The future of the Dead Sea

You could say that Ein Gedi is literally after miles of endless highway, past scattered kibbutzim. This windy beach on the western coast of the Dead Sea was teeming with hordes of tourists plastering themselves with mud and floating on the water to the backdrop of Cutting Crew’s “(I just) died in your arms tonight” and lots of human poo on the beach and on the sea itself (which dissuaded us from getting more adventurous). Although  it was late autumn, it was warm (around 24-25 deg C); the sun shone in all his glory, but (incongruously) we noticed the lack of searing heat (explained by being located in the lowest altitude in the world at around 415 m below sea level- due to the high barometric pressure, UV radiation is low).

A misnomer, Dead Sea is a saline lake, extending for approx. 60 kms, located in the Jordan Rift Valley and sandwiched between Lake Tiberias in the North and the formidable Red Sea in the south and surrounded by hostile hills and mountains. The adjective 'dead' illustrates that the lake is practically devoid of life due to its extreme saline content (nearly 9 times more saline than the oceans). There were some exceptions (the Dunaliella algae which nourished halobacteria) when the salinity dropped due to flooding. The surrounding barren terrain has wildlife (hares, ibex, jackals, etc). The water is supposedly curative and therapeutic and there is a booming mineral/salts/mud industry (I too have a hand cream of Dead Sea salts- and I must admit that it does its job).

The Dead Sea is historically significant. The Bible refers to it as the Sea of Salt (Genesis 14:3) or the Eastern Sea. More significantly, the destroyed towns of Sodom & Gomorrah ("the cities of the plain") are said to be under the lake (others maintain that the towns were in Mt Sodom); indeed, overlooking the lake is a rock formation considered to be Lot's wife who was transformed into a pillar of salt when she disobeyed the angels' instructions and turned back to look at the cities being destroyed by God. David hid from Saul in the wilderness surrounding the lake and several centuries later, people used to hide in the caves by the hills bordering the lake.

The major sources of the lake are the Jordan River itself and the Dead Sea wadis. However, the river water is now predominantly diverted for human purposes by three countries (Israel, Jordan, and Syria). Since the lake is in the rain shadow area, rainfall is negligible (2-4 inches per annum). Compounding this is the high evaporation rate due to high temperatures and low humidity. All of this has contributed to a rather grave situation- the shrinking of the lake (more popularly known as the Death of the Dead Sea). Some sources state that the lake has lost a third of its surface area, with the water level falling by more than 80 ft in the past 8-9 decades (and a fall of around 2-3 ft each year). Indeed, as seen in the satellite map, the southern half of the Dead Sea is separated from the northern half, connected by a canal, which prevents the southern part from drying up completely.

On the flip side, many industries depend on the lake for their profits (and even existence). Many are the hotels and resorts by the Dead Sea with customers keen on either floating in water (due to the high salt concentration) or taking advantage of the supposedly therapeutic nature of the mud and water. And there is also a lucrative trade on Dead Sea minerals and chemicals (who are also identified as one of the banes of the lake since they evaporate the waters to obtain the products).

Some preventive measures have been proposed:
1. Siphoning water via a canal (specifically, from the Gulf of Eilat): The intention is to desaline the waters from the Red Sea and diverting the desalinated water towards Jordan and discharging the brine in the Dead Sea. Proponents justify this by pointing out how the waters in the lake would be replenished and surrounding countries address water and electricity problems. However, this does not consider the impacts (and consequences) on the lake's limnology, geochemistry, and ecology (Gavrieli et al, 2005). For instance, there would be increased evaporation due to the relative dilution- which could also result in blooming; another consequence is the change in composition and the accumulation of sea salts- one outcome of this would be a reduction in the therapeutic qualities.
2. A sustainable method of harvesting the Dead Sea minerals (instead of evaporation)
3. Efficient harvesting of the even-if-minimal rainwater. This would decrease the dependency on Jordan River.
4.  Increasing the flow of water from Jordan River which might be achieved by reducing farming in the region

Any thoughts on what else could be done?
 Radwan A. Al-Weshah (2000). The water balance of the Dead Sea: an integrated approach Hydrological Processes, 14 (1), 145-154 DOI: 10.1002/(SICI)1099-1085(200001)14:1
Gertman, I., Hecht, A (2002). The Dead Sea hydrography from 1992 to 2000. Journal of Marine Systems, 35, 3–4, 169–181.
Gavrieli, I, Bein, A., Oren, A. (2005). The Expected Impact of the Peace Conduit Project (The Red Sea – Dead Sea Pipeline) on the Dead Sea. Mitigation and Adaptation Strategies for Global Change, 10, 1, 3-22,

References:

Image source: Google maps

Sunlight on the sea

In this last week the Brazilian cities of Sao Paulo and Recife have experienced records levels of UV exposure. While a UV index of 6-7 is ¨high risk", and "very high risk" is 8-10, Sao Paulo was scorched with an index of 14.

As the sun burns us it also beats down on the ocean surface and the algae that live there. What happens next is the subject of the CLAW hypothesis, which proposes a negative feedback loop, as follows.....

Dimethylsulphide produced by phytoplankton is oxidised by bacteria to produce a sulphate aerosol on the sea surface which is a major source of cloud condensation nuclei. So more clouds, less photosynthesis and a feedback loop.

That´s fine, but of course the real world is much more complicated than that. For instance, solar radiation is a double edged sword. There is increased photosynthesis, and temperature for growth, but what of UV? UV-B damages DNA in the bacteria required for DMS oxidation, killing them. It also harms the phytoplankton, who respond by producing anti-oxidants, including DMS. Together these factors increase considerably the amount of DMS in the ocean, so oceanic [DMS] and levels of UV are linked through the year. But DMS in the atmosphere and the surface waters is attacked by UV, leading to it´s photo destruction.

So what happens when UV increases beyond previous levels? Does the extra production of DMS still lead to more cloud cover, a negative feedback? Or does UV kill off the oxidising bacteria and cause photodestruction in the atmosphere, leading to less cloud clover, and in turn, more UV exposure - a positive feedback loop? Oceanic acidification, as described previously by Ruth, changes water chemistry and inhibits phytoplankton growth, and so complicates matters still further.

The processes mentioned here take place on such a massive scale that they affect deeply the world climate. They are incredibly complex, and rely on a interlinked series of feedback loops. What happens when feedback is disrupted has yet to be seen.

For more detail see;

Miles, CJ, Bell, TG, Lenton, TM 2009. Testing the relationship between the solar radiation dose and surface DMS concentrations using ub situ data. Biogeosciences, 6, 1927-1934.

Miles, C., Bell, T., & Lenton, T. (2009). Testing the relationship between the solar radiation dose and surface DMS concentrations using in situ data Biogeosciences, 6 (9), 1927-1934 DOI: 10.5194/bg-6-1927-2009