A couple of month ago, last June to be exact, notable newspapers and websites spread out an alarming news: ice is melting at an increasing rate!
In particular, melting of ice sheets both in the Arctic and the Antarctic regions is the phenomenon that worries scientists and environmentalists the most since this could have important implications on our planet.
Among the many consequences that could be mentioned at this topic, I would like to focus on two of them: global warming and oceans’ salinity.
One of the most visible effects of the rise in earth’s temperature is the melting of ice sheets. However, few people know that this event in its turn triggers a mechanism that accelerates and further increases the extent of this phenomenon. This could clearly be explained by comparing the so-called ‘Albedo effect’ to its opposite ‘Albedo flip’ as renowned scientist James Hanson uses to call it.
In the first case, we usually refer to the property of ice sheets to reflect solar heat away from the earth, and this represents an important contribution to the global temperature control. On the contrary, the increasing deep dark sea surface, as a direct consequence of ice melting, favors the opposite phenomenon – Albedo flip – where solar radiations are absorbed by the sea leading oceans to warmer temperatures. At this regard, scientists express their main concern since we are running the risk of having longer melting seasons and more intense melting phenomena. This is due to the fact that water has a larger heat capacity than air. And therefore, warmer oceans can melt ice sheets quicker and more intensely than warmer air could do.
And what should we expect after that?
Besides the most visible effect of sea level rise that will affect thousands of people now living on coastal areas, another side effect is worth to be mentioned: impacts on the so-called ‘Ocean Conveyor’.
This expression refers to the global ocean circulation system. In the tropical regions water is warmer and saltier since high temperatures increase the rate of evaporation. This warm water that lies in the surface of the ocean is transported to the East Coast of the Unitd States by the Gulf Stream. Later on, is the North Atlantic Drift that pushes it toward Europe. Once the warm water reaches the North, it releases heat to the atmosphere and becomes colder and denser. As a consequence, it sinks to the depth of the ocean and flows back to the tropics where it will be warmed again.
As it’s clearly understandable, temperature and salinity are the two main aspects that drive the ocean circulation. The increasing melt of ice sheets contributes to add more fresh water to the ocean and therefore it decreases its salinity rate. This leads to get less dense water with important implications on the above mentioned circulation system and therefore on global climate and weather.
Moreover, another looming risk has to be considered: oceans could further loose their ability to absorb atmospheric carbon dioxide since it depends on a combination of CO2 levels and seawater chemistry. Generally speaking warm water can hold less dissolved CO2 than the cold one. And if oceans temperature will keep on warming, carbon dioxide concentration will keep on rising with important consequences on global warming.
To conclude, I’d like to take a step back to the article I wrote one month ago about osmotic power technologies. In this case, the process applied to get energy relies on the difference in salt concentration between sea water and fresh water from the rivers. The higher the salinity gradient is, the more efficient this technology becomes.
What happended if the oceans’ salinity would steady decrease? Would this renewable energy source still be considered a viable solution?
We are deeply affecting the balance of the planet and this will not only threat our life on it, but also undermine any effort towards climate change mitigation.