Copyright Year 2012
![]()
Copyright Holder Springer Science+Business Media B.V.
| Corresponding Author | Family Name | Gertman |
| Particle | ||
| Given Name | Isaac | |
| Suffix | ||
| Division/Department | Department of Physical Oceanography | |
| Organization/University | Israel Oceanographic & Limnological Research | |
| Street | Tel-Shikmona | |
| Postbox | P.O.B. 8030 | |
| City | Haifa | |
| Postcode | 31080 | |
| Country | Israel | |
| Phone | (972) 4 8565 277 | |
| Fax | (972) 4 8511 911 | |
| isaac@ocean.org.il | ||
| URL | http://isramar.ocean.org.il |
3 Isaac Gertman
4 Israel Oceanographic & Limnological Research,
5 Haifa, Israel
6 Synonyms
7 Al-Bahr al-Mayyit – the Dead Sea (Arabic); Sea of
8 Asphaltites – (Attic Greek); Yam Ha-Mavet – the Dead
9 Sea (Hebrew); Yam Ha-Melah – the Salt Sea (Hebrew)
10 Definition
11 The Dead Sea is a terminal hypersaline lake situated in the
12 land lowest depression of the Jordan Rift Valley between
13 Arabian and Sinai tectonic plates
14 Introduction
15 During the late Pleistocene, the Arabian and Sinai plates
16 were separated by the Dead Sea precursor – Lisan Lake
17 which covered the Jordan Rift Valley entirely about
18 25,000 years ago. The surface level at that time was about
19 180 m below mean sea level (bmsl). The modern Dead Sea
20 was formed as a result of recession in the Lisan surface
21 level about 10,000–14,000 years ago (Oren, 2003). Until
22 the beginning of the twentieth century, the seawater level
23 underwent natural fluctuations from about 380 to 420 m
24 bmsl which were associated with interannual variability
25 precipitation in the Levant region (Kushnir and Stein,
26 2010). Since the early 1960s, anthropogenic reduction
27 in the Dead Sea freshwater budget outweighed its
28 natural variability because of the countries controlling
29 the freshwatershed of the Dead Sea (i.e., Israel, Syria,
30 and Jordan, Figure 1) increased the water consumption
31 intensively.
Moreover, Israel and Jordan use the Dead Sea water for 32 the production of minerals, contributing to the water 33 deficit. As a result, sea level decreases rapidly (Niemi 34 et al., 1997). Until 1978, the morphology of the Dead 35 Sea consisted of a large and deep northern basin and 36 a smaller and shallower southern basin connected via 37 the Lynch straits (Neev and Emery, 1967). Following the 38 recession of the water level, the entire southern basin 39 would have dried up. However, dikes were erected to 40 transform the southern basin into evaporation ponds for 41 mineral production. During the period 1996–2010, 42
the northern basin surface level decreased at a rate of 43 1 m/year, and the area shrunk with a rate of 2.4 km 44 2 /year. In 2010, the Dead Sea dimensions were: surface level 45 424 m bmsl, maximal depth 295 m, area 609 km 46 2 , volume 130 km 47 3 maximal north-south extension 50 km, and maximal west-east extension 16 km. 48 Water salinity was 280 g/kg, and water density was 49 1,240 kg/m 50 3 at 25C.
Water budget During the drought years 1996–2010, the major source 52 of freshwater was still the lower Jordan River: 60–150 53 10 54 6 m3 /year. The total freshwater inflow (including precipitation and floods) was 265–335 10 55 6 m3 /year. Evaporation rates derived from energy budget were 56 1.1–1.2 m/year. The low evaporation rate of Dead Sea, 57 compared with fresh lake in similar conditions 58
(1.4–1.5 m/year for the Sea of Galilee, Rimmer et al., 59 2009), is connected with the high hydroscopic ability 60 of the Dead Sea brine (Krumgalz et al., 2000; Lensky 61 et al., 2005). The total water deficit of the lake is 690 62 10 63 6 m3 /year. About 36% of this amount is due to the activity of the chemical industries in the southern basin of the 64 Dead Sea (Lensky et al., 2005).
L. Bengtsson, R.W. Herschy, R.W. Fairbridge (eds.), Encyclopedia of Lakes and Reservoirs, DOI 10.1007/978-1-4020-4410-6,Springer Science+Business Media B.V. 2012
Meteorology The climate in the Dead Sea area is highly arid, with a mean annual rainfall less than 100 mm (Goldreich, 1998). Air temperature over sea has been observed between 7.5C and 43.4C. While typical relative humidity over the Dead Sea is between 33% and 52%. On average, August is the hottest month with air temperature of 33C and July is the driest (39% humidity). The coldest and most humid month is January with an average temperature of 18C and 47% humidity. Air temperature changes are
closely associated with the arrival of the Mediterranean breeze as well as with the onset of the local breeze. The daily maximal temperature occurs 4 h later than along the Mediterranean coast. The atmosphere above the sea surface differs from that on land. Air temperature above the sea is colder by about 0.5–1C during summer and warmer by about 1–2C during winter. Relative humidity above sea is higher by about 4–5%. Air pressure at the Dead Sea surface is higher than at the mean sea level by about 50 mb. The typical speed of winds is 4–6 m/s. In general, during summer, winds are mostly northerly. During winter, there is an increase in the southerly winds. During winter, strong winds (10–20 m/s), although rare, occur more frequently than during summer. Westerly winds, associated with the Mediterranean breeze, occur at the same rate throughout the year. They appear in the late afternoon and can reach 20 m/s at midnight. Wind strength diminishes in the morning with the weakest winds occurring around 13:00 (Hecht and Gertman, 2003). The maximal wind wave heights observed were at 3 mwith 8 s period (Hecht et al., 1997).
Chemical composition The salinity of the Dead Sea water is about eight times larger than that of oceanic water, being supersaturated in respect to halite and perhaps other minerals. Dead Sea water has particular ionic composition, which is dominated by magnesium chloride, unlike oceanic water which s dominated by sodium chloride (Figure 2). The extremely high salinity of the Dead Sea water as well as its unique ionic composition prevents the implementation of inexpensive methods of ocean water salinity measurenment. Therefore, in order to characterize the Dead Sea haline structure and variability, one uses its density anom113 aly from 1,000 kg/m3 at 25C (Anati, 1997). This is defined as quasi-salinity. Since the early 1980s, massive amounts of halite have precipitated from the water column as halite crystals (Gavrieli, 1997). A subject submerged in the Dead Sea water with temperature below 25C is covered by halite crystals (Figure 3). or hundreds of years the Dead Sea was a meromictic lake (see Meromictic Lakes) with stable haline stratification, supported by runoff. Winter convection was limited, and below the halocline was not affected by atmosphere. As a result of the runoff reduction, the upper-mixed layer (UML) salinity increased, and the gravitational stability diminished. Eventually, during the winter of 1978–1979, the lake water overturned, ending the long-term stable hydrological regime (Steinhorn and Gat, 1983; Anati,
1997). Since then, the lake entered a new phase in which its hydrological regime is either holomictic or
meromictic. Since 1979, the meromictic regime is established twice only after extremely rainy winters: dur- ing 1980–1982 and during 1992–1995. Regardless of regime, deep water temperature remains in the range 22–24 147 C, while quasi-salinity has increasedsince 1978 from 232 kg/m 148 3 at a rate of 0.35 kg/m3 year(Anati, 1997; Gertman and Hecht, 2002). Seasonal thermocline is formed in the middle of March. UML during meromictic winter has low quasi-salinity (200–210 kg/m 152 3) and can be colder than the deep layer due to hydrostatic stability which limits winter convection e.g., in winter 1993, temperature dropped to 15 154 C (Beyth et al., 1993)). During summer, the UML reaches 15 maximal temperature (32–35 156 C), and the quassalinity value is 3 kg/m 157 3 higher than at the deep water. The UML thickness during meromictic periods and holomictic summer fluctuates between 15 and 30 m. Convective mixing of the entirely water body occurs during the second half of November in the holo mictic regime (Figure 4). Extremely hot and dense water (up to 44 162 C and 1,350 kg/m 163 3Lensky et al., 2005) entering in the southern part of the Dead Sea from the evaporation ponds propagates as gravitation currents northward following the bathymetry. During the summer, this water forms a bottom layer in the entire deep region. The layer is warmer (0.5 168 C) and saltier (0.5 kg/m3 ) than the main water body layer above it. Double diffusion builds steplike profiles of water properties in the bottom layer (Gertman and Hecht, 2002).
