New Hypothesis Explaining Abrupt Climate Change at the End of Iceages
20.02.2007 - Other
In a recent article in Climatic Change, D.G. Martinson and W.C. Pitman III discuss a new hypothesis explaining how the climate could change abruptly between ice ages and inter-glacial (warm) periods. They argue that the changes in Earth's orbit around the sun (Milankovitch cycle) are not sufficient on their own to explain the estimated high rate of change, and that there must be an amplifying feedback process at work.
Their hypothesis to explain the very abrupt terminations that end most of the glacial episodes is that the fresh water input works in concert with the Milankovitch cycle and the albedo feedback.
These terminations could be caused by a glacial build-up of sufficient magnitude to isolate the Arctic, reducing the inflow of fresh water. The increased salinity in the water surface layer would have caused the Arctic Ocean to overturn (through the effect on the atmospheric circulation and the ocean currents). This overturning brings warmer deep water to the surface melting the sea-ice before cooling down and sinking again.
So far, this proposed hypothesis by Martinson and Pitman III is merely a speculation, and needs to be tested through numerical model experiments (which would require higher resolution sea-ice and ocean models than used in today's global climate models). The hypothesis is thoroughly discussed in an excellent post on the RealClimate website.
