Laboratory Studies on the Influence of Breaking Waves on Air-Sea Gas Transfer

A large variety of low molecular weight compounds are produced or consumed in surface marine waters as a result of biologicat and/or photochemical activity. Many of these gases (e.g. carbon dioxide (COz, nitrous oxide (NzO), methane (CFI4), dimethyl sulphide (DMS) and methyl bromide (CHiBr) aie relevant to climate change and may also play impoftant roles in the chemistry of the atmosphere. The rate of exchange between the ocean and the atmosphere for all of these poorly soluble gases is slow and is typically expressed as an exchange coefficient, the air-sea transfer velocity 'k'. For a non-reactive gas, this is usually assumed to be dependent on molecular and turbulent transfer ii the sea surface micro-layer. Values of k for different gases and their dependence on environmental conditions (in particular wind speed) are known only approximately. Most estimates of the magnitude of ihe or"- source/sink of biogenic gases have been determined from the product of the concentration difference between the atmosphere and ocean and values ofk derived from parameterisations with wind speed.