Expected future of the Dead Sea The sea surface level is expected to decrease in the course of the nearest 500 years. However, some deceleration of the sea level decent has been predicted by different models even if the runoff and industrial water consumption will not change in the future (Yechieli et al., 1998; Krumgalz et al., 2000; Asmar and Ergenzinger, 2002). In all the models, the evaporation rate is inversely proportional to the concentration of ions. Moreover, the integral evapora181 tion decreases with the sea surface area decrease. A critical ionic concentration will diminish the evaporation dramat183 ically when the sea level reaches 500 m bmsl. Several proposals were made for stabilizing the Dead Sea water level by connecting the Dead Sea with the Mediterranean or the Red Sea. The main idea is to utilize more than 400 m difference in sea levels to generate hydroelectric energy. Additional profit can be achieved due to desalinization of the seawater on the way to the Dead Sea. In 2005, the governments of the Israel, Jordan, and the Palestinian territories supported by the World Bank agreed to conduct a feasibility study for a cannel or pipeline between the Gulf of Aqaba and the Dead Sea along the Arava Valley transporting initially Red Sea water and eventually high salinity end brines (by-product of desali nization) into the Dead Sea. The most eviden problems concerning this proposal are: restoration of meromictic stratification, mass precipitation of gypsum, and development of new life-forms (Oren, 2003).
Summary For hundreds of years prior to 1950, the Dead Sea surface level was about 400 20 m bmsl. During this period, dilu203 tion of the upper layer by the freshwater runoff was suffi 204 cient to support stable stratification even during the winter seasons. Anthropogenic reduction of runoff and water consu mption for industrial mineral production led to sig207 nificant changes in dimensions and hydrology of the Dead Sea. Israel Dead Sea Works Ltd. and the Jordanian Arab Potash Co. pump water from the nort hern part into indus210 trial evaporation ponds located where the southern part used to be. After the extraction of potassium and bromide salts, the remaining extremely dense water is returned to the northern part. During 1978–2010, the northern part sea level descended by 23 m, the area shrank by 58 km2 and the volume decreased by 15 km3 . Gradual salinity increase in the upper layer led to the first overturn in winter 1978–1979. Stable haline stratification, preventing winter overturns, was restored twice after extremely rainy winters of 1980 and 1992, and lasted for 3–4 years each time. The main body water density increased since 1979 from 1,232 kg/m3 to 1,241 kg/m3 due to increased ionic concentration. Halite is saturated since about 1980, and permanent precipitation is observed on submerged objects. Increase of ionic concentration leads to decreased evaporation rate; therefore, sea level drop rate is expected to decrease in the future. Different estimates of the future Dead Sea water budget came to a common conclusion that in about 500 years, the sea level will be 500 m bmsl.
Bibliography Anati, D. A., 1997. The hydrography of a hypersaline lake. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 89–103.
Asmar, B. N., and Ergenzinger, P., 2002. Long-term prediction of the level and salinity in the Dead Sea. Hydrological Processes, 16, 2819–2831. Beyth, M., Gavrieli, I., Anati, D., and Katz, O., 1993. Effects of the
December 1991–May 1992 floods on the Dead Sea vertical structure. Israel Journal of Earth Science, 41, 45–48. Gavrieli, I., 1997. Halite deposition in the Dead Sea: 1960–1993. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 161–170. Gavrieli, I., and Oren, A., 2004. The Dead Sea as a dying lake. In Nihoul, J. C. J., Zavialov, P. O., and Micklin, P. P. (eds.), Dying and Dead Seas, Climatic Versus Anthropogenic Causes. Dordrecht: Kluwer Academic, pp. 287–305. Gertman, I., and Hecht, A., 2002. The Dead Sea hydrography from 1992 to 2000. Journal of Marine Systems, 35, 169–181. 249 Gertman, I., Kress, N., Katsenelson, B., and Zavialov, P., 2010.
Equations of State for the Dead Sea and Aral Sea: Searching b for Common Approaches. Final Report. IOLR report 12/210. Goldreich, Y., 1998. The Climate of Israel. Observations, Research 2 and Applications. Bar Ilan University Publishers and I. L. Magnes Press, Ramat-Gan (in Hebrew). 292 pp. 255 Hall, J. K., 1997. Topography and bathymetry of the Dead Sea depression. In Niemi, T., Ben-Avraham, Z., and Gat, J. R.
(eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 11–21. 259 Hecht, A., and Gertman, I., 2003. Dead Sea meteorological climate. 260 Chapter 4. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal 26 Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G. 262 325 pp. 263 Hecht, A., Ezer, T., Huss, A., and Shapira, A., 1997. Wind waves on Dead Sea. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 114–121. Krumgalz, B. S., Hecht, A., Starinsky, A., and Katz, A., 2000. Thermodynamic constraints on Dead Sea evaporation: Can the Dead Sea dry up? Chemical Geology, 165, 1–11. Kushnir, Y., and Stein, M., 2010. North Atlantic influence on 19th– 20th century rainfall in the Dead Sea watershed, teleconnections with the Sahel, and implication for Holocene climate fluctuations. Quaternary Science Reviews, 29, 3843–3860. Lensky, N., Dvorkin, Y., Lyakhovsky, V., Gertman, I., and Gavrieli, I., 2005. Water, salt, and energy balance of the Dead Sea. Water Resources Research, 41, doi:10.1029/ 2005WR004084. Neev, D., and Emery, K.O., 1967. The Dead Sea. Depositional processes and environments of evaporites. Bulletin No. 41, State of Israel, Ministry of Development, Geological Survey, 147 p. Niemi, T. M., Ben-Avraham, Z.and Gat, J. R., 1997. Dead Sea research – an introduction. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 3–7. Oren, A., 2003. Physical and Chemical Limnology of the Dead Sea. Chapter 3. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G, pp. 45–67. 325 pp. Rimmer, A., Samuels, R., and Lechinsky, Y., 2009. A comprehensive study across methods and time scales to estimate surface fluxes from Lake Kinneret, Israel. Journal of Hydrology, 379, 181–192.Steinhorn, I., 1981. A Hydrographical and Physical Study of the
295 Dead Sea During the Destruction of its Long-Term Meromictic 296 stratification. PhD Thesis, Weizmann Institute, Israel, 323 pp. 297 Steinhorn, I., and Gat, J. R., 1983. The Dead Sea. Scientific
298 America, 249, 102–109. 299 Yechieli, Y., Gavrieli, I., Berkowitz, B., and Ronen, D., 1998. Will
300 the Dead Sea die? Geology, 26, 755–758
Cross-references
Meromictic Lakes
The Dead Sea, Figure 1 The Dead Sea watershed. Insertion shows profile along the Jordan Rift Valley toward Gulf of Eilat (Aqaba).(Adopted from Niemi et al., 1997.)
Dead Sea, Figure 2 Percentage of ionic concentrations in the Sea water. D – ocean water, ○ – Dead Sea water during 2008, ▬ – Dead Sea water during 1960–1996, □ – end brines from evaporation ponds. (Data derived from Steinhorn (1981);Gavrieli (1997), Oren (2003), Gertman et al. (2010).)
