Observations of Unexpected Short-Term Heating in the Uppermost Layer of the Dead Sea after a Sharp Decrease in Solar Radiation

The Dead Sea is one of the saltiest bodies of water in the world. Observational evidence has been obtained of unexpected short-term water heating in the 2-m uppermost layer of this hypersaline lake, following a sharp drop in solar radiation under weak winds. This was carried out using Dead Sea buoy measurements. Passing frontal cloudiness mixed 30 with significant dust pollution over the Judean Mountains and the Dead Sea, which occurred on March 22, 2013, led to a dramatic drop in noon solar radiation from 860 W m -2 to 50 W m -2 . This drop in solar radiation caused a short-term (1-hour) pronounced temperature rise in the uppermost layer of the sea down to 2 m depth. After the sharp drop in noon solar radiation, in the absence of water mixing, buoy measurements 35 showed that the temperature rise in the uppermost layer of the Dead Sea took place for a shorter time and was more pronounced than the temperature rise under the regular diurnal solar cycle. The water heating could be explained by gravitational instability in the skin-surface layer, when the warm surface water with the increased salinity and density submerged, thereby increasing temperature in the layers below. 40