observations on buoys and research ship campaigns to the longstanding Voluntary Observing Ship (VOS) scheme. In addition to flux products based on in situ data, satellite measurements and numerical weather prediction, several hybrid products have been developed which combine data from these different sources. Satellite monitoring of sea ice has been extended to more accurate and higher resolution estimation of ice extent and quantification of ice thickness. Global air-sea CO2 flux products are now based on significantly better-sampled datasets reducing the uncertainty in the ocean carbon budget. Despite these advances, considerable gaps remain in our understanding of air-sea fluxes, for example, at both high and low wind speeds, for gas and aerosol exchange and in marginal ice zones. Furthermore, there are serious concerns about the recent decline in the number of VOS observations. Closure of global and regional energy balances still cannot be achieved without adjustments to the flux fields and/or the underlying surface meteorological variables. The impact of sampling on interannual variability of fluxes makes estimates of climate tendencies in air-sea exchanges highly uncertain. In order to meet these challenges we formulate a future vision of a surface flux observing system, which provides a synergy of in situ measurements (buoys, research vessels and merchant ships), remote sensing and models.