Updated July 31st at 3:52 pm
The Greenland Ice Sheet is experiencing dramatic melting right now at its surface. Capital Weather Gang has written a great article on the meteorological and related processes associated with this recent melt event. They discuss the role of the weather system (a dome of heat) associated with the recent European heat wave and how it has shifted to the Arctic. Dr. Thomas Mote is a colleague at the University of Georgia. He is also one of the foremost international climate experts on Greenland. He and his colleagues have been sounding the alarm about this melt event for several days. Here's why Dr. Mote and his peers are saying "wow" about this particular event.
It is useful to provide important context about Greenland before delving too deeply into the current melting event. While often exaggerated in "doomsday" scenarios, Greenland could raise global sea level by 20 feet if the entire ice sheet melted. Of course, that is not likely to happen. However, changes to the Greenland Ice Sheet are rightfully scrutinized. In addition to contributing to sea level, freshwater melting from the Greenland Ice Sheet also affects marine ecosystems and important ocean circulations. According to the National Snow and Ice Data Center,
Melting in Greenland through the end of spring has been significantly higher than the 1981 to 2010 average, with several areas exceeding 10 days of additional melt above the average, and a few regions with more than 20 days. Only the southernmost tip of the island and a region along the southwestern side of the ice sheet are below the average to date.
Tom Mote was one of the scientists that discovered an anomalous Greenland melt event in 2012. Using satellite-derived data, the researchers found that Greenland's surface melting exceeded anything observed in the satellite era (1979 and onward). During that event, 97% of the ice sheet was experiencing surface melting. That event was associated with a high pressure system and very warm temperatures.
Why is the current event garnering attention? The event this week is an extensive melt episode, and like the 2012 event, surface melting reached the highest elevation in Greenland. Mote says prior to this decade, it last happened in the 1880s. Prior to the 1880s, scientists estimate that around the year 1100 was the last event of this magnitude. Such estimates are based on ice core and other proxy analyses that climatologists utilize to extend data records. Though a climate scientist, I do not study cryospheric processes. However, I cannot help but notice that two of these "record" melting events have happened in the past 10 years after not happening for over 100 years. One of Mote's recent doctoral students, Kyle Mattingly, has revealed a connection between plumes of moisture called atmospheric rivers and these extensive surface melting events. Other factors like the positioning of blocking highs and processes associated with climate warming are likely related as well.
Although the greatest extent of the season, the key "wow" is melt at the summit...A unique event in that we saw warm air mass moving in from the east which appears to be related to the record breaking European heat wave.
Most of our large melt days are associated with advection of heat and moisture from the southwest over the ice sheet. It may have happened, but I don’t recall a big melt event from the east. I think this speaks to the magnitude of the heat dome that was across Europe.
Dr. Christopher Shuman is a cryospheric scientist at NASA. Shuman, a colleague of Mote's (and mine during my NASA days), confirmed temperatures at the highest elevation of 0.55 degrees C, which is above the freezing point of water. Mote also said, "got a message from the ICECAPS group indicating melt at Summit." These independent verifications of the satellite-indicated melting suggest that the observations are credible.
By the way, the topographic profile of Greenland is revealed in this data provided by the Geoscience Laser Altimeter System aboard NASA's ICESat mission. Roughly 85% of Greenland, which is the largest ice sheet in the world that is not located in Antarctica, is typically covered in ice. While the coastal regions of the ice sheet are near sea level, the NASA Earth Observatory website points out:
the ice’s elevation rises dramatically between sea level around the coastline and the east-central interior, where elevations reach 3,200 meters (10,499 feet). The bright line running north to south roughly through the center of the island shows where the ice sheet peaks in a long island-spanning ridge. Fainter (lower elevation) ridgelines are visible near the northwest coast. The deeper shadows on the eastern (right) side of the major ridgeline indicate that the elevation drops off to the sea more rapidly. On the western slopes, the descent is more gradual.
