My main fields of expertise and teaching include physical oceanography, meteorology, and climatology with an emphasis on numerical modeling. My recent and current research focuses mainly on the development and application of ocean circulation models for theoretical investigations, operational forecasting and environmental impact assessment in the eastern Mediterranean, the Gulf of Elat (Aqaba), and the Dead Sea. Active projects include studying the impact of desalination discharge brine, dispersion of oil spills, and the circulation of the Dead Sea. I am also using a regional coupled atmosphere-ocean model to study air sea interaction over the Mediterranean region with a focus on seasonal forecasting and the development of extreme hurricane-like storms.

Recent projects

Red Sea - Dead Sea Water Conveyance Project (RDC)

This project was conducted as part of the overall feasibility study to assess the viabaility  and potential environmental consequences of pumping large amounts of water from the northern Gulf of Eilat (Aqaba), part of which would be desalinated to provide fresh water mainly to the Kingdom of Jordan, while the remaining salty brine would be poured into the Dead Sea. Funding was provided by the World Bank. I served as the Deputy Team Leader and Scientific Coordinator of the Red Sea component of the RDC study, which was conducted under the auspices of Thetis, an Italian engineering and environmental services company. The other partners in this project included scientists from the Interuniversity Institute for Marine Research in Eilat, the Hebrew University, Israel Oceanographic and Limnological Research, the Marine Sciences Station in Aqaba, and Stanford University.

In addition to the administrative tasks, I was responsible for the development and application of the simulation models used to assess the potential environmental impacts of withdrawing water from the northern Gulf of Eilat.

In the Dead Sea component of the study, I adapted a three dimensional ocean circulation model to study the dispersion of the salty desalination brine discharge in the unique conditions of the Dead Sea. This component was conducted under the auspices of TAHAL and the Geological Survey of Israel (GSI), a government institute operating under the Earth Science Research Administration within the Ministry of National Infrastructures.

Current projects

Circulation in the Dead Sea

The Dead Sea is a hypersaline, terminal lake located at the lowest point on the land surface of the Earth. Its current level is more than 429 m below MSL, and due to a negative water balance (mainly anthropogenic), the lake level has been dropping at an average rate of more than 1 m/yr for more than 30 years. The mean salinity has also been steadily increasing and today is close to 280 psu. The region of the Dead Sea is a unique landscape that has important historical, cultural, and economic value and therefore such an extreme change of the lake has significant environmental and economic consequences. In recent years there has been a notable increase in observing and monitoring of the lake through continuous measurements from several fixed buoys as well as during quasi-regular cruises. In order to complement the measurements and improve our understanding of the dynamics of this unique lake a three dimensional circulation model based on the Princeton Ocean Model is being developed. Previous modeling efforts were limited mainly to a one dimensional column model which was coupled to a comprehensive physio-chemical model and used for long term multi-decadal simulations. In this study the focus is on understanding the dynamical processes that control the lake-wide circulation on time scales ranging from days to seasons. The first step was to replace the equation of state with an equation appropriate for the hypersaline conditions, in addition to some minor tuning of the turbulence closure scheme. Preliminary simulations focused the role of wind forcing in various seasons. Next, a case study of a recent unusual winter flooding event, during which the lake level rose by more than 20 cm over a two month period, was considered. The model successfully simulated the observed transition from holomictic (complete vertical mixing) to meromictic (patial vertical mixing) conditions and epilimnion dilution during this event, as well as the restoration of holomictic conditions when the level started to drop again. 

More recently the model has been used to study seiches and internal waves in the Dead Sea. Seiches and internal waves in stratified lakes, which are generated on the thermocline, are affected by the seasonally varying stratification and by wind forcing. Seasonally, the amplitude of the thermocline fluctuations are anti-correlated with the density difference between the water layers, with the largest fluctuations when stratification is weak in spring/fall and moderate to weak fluctuations in mid-summer when stratification is fully developed. Power spectra of the observed wind as well as the measured and simulated lake level and thermocline depth show a pronounced diurnal period during summer, suggesting forcing by the diurnally varying wind. During spring and fall, when the water column stability is weaker, longer wind periods appear in addition to the diurnal mode. Accordingly, the lake level and thermocline depth fluctuations respond at lower frequencies. The longer wind periods are closer to the lake’s first vertical normal mode, suggesting that resonant amplification of the internal waves may explain the observed lower frequency response of the level and thermocline oscillations. Systematic decrease of the stratification stability originating from anthropogenic intervention over the past four decades (due to the dropping lake level and increasing salinity), has led to an increase in the amplitudes and periods of the internal waves.

