Geology Reference
In-Depth Information
the ocean at pH 8. Ocean-atmosphere exchange processes for gases such
as CO
2
and DMS may play an important role in climate change.
Both temperature and salinity affect the solubility of gases in water.
Empirical relationships can be found elsewhere.
9,10
The trends are such
that gas solubility increases with a decrease in temperature or an
increase in salinity. The changes in solubility are non-linear and differ
dramatically for various gases. Whereas Figure 6 depicts the solubility of
several gases as a function of temperature, Figure 7 shows the influence
of both salinity and temperature on the solubility of molecular nitrogen.
At the ocean-atmosphere interface, the exchange of gases occurs to
achieve equilibrium between the two systems, and consequently gases
become saturated in the water. However, supersaturation can be
achieved by several mechanisms. Firstly, bubbles that form from white
cap activity can be entrained and are dissolved at depth. The slight but
significantly greater pressure at depth relative to the surface favours gas
dissolution, and establishes a higher equilibrium concentration. Sec-
ondly as evident from Figure 6, if two water masses that have been
Figure 6 The solubility of various gases in seawater as a function of temperature
(Adapted from Broecker and Peng, 1982.
11
)
