As the climate crisis continues to bring extreme weather around the world – including Europe – there’s another consequence of global warming that you might not have registered.
The ocean is getting saltier – well, parts of it anyway.
Yep, amid growing concerns about the ice caps melting, the Earth’s waters getting too warm and sea levels rising, it turns out the salinity (salt content) of the ocean changes, too.
When ice caps melt, they add fresh water to the ocean – not salty water. So, if a body of water gets its supply from ice sheets which are melting, it will be less salty, not more.
But, if a body of water is not refilled with water which has come from the melting ice caps, it’s more likely to be vulnerable to evaporation, which does makes it saltier.
The Med is almost completely enclosed by land which prevents much fresh water getting into it, and so the evaporation of the water is greater than the contribution of the rivers which flow into the sea.
And, as pointed out on The Naked Scientists’ website last September, more evaporation occurs in areas like the Mediterranean, meaning the concentration of saline in the ocean gets higher. High temperatures mean the water is taken out of the ocean, but not the salt.
It has also been incredibly hot around the Mediterranean recently – wildfires have swept across the region after a prolonged heatwave – and this heat is not just limited to the land.
The Spanish research institute, ICM-CSIC, found in a new study that the water in this area is warming by 2C per century (and even up to 3C in some places) – along with the salt concentration.
And, another study from 2010 found that the temperature of the deep layer of the Western Mediterranean increases by 0.002C every year, while the salt levels increase by 0.001 units of salinity.
The study, detailed in the April 1 edition of the Journal of Geophysical Research, explained that the salinity and temperature increase every year, but this rate has been increasing over time due to global warming.
An increase in ocean salinity suggests an increase in the net evaporation of the water (the difference between evaporation and precipitation).
It’s worth noting that the scientists suggested other factors, such as humidity and the temperature of the atmosphere, were helping to speed up the Mediterranean’s evaporation, too.
But what happens in other seas?
In places where fresh water meets salt water, the salted liquid will sink because it’s much more dense – that’s what happens in the North Atlantic and the Arctic Ocean.
Much like other parts of the environment, climate change seems to exacerbate existing issues.
Research published on Nature.com found that between the 1870s and 1950s, salty areas in the ocean seem to be getting saltier and fresh areas fresher.
As the World Economic Forum pointed out in 2021, the changing levels of salt detected on an ocean’s surface can help explain how it has been impacted by climate change.