Corresponding Author
Family Name
Gertman
Particle
Given Name
Isaac
Suffix
Division/Department
Department of Physical Oceanography
Organization/University
Israel Oceanographic & Limnological Research
Street
Tel-Shikmona
Postbox
P.O.B. 8030
City
Haifa
Postcode
31080
Country
Israel
Phone
(972) 4 8565 277
Fax
(972) 4 8511 911
isaac@ocean.org.il
URL
http://isramar.ocean.org.il
3 Isaac Gertman
4 Israel Oceanographic & Limnological Research,
5 Haifa, Israel
6 Synonyms
7 Al-Bahr al-Mayyit – the Dead Sea (Arabic); Sea of
8 Asphaltites – (Attic Greek); Yam Ha-Mavet – the Dead
9 Sea (Hebrew); Yam Ha-Melah – the Salt Sea (Hebrew)
10 Definition
11 The Dead Sea is a terminal hypersaline lake situated in the
12 land lowest depression of the Jordan Rift Valley between
13 Arabian and Sinai tectonic plates
14 Introduction
15 During the late Pleistocene, the Arabian and Sinai plates
16 were separated by the Dead Sea precursor – Lisan Lake
17 which covered the Jordan Rift Valley entirely about
18 25,000 years ago. The surface level at that time was about
19 180 m below mean sea level (bmsl). The modern Dead Sea
20 was formed as a result of recession in the Lisan surface
21 level about 10,000–14,000 years ago (Oren, 2003). Until
22 the beginning of the twentieth century, the seawater level
23 underwent natural fluctuations from about 380 to 420 m
24 bmsl which were associated with interannual variability
25 precipitation in the Levant region (Kushnir and Stein,
26 2010). Since the early 1960s, anthropogenic reduction
27 in the Dead Sea freshwater budget outweighed its
28 natural variability because of the countries controlling
29 the freshwatershed of the Dead Sea (i.e., Israel, Syria,
30 and Jordan, Figure 1) increased the water consumption
31 intensively.
Moreover, Israel and Jordan use the Dead Sea water for 32 the production of minerals, contributing to the water 33 deficit. As a result, sea level decreases rapidly (Niemi 34 et al., 1997). Until 1978, the morphology of the Dead 35 Sea consisted of a large and deep northern basin and 36 a smaller and shallower southern basin connected via 37 the Lynch straits (Neev and Emery, 1967). Following the 38 recession of the water level, the entire southern basin 39 would have dried up. However, dikes were erected to 40 transform the southern basin into evaporation ponds for 41 mineral production. During the period 1996–2010, 42
the northern basin surface level decreased at a rate of 43 1 m/year, and the area shrunk with a rate of 2.4 km 44 2 /year. In 2010, the Dead Sea dimensions were: surface level 45 424 m bmsl, maximal depth 295 m, area 609 km 46 2 , volume 130 km 47 3 maximal north-south extension 50 km, and maximal west-east extension 16 km. 48 Water salinity was 280 g/kg, and water density was 49 1,240 kg/m 50 3 at 25C.
Water budget During the drought years 1996–2010, the major source 52 of freshwater was still the lower Jordan River: 60–150 53 10 54 6 m3 /year. The total freshwater inflow (including precipitation and floods) was 265–335 10 55 6 m3 /year. Evaporation rates derived from energy budget were 56 1.1–1.2 m/year. The low evaporation rate of Dead Sea, 57 compared with fresh lake in similar conditions 58
(1.4–1.5 m/year for the Sea of Galilee, Rimmer et al., 59 2009), is connected with the high hydroscopic ability 60 of the Dead Sea brine (Krumgalz et al., 2000; Lensky 61 et al., 2005). The total water deficit of the lake is 690 62 10 63 6 m3 /year. About 36% of this amount is due to the activity of the chemical industries in the southern basin of the 64 Dead Sea (Lensky et al., 2005). L. Bengtsson, R.W. Herschy, R.W. Fairbridge (eds.), Encyclopedia of Lakes and Reservoirs, DOI 10.1007/978-1-4020-4410-6,Springer Science+Business Media B.V. 2012
Meteorology The climate in the Dead Sea area is highly arid, with a mean annual rainfall less than 100 mm (Goldreich, 1998). Air temperature over sea has been observed between 7.5C and 43.4C. While typical relative humidity over the Dead Sea is between 33% and 52%. On average, August is the hottest month with air temperature of 33C and July is the driest (39% humidity). The coldest and most humid month is January with an average temperature of 18C and 47% humidity. Air temperature changes are
closely associated with the arrival of the Mediterranean breeze as well as with the onset of the local breeze. The daily maximal temperature occurs 4 h later than along the Mediterranean coast. The atmosphere above the sea surface differs from that on land. Air temperature above the sea is colder by about 0.5–1C during summer and warmer by about 1–2C during winter. Relative humidity above sea is higher by about 4–5%. Air pressure at the Dead Sea surface is higher than at the mean sea level by about 50 mb. The typical speed of winds is 4–6 m/s. In general, during summer, winds are mostly northerly. During winter, there is an increase in the southerly winds. During winter, strong winds (10–20 m/s), although rare, occur more frequently than during summer. Westerly winds, associated with the Mediterranean breeze, occur at the same rate throughout the year. They appear in the late afternoon and can reach 20 m/s at midnight. Wind strength diminishes in the morning with the weakest winds occurring around 13:00 (Hecht and Gertman, 2003). The maximal wind wave heights observed were at 3 mwith 8 s period (Hecht et al., 1997).
Chemical composition The salinity of the Dead Sea water is about eight times larger than that of oceanic water, being supersaturated in respect to halite and perhaps other minerals. Dead Sea water hasparticular ionic composition, which is domi ted by magnesium chloride unlike oceanic water which s dominated by sodium chloride (Figure 2). The extremely high salinity of the Dead Sea water as well as its unique ionic composition prevents the implementation of inexpensive methods of ocean water salinity measurenment. Therefore, in order to characterize the Dead Sea haline structure and variability, one uses its density anom113 aly from 1,000 kg/m3 at 25C (Anati, 1997). This is defined as quasi-salinity. Since the early 1980s, massive amounts of halite have precipitated from the water column as halite crystals (Gavrieli, 1997). A subject submerged in the Dead Sea water with temperature below 25C is covered by halite crystals (Figure 3). or hundreds of years the Dead Sea was a meromictic lake (see Meromictic Lakes) with stable haline stratification, supported by runoff. Winter convection was limited, and below the halocline was not affected by atmosphere. As a result of the runoff reduction, the upper-mixed layer (UML) salinity increased, and the gravitational stability diminished. Eventually, during the winter of 1978–1979, the lake water overturned, ending the long-term stable hydrological regime (Steinhorn and Gat, 1983; Anati,
1997). Since then, the lake entered a new phase in which its hydrological regime is either holomictic or
meromictic. Since 1979, the meromictic regime is established twice only after extremely rainy winters: during 1980–1982 and during 1992–1995. Regardless of regime, deep water temperature remains in the range 22–24 147 C, while quasi-salinity has increased since 1978 from 232 kg/m 148 3 at a rate of 0.35 kg/m3 year(Anati, 1997; Gertman and Hecht, 2002). Seasonal thermocline is formed in the middle of March. UML during meromictic winter has low quasi-salinity (200–210 kg/m 152 3) and can be colder than the deep layer due to hydrostatic stability which limits winter convection e.g., in winter 1993, temperature dropped to 15 154 C (Beyth et al., 1993)). During summer, the UML reaches 15 maximal temperature (32–35 156 C), and quasi salinity value is 3 kg/m 157 3 higher than at the deep water. The UML thickness during meromictic periods and holomictic summer fluctuates between 15 and 30 m. Convective mixing of the entirely water body occurs during the second half of November in the holo mictic regime (Figure 4). Extremely hot and dense water (up to 44 162 C and 1,350 kg/m 163 3Lensky et al., 2005) entering in the southern part of the Dead Sea from the evaporation ponds propagates as gravi tation currents northward following the bathymetry. During the summer, this water forms a bottom layer in the entire deep region. The layer is warmer (0.5 168 C) and saltier (0.5 kg/m3 ) than the main water body layer above it. Double diffusion builds step- like profiles of water properties in the bottom layer (Gertman and Hecht, 2002).
