The modern rapid melting of Antarctica's ice may be due to the fact that the thickness of its ice cap has been continuously shrinking for three centuries.
|Is the Antarctic ice melting?|
This conclusion was reached by climatologists, the results of which were published by the scientific journal Scientific Reports.
Ice melting in antarcticaIn fact, the rate of ice melting in Antarctica began to grow in the 1400s, but it was not until the 18th century that it exceeded the typical climate fluctuations of the last six thousand years.
The reason for this is most likely an increase in western and polar winds. Both of these factors will not disappear in the future, therefore the melting of the southern ice will only increase.
Climatologists, oceanologists and other scientists have long believed that climate change threatens to destroy mainly northern reserves of ice on Earth, including the glaciers of Greenland and the ice cap at the North Pole.
Recently, scientists have found evidence that the first to disappear is not the northern ice, but part of the glaciers of Antarctica, which will lead to catastrophic sea level rise.
How long will it take for all the ice to melt?Two years ago one of the last fragments of the Larsen Ice Shelf on the Antarctic Peninsula collapsed. As a result, a giant "mega-iceberg" weighing a trillion tons has emerged. Two other pieces of this glacier have already "swam away" into the sea in 1995 and 2002.
An international team of climatologists led by James Smith of the British Antarctic Survey has found a possible explanation for all these processes, having studied the history of melting ice on the peninsula.
To do this, Smith and his colleagues analyzed the sediments of plankton shells, which formed off the coast of the peninsula for several tens of thousands of years. Fluctuations in water temperature, as scientists explain, strongly affect the isotopic and chemical composition of the shell of some algae and zooplankton.
|Enhanced glacial discharge from the eastern Antarctic Peninsula since the 1700s associated with a positive Southern Annular Mode|
This feature of algae shells allows them to be used as a kind of "climate chronicle" in which information is preserved not only about the temperature of the water, but also about where and how the currents and winds moved. Analysis of these data has brought several unexpected discoveries at once.
The Fate of AntarcticaOn the one hand, until recently the glaciers of Antarctica were relatively stable, serious fluctuations in their thickness began only 1.6 thousand years ago.
However, for most of the subsequent time, the typical ice cap sizes remained roughly the same, and deviations were associated with the strengthening and weakening of various climatic phenomena, such as El Nino.
On the other hand, the situation changed dramatically about 600 and 300 years ago, when the amount of fresh meltwater off the coast of Antarctica, as indicated by the proportion of oxygen isotopes in the shells of algae, began to grow sharply.
At this time, the thickness of glaciers began to gradually decline, and the rate of this decline gradually increased, exceeding the typical maximum values.
The reason for this acceleration, as scientists suggest, based on changes in the nature of movement of currents, as well as on other climatic indicators, was that polar and so-called western winds sharply increased, accelerated their movement and about 500 years ago moved towards Antarctica.
This accelerated both the melting of surface ice deposits, which warms the air, and the underwater part of the ice sheet, which began to actively wash warm currents.
In the future, thanks to rising annual average temperatures and long-term climate trends, these winds will only increase, which will further accelerate the melting of Antarctic ice, scientists believe.
Further observations of these air flows, as Smith and his colleagues hope, will help us predict how quickly this process will occur and whether we should expect a sharp rise in