Here's a message that Chris Shuman from UMBC/NASA Goddard posted on cryolist concerning the Summit Greenland temperatures. I am also attaching an updated figure from Chris showing that temperatures at Summit reached high values again over the past few days. I quickly looked at satellite data and though I could not see any melting for those days, the area undergoing melting was going up again. I will post an update later.
The recently observed melt extent record over Greenland has shown the capabilities of remote sensing data to monitor large areas on a daily basis. The melting observed at high elevations over Greenland did not generate meltwater that contributed (or could have contributed) directly to sea level rise, mainly because liquid water refroze after the event, creating the ice layer that has been used to confirm the event. The same remote sensing tools are used to observe melting at lower elevations, where it happens every summer. Here, meltwater can either directly contribute to SLR or it can impact ice sheet dynamics, modulating the ice velocity and shaping the evolution of the englacial summer system of channels through which meltwater flows (see this video, for example). Over the past years, surface melting over Greenland has been increasing, setting new a new record in 2010 and a close-to-record melting season in 2011.
So, what happened in 2012 over the rest of Greenland while the warm air was climbing up Summit ?
The graph below shows the Standardized Melting Index (SMI, obtained from the melting index by subtracting the mean for the period 1979 - 2012 and dividing by the standard deviation for the same period) for the period June 1st - July 20th. Values above 0 indicate those cases when melting was above the 1979 - 2012 mean. For the period when data is available, therefore, the SMI set a new record for the satellite era.
Chris Shuman, from UMBC/NASA GSFC has posted this update concerning surface temperature at Summit. The original message to cryolist follows ....
For those of you interested in the reported air temperatures at Summit, the NOAA data for 2012 is illustrated here relative to several previous years of their JJA data (up to July 25th so far).
The data shown will be updated periodically through the end of August. And it bears repeating that the snow surface temperature (as tracked by MODIS or the passive microwave sensors, see the NASA press release) can differ by several degrees from the nominal 2 meter air temperature.
Christopher A. Shuman - Assoc. Research Scientist
UMBC Joint Center for Earth Systems Technology
Cryospheric Sciences Laboratory, Code 615
Greenbelt, MD 20771 - USA
(301) 614-5706 voice (301) 614-5666 fax
Here's a video of the Watson bridge taken on July 21 from the helicopter flying us back from the ice. The bridge collapsed on July 12, 2012 because of the river flood. Great images here from the Earth Observatory website. More videos filmed during the collapse are also below.
Considering the large coverage of the news of the large melt extent over Greenland reported by NASA, I thought it would be helpful to report some of the previously detected melt extent 'anomalies'.
The melt extent observed during July 2012 is unprecedented (during the satellite era, 1979 - to date) but I can recall at least two cases (one in Greenland and one in Antarctica) when melt extent was out of the ordinary.