Millennial to orbital-scale ice sheet effects on drought intensity in the Eastern Mediterranean

Abstract:

Millennial to orbital-scale rainfall changes in the Mediterranean region and corresponding variations in vegetation patterns were the result of large-scale atmospheric reorganizations. In spite of recent efforts to reconstruct this variability using a range of proxy archives, the underlying physical mechanisms remained elusive.

Here we present results from a new high-resolution sedimentary section from Lake Van (Turkey, ICDP Paleovan) along with two simulations of an Earth system model (LOVECLIM). We identified a pervasive link between periods of enhanced North Atlantic glacial iceberg calving, weaker Atlantic Meridional Overturning Circulation, Dansgaard-Oeschger cold conditions and massive droughts in the Eastern Mediterranean for the past three glacial cycles. On orbital-timescales, our paleorecord/model data suggests that the topographic effect of large Northern Hemisphere ice sheets and periods with minimum boreal insolation seasonality further exacerbated drought intensities by suppressing both summer and winter precipitation.

Furthermore, we reconciled the seemingly contradictive regional orbital-scale lake-level variations of Lake Van in Turkey and Lake Lisan in the Dead Sea Basin (DSB) by conducting a thought experiment- an idealized lake-level model over the past 80 kyr for Lake Van and Lake Lisan was forced with the simulated regional precipitation and evaporation data of the orbital-scale LOVECLIM experiment. It shows that reduced glacial precipitation can lead to either higher or, lower lake levels, depending on the delicately balanced relative changes in temperature-driven evaporation. Therefore, decreasing simulated and reconstructed glacial precipitation in the Eastern Mediterranean region is not inconsistent with the high glacial lake stands in DSB lakes.