The oceans are getting saltier, and it’s apparently in direct response to man-made climate change. Peter Stott, head of climate monitoring and attribution at the Met Office in Exeter, England, determined this after studying 50 years’ worth of data and comparing it to climate models “that correct for naturally occurring salinity variations,” according to ScienceDaily.

Stott and his team found that global warming resulting from man-made emissions (as opposed to emissions from natural sources like volcano eruptions) were likely responsible for the increasing salinity of the North Atlantic. Slight rises in salinity — less than 1 percent — have already been recorded in subtropical regions of the Atlantic.

Stott hypothesizes that global warming is changing the patterns of rainfall across the planet: As high temperatures zap away water in subtropical zones, the atmosphere carries that extra moisture toward the poles, as well as toward the Pacific via the trade winds. Since that moisture ends up in another part of the planet, the water left behind in the North Atlantic becomes more concentrated — and its salinity increases slightly.

So why is this an issue if the increases are so small? Salinity levels (along with temperature) affect the density of seawater. Because saltier water is denser than freshwater, it circulates differently. And since Earth’s climate is regulated by currents, switching them up — even a little bit — might drastically alter the world’s climate.

Find out more:
How Salt Works
How Ocean Currents Work
How Weather Works
How Global Warming Works