Researchers from the University of Leeds (UK) have found out how much the geomorphology of one of the northernmost landmasses on Earth has changed in just three decades. To do this, they used satellite images collected by the program Landsat Geological Survey (USGS) and the National Aeronautics and Space Administration (NASA) USA. It is one of the largest remote sensing (RS) data sets, and also the most comprehensive in terms of long-term observation – the program began in the early 1970s and continues to this day.
To verify methods for analyzing satellite images, scientists visited 89 locations in Greenland, their reliability (kappa coefficient) was 0.81. In other words, in this study it was possible to achieve a high degree of reliability in studying the real geomorphological situation based on remote sensing data of relatively low resolution (30 meters per pixel). A scientific work with detailed conclusions and a description of all the methods used by its authors, published in a peer-reviewed journal Nature Scientific Reportsits text is in the public domain.
Briefly, the results of the study are as follows:
- Over the 30 years since 1980, the area of Greenland’s glaciers has decreased by 28,700 square kilometers. But this value, firstly, has the largest error of all measured (9,700 kilometers), and secondly, this area is insignificant compared to the total size of the ice sheet on the island (over 1.7 million square kilometers).
- Greenland’s vegetation cover increased by 111 percent, adding 87,475 square kilometers of tundra, shrubland, swamps and grasslands. Simply put, the island has doubled in greenery in three decades.
- Surprisingly, the area of freshwater bodies of water has decreased by 10 percent, although the error in the data is large, and it is not yet possible to reliably verify this parameter.
- The area of wetlands has increased the most (wetlands), almost quadrupled, they now occupy 30,300 square kilometers of Greenland.
- In addition to the changes in the island’s geomorphology described above, the researchers assessed the volume and area of meltwater flows, sediment outcrops, bedrock outcrops, and bare terrain (not covered by vegetation, ice, or swamps). However, for each of these parameters, the results of the analysis are contradictory and further work is required.
Comparison of Greenland geomorphology in the late 1980s and late 2010s. Snow and ice are shown in white, melt water in blue, fresh water in blue, sediment deposits with different particle sizes (large or small) in orange and yellow, bedrock outcrops in brown, tundra in light green, shrubs in dark green, swamps and other dense vegetation (not tundra) / © University of Leeds
The greening of Greenland is a process that can hardly be called negative. The problem is that at the same time the area of swamps is increasing, and they, in turn, act as a powerful source of methane. Some of these emissions almost immediately bind the tundra soils, but the overall balance is still positive, and a lot of gas enters the atmosphere, which has a much greater greenhouse effect than carbon dioxide.
Another concern the researchers mentioned was the positive feedback loop of warming in the region. The largest island is already warming faster than the rest of the world. And the earth’s surface, deprived of ice, accumulates heat better in both winter and summer. Snow reflects most of the sunlight, which is why rocks even under thin, multi-year glaciers never thaw.
As a result, the more marshes that form in Greenland as warming occurs, the more of them will continue to thaw. Likewise for bare ground. In those places where vegetation has been able to gain a foothold, the process goes even faster – it has a lower albedo than many rocks, keeps the soil from being washed away and increases its heat capacity.
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2024-02-14 19:07:30
