Arctic sea ice has diminished drastically over the last 40 years. Now a study shows that the southern half of the US may be suffering from more summer heatwaves as a consequence.

Dagmar Budikova, a climatologist at Illinois State University, and colleagues used satellite data to measure the ebb and flow of Arctic sea ice in the Hudson Bay region since 1979 and compared this with heatwave frequency across the US. Their results, published in the Journal of Geophysical Research: Atmospheres, show that summer heatwaves were far more common across the southern US in the years when the Hudson Bay basin experienced a warm spring and reduced sea ice.

That’s because these conditions reduce the north-south temperature contrast, resulting in slacker winds and a loopier jet stream: the perfect breeding ground for lingering high-pressure systems and summer heatwaves over the southern plains.

So how is this summer shaping up? Thankfully spring temperatures and sea ice were near normal levels across Hudson Bay this year and unlikely to trigger heatwaves in the southern US. “This, however, does not mean that the southern US will not see heatwaves, just not those triggered by sea ice in the Hudson Bay area,” explains Budikova.