2010 Greenland Record over the Greenland Ice Sheet
by Cryospheric Processes Laboratory, The City College of New York
Remote sensing data, surface observations and models indicate new records in 2010 for surface melt and albedo, runoff, the number of days when bare ice is exposed and surface mass balance of the Greenland ice sheet. This was especially true over over its west and southwest regions.
Melting is a crucial factor in both surface and subglacial processes. Here’s a video showing melting streams, supraglacial lakes and meltwater flowing through ice cracks that we recorded in 2009 and 2010.
If interested, here’s some B-roll used to create the video. Feel free to ask for a high-resolution version.
Broll 1: Meltwater from a stream of a supraglacial lake flowing into a large crack.
Broll 2: Supraglacial lake at the sunset
Broll 3: Rapids of meltwater in Greenland
In summer 2010, early melt onset in spring was triggered by above-normal near-surface air temperatures. This contributed to accelerated snowpack metamorphism (snow melts faster and in turns it gets ‘older’ sooner, with large grain sizes responsible for more solar radiation absorbed) and premature bare ice exposure, rapidly reducing the surface albedo. This implies that more solar energy is absorbed and hence more melting is occurring. Warm conditions persisted through summer, with the positive albedo feedback mechanism being a major contributor to large negative surface mass balance anomalies (e.g., more melting than what was accumulated during the previous year). Summer snowfall was below average. This helped to maintain low albedo through the 2010 melting season, which also lasted longer than usual, until around mid September.
The figure on the left shows the anomaly map of melting days for 2010 derived from passive microwave data. Red areas indicate where melting lasted longer than average (up to 50 days).
The figure above shows the standardized melting index anomaly for the period 1979–2010. In simple words, each bar tells us by how many standard deviations melting in a particular year was above the average. For example, a value of ~2 for 2010 means that melting was above the average by two times the ‘variability’ of the melting signal along the period of observation. Previous record was set in 2007 and a new one was set in 2010. Negative values mean that melting was below the average. Note that highest anomaly values (high melting) occurred over the last 12 years, with the 8 highest values within the period 1998–2010. The increasing melting trend over Greenland can be observed from the figure. Over the past 30 years, the area subject to melting in Greenland has been increasing at a rate of ~17,000 km²/year.
This is equivalent to adding a melt-region the size of Washington State every ten years. Or, in alternative, this means that an area of the size of France melted in 2010 which was not melting in 1979.
The figure above shows the monthly standardized anomalies for 2010 (relative to 1979–2009) for near-surface temperature, albedo, snowfall, meltwater, bare ice area and melt area excluding bare ice simulated by the model described in the paper.Here’s the link to the accepted version of the paper. ERL_Tedesco_et_al._2010_Greenland_record
The full paper will be available on Friday, January 21, at: http://dx.doi.org/10.1088/1748-9326/6/1/014005.
All images should be referenced as M. Tedesco or M. Tedesco/WWF, as indicated in each photograph. Click on the pictures to see them in a new page or download them.
Supraglacial lakes view from the helicopter. these lakes from from meltwater that collects in areas of the ice sheet, mainly as a consequence of surface topography.
Detail of a supraglacial lake from the above picture. Note the streams feeding the lake and the darker area at the bottom. This could be cryoconite, a dark mixture of soot, sediments and organic matter.
View of the supraglacial lake ‘Olivia’, where we camped in 2010. The diameter of the lake is ~1 km.
Canyon over the ice sheet formed as a consequence of the flow of meltwater. The field of cracks is well visible. This is the consequence of the continuous sliding of the ice on the bedrock: as the ice at the bottom is slower than that at the surface, a ‘stress’ occurs at the surface, provoking cracks.
Fieldwork equipment and deployment of a remotely controlled boat to study supraglacial lakes from in-situ measurements.
Camp on the side of a supraglacial stream leaving a supraglacial lake.
Streamflow of meltwater draining into a crack in the ice. The water can reach the bedrock supporting the development of the subglacial hydrological system. Because of the flow of the water, the crack enlarges, becoming more and more tubular in shape
We searched for the crack for several hours at night, following the stream on the ice. It took us a long walk but we were extremely excited at the end! Note an old moulin on the back of the one that is forming from the flow.
Here’s a detail showing the crack propagating on the ice and meeting the streamflow, where it gets larger and accommodates the meltwater from the lake.
Posts
No comments:
Post a Comment