An anonymous reader quotes a report from The Guardian: There was a dramatic melting of Greenland’s ice sheet in the summer of 2019, researchers have confirmed, in a study that reveals the loss was largely down to a persistent zone of high pressure over the region. The ice sheet melted at a near record rate in 2019, and much faster than the average of previous decades. Figures have suggested that in July alone surface ice declined by 197 gigatons — equivalent to about 80 million Olympic swimming pools. Now experts have examined the level of melting in more detail, revealing what drove it. Crucially, the team note, the high pressure conditions lasted for 63 of the 92 summer days in 2019, compared with an average of just 28 days between 1981 and 2010. A similar situation was seen in 2012, a record bad year for melting of the ice sheet. Writing in the journal the Cryosphere, [researchers] report how they used satellite data, climate models and global weather patterns to explore the melting of the surface of the ice sheet last year. Among their findings the team report that almost 96% of the ice sheet underwent melting at some time in 2019, compared with an average of just over 64% between 1981 and 2010. Using models, the pair also found that about 560Gt of meltwater runoff was generated in the summer of 2019. The surface mass balance, the amount of ice the sheet gained from rain and snowfall minus the amount lost through meltwater run off and evaporation, was just 54Gt a year — about 320Gt a year lower than the average across the earlier decades, and the greatest such drop on record. Further analysis showed the level and distribution of melting to be closely tied to a number of factors, including levels of snowfall and reflection of sunlight — known as albedo — as well as cloudiness and absorption of sunlight. All of these, they note, were influenced by the persistent high pressure zone over the ice sheet last summer. Read more of this story at Slashdot.