Arctic sea ice hit a record low for the end of the region’s winter last month, in a stark sign of how climate change is opening up the North Pole to a geopolitical race for military and energy exploration.

March was the fourth consecutive month in which sea ice reached a record low for that calendar period, based on a 47-year satellite record, EU earth observation agency Copernicus reported on Tuesday.

Military and commercial vessels, particularly from Russia, are stepping up activity in the region, some of which is expected to be ice-free during summer within a decade, said Rebecca Pincus, former director of the Wilson Center’s Polar Institute. US President Donald Trump’s desire to take control of Greenland has increased attention on the area’s critical minerals and importance for trade and military strategy.