New Dynamical Explanation for the Abrupt Temperature Rise in the Beginning of the Holocene

The abrupt temperature rise in the beginning of the Holocene is the most dramatic climatic change of the last 80,000 years. It is suggested here that the change is due to the abrupt opening of the Bering Strait which we hypothesize was initially jammed with icebergs, common during the termination of the last glaciation. Once sea-level rose beyond a critical point, the dam broke allowing low salinity water (which dominated the Atlantic during the Younger Dryas) to be flushed out of the Atlantic. This then, allowed the global wind field to force more Southern Ocean water into the Atlantic. A new analytical coupled ocean-atmosphere model was developed and applied to the North Atlantic, in an attempt to quantify the temperature change due to the opening and closing of the Bering Strait. Heat, salt and mass are all conserved within a box in the North Atlantic. A convection condition allows water to enter the deep layer, and the ocean and atmosphere are connected through their Ekman layers. Restarting convection, through the opening of the Bering Strait, increases mean oceanic and atmospheric temperatures by 2-4 ºC and 14-17 ºC, respectively. These values are favorably compared to those found in both the CEREGE alkenone and GISP II Greenland ice core records. The temporary damming/jamming of the Bering Strait due to large icebergs was examined using a simple laboratory box model. Results show the stability of the dam to be dependent on the rate of sea level rise, which at 1 cm yr -1, should be sufficiently slow to allow a temporary dam to exist for several thousands of years. Sea ice probably fused icebergs together, and through ridging could have created a 30-40 m vertical ice wall.