Air-sea exchanges of heat and freshwater plays an important role in driving the circulations of both the atmosphere and ocean. These fluxes are parameterised to force numerical models of the ocean and atmosphere and measurements are essential for validation of coupled ocean-atmosphere models. Despite their importance these fluxes are poorly known and the quality of their representation in models not well quantified. The turbulent fluxes of sensible and latent (evaporative) heat are difficult to measure directly and quantitative measurements of precipitation over the ocean from both rain gauges and remote sensing are notoriously unreliable.
From the limited information available there is little evidence for major changes in air-sea fluxes of heat and water in regions around the UK, despite important changes in variables such as sea temperature on which the fluxes depend. Natural variability is high, and the confidence in the measurements low, making the signal to noise ratio unfavourable. The global water cycle is likely to intensify but the effect of this change within the UK is uncertain.
Current research which may in time improve our knowledge of the air-sea fluxes of heat and water includes: planned long time series of direct flux measurements; improved parameterisations of the fluxes; bias adjustments of marine meteorological observations used as input to the parameterisations; and crucially improved representation of the fluxes in numerical weather prediction and climate models.
Confidence in regional estimates of both present and future changes is low.
Elizabeth Kent, Simon Josey, David Berry, and Margaret Yelland
National Oceanography Centre,
European Way,
Southampton, SO14 3ZH
Executive summary