Changes in the rate of evaporation from the dead sea

Abstract

Heat balance calculations indicate that during the last 40 years a marked decrease in the evaporation rate from the Dead Sea has accompanied its increased salinity. Two-thirds of the estimated 17 per cent decrease is attributed to the reduced vapour pressure of its now salt-saturated waters, the remaining one-third to the reduction in radiation balance caused by the greater longwave loss from its warmer sea surface. The rate of evaporation from a hypothetical Dead Sea with a surface level restored to previous levels by an influx of Mediterranean waters was estimated to be 158 per cent of its current rate, which is 1.05 m per year. Two-thirds of this increase was attributed to the greater vapour pressure gradient between the less saline surface water and the atmosphere, one-third to the increased radiation balance at its cooler sea surface. Although the mechanism for these changes are well understood and easily calculated, a number of complex interactions exist between the various effects that do not allow a quantitative relationship to be established analytically between the Dead Sea's surface level or salinity and rate of evaporation. However, empirically, the linear relationship between annual evaporation, E (m year-'), and surface density, D (g cm-3), E = 4.701 -2.926 D, accounts for 98 per cent of the variation between evaporation from a salt-free and from a salt-saturated Dead Sea.

Dead Sea evaporation by eddy covariance measurements vs. aerodynamic, energy budget, Priestley–Taylor, and Penman estimates

“…Even though evaporation is of particular importance for the Dead Sea water budget, the variation in evaporation estimates is high. The spread of the evaporation estimates ranges from 1.05 to 2.00 m a −1 , which is comparable to a volume loss of 700-1334 × 10 6 m 3 a −1 (Stanhill, 1994;Salameh and ElNaser, 1999). It is important to reduce these uncertainties and assess the water budget components of the Dead Sea for a climatological purpose, but it is also of importance for the people in the area and the socio-economic development of the region to anticipate the evolution of these components and the resulting consequences for the environment.…”

“…Previous studies on the Dead Sea evaporation used indirect methods, such as water budget calculations (Salameh, 1996;Salameh and El-Naser, 2000); the energy budget approach (Stanhill, 1994;Lensky et al, 2005); aerodynamic methods (Salhotra et al, 1985;Oroud, 1994); or the combination of the latter two methods, called the combination approach (Calder and Neal, 1984;Asmar and Ergenzinger, 1999;Oroud, 2011). Variations in evaporation estimates between the studies result from assumptions on single water budget components such as groundwater inflow, different lengths of the time series of input variables, different measurement locations, and measurement uncertainties.…”

Remote sensing of the Dead Sea surface temperature

“…A hydrometeorological buoy was placed in the center of the Dead Sea in 1992, and since then (except for a gap between 2002 and 2004), it has been recording meteorological data over the Dead Sea surface and the temperature profile from the surface down to a depth of 40 m [Gertman and Hecht, 2002;Hecht and Gertman, 2003]. This data set led to the formulation of its mass and energy balances [Lensky et al, 2005;Neumann, 1958;Stanhill, 1985]. However, because of the lack of data on the spatial variations of sea surface temperature (SST), it is unclear to what extent the measured surface temperature in a single location represents the surface temperature of the whole Dead Sea area.…”

Dead Sea Rate of Evaporation

“…The present rate of evaporation from the Dead Sea is not well defined yet. Estimates range from 1.05 m/year [9] to 2 m/year [8] for the current salinity. The first value was determined using heat balance approach while the latter value was found based on water balance calculations.…”