An international team of scientists led by Ian Howat of Ohio University, which is studying the state of the Greenland ice sheet, discovered that two large subglacial lakes have recently dried up, according to Science Daily.
Scientists have dedicated a separate article to each case, an article in The Cryosphere is devoted to the description of the disappearance of a lake in the southwest of the island, and an article in the latest issue of Nature is devoted to the lake in the northwest.
The fact that under the ice of Greenland there are huge reservoirs of melt water, people learned relatively recently during a project to map the glacier. They suggested that these lakes have been relatively stable for at least the past 40 years. However, as recent studies have shown, two rather large lakes can dry out almost instantly, by geological standards.
One of the lakes, located in the southwest of Greenland and containing millions of liters of water, as shown by a comparison of satellite photographs, dried up in a few weeks, resulting in a crater 70 m deep.
A second lake, in the northeast of the island, has dried up and re-filled with water twice in the past few years, as observations have shown. The researchers believe that the summer is very warm. This unusual behavior of the lakes could lead to accelerated melting of glaciers, since in this case the glacier melts not only under the influence of heat and sun, but also from contact with melt water from below.
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In the meantime, it turned out that the glaciers of Greenland are melting faster than scientists predicted
A team of biologists from the University of Buffalo (USA), led by Dr. Beata Xato, found that all the mathematical models created so far for the melting of Greenland ice were overly optimistic: this threatening process is actually going faster. The study, the full results of which are published in the latest issue of the journal Proceedings of the National Academy of Sciences (PNAS), is reported by (e) ScienceNews.
Greenland is the second largest glacier massif on Earth, after Antarctica. If all the ice on it melts, the world ocean level will rise by an average of 6 m, which threatens the inhabitants of coastal regions of many countries with disasters. It is not surprising that scientists have been studying the melting of the Greenland ice for a long time and constructing models that should allow predicting its dynamics.
Scientists from the University of Buffalo have shown that so far all of these models have been simplistic and overly optimistic. To do this, Dr. Xato and his colleagues analyzed a large array of data obtained, firstly, from the NASA ICESat satellite, created and launched into orbit just for these purposes, and, secondly, from field research in Greenland, carried out as part of Project Operation IceBridge ("Operation" Ice Bridge "). In general, data from 100 thousand locations were analyzed for the period from 1993 to 2012.
The analysis of such a vast and complete information showed that the Greenland glaciers behave more complex than previously thought. While some of them are steadily melting, the thickness of the second, on the contrary, increases. And still others do "pulsate". All this depends on a complex combination of factors - local climatic and hydrological conditions, the shape of the glacier, hydrology, and so on. In total, geologists from the University of Buffalo counted over 240 glaciers in Greenland with a width of 1.5 km or more, and divided them, according to the characteristics of their behavior, into 7 groups.
It was a detailed approach. If we take the whole picture as a whole, it turned out that in fact from 2003 to 2009 (for this period there is the most complete data), the Greenland ice cover lost 243 gigatons of ice, which annually led to an increase in the level of the World Ocean by 0.68 millimeters. … This is more than scientists have assumed until now.
The authors of the study hope that their results will now allow them to build more accurate models of the melting ice of Greenland. “The division of glaciers into groups that we have carried out will help to select the most representative samples from them, and based on their parameters, based on their parameters, models of what is happening are closer to reality,” said Dr. Xato.
