| Summary: | Observations of a set of climatic and environmental parameters in ice cores indicate oscillations of the Earth system between a cold and a mild climatic state during the Wisconsin glaciation. The two states are determined by ocean circulation patterns: a cold state for deep water formation in the North Atlantic ocean turned off and a mild state for deep water formation turned on. One might speculate that turning off of deep water formation together with a consequent thermal decoupling of high latitudes is an important element of the mechanisms initiating a glaciation. Beside information from ocean sediment studies in the North Atlantic, indications for the oceanic flip-flop mechanism are rapid changes in the atmospheric CO2-concentration parallel to the changes between the mild and cold climatic states. These shifts probably reflect a steering effect by ocean dynamics on the oceans’ biological pump which controls the atmospheric pCO2. Major changes in climate, CO2 and CH4 show a correlation during glacial-interglacial changes. Whereas the temperature — CH4 correlation is almost perfect, the temperature — CO2 relationship shows a pecularity: During a deglaciation temperature and CO2 increase essentially in phase, but after a high CO2 concentration at the end of a transition is established, CO2 decreases during a few millenia before recovering to the final interglacial value. During a cooling period the CO2 decrease lags the temperature decrease by a few millenia. It seems plausible that this hysteresis type of relationship between temperature and CO2 reflects the uptake of CO2 from the atmosphereocean system to build up vegetation on continent areas which became ice-free after deglaciation and the release of CO2 due to a decrease of biomass during a cooling period leading to a glaciation. From two ice core drilling projects which are currently taking place in the summit area of the Greenland ice sheet important information is expected which will enable to confirm or discard the working hypotheses outlined in this ...
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