Expected future of the Dead Sea The sea surface level is expected to decrease in the course of the nearest 500 years. However, some deceleration of the sea level decent has been predicted by different models even if the runoff and industrial water consumption will not change in the future (Yechieli et al., 1998; Krumgalz et al., 2000; Asmar and Ergenzinger, 2002). In all the models, the evaporation rate is inversely proportional to the concentration of ions. Moreover, the integral evapora181 tion decreases with the sea surface area decrease. A critical ionic concentration will diminish the evaporation dramat183 ically when the sea level reaches 500 m bmsl. Several proposals were made for stabilizing the Dead Sea water level by connecting the Dead Sea with the Mediterranean or the Red Sea. The main idea is to utilize more than 400 m difference in sea levels to generate hydroelectric energy. Additional profit can be achieveddue to desalinization of the seawater on the way to the Dead Sea. In 2005, the governments of the Israel, Jordan, and the Palestinian territories supported by the World Bank agreed to conduct a feasibility study for a cannel or pipeline between the Gulf of Aqaba and the Dead Sea along the Arava Valley transporting initially Red Sea water and eventually high salinity end brines (by-product of desali nization) into the Dead Sea. The most eviden problems concerning this proposal are: restoration of meromictic stratification, mass precipitation of gypsum, and development of new life-forms (Oren, 2003).
Summary For hundreds of years prior to 1950, the Dead Sea surface level was about 400 20 m bmsl. During this period, dilu 203 tion of the upper layer by the freshwater runoff was suffi 204 cient to support stable stratification even during the winter seasons. Anthropogenic reduction of runoff and water consu mption for industrial mineral production led to sig207 nificant changes in dimensions and hydrology of the Dead Sea. Israel Dead Sea Works Ltd. and the Jordanian Arab Potash Co. pump water from the nort hern part into indus210 trial evaporation ponds located where the southern part used to be. After the extraction of potassium and bromide salts, the remaining extremely dense water is returned to the northern part. During 1978–2010, the northern part sea level descended by 23 m, the area shrank by 58 km2 and the volume decreased by 15 km3 . Gradual salinity increase in the upper layer led to the first overturn in winter 1978–1979. Stable haline stratification, preventing winter overturns, was restored twice after extremely rainy winters of 1980 and 1992, and lasted for 3–4 years each time. The main body water density increased since 1979 from 1,232 kg/m3 to 1,241 kg/m3 due to increased ionic concentration. Halite is saturated since about 1980, and permanent precipitation is observed on submerged objects. Increase of ionic concentration leads to decreased evaporation rate; therefore, sea level drop rate is expected to decrease in the future. Different estimates of the future Dead Sea water budget came to a common conclusion that in about 500 years, the sea level will be 500 m bmsl.
Bibliography Anati, D. A., 1997. The hydrography of a hypersaline lake. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 89–103.
Asmar, B. N., and Ergenzinger, P., 2002. Long-term prediction of the level and salinity in the Dead Sea. Hydrological Processes, 16, 2819–2831. Beyth, M., Gavrieli, I., Anati, D., and Katz, O., 1993. Effects of the
December 1991–May 1992 floods on the Dead Sea vertical structure. Israel Journal of Earth Science, 41, 45–48. Gavrieli, I., 1997. Halite deposition in the Dead Sea: 1960–1993. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 161–170. Gavrieli, I., and Oren, A., 2004. The Dead Sea as a dying lake. In Nihoul, J. C. J., Zavialov, P. O., and Micklin, P. P. (eds.), Dying and Dead Seas, Climatic Versus Anthropogenic Causes. Dordrecht: Kluwer Academic, pp. 287–305. Gertman, I., and Hecht, A., 2002. The Dead Sea hydrography from 1992 to 2000. Journal of Marine Systems, 35, 169–181. 249 Gertman, I., Kress, N., Katsenelson, B., and Zavialov, P., 2010.
Equations of State for the Dead Sea and Aral Sea: Searching b for Common Approaches. Final Report. IOLR report 12/210. Goldreich, Y., 1998. The Climate of Israel. Observations, Research 2 and Applications. Bar Ilan University Publishers and I. L. Magnes Press, Ramat-Gan (in Hebrew). 292 pp. 255 Hall, J. K., 1997. Topography and bathymetry of the Dead Sea depression. In Niemi, T., Ben-Avraham, Z., and Gat, J. R.
(eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 11–21. 259 Hecht, A., and Gertman, I., 2003. Dead Sea meteorological climate. 260 Chapter 4. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal 26 Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G. 262 325 pp. 263 Hecht, A., Ezer, T., Huss, A., and Shapira, A., 1997. Wind waves on Dead Sea. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 114–121. Krumgalz, B. S., Hecht, A., Starinsky, A., and Katz, A., 2000. Thermodynamic constraints on Dead Sea evaporation: Can the Dead Sea dry up? Chemical Geology, 165, 1–11. Kushnir, Y., and Stein, M., 2010. North Atlantic influence on 19th– 20th century rainfall in the Dead Sea watershed, teleconnections
with the Sahel, and implication for Holocene climate fluctuations. Quaternary Science Reviews, 29, 3843–3860. Lensky, N., Dvorkin, Y., Lyakhovsky, V., Gertman, I., and Gavrieli, I., 2005. Water, salt, and energy balance of the Dead Sea. Water Resources Research, 41, doi:10.1029/ 2005WR004084. Neev, D., and Emery, K.O., 1967. The Dead Sea. Depositional processes and environments of evaporites. Bulletin No. 41, State of Israel, Ministry of Development, Geological Survey, 147 p. Niemi, T. M., Ben-Avraham, Z.and Gat, J. R., 1997. Dead Sea research – an introduction. In Niemi, T., Ben-Avraham, Z., and
Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 3–7. Oren, A., 2003. Physical and Chemical Limnology of the Dead Sea. Chapter 3. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G, pp. 45–67. 325 pp. Rimmer, A., Samuels, R., and Lechinsky, Y., 2009. A comprehensive study across methods and time scales to esti-
mate surface fluxes from Lake Kinneret, Israel. Journal of Hydrology, 379, 181–192.Steinhorn, I., 1981. A Hydrographical and Physical Study of the
295 Dead Sea During the Destruction of its Long-Term Meromictic
296 stratification. PhD Thesis, Weizmann Institute, Israel, 323 pp.
297 Steinhorn, I., and Gat, J. R., 1983. The Dead Sea. Scientific
298 America, 249, 102–109.
299 Yechieli, Y., Gavrieli, I., Berkowitz, B., and Ronen, D., 1998. Will
300 the Dead Sea die? Geology, 26, 755–758
Cross-references
Meromictic Lakes
Dead Sea, Figure 1 The Dead Sea watershed. Insertion shows profile along the Jordan Rift Valley toward Gulf of Eilat (Aqaba).(Adopted from Niemi et al., 1997.)
Dead Sea, Figure 2 Percentage of ionic concentrations in the Sea water. D – ocean water, ○ – Dead Sea water during 2008, ▬ – Dead Sea water during 1960–1996, □ – end brines from evaporation ponds. (Data derived from Steinhorn (1981);Gavrieli (1997), Oren (2003), Gertman et al. (2010).)
