GREENBELT, Md. (NASA Goddard) – New NASA images released Tuesday, July 24, 2012 show the Greenland surface melt from July 8 to July 12, revealing the fastest melt of this region documented since 1890. Maria-José Viñas with NASA’s Earth Science News Team says, “For several days this month, Greenland’s surface ice cover melted over a larger area than at any time in more than 30 years of satellite observations. Nearly the entire ice cover of Greenland, from its thin, low-lying coastal edges to its two-mile-thick center, experienced some degree of melting at its surface, according to measurements from three independent satellites analyzed by NASA and university scientists. According to satellite data, an estimated 97 percent of the ice sheet surface thawed at some point in mid-July. Melt maps derived from the three satellites showed that on July 8, about 40 percent of the ice sheet’s surface had melted. By July 12, 97 percent had melted.” However, this is not an unprecedented event.
“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening around 1890, this event is right on time,” says Lora Koenig, a Goddard glaciologist and a member of the research team analyzing the satellite data. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”
“The Greenland ice sheet is a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story,” said Tom Wagner, NASA’s cryosphere program manager in Washington. “Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system.”
H. Joe Witte, with Adnet/NASA Goddard Earth Science Outreach, offers these explanations as to why this July’s melting was so incredibly fast.
- Huge ridge in June sets the stage. Look at the upper air anomalies, which are about +100 meters above normal. There has been a heat dome present over Greenland.
You can also view the upper air anomalies in July as a time-lapse from mid-June through mid-July (7th -13th). CLICK HERE to watch an animation of these anomalies.
- June surface temperatures, as we already know, were much warmer than normal over Eastern North America and Greenland, helping to set stage for July’s rapid melting.
IMAGE: NOAA, “red-blue dots” are surface temperature anomalies
- Weather data via WeatherUnderground from Summit-US, Greenland, lat=72-34N, lon 38.30W, high at Summit = 36 F on the 11th at 10,500 feet weather station shows melting.
- SST’s along the west coast of Greenland have jumped in July with some surface water areas reaching 40 F, or 5 to 10 degrees F warmer than normal. CLICK HERE and select parameter: “SST anomalies” for colorful image.
- Notice the abnormal lack of ice along the western shore of Greenland. This NSIDC Image shows normally there’s lots of ice that keeps the Sea Surface Temperature at 32 degrees Fahrenheit. No ice means water can be warmed by the sunshine.
- Historical perspective: What was the weather like in 1889? Click here for an interesting sidebar on Science Daily. This discussion is about winter 1889 and winter 2012, and NOT the summer. But are the some parallels? This needs more searching for data from summer of 1889.
So there are many questions to be answered about this Summer’s melting event, but we do know it is rare and extreme, with its impacts to come not fully understood.
Extent of surface melt over Greenland’s ice sheet on July 8 (left) and July 12 (right). Measurements from three satellites showed that on July 8, about 40 percent of the ice sheet had undergone thawing at or near the surface. In just a few days, the melting had dramatically accelerated and an estimated 97 percent of the ice sheet surface had thawed by July 12. In the image, the areas classified as “probable melt” (light pink) correspond to those sites where at least one satellite detected surface melting. The areas classified as “melt” (dark pink) correspond to sites where two or three satellites detected surface melting. The satellites are measuring different physical properties at different scales and are passing over Greenland at different times. As a whole, they provide a picture of an extreme melt event about which scientists are very confident. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory
Meteorologist Carrie Rose, WTVR
Story contributor: H. Joe Witte, Adnet/NASA Goddard Earth Science Outreach
