The thermal stratification of the Dead Sea was observed in high spatial and temporal resolution by means of fiber optics temperature sensing. The aim of the research was to explore the dynamics of the metalimnion, including: i) short period fluctuations of the thermocline's depth, and ii) seasonal sharpening of the metalimnion and the role of double diffusion flux. A 55 m long profiling system was placed vertically through the water column with spatial resolution of 18 cm. The profiler covered the upper mixed layer (~20 m), metalimnion and the hypolimnion. Temperature profiles were recorded every 5 minutes along the stratification period (MAY-DEC 2012). The analysis of the profiles was based on defining objective key locations within the metalimnion, based on the temperature depth profile and its depth derivatives. We found strong anti-correlation of the metalimnion depth fluctuations to measured lake level fluctuations; e.g. - typical level rise of ~1 cm correlated with deepening of the thermocline by a few meters.3D model runs (POM), using measured meteorological boundary conditions revealed similar lake level and metalimnion fluctuations. These correlations (r=0.8), together with similar correlations to the variations in the vertically integrated apparent heat content, suggest that we observed, 1 dimensionally, a spatial phenomena, related to internal waves in the lake. These, are the source of lateral heat advection explaining the dramatic variations in the observed heat content within the few hours scale. In the seasonal scale, the metalimnion's temperature depth profile is sharpening, starting from a gradual round temperature profile, to distinct staircases, through merging of the staircases down to a single sharp step (<1m), achieved in early fall. Additional observations pointing of heat and salt fluxes between the strata are synchronous with the metalimnion sharpening, associating those fluxes to the double diffusion phenomena, typically characterized by interface sharpening and staircases.
|Title of host publication
|The Israeli Association For Aquatic Sciences 13th Annual Meeting, 27 Oct 2016
|Published - 2016