Time series of observed thermocline depth fluctuations in May, August, and October

Progression of the sieche in of the seiche in the surface height (left) and in the depth of the thermocline (right), for the three-day model period 16 Oct 2012, 00:00 to 19 Oct 2012, 00:00. The time in hours since the 16Oct 00:00 is noted on each panel.

Oil spill modeling in the eastern Mediterranean

Since the discovery of major reserves in the eastern Levantine basin over the past six to seven years, exploration and drilling for natural gas and oil has proceeded at an accelerated pace. Israel and Cyprus are at advanced stages of exploration and preliminary production. A major gas reserve has just been discovered off the coast of Egypt and Lebanon has mapped blocks for licensing. As drilling and production proceed in this confined region the risk of a potential oil spill increase significantly. The highly variable ocean currents and winds will transport and spread any slick and spills, often in unanticipated directions. Deep water wells are especially prone to cross border transport. This risk has been assessed through a series of hindcast simulations with the MEDSLIK oil spill model forced with currents produced with a high resolution ocean model dynamical downscaling of the MOON/MyOcean Mediterranean Sea reanalysis and winds from the ECMWF atmospheric reanalysis. The scenarios considered are defined as worst case, uncontrolled well blowouts, located in the drilling zones of each of the countries mentioned above, that continue to discharge oil for several weeks.

Long term dispersion of the discharge brine from multiple desalination facilities

In recent years Israel has become a world leader in the technology and use of desalination to supplement the meager and dwindling natural fresh water supplies which are further stressed due to increasing population. Today nearly 50% of the water consumed in Israel is supplied from desalination. Five desalination facilities located along the coast produce nearly 90% of this amount through desalination of seawater (~600 MCM/yr). A roughly equivalent amount of reject brine with salinity nearly twice that of the intake seawater is discharged back into the sea. In order to assess the long term dispersion and potential effects of the discharge brine, a series of high spatial resolution (~440 m grid) simulations were conducted with the three dimensional Princeton ocean model run for a period of five years. The "discharge" simulation included the five discharge outlets, two located near the surface at the coast (Ashkelon and Hadera), and three submerged outfalls (Ashdod, Soreq, and Palmahim) located in water depth of ~20 m. The following figures show the near bottom salinity in the fifth year of the desalination simulation. After the initial nearfield dilution, the diluted brine plume will be dispersed by the far field currents. For the three subsurface discharges, after the initial dilution and plume rise, the brine will still be denser than the ambient seawater and therefore sinks and spreads near the sea floor. The two surface discharges (Ashkelon and Hadera) are mixed with cooling water from the power plants (7-10°C above ambient temperature) in ratios of 4.7:1 and 8.3:1, respectively. This offsets the density increase due to the higher salinity of the brine and therefore the plume is dispersed more effectively throughout the water column.

In summer the brine is mainly transported to the north while in winter and in the transition seasons the brine is more likely to be transported across the shelf and downslope. The discharges diluted with cooling water from power plants appear to mix and disperse more effectively than the subsurface brine discharges

Sensitivity of high impact weather events to changes in the Mediterranean sea surface temperature 

Local air-sea interaction over the Mediterranean may amplify the effects of climate change. This study investigates the sensitivity of simulations of two different high impact weather events to changes in the specification of sea surface temperature (SST) using a regional atmospheric model. First we assess the impact of specifying SST from two reanalysis data sets with differing spatial resolution. The simulated tropical like cyclone is slightly stronger in the case of the lower resolution SST which is warmer over the formation region, most notably in the maximum rainfall which is ~7% higher. The differences in the two explosive cyclone simulations are negligible, most likely due to intensification occurring mainly over land. We then test the sensitivity of the storms to a range of SST anomalies. The TLC showed a clear trend of increasing storm intensity as SST rises. These results suggest that SST plays a direct role in determining the intensity of the storm. For the explosive cyclone there is no clear trend in dynamical intensity except for the highest warming anomalies. However the rainfall increases with the magnitude of the SST anomaly. Our results suggest that extreme weather events over the Mediterranean will become more extreme if SST increases as the climate warms, assuming that upper air conditions do not change.