ABSTRACT

During the last climatic cycle, sea surface temperature and salinity changed in the whole ocean, noticeably in the North Atlantic, which is an area of deep water formation. This change resulted in major variations of the thermo-haline circulation and the CO2 cycle. This chapter describes the main mechanisms responsible for these changes: (a) insolation forcing responsible for changes in the climate system exhibiting periodicities of 19, 23, and 41 kyr and (b) interaction between the cryosphere and the ocean, which resulted in rapid (centennial) climatic changes.

The paleoclimatic record shows that the thermo-haline circulation and the Earth's climate are extremely sensitive to minor perturbations, such as freshwater discharge at high latitude into the North Atlantic Ocean. Under pure natural conditions, the geological data indicate that warm times are associated with active thermo-haline circulation, whereas reduced thermo-haline circulation prevailed during glacial times. If the global warming induced by human activities would result in enhanced precipitation over the North Atlantic, the resulting salinity changes might act as a massive iceberg discharge occurring during the glaciation. This would reduce the mean flux of deep water formed annually, the rate of thermo-haline circulation, and the oceanic heat flux brought to the Norwegian Sea, and it would deeply affect the European climate.