Global warming is accelerating the water cycle, with relevant climatic consequences, such as the intensification of storms in specific areas and an increase in melting ice at the poles, according to a new study led by the Institute of Marine Sciences (ICM-CSIC) in Barcelona.

The work, published in the journal Scientific Reports, has analysed data on ocean surface salinity obtained by satellite, which have been complemented with in situ measurements and have improved the accuracy of ocean models. According to ICM-CSIC researcher Estrella Olmedo, this acceleration of the water cycle is due to an increase in the evaporation of water from the seas and oceans as a result of the rise in temperature.

Acceleration of the water cycle and storms

As a result, more water is circulating in the atmosphere as vapour, 90 % of which will eventually precipitate back into the sea, while the remaining 10 % will precipitate over the continent. "The acceleration of the water cycle has implications both at sea and on the continent, where storms could become increasingly intense, and this increase in water circulating in the atmosphere could explain the increase in rainfall that is being detected in some polar areas, where the fact that it is raining instead of snowing is further accelerating the melting of ice," according to Olmedo.

The work also shows that the decrease in wind in some areas of the ocean, which favours stratification of the water column, i.e. water not mixing in the vertical direction, could also be contributing to the acceleration of the water cycle.

"Where the wind is no longer so strong, the surface water warms up, but does not exchange heat with the water below, allowing the surface to become more saline than the lower layers and the effect of evaporation to be observed with satellite measurements," said Antonio Turiel, another of the study's authors.

According to the researcher, "this tells us that the atmosphere and the ocean interact in a stronger way than we imagined, with important consequences for the continents and the poles".

Ocean salinity

To conduct the study, scientists analysed surface salinity data - as measured by satellites - from different areas of the ocean.

Unlike the subsurface salinity data - obtained with in situ instruments - the satellite data allowed them to detect this acceleration of the water cycle and, for the first time, the effect of stratification over very large regions of the ocean.

He believes this is due to the ability of satellites to measure data continuously, regardless of environmental conditions and the accessibility of different areas of the ocean.

"We have been able to see that surface salinity is showing an intensification of the water cycle that subsurface salinity does not show. Specifically, in the Pacific we have seen that surface salinity decreases more slowly than subsurface salinity and there is an increase in sea surface temperature and a decrease in the intensity of winds and the depth of the mixing layer," according to Olmedo.

The scientists have used algorithms and other data analysis products that the Barcelona Expert Center (BEC), a member of the ICM-CSIC, has generated in recent years for the European Space Agency (ESA) with the aim of improving ocean salinity observations, which are essential for understanding ocean circulation, one of the key factors in understanding global climate. According to scientists, this circulation depends mainly on the density of the water, which is determined by its temperature and salinity.

"Therefore, changes in these two parameters, however small they may be, can end up having important consequences on the global climate, which makes it essential to monitor them closely," Turiel concluded. EFEverde