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salinity of oceansuface salinity changeMeasurement of surface salinityGlobal conveyor beltNASA's aquariusDesalination capacity in GulfFuture desalination capacity-projectedDesalination processBrine characterstics from desal plantsThere is a growing evidence that shows increasing salinity of seawater affects the “water cycle” resulting in climate change. Apart from the natural cycle, the highly saline brine discharged from man-made “desalination” plants around the world also contributes to the increasing salinity of seawater. There are only few desalination plants suppliers world-wide who build such large-scale desalination plants and they use only decades old desalination technologies. They recover 35% of fresh water and discharge 65% highly concentrated, toxic effluent back into the sea. Their main focus of innovation is to cut the energy consumption because it is an energy intensive process. Such energy comes mainly from fossil fuels. The result is unabated Carbon emission, toxic brine discharge into the ocean, warm saline water discharge into the ocean from “once through cooling towers” from co-located power and desalination plants. Currently about 5000 million cubic meters of fresh water is generated  yearly from seawater desalination plants around the world; this capacity is expected to increase to 9000 million cubic meter per year by 2030.The brine outfall from desalination plants will amount to a staggering 30 billion cubic meters/yr. Such a huge volume of saline water with salinity ranging 70,000 ppm up to 95,000 ppm will certainly alter the water chemistry of the ocean. Desalination plant suppliers  are not interested in “innovation” that can recover fresh water without “polluting” the sea. They rather justify using “environmental impact study” which invariably concludes there is absolutely no impact on environment and any toxic discharge into the sea is “harmless”. This practice is going on for decades without any check. Dwindling fish population world–wide is a direct impact of such discharge. Financial institutions such as world bank, Asian development bank etc are willingly finance such projects without questioning such technologies and their impact on marine environment. Their focus is only “return on investment”–the only criteria that is required for funding and not the “cost and benefit analysis”. A detailed analysis will reveal  “handful of rich and powerful” Governments and individuals  can influence the world’s climate  intentionally or unintentionally. The same “rich and powerful” can shun any innovations “that might threaten their business model” and “ nip such innovations or inventions at their bud” because they simply do not believe in Research and Development or unwilling to direct their “cash flow” into R&D because they do not want any  threat for their existing technologies. There are very few financial professionals who can think “outside the box” or predict their financial impact due to innovative technologies of the future. Their financial decisions reflect the sentiments of the financial institutions, namely “the return on investment”.

“When you read about human-induced climate change it’s often about melting glaciers and sea ice, increasing frequency of heat waves and powerful storms. Occasionally you’ll hear about the acidification of the oceans too. What you don’t often hear about is the saltiness of the seas. But according to a new piece of research just published inGeophysical Research Letters that is changing too.The saltiness, or salinity, of the oceans is controlled by how much water is entering the oceans from rivers and rain versus how much is evaporating, known as ‘The Water Cycle’. The more sunshine and heat there is, the more water can evaporate, leaving the salts behind in higher concentrations in some places. Over time, those changes spread out as water moves, changing the salinity profiles of the oceans. Oceanographers from Scripps Institution of Oceanography and Lawrence Livermore National Laboratory fingerprinted salinity changes from 1955 to 2004 from 60 degrees south latitude to 60 degrees north latitude and down to the depth of 700 meters in the Atlantic, Pacific and Indian oceans.

They found salinity changes that matched what they expected from such natural changes as El Niño or volcanic eruptions (the latter can lower evaporation by shading and cooling the atmosphere).

Next the ocean data was compared to 11,000 years of ocean data generated by simulations from 20 of the latest global climate models. When they did that they found that the changes seen in the oceans matched those that would be expected from human forcing of the climate. When they combined temperature changes with the salinity, the human imprint is even clearer, they reported.“These results add to the evidence that human forcing of the climate is already taking place, and already changing the climate in ways that will have a profound impact on people throughout the world in coming decades,” the oceanographers conclude.”

(Ref: Larry O’Hanlon, Discovery News)

Salinity

 

Although everyone knows that seawater is salty, few know that even small variations in ocean surface salinity (i.e., concentration of dissolved salts) can have dramatic effects on the water cycle and ocean circulation. Throughout Earth’s history, certain processes have served to make the ocean salty. The weathering of rocks delivers minerals, including salt, into the ocean. Evaporation of ocean water and formation of sea ice both increase the salinity of the ocean. However these “salinity raising” factors are continually counterbalanced by processes that decrease salinity such as the continuous input of fresh water from rivers, precipitation of rain and snow, and melting of ice.

 

Salinity & The Water Cycle 

Understanding why the sea is salty begins with knowing how water cycles among the ocean’s physical states: liquid, vapor, and ice. As a liquid, water dissolves rocks and sediments and reacts with emissions from volcanoes and hydrothermal vents. This creates a complex solution of mineral salts in our ocean basins. Conversely, in other states such as vapor and ice, water and salt are incompatible: water vapor and ice are essentially salt free.

Since 86% of global evaporation and 78% of global precipitation occur over the ocean, ocean surface salinity is the key variable for understanding how fresh water input and output affects ocean dynamics. By tracking ocean surface salinity we can directly monitor variations in the water cycle: land runoff, sea ice freezing and melting, and evaporation and precipitation over the oceans. 

Salinity, Ocean Circulation & Climate

Surface winds drive currents in the upper ocean. Deep below the surface, however, ocean circulation is primarily driven by changes in seawater density, which is determined by salinity and temperature. In some regions such as the North Atlantic near Greenland, cooled high-salinity surface waters can become dense enough to sink to great depths. The ‘Global Conveyor Belt’ visualization (below) shows a simplified model of how this type of circulation would work as an interconnected system.
The ocean stores more heat in the uppermost three (3) meters than the entire atmosphere. Thus density-controlled circulation is key to transporting heat in the ocean and maintaining Earth’s climate. Excess heat associated with the increase in global temperature during the last century is being absorbed and moved by the ocean. In addition, studies suggest that seawater is becoming fresher in high latitudes and tropical areas dominated by rain, while in sub-tropical high evaporation regions, waters are getting saltier. Such changes in the water cycle could significantly impact not only ocean circulation but also the climate in which we live.

(Ref: NASA earth science)

The four main forces that control the earth’s climate are “Sea, Sun, Moon and earth’s rotation”  and  interference by human beings will alter the equilibrium of the system. In order to keep up its equilibrium, Nature is forced to change the climate unpredictably with devastating effects. We cannot underestimate the pollution caused by human beings because they are capable of altering the Nature’s equilibrium over a period no matter how “miniscule” (parts per millions or billions) the pollution may be. Any future investment on large-scale infrastructures should take into account the “human induced climate change” in their model and projections, failing which “climate change” will prove them wrong and the consequences will be dire.

Reference :  Environmental Impacts of Seawater Desalination: Arabian Gulf Case Study

Mohamed A. Dawoud1 and Mohamed M. Al Mulla

1 Water Resources Department, Environment Agency, Abu Dhabi, United Arab

Emirates

2Ministry of Environment and Water, Dubai, United Arab Emirates

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