Climate change is changing the salinity of the seas

Photo by: cinoby / iStock

A study conducted by scientists at the Institute of Marine Sciences (ICM) in Barcelona has revealed an acceleration of the water cycle by analysing ocean surface salinity. Sea surface salinity reflects the balance between precipitation and evaporation over the ocean. Measurements of salinity are made by satellite — at the ocean surface — and in situ — a few metres below the surface. Satellite measurements reveal an intensification of the water cycle (salinity irregularity — less saline waters become even less saline and vice versa), which is not observed in in situ salinity measurements.

“Where the wind is no longer as strong, surface waters warm but do not exchange heat with the water below, making the surface more saline than in the lower layers and allowing the effect of evaporation to be observed using satellite measurements,” said study co-author Antonio Turiel in a press release.

“The acceleration of the water cycle has implications both in the ocean and on the continent, where storms can become increasingly severe,” lead study author Estrella Olmedo said in the press release.

Numerous studies show that climate change is affecting the natural water cycle. In recent years, the uneven distribution of precipitation around the world has become increasingly visible, with monsoons and heavy rains in some places and severe drought in others. Now it also appears that the salinity of sea water is becoming unequal due to global warming.

Water contained in lakes, rivers, oceans and seas is constantly being heated by the sun, evaporating and turning to steam. In the air, the vapour begins to cool and condense, forming clouds that can travel across the planet in horizontal bands (the atmospheric rivers effect), a key feature of the global cycle that feeds weather systems. Atmospheric rivers provide rapid moisture transport from the tropics to mid and high latitudes. When enough water vapour collects in clouds, it turns into water droplets and falls to the ground as rain, snow or hail. The precipitation fuels rivers, lakes and other bodies of water, then the cycle begins again.

Higher temperatures heat the lower layers of the atmosphere and increase evaporation. The more water in the air, the more likely it is that precipitation will fall, often in the form of violent storms.

By the way, about 97% of the world’s limited water supply is saline. Rising global temperatures are on the one hand pushing melting glaciers and sea levels higher and on the other hand causing seawater to evaporate in large quantities, which disturbs the natural water-soil balance. Thus, the ICM study has once again demonstrated how human activities are disrupting the crucial water cycle system that makes all life on Earth possible.

Cover photo: Naeblys / iStock