The Red Sea during the Last Glacial Maximum: implication on sea level reconstruction

Hezi Gildor

Department of Environmental Sciences & Energy Research (ESER)
Weizmann Institute of Science, Israel

Absract

The Red Sea (RS) is a semi-enclosed basin connected to the Indian Ocean via a narrow and shallow strait, surrounded by arid areas, and exhibits high sensitivity to atmospheric changes and sea level reduction. We have used the MIT GCM to investigate the hydrogrophy and circulation in the RS in response to reduced sea level, variability in the Indian monsoons, changes in atmospheric temperature, and humidity occurring during the Last Glacial Maximum (LGM). The model results show high sensitivity to sea level reduction especially in the salinity field (increasing with the reduction in sea level) with a mild atmospheric impact as well. Sea level reduction decreases the stratification, increases the subsurface temperatures, and alters the circulation pattern at the Strait of Bab el Mandab, which experiences a transition from submaximal flow to maximal flow. The reduction in sea level alters the deep water formation site, forming in the open sea convective site in the northern part of the RS compared to present day deep water formation from the Gulf of Suez outflow.
Based on both the GCM and on a simple hydraulic control model which take into account mixing process at the Strait of Bab El Mandeb, the sea level was reduced by only ~100 m in the Bab El Mandeb region during the LGM, i.e. the water depth at the Hanish sill (the shallowest part in the Strait Bab el Mandab) was around 34 m. This result agree with recent reconstruction of the LGM low stand of the sea (ICE-5G (VM2) model of Peltier (2004)