The ocean and the atmosphere are closely linked systems, which exchange gases, particles (dust, aerosols), heat, and momentum. Atmospheric reservoirs of carbon dioxide, stable in medieval times and until the 19th century, have risen dramatically in the past 200 years resulting in a 38% increase since the beginning of the Industrial Revolution.
Carbon dioxide is largely responsible for trapping heat in the atmosphere, enhancing the natural green-house effect that other atmospheric gases (mainly water vapour) have on our planet. The observed rapid increase of the Earth’s temperature over the past century is thought to be a result of the high levels of green-house gas emissions caused by various human activities. This alteration certainly affects the heat exchanges across the air-sea interface, with predictable consequences on marine processes such as ocean dynamics (stratification and circulation patterns), ecosystem productivity, and the distribution of organisms.
The ocean also directly absorbs carbon dioxide from the atmosphere. Over the past 200 years about a third of the anthropogenic carbon dioxide emissions have sunk into the oceans. This is causing the seawater to become more acidic (decrease in pH), a process known as ocean acidification. Even if we succeeded in curbing the present-day carbon dioxide emissions, the acidification process will still affect marine ecosystems during the full course of the century.