New research finds that unusual rain may be contributing to the sea level rise in the Arctic, possibly accelerating it beyond the current predictions. Researchers warn that such rains may be more common in parts of the Greenland ice sheet.

Unusual Rain

Greenland is already losing ice each year because of warming, and it is believed to be losing 270 billion tons of ice each year. Until recently, most of the ice loss is believed to come from icebergs breaking off from the sheet and into the ocean, but a new study found that direct surface melting now accounts for 70 percent of the loss.

What’s more, they found that unusual rain, particularly in the winter, largely contributes to the melting. What’s worrying is that the trend may even spread as the Earth continues to warm.

Rain-Related Ice Melt

The researchers used satellite imagery from 1979 to 2012 to see what triggered the ice melt in specific places, and they did so because the satellite images can distinguish between snow and liquid water. They also used camera-equipped drones to map the area, and they also scoured the temperature and precipitation data from 20 automated weather stations on the ice sheet.

The researchers found over 300 melting events that were triggered by rain, with almost a third of the total meltwater runoff associated with it. Such rain-related melting events actually doubled in the summer and tripled in the winter.

Furthermore, they found that while the amount of precipitation did not increase, the form of precipitation changed. Instead of snow, the ice sheet was getting rain because of the warmer air.

Sea Level Rise

With rains becoming increasingly common in some parts of the Greenland ice sheet, it could possibly accelerate the sea level rise more than the current predictions. So far, the global sea level rise accelerated from 2.2 millimeters per year in 1993 to 3.3 millimeters per year on 2014, most of it attributed to the melting of the Greenland ice sheet.

The study is published in The Cryosphere.