Corresponding Author
Family Name
Gertman
Particle
Given Name
Isaac
Suffix
Division/Department
Department of Physical Oceanography
Organization/University
Israel Oceanographic & Limnological Research
Street
Tel-Shikmona
Postbox
P.O.B. 8030
City
Haifa
Postcode
31080
Country
Israel
Phone
(972) 4 8565 277
Fax
(972) 4 8511 911
isaac@ocean.org.il
URL
http://isramar.ocean.org.il
3 Isaac Gertman
4 Israel Oceanographic & Limnological Research,
5 Haifa, Israel
6 Synonyms
7 Al-Bahr al-Mayyit – the Dead Sea (Arabic); Sea of
8 Asphaltites – (Attic Greek); Yam Ha-Mavet – the Dead
9 Sea (Hebrew); Yam Ha-Melah – the Salt Sea (Hebrew)
10 Definition
11 The Dead Sea is a terminal hypersaline lake situated in the
12 land lowest depression of the Jordan Rift Valley between
13 Arabian and Sinai tectonic plates
14 Introduction
15 During the late Pleistocene, the Arabian and Sinai plates
16 were separated by the Dead Sea precursor – Lisan Lake
17 which covered the Jordan Rift Valley entirely about
18 25,000 years ago. The surface level at that time was about
19 180 m below mean sea level (bmsl). The modern Dead Sea
20 was formed as a result of recession in the Lisan surface
21 level about 10,000–14,000 years ago (Oren, 2003). Until
22 the beginning of the twentieth century, the seawater level
23 underwent natural fluctuations from about 380 to 420 m
24 bmsl which were associated with interannual variability
25 precipitation in the Levant region (Kushnir and Stein,
26 2010). Since the early 1960s, anthropogenic reduction
27 in the Dead Sea freshwater budget outweighed its
28 natural variability because of the countries controlling
29 the freshwatershed of the Dead Sea (i.e., Israel, Syria,
30 and Jordan, Figure 1) increased the water consumption
31 intensively.
Moreover, Israel and Jordan use the Dead Sea water for 32 the production of minerals, contributing to the water 33 deficit. As a result, sea level decreases rapidly (Niemi 34 et al., 1997). Until 1978, the morphology of the Dead 35 Sea consisted of a large and deep northern basin and 36 a smaller and shallower southern basin connected via 37 the Lynch straits (Neev and Emery, 1967). Following the 38 recession of the water level, the entire southern basin 39 would have dried up. However, dikes were erected to 40 transform the southern basin into evaporation ponds for 41 mineral production. During the period 1996–2010, 42
the northern basin surface level decreased at a rate of 43 1 m/year, and the area shrunk with a rate of 2.4 km 44 2 /year. In 2010, the Dead Sea dimensions were: surface level 45 424 m bmsl, maximal depth 295 m, area 609 km 46 2 , volume 130 km 47 3 maximal north-south extension 50 km, and maximal west-east extension 16 km. 48 Water salinity was 280 g/kg, and water density was 49 1,240 kg/m 50 3 at 25C.
Water budget During the drought years 1996–2010, the major source 52 of freshwater was still the lower Jordan River: 60–150 53 10 54 6 m3 /year. The total freshwater inflow (including precipitation and floods) was 265–335 10 55 6 m3 /year. Evaporation rates derived from energy budget were 56 1.1–1.2 m/year. The low evaporation rate of Dead Sea, 57 compared with fresh lake in similar conditions 58
(1.4–1.5 m/year for the Sea of Galilee, Rimmer et al., 59 2009), is connected with the high hydroscopic ability 60 of the Dead Sea brine (Krumgalz et al., 2000; Lensky 61 et al., 2005). The total water deficit of the lake is 690 62 10 63 6 m3 /year. About 36% of this amount is due to the activity of the chemical industries in the southern basin of the 64 Dead Sea (Lensky et al., 2005).
L. Bengtsson, R.W. Herschy, R.W. Fairbridge (eds.), Encyclopedia of Lakes and Reservoirs, DOI 10.1007/978-1-4020-4410-6,Springer Science+Business Media B.V. 2012
Meteorology The climate in the Dead Sea area is highly arid, with a mean annual rainfall less than 100 mm (Goldreich, 1998). Air temperature over sea has been observed between 7.5C and 43.4C. While typical relative humidity over the Dead Sea is between 33% and 52%. On average, August is the hottest month with air temperature of 33C and July is the driest (39% humidity). The coldest and most humid month is January with an average temperature of 18C and 47% humidity. Air temperature changes are
closely associated with the arrival of the Mediterranean breeze as well as with the onset of the local breeze. The daily maximal temperature occurs 4 h later than along the Mediterranean coast. The atmosphere above the sea surface differs from that on land. Air temperature above the sea is colder by about 0.5–1C during summer and warmer by about 1–2C during winter. Relative humidity above sea is higher by about 4–5%. Air pressure at the Dead Sea surface is higher than at the mean sea level by about 50 mb. The typical speed of winds is 4–6 m/s. In general, during summer, winds are mostly northerly. During winter, there is an increase in the southerly winds. During winter, strong winds (10–20 m/s), although rare, occur more frequently than during summer. Westerly winds, associated with the Mediterranean breeze, occur at the same rate throughout the year. They appear in the late afternoon and can reach 20 m/s at midnight. Wind strength diminishes in the morning with the weakest winds occurring around 13:00 (Hecht and Gertman, 2003). The maximal wind wave heights observed were at 3 mwith 8 s period (Hecht et al., 1997).
Chemical composition The salinity of the Dead Sea water is about eight times larger than that of oceanic water, being supersaturated in respect to halite and perhaps other minerals. Dead Sea water hasparticular ionic composition, which is domi ted by magnesium chloride unlike oceanic water which s dominated by sodium chloride (Figure 2). The extremely high salinity of the Dead Sea water as well as its unique ionic composition prevents the implementation of inexpensive methods of ocean water salinity measurenment. Therefore, in order to characterize the Dead Sea haline structure and variability, one uses its density anom113 aly from 1,000 kg/m3 at 25C (Anati, 1997). This is defined as quasi-salinity. Since the early 1980s, massive amounts of halite have precipitated from the water column as halite crystals (Gavrieli, 1997). A subject submerged in the Dead Sea water with temperature below 25C is covered by halite crystals (Figure 3). or hundreds of years the Dead Sea was a meromictic lake (see Meromictic Lakes) with stable haline stratification, supported by runoff. Winter convection was limited, and below the halocline was not affected by atmosphere. As a result of the runoff reduction, the upper-mixed layer (UML) salinity increased, and the gravitational stability diminished. Eventually, during the winter of 1978–1979, the lake water overturned, ending the long-term stable hydrological regime (Steinhorn and Gat, 1983; Anati,
1997). Since then, the lake entered a new phase in which its hydrological regime is either holomictic or
meromictic. Since 1979, the meromictic regime is established twice only after extremely rainy winters: dur- ing 1980–1982 and during 1992–1995. Regardless of regime, deep water temperature remains in the range 22–24 147 C, while quasi-salinity has increasedsince 1978 from 232 kg/m 148 3 at a rate of 0.35 kg/m3 year(Anati, 1997; Gertman and Hecht, 2002). Seasonal thermocline is formed in the middle of March. UML during meromictic winter has low quasi-salinity (200–210 kg/m 152 3) and can be colder than the deep layer due to hydrostatic stability which limits winter convection e.g., in winter 1993, temperature dropped to 15 154 C (Beyth et al., 1993)). During summer, the UML reaches 15 maximal temperature (32–35 156 C), and quasi-salinity value is 3 kg/m 157 3 higher than at the deep water. The UML thickness during meromictic periods and holomictic summer fluctuates between 15 and 30 m. Convective mixing of the entirely water body occurs during the sec- ond half of November in the holo mictic regime (Figure 4). Extremely hot and dense water (up to 44 162 C and 1,350 kg/m 163 3Lensky et al., 2005) entering in the southern part of the Dead Sea from the evaporation ponds propagates as gravi tation currents northward following the bathymetry. During the summer, this water forms a bottom layer in the entire deep region. The layer is warmer (0.5 168 C) and saltier (0.5 kg/m3 ) than the main water body layer above it. Double diffusion builds step- like profiles of water properties in the bottom layer (Gertman and Hecht, 2002).
