Coast to Coast Seminar Series: "Climate Impacts of Freshwater Forcing of the Ocean General Circulation"

Abstract

During the past million years of Earth history, climate variability has been dominated by a 100 kyr cycle of continental scale glaciation and deglaciation. Each of these quasi-periodic events owed its existence to the minute variations in the distribution of solar radiation caused by gravitational n-body effects in the solar system. In each cycle of this process continental glaciation was accompanied by a fall of mean sea level of approximately 120 m. The glaciation phase of each cycle persisted for approximately 90,000 years whereas the deglaciation phase was much more rapid, lasting approximately 10,000 years. During deglaciation, the return of freshwater to the ocean basins was responsible for highly significant disruptions of climate, foremost among which was the so-called "Younger-Dryas" climate reversal during which northern hemisphere surface temperatures were forced to return to near full-glacial cold conditions even as the system was in the process of returning to a state of modern warmth. This phenomenon provides a target for testing the transient response of the global climate models that are employed to make predictions of the influence of global warming due to increasing concentrations of the atmospheric greenhouse gases. This test will be described in detail.