ALBERT

Description: The Dead Sea is the saltiest and lowest terminal lake in the world. Currently, the Dead Sea’s water level is dropping by more than 1 m per year, due to excessive use of the water that previously flowed into it. The Dead Sea constitutes a unique environment and is important from economic, environmental, and touristic points of view. The winter deep convection of the Dead Sea and its deep and narrow basin suggest that non-hydrostatic effects may significantly affect its circulation. Despite these factors, the expected non-hydrostatic effects on the circulation of the Dead Sea have not been investigated. Here we perform high resolution (100 m) ocean general circulation model (the MITgcm) simulations of the Dead Sea and show that the non-hydrostatic results are very different from the hydrostatic ones. Specifically, we show that the winter non-hydrostatic simulations resulted in a layer of dense water overlaying slightly lighter water during the several last hours of the night; this convection process involved plumes of heavier sinking water and the entrainment of the plumes. We also studied the effect of the wind stress’s diurnal variability and found it to be important, especially during the summer when the wind’s variability drastically increased the surface kinetic energy; however, it did not alter the depth density profile. The results presented here may be important for the Dead Sea’s potash industry and for the planned Red Sea-Dead Sea canal that aims to stop and, possibly, to increase the level of the Dead Sea using the Red Sea’s water.

Description: Nan-Wan Bay in Taiwan and the Gulf of Elat in Israel are two different coastal environments, and as such, their currents are expected to have different statistical properties. While Nan-Wan Bay is shallow, has three open boundaries, and is directly connected to the open ocean, the Gulf of Elat is deep, semi-enclosed, and connected to the Red Sea via the Straits of Tiran. Surface currents have been continuously measured with fine temporal (less than or equal to 1 h) and spatial resolution (less than or equal to 1 km) for more than a year in both environments using coastal radars (CODARs) that cover a domain of roughly 10  ×  10 km. These measurements show that the currents in Nan-Wan Bay are much stronger than those in the Gulf of Elat and that the mean current field in Nan-Wan Bay exhibits cyclonic circulation, which is stronger in the summer; in the Gulf of Elat, the mean current field is directed southward and is also stronger during the summer. We have compared the statistical properties of the current speeds in both environments and found that both exhibit large spatial and seasonal variations in the shape parameter of the Weibull distribution. However, we have found fundamental and significant differences when comparing the temporal asymmetry of the current speed (i.e., the ratio between the time during which the current speed increases and the total time). While the Nan-Wan Bay currents are significantly asymmetric, those of the Gulf of Elat are not. We then extracted the tidal component of the Nan-Wan Bay currents and found that it is strongly asymmetric, while the asymmetry of tidally filtered currents is much weaker. We thus conclude that the temporal asymmetry of the Nan-Wan Bay currents reported here is due to the strong tides in the region. We show that the asymmetry ratio in Nan-Wan Bay varies spatially and seasonally: (i) the currents increase rapidly and decay slowly in the northern part of the domain and vice versa in the southern part, and (ii) the asymmetry is stronger during summer.