Expected future of the Dead Sea The sea surface level is expected to decrease in the course of the nearest 500 years. However, some deceleration of the sea level decent has been predicted by different models even if the runoff and industrial water consumption will not change in the future (Yechieli et al., 1998; Krumgalz et al., 2000; Asmar and Ergenzinger, 2002). In all the models, the evaporation rate is inversely proportional to the concentration of ions. Moreover, the integral evapora181 tion decreases with the sea surface area decrease. A critical ionic concentration will diminish the evaporation dramat183 ically when the sea level reaches 500 m bmsl. Several proposals were made for stabilizing the Dead Sea water level by connecting the Dead Sea with the Mediterranean or the Red Sea. The main idea is to utilize more than 400 m difference in sea levels to generate hydroelectric energy. Additional profit can be achieveddue to desalinization of the seawater on the way to the Dead Sea. In 2005, the governments of the Israel, Jordan, and the Palestinian territories supported by the World Bank agreed to conduct a feasibility study for a cannel or pipeline between the Gulf of Aqaba and the Dead Sea along the Arava Valley transporting initially Red Sea water and eventually high salinity end brines (by-product of desali nization) into the Dead Sea. The most eviden problems concerning this proposal are: restoration of meromictic stratification, mass precipitation of gypsum, and development of new life-forms (Oren, 2003).
Summary For hundreds of years prior to 1950, the Dead Sea surface level was about 400 20 m bmsl. During this period, dilu203 tion of the upper layer by the freshwater runoff was suffi204 cient to support stable stratification even during the winter seasons. Anthropogenic reduction of runoff and water consu mption for industrial mineral production led to sig207 nificant changes in dimensions and hydrology of the Dead Sea. Israel Dead Sea Works Ltd. and the Jordanian Arab Potash Co. pump water from the nort hern part into indus210 trial evaporation ponds located where the southern part used to be. After the extraction of potassium and bromide salts, the remaining extremely dense water is returned to the northern part. During 1978–2010, the northern part sea level descended by 23 m, the area shrank by 58 km2 and the volume decreased by 15 km3 . Gradual salinity increase in the upper layer led to the first overturn in winter 1978–1979. Stable haline stratification, preventing winter overturns, was restored twice after extremely rainy winters of 1980 and 1992, and lasted for 3–4 years each time. The main body water density increased since 1979 from 1,232 kg/m3 to 1,241 kg/m3 due to increased ionic concentration. Halite is saturated since about 1980, and permanent precipitation is observed on submerged objects. Increase of ionic concentration leads to decreased evaporation rate; therefore, sea level drop rate is expected to decrease in the future. Different estimates of the future Dead Sea water budget came to a common conclusion that in about 500 years, the sea level will be 500 m bmsl.
Bibliography Anati, D. A., 1997. The hydrography of a hypersaline lake. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 89–103.
Asmar, B. N., and Ergenzinger, P., 2002. Long-term prediction of the level and salinity in the Dead Sea. Hydrological Processes, 16, 2819–2831. Beyth, M., Gavrieli, I., Anati, D., and Katz, O., 1993. Effects of the
December 1991–May 1992 floods on the Dead Sea vertical structure. Israel Journal of Earth Science, 41, 45–48. Gavrieli, I., 1997. Halite deposition in the Dead Sea: 1960–1993. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 161–170. Gavrieli, I., and Oren, A., 2004. The Dead Sea as a dying lake. In Nihoul, J. C. J., Zavialov, P. O., and Micklin, P. P. (eds.), Dying and Dead Seas, Climatic Versus Anthropogenic Causes. Dordrecht: Kluwer Academic, pp. 287–305. Gertman, I., and Hecht, A., 2002. The Dead Sea hydrography from 1992 to 2000. Journal of Marine Systems, 35, 169–181. 249 Gertman, I., Kress, N., Katsenelson, B., and Zavialov, P., 2010.
Equations of State for the Dead Sea and Aral Sea: Searching b for Common Approaches. Final Report. IOLR report 12/210. Goldreich, Y., 1998. The Climate of Israel. Observations, Research 2 and Applications. Bar Ilan University Publishers and I. L. Magnes Press, Ramat-Gan (in Hebrew). 292 pp. 255 Hall, J. K., 1997. Topography and bathymetry of the Dead Sea depression. In Niemi, T., Ben-Avraham, Z., and Gat, J. R.
(eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 11–21. 259 Hecht, A., and Gertman, I., 2003. Dead Sea meteorological climate. 260 Chapter 4. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal 26 Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G. 262 325 pp. 263 Hecht, A., Ezer, T., Huss, A., and Shapira, A., 1997. Wind waves on Dead Sea. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 114–121. Krumgalz, B. S., Hecht, A., Starinsky, A., and Katz, A., 2000. Ther- modynamic constraints on Dead Sea evaporation: Can the Dead Sea dry up? Chemical Geology, 165, 1–11. Kushnir, Y., and Stein, M., 2010. North Atlantic influence on 19th– 20th century rainfall in the Dead Sea watershed, teleconnections
with the Sahel, and implication for Holocene climate fluctua- tions. Quaternary Science Reviews, 29, 3843–3860. Lensky, N., Dvorkin, Y., Lyakhovsky, V., Gertman, I., and Gavrieli, I., 2005. Water, salt, and energy balance of the Dead Sea. Water Resources Research, 41, doi:10.1029/ 2005WR004084. Neev, D., and Emery, K.O., 1967. The Dead Sea. Depositional pro- cesses and environments of evaporites. Bulletin No. 41, State of Israel, Ministry of Development, Geological Survey, 147 p. Niemi, T. M., Ben-Avraham, Z.and Gat, J. R., 1997. Dead Sea research – an introduction. In Niemi, T., Ben-Avraham, Z., and
Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 3–7. Oren, A., 2003. Physical and Chemical Limnology of the Dead Sea. Chapter 3. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G, pp. 45–67. 325 pp. Rimmer, A., Samuels, R., and Lechinsky, Y., 2009. A comprehensive study across methods and time scales to esti-
mate surface fluxes from Lake Kinneret, Israel. Journal of Hydrology, 379, 181–192.Steinhorn, I., 1981. A Hydrographical and Physical Study of the
295 Dead Sea During the Destruction of its Long-Term Meromictic
296 stratification. PhD Thesis, Weizmann Institute, Israel, 323 pp.
297 Steinhorn, I., and Gat, J. R., 1983. The Dead Sea. Scientific
298 America, 249, 102–109.
299 Yechieli, Y., Gavrieli, I., Berkowitz, B., and Ronen, D., 1998. Will
300 the Dead Sea die? Geology, 26, 755–758
Cross-references
Meromictic Lakes
Dead Sea, Figure 1 The Dead Sea watershed. Insertion shows profile along the Jordan Rift Valley toward Gulf of Eilat (Aqaba).(Adopted from Niemi et al., 1997.)
Dead Sea, Figure 2 Percentage of ionic concentrations in the Sea water. D – ocean water, ○ – Dead Sea water during 2008, ▬ – Dead Sea water during 1960–1996, □ – end brines from evaporation ponds. (Data derived from Steinhorn (1981);Gavrieli (1997), Oren (2003), Gertman et al. (2010).)
