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.
Standardized melting index for the period 1979 - 2012 when considering only the period June 1st - July 20th
The image below shows the cumulative number of melting days over Greenland for the period June 1st - July 25th. Beside the large melt extent occurring in July 2012, note the high number of melting days along the southeast coast as well as the width of the area subject to considerable melting along west Greenland. Over the southeast coast, during the period June 1st - July 25th, melting lasted up to 30 days above the mean.
Number of melting days estimated for the period June 1st - July 25th of every year from space borne microwave data
Since the past week or so, melting has decreased with respect to the breaking-record values of June and mid July, mostly as a consequence as the shift to a neutral phase of the NAO. Depending on how melting will evolve in August, the 2012 melting season might set a new melting record. Nevertheless, 2012 is already positioning among the top melting years, with the cumulative melting index until July 25th being close to the cumulative melting index for the whole 2010 and higher than the one for the 2011 season.