The research results were published in the latest issue of Science. Where did the melted water in the cracked ice lake go? On April 18, the British Independent newspaper quoted the latest research results as saying that huge cracks would suddenly appear at the bottom of the glacial lake formed in summer, and millions of tons of glacial lake water would go straight through the ice sheet with a thickness of about 975 meters along the cracks and inject into the junction between the bottom of the ice sheet and the bedrock.
The large glacial lake observed by scientists was formed in the summer of 2006, with an area of about 5.63 square kilometers and a water depth of about 12. 19 meters. They placed measuring instruments around the lake and successfully detected a huge crack at the bottom of the lake. About 43.9 billion liters of molten water flowed into the bottom of the ice sheet along the cracks within 24 hours, and the water flow speed exceeded Niagara Falls.
It has also been found that the meltwater flowing into the junction of the bottom of the ice sheet and bedrock can generate strong pressure, which can raise the ice sheet by up to 6 meters. This research is of great significance. Scientists hope to further explore whether a large amount of molten water flowing into the bottom of the ice sheet will accelerate the movement of the ice sheet to the coast, causing icebergs to fall into the ocean and eventually accelerating the rise of sea level.
Hydraulic fracturing Some scientists believe that cracks at the bottom of glacial lakes are formed by water pressure. Sarah Das, a researcher in woods hole oceanographic institution, Massachusetts, said: "We have found conclusive evidence that Greenland Glacial Lake can produce cracks through the ice sheet through water pressure."
Das also said that if there is a big enough crack on the surface of the ice sheet and there is enough molten water to fill the crack, then a channel can be formed, which goes straight to the bottom of the ice sheet.
Although scientists can theoretically prove that water pressure is the "culprit" that leads to the disappearance of glacial lakes, it is still difficult for them to imagine how the meltwater on the surface of the ice sheet penetrates through the thick ice sheet and forms cracks that go straight to the bottom of the ice sheet. Therefore, whether the hydraulic fracturing process really exists is controversial in the scientific community.
Glacier melting In recent years, the temperature in the Arctic has been rising continuously, leading to the formation of more glacial lakes on the surface of Greenland ice sheet in summer. Scientists have installed instruments around the world to record the horizontal movement of ice sheets. Instrumental tests show that the ice sheet in Greenland's Great Glacier Lake area is accelerating towards the ocean at twice the normal speed.
Das said: "If the ice sheet is fixed on the bedrock and there is almost no liquid water between them, the moving speed of the ice sheet will slow down. The meltwater injected into the bottom of the ice sheet by glacial lake reduces the friction between the ice sheet and bedrock and plays a lubricating role, thus accelerating the movement of the ice sheet. " However, scientists have also found that the speed of ice sheet movement near Greenland coastline has not been greatly affected.
Therefore, scientists believe that the speed at which icebergs on the coastline break away from the ice sheet and fall into the ocean is determined by many very complicated reasons, and the disappearance of glacial lakes in summer does not necessarily accelerate the melting of glaciers. Although the melting of ice on the surface of the ice sheet will accelerate the movement of the ice sheet, it will not have a significant impact on sea level rise. (Excerpted from China Meteorological News on April 24, 2008: Yang Meiju)