Corresponding Author
Family Name
Gertman
Particle
Given Name
Isaac
Suffix
Division/Department
Department of Physical Oceanography
Organization/University
Israel Oceanographic & Limnological Research
Street
Tel-Shikmona
Postbox
P.O.B. 8030
City
Haifa
Postcode
31080
Country
Israel
Phone
(972) 4 8565 277
Fax
(972) 4 8511 911
isaac@ocean.org.il
URL
http://isramar.ocean.org.il
3 Isaac Gertman
4 Israel Oceanographic & Limnological Research,
5 Haifa, Israel
6 Synonyms
7 Al-Bahr al-Mayyit – the Dead Sea (Arabic); Sea of
8 Asphaltites – (Attic Greek); Yam Ha-Mavet – the Dead
9 Sea (Hebrew); Yam Ha-Melah – the Salt Sea (Hebrew)
10 Definition
11 The Dead Sea is a terminal hypersaline lake situated in the
12 land lowest depression of the Jordan Rift Valley between
13 Arabian and Sinai tectonic plates
14 Introduction
15 During the late Pleistocene, the Arabian and Sinai plates
16 were separated by the Dead Sea precursor – Lisan Lake
17 which covered the Jordan Rift Valley entirely about
18 25,000 years ago. The surface level at that time was about
19 180 m below mean sea level (bmsl). The modern Dead Sea
20 was formed as a result of recession in the Lisan surface
21 level about 10,000–14,000 years ago (Oren, 2003). Until
22 the beginning of the twentieth century, the seawater level
23 underwent natural fluctuations from about 380 to 420 m
24 bmsl which were associated with interannual variability
25 precipitation in the Levant region (Kushnir and Stein,
26 2010). Since the early 1960s, anthropogenic reduction
27 in the Dead Sea freshwater budget outweighed its
28 natural variability because of the countries controlling
29 the freshwatershed of the Dead Sea (i.e., Israel, Syria,
30 and Jordan, Figure 1) increased the water consumption
31 intensively.
Moreover, Israel and Jordan use the Dead Sea water for 32 the production of minerals, contributing to the water 33 deficit. As a result, sea level decreases rapidly (Niemi 34 et al., 1997). Until 1978, the morphology of the Dead 35 Sea consisted of a large and deep northern basin and 36 a smaller and shallower southern basin connected via 37 the Lynch straits (Neev and Emery, 1967). Following the 38 recession of the water level, the entire southern basin 39 would have dried up. However, dikes were erected to 40 transform the southern basin into evaporation ponds for 41 mineral production. During the period 1996–2010, 42
the northern basin surface level decreased at a rate of 43 1 m/year, and the area shrunk with a rate of 2.4 km 44 2 /year. In 2010, the Dead Sea dimensions were: surface level 45 424 m bmsl, maximal depth 295 m, area 609 km 46 2 , volume 130 km 47 3 maximal north-south extension 50 km, and maximal west-east extension 16 km. 48 Water salinity was 280 g/kg, and water density was 49 1,240 kg/m 50 3 at 25C.
Water budget During the drought years 1996–2010, the major source 52 of freshwater was still the lower Jordan River: 60–150 53 10 54 6 m3 /year. The total freshwater inflow (including precipitation and floods) was 265–335 10 55 6 m3 /year. Evaporation rates derived from energy budget were 56 1.1–1.2 m/year. The low evaporation rate of Dead Sea, 57 compared with fresh lake in similar conditions 58
(1.4–1.5 m/year for the Sea of Galilee, Rimmer et al., 59 2009), is connected with the high hydroscopic ability 60 of the Dead Sea brine (Krumgalz et al., 2000; Lensky 61 et al., 2005). The total water deficit of the lake is 690 62 10 63 6 m3 /year. About 36% of this amount is due to the activity of the chemical industries in the southern basin of the 64 Dead Sea (Lensky et al., 2005).
L. Bengtsson, R.W. Herschy, R.W. Fairbridge (eds.), Encyclopedia of Lakes and Reservoirs, DOI 10.1007/978-1-4020-4410-6,Springer Science+Business Media B.V. 2012
Meteorology The climate in the Dead Sea area is highly arid, with a mean annual rainfall less than 100 mm (Goldreich, 1998). Air temperature over sea has been observed between 7.5C and 43.4C. While typical relative humidity over the Dead Sea is between 33% and 52%. On average, August is the hottest month with air temperature of 33C and July is the driest (39% humidity). The coldest and most humid month is January with an average temperature of 18C and 47% humidity. Air temperature changes are
closely associated with the arrival of the Mediterranean breeze as well as with the onset of the local breeze. The daily maximal temperature occurs 4 h later than along the Mediterranean coast. The atmosphere above the sea surface differs from that on land. Air temperature above the sea is colder by about 0.5–1C during summer and warmer by about 1–2C during winter. Relative humidity above sea is higher by about 4–5%. Air pressure at the Dead Sea surface is higher than at the mean sea level by about 50 mb. The typical speed of winds is 4–6 m/s. In general, during summer, winds are mostly northerly. During winter, there is an increase in the southerly winds. During winter, strong winds (10–20 m/s), although rare, occur more frequently than during summer. Westerly winds, associated with the Mediterranean breeze, occur at the same rate throughout the year. They appear in the late afternoon and can reach 20 m/s at midnight. Wind strength diminishes in the morning with the weakest winds occurring around 13:00 (Hecht and Gertman, 2003). The maximal wind wave heights observed were at 3 mwith 8 s period (Hecht et al., 1997).
Chemical composition The salinity of the Dead Sea water is about eight times larger than that of oceanic water, being supersaturated in respect to halite and perhaps other minerals. Dead Sea water hasparticular ionic composition, which is domi ted by magnesium chloride unlike oceanic water which s dominated by sodium chloride (Figure 2). The extremely high salinity of the Dead Sea water as well as its unique ionic composition prevents the implementation of inexpensive methods of ocean water salinity measurenment. Therefore, in order to characterize the Dead Sea haline structure and variability, one uses its density anom113 aly from 1,000 kg/m3 at 25C (Anati, 1997). This is defined as quasi-salinity. Since the early 1980s, massive amounts of halite have precipitated from the water column as halite crystals (Gavrieli, 1997). A subject submerged in the Dead Sea water with temperature below 25C is covered by halite crystals (Figure 3). or hundreds of years the Dead Sea was a meromictic lake (see Meromictic Lakes) with stable haline stratification, supported by runoff. Winter convection was limited, and below the halocline was not affected by atmosphere. As a result of the runoff reduction, the upper-mixed layer (UML) salinity increased, and the gravitational stability diminished. Eventually, during the winter of 1978–1979, the lake water overturned, ending the long-term stable hydrological regime (Steinhorn and Gat, 1983; Anati,
1997). Since then, the lake entered a new phase in which its hydrological regime is either holomictic or
meromictic. Since 1979, the meromictic regime is established twice only after extremely rainy winters: dur- ing 1980–1982 and during 1992–1995. Regardless of regime, deep water temperature remains in the range 22–24 147 C, while quasi-salinity has increasedsince 1978 from 232 kg/m 148 3 at a rate of 0.35 kg/m3 year(Anati, 1997; Gertman and Hecht, 2002). Seasonal thermocline is formed in the middle of March. UML during meromictic winter has low quasi-salinity (200–210 kg/m 152 3) and can be colder than the deep layer due to hydrostatic stability which limits winter convection e.g., in winter 1993, temperature dropped to 15 154 C (Beyth et al., 1993)). During summer, the UML reaches 15 maximal temperature (32–35 156 C), and quasi-salinity value is 3 kg/m 157 3 higher than at the deep water. The UML thickness during meromictic periods and holomictic summer fluctuates between 15 and 30 m. Convective mixing of the entirely water body occurs during the sec- ond half of November in the holo mictic regime (Figure 4). Extremely hot and dense water (up to 44 162 C and 1,350 kg/m 163 3Lensky et al., 2005) entering in the southern part of the Dead Sea from the evaporation ponds propagates as gravi tation currents northward following the bathymetry. During the summer, this water forms a bottom layer in the entire deep region. The layer is warmer (0.5 168 C) and saltier (0.5 kg/m3 ) than the main water body layer above it. Double diffusion builds step- like profiles of water properties in the bottom layer (Gertman and Hecht, 2002).
