Record Ice Loss In Greenland In 2019 Was Driven By Unusually Clear Skies

2019 is listed as one of the worst years on record for the Greenland ice sheet. During the year, the sheet lost hundreds of billions of tons of ice. The incredible ice loss wasn't caused by warming temperatures alone, according to a new study. The study found that there was another factor that significantly contributed to the ice loss in Greenland.

The study points to atmospheric circulation patterns that contributed in a significant way to the rapid loss of ice mass in 2019. Researchers participating in the study used satellite data, ground measurements, and climate models to analyze changes in the ice sheet during the summer of 2019. The researchers found was that while 2019 saw the second-highest amount of runoff from melting ice ever, the year also saw the biggest drops in surface mass balance since record-keeping started in 1948.

Surface mass balance takes into account gains in the sheets mass, such as through snowfall, as well as losses from the surface melt water runoff. The researchers say that in 2019 the ice sheet surface mass balance dropped by about 320 billion tons. At the same time, the surface mass gained about 50 billion tons of ice. The average gain between 1981 and 2010 was about 375 billion tons of ice per year.

The mass gain was offset by the sheet losing hundreds of billions of tons of ice as icebergs break off into the ocean. One major reason why so much ice was lost in 2019 has to do with high-pressure conditions that prevailed over Greenland for unusually long periods. Those high-pressure conditions prevented the formation of clouds in the southern portion of Greenland, resulting in clear skies.

The clear skies resulted in more sunlight that melted the surface of the sheet. No clouds also meant less snowfall. Scientists say that warm and moist clouds that did form trapped heat that normally radiated off the ice and created a small-scale greenhouse effect. Those combined effects in the summer of 2019 led to the highest annual mass loss from Greenland's surface since record-keeping began.