Last Thursday, August 1, the Greenland ice sheet experienced its largest single-day volume loss on record, sending an estimated 12.5 billion tons of ice pouring into the ocean. Per a Twitter post by climate scientist Martin Stendel, the amount of ice collectively lost on Thursday and Wednesday—the ice sheet’s biggest surface melt day since 2012, with around 60 percent of the frozen expanse undergoing at least 1 millimeter of melting—would be enough to cover Florida in almost five inches of water.
As Andrew Freedman and Jason Samenow report for the Washington Post, Thursday’s melting event outpaced all data collected since 1950, when scientists first started tracking the ice sheet's daily mass loss.
“This model, which uses weather data and observations to build a record of ice and snowfall, and net change in mass of the ice sheet, is remarkably accurate,” Ted Scambos, a senior researcher at Colorado’s National Snow and Ice Data Center (NSIDC), tells the Post. “I would accept the result as fact.”
The momentous single-day melt followed another record-breaking episode recorded the day before. According to the Polar Portal, a monitoring website run by Danish polar research institutions in conjunction with the NSIDC, the ice sheet shed more than 10 billion tons of ice from 60 percent of its surface on Wednesday, July 31.
Ongoing extreme melt event in #Greenland. The amount of ice that melted from the surface of the ice sheet just during the last two days would be enough to cover #Florida with almost five inches of water. pic.twitter.com/c4zeD8YNCT— Martin Stendel (@MartinStendel) August 2, 2019
In 2012, about 97 percent of the ice sheet’s surface underwent some level of melting. That surface melt event did cover more ground than the most recent, but disturbingly, Greenland’s highest point, Summit Station, experienced heat greater “in both magnitude and duration” during the 2019 episode, says Christopher Shuman, a glaciologist at the University of Maryland-Baltimore County and NASA Goddard Space Flight Center.
In a separate Washington Post article, Samenow and Freedman explain that this summer’s melting event was sparked by the same high pressure weather system responsible for Europe’s record-breaking July heat wave. The burst of hot air, which pushed Greenland’s temperatures upward of 15 to 30 degrees above average, has transformed the ice sheet’s surface from a pristine blanket of white to an ash-colored stretch of land disrupted by pockets of melt water.
For the Conversation, Australian National University climate researcher Nerilie Abram points out that the Arctic is especially sensitive to climate change. Here, rising temperatures are spurring rampant ice loss that, in turn, drives the thermometer even further upward in a self-reinforcing vicious cycle. (Melting snow and ice darken the ice sheet’s surface, enabling it to absorb more heat and melt at a higher rate.) As a result, temperatures in the region are rising twice as fast as the global average.
This is a roaring glacial melt, under the bridge to Kangerlussiauq, Greenland where it's 22C today and Danish officials say 12 billions tons of ice melted in 24 hours, yesterday. pic.twitter.com/Rl2odG4xWj— Laurie Garrett (@Laurie_Garrett) August 1, 2019
This year's melting season began several weeks earlier than unusual. Per National Geographic’s Alejandra Borunda, Greenland’s mild, dry winter and spring exacerbated the effects of the prolonged heat wave, failing to balance out melting ice with fresh snowfall. This year alone, Marco Tedesco of Columbia University’s Lamont Doherty Earth Observatory says, the ice sheet has lost an estimated 248 billion tons—roughly on par with the 250 billion tons of melt recorded by the end of July 2012.
“We’re basically on pace,” Tedesco tells Borunda. “We’re in the ballpark of the 2012 record.”
In July specifically, Ruth Mottram of the Danish Meteorological Institute writes on Twitter, Greenland’s ice sheet lost 197 billion tons of water, or enough to raise sea levels by 0.5 millimeters over a one-month period.
According to Borunda, global sea levels have risen by 7 to 8 inches over the past century. By 2100, Greenland’s ice loss and surface melting could contribute another 2 to 13 inches of water to this figure.
“This season alone won’t make or break global sea levels,” Borunda concludes. “But this season, on top of many others like it, will have an impact.”