Expected future of the Dead Sea The sea surface level is expected to decrease in the course of the nearest 500 years. However, some deceleration of the sea level decent has been predicted by different models even if the runoff and industrial water consumption will not change in the future (Yechieli et al., 1998; Krumgalz et al., 2000; Asmar and Ergenzinger, 2002). In all the models, the evaporation rate is inversely proportional to the concentration of ions. Moreover, the integral evapora181 tion decreases with the sea surface area decrease. A critical ionic concentration will diminish the evaporation dramat183 ically when the sea level reaches 500 m bmsl. Several proposals were made for stabilizing the Dead Sea water level by connecting the Dead Sea with the Mediterranean or the Red Sea. The main idea is to utilize more than 400 m difference in sea levels to generate hydroelectric energy. Additional profit can be achieveddue to desalinization of the seawater on the way to the Dead Sea. In 2005, the governments of the Israel, Jordan, and the Palestinian territories supported by the World Bank agreed to conduct a feasibility study for a cannel or pipeline between the Gulf of Aqaba and the Dead Sea along the Arava Valley transporting initially Red Sea water and eventually high salinity end brines (by-product of desali nization) into the Dead Sea. The most eviden problems concerning this proposal are: restoration of meromictic stratification, mass precipitation of gypsum, and development of new life-forms (Oren, 2003).
Summary For hundreds of years prior to 1950, the Dead Sea surface level was about 400 20 m bmsl. During this period, dilu203 tion of the upper layer by the freshwater runoff was suffi204 cient to support stable stratification even during the winter seasons. Anthropogenic reduction of runoff and water consu mption for industrial mineral production led to sig207 nificant changes in dimensions and hydrology of the Dead Sea. Israel Dead Sea Works Ltd. and the Jordanian Arab Potash Co. pump water from the nort hern part into indus210 trial evaporation ponds located where the southern part used to be. After the extraction of potassium and bromide salts, the remaining extremely dense water is returned to the northern part. During 1978–2010, the northern part sea level descended by 23 m, the area shrank by 58 km2 and the volume decreased by 15 km3 . Gradual salinity increase in the upper layer led to the first overturn in winter 1978–1979. Stable haline stratification, preventing winter overturns, was restored twice after extremely rainy winters of 1980 and 1992, and lasted for 3–4 years each time. The main body water density increased since 1979 from 1,232 kg/m3 to 1,241 kg/m3 due to increased ionic concentration. Halite is saturated since about 1980, and permanent precipitation is observed on submerged objects. Increase of ionic concentration leads to decreased evaporation rate; therefore, sea level drop rate is expected to decrease in the future. Different estimates of the future Dead Sea water budget came to a common conclusion that in about 500 years, the sea level will be 500 m bmsl.
Bibliography Anati, D. A., 1997. The hydrography of a hypersaline lake. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 89–103.
Asmar, B. N., and Ergenzinger, P., 2002. Long-term prediction of the level and salinity in the Dead Sea. Hydrological Processes, 16, 2819–2831. Beyth, M., Gavrieli, I., Anati, D., and Katz, O., 1993. Effects of the
December 1991–May 1992 floods on the Dead Sea vertical structure. Israel Journal of Earth Science, 41, 45–48. Gavrieli, I., 1997. Halite deposition in the Dead Sea: 1960–1993. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 161–170. Gavrieli, I., and Oren, A., 2004. The Dead Sea as a dying lake. In Nihoul, J. C. J., Zavialov, P. O., and Micklin, P. P. (eds.), Dying and Dead Seas, Climatic Versus Anthropogenic Causes. Dordrecht: Kluwer Academic, pp. 287–305. Gertman, I., and Hecht, A., 2002. The Dead Sea hydrography from 1992 to 2000. Journal of Marine Systems, 35, 169–181. 249 Gertman, I., Kress, N., Katsenelson, B., and Zavialov, P., 2010.
Equations of State for the Dead Sea and Aral Sea: Searching b for Common Approaches. Final Report. IOLR report 12/210. Goldreich, Y., 1998. The Climate of Israel. Observations, Research 2 and Applications. Bar Ilan University Publishers and I. L. Magnes Press, Ramat-Gan (in Hebrew). 292 pp. 255 Hall, J. K., 1997. Topography and bathymetry of the Dead Sea depression. In Niemi, T., Ben-Avraham, Z., and Gat, J. R.
(eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 11–21. 259 Hecht, A., and Gertman, I., 2003. Dead Sea meteorological climate. 260 Chapter 4. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal 26 Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G. 262 325 pp. 263 Hecht, A., Ezer, T., Huss, A., and Shapira, A., 1997. Wind waves on Dead Sea. In Niemi, T., Ben-Avraham, Z., and Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 114–121. Krumgalz, B. S., Hecht, A., Starinsky, A., and Katz, A., 2000. Ther- modynamic constraints on Dead Sea evaporation: Can the Dead Sea dry up? Chemical Geology, 165, 1–11. Kushnir, Y., and Stein, M., 2010. North Atlantic influence on 19th– 20th century rainfall in the Dead Sea watershed, teleconnections
with the Sahel, and implication for Holocene climate fluctua- tions. Quaternary Science Reviews, 29, 3843–3860. Lensky, N., Dvorkin, Y., Lyakhovsky, V., Gertman, I., and Gavrieli, I., 2005. Water, salt, and energy balance of the Dead Sea. Water Resources Research, 41, doi:10.1029/ 2005WR004084. Neev, D., and Emery, K.O., 1967. The Dead Sea. Depositional pro- cesses and environments of evaporites. Bulletin No. 41, State of Israel, Ministry of Development, Geological Survey, 147 p. Niemi, T. M., Ben-Avraham, Z.and Gat, J. R., 1997. Dead Sea research – an introduction. In Niemi, T., Ben-Avraham, Z., and
Gat, J. R. (eds.), The Dead Sea – the Lake and Its Setting. Oxford: Oxford University Press, pp. 3–7. Oren, A., 2003. Physical and Chemical Limnology of the Dead Sea. Chapter 3. In Nevo, E., Oren, A., and Wasser, S. P. (eds.), Fungal Life in the Dead Sea. Ruggell: A.R.G. Ganter Verlag K.G, pp. 45–67. 325 pp. Rimmer, A., Samuels, R., and Lechinsky, Y., 2009. A comprehensive study across methods and time scales to esti-
mate surface fluxes from Lake Kinneret, Israel. Journal of Hydrology, 379, 181–192.Steinhorn, I., 1981. A Hydrographical and Physical Study of the
295 Dead Sea During the Destruction of its Long-Term Meromictic
296 stratification. PhD Thesis, Weizmann Institute, Israel, 323 pp.
297 Steinhorn, I., and Gat, J. R., 1983. The Dead Sea. Scientific
298 America, 249, 102–109.
299 Yechieli, Y., Gavrieli, I., Berkowitz, B., and Ronen, D., 1998. Will
300 the Dead Sea die? Geology, 26, 755–758
Cross-references
Meromictic Lakes
Dead Sea, Figure 1 The Dead Sea watershed. Insertion shows profile along the Jordan Rift Valley toward Gulf of Eilat (Aqaba).(Adopted from Niemi et al., 1997.)
Dead Sea, Figure 2 Percentage of ionic concentrations in the Sea water. D – ocean water, ○ – Dead Sea water during 2008, – Dead Sea water during 1960–1996, □ – end brines from evaporation ponds. (Data derived from Steinhorn (1981);Gavrieli (1997), Oren (2003), Gertman et al. (2010).)
Dead Sea, Figure 2 Percentage of ionic concentrations in the Dead Sea water. D – ocean water, ○ – Dead Sea water during 2008, – Dead Sea water during 1960–1996, □ – end brines from evaporation ponds. (Data derived from Steinhorn (1981); Gavrieli (1997), Oren (2003), Gertman et al. (2010).)
Dead Sea, Figure 4 Vertical profiles of potential temperature (left panel) and quasi-salinity (right panel) in the deep region of the Dead Sea during February and August 2009
