Chemistry Reference
In-Depth Information
mous capacity to absorb and release both heat and gases. The oceans play
an important role as sink for carbon (the yearly absorption capacity is
about three Gigatons of carbon). In recent years, global climate change and
the growing pollution in atmosphere and oceans have drawn the attention
to small-scale transfer processes at the air/water interface.
Fig. 1.
Which of the three commonly used models best describes the mass transfer
across the aqueous boundary layer: surface renewal, turbulent diffusion or mo-
lecular diffusion?
The exchange of inert gases including greenhouse gases (e.g., carbon
dioxide, methane) is governed by the interplay of turbulent transport and
molecular diffusion in the aqueous boundary layer. This 20-300 Pm thick
layer constitutes the bottleneck for the exchange of gases between atmos-
phere and ocean. Although the underlying turbulent transport mechanisms
are extremely complex and difficult to quantify, knowledge about the envi-
ronmental parameters influencing air-sea gas exchange has increased con-
siderably in recent years. Nevertheless, the commonly used semi-empirical
parameterisations of the gas exchange rate with wind speed (e.g., Liss and
Merlivat 1986, Wanninkhof 1992, Wanninkhof and McGillis 1999) predict
a global carbon uptake that differ by a factor of three (Donelan and
Wanninkhof 2002). Theoretical gas exchange models (surface renewal and
