Comment [on “Influence of Mediterranean Outflow on climate”]



The Rahmstorf large-scale circulation model lacks the high resolution needed to reveal the critical fine structure of oceanic circulation, both known and predicted, upon which the ice-age initiation hypothesis is based [Johnson, 1997]. Consequently, it is unable to correctly evaluate the consequences of presently increasing Mediterranean salinity and Outflow. Rahmstorf also seriously misrepresents important elements of the hypothesis.

1) It is not simply an increase in evaporation rate in the warmer Labrador Sea that initiated the Wisconsinan Glaciation. Instead, the larger temperature contrast between cold land and adjacent warmer sea surfaces steered the northeastward-moving cyclonic storm systems into the Baffin area and away from their interglacial path toward Iceland and Scandinavia. This switch in circulation is indicated by the sudden onset of heavy precipitation in northeastern Canada, inferred from a large increase in hematite and clay deposited on the Bermuda Rise about 120,000 year ago when the Wisconsinan Glaciation began [Adkins et al., 1997]. This regional circulation switch could be duplicated only in a very high-resolution model. Note that at this time the Milankovitch insolation was nearly identical to present and there was no CO2 warming or artificial loss of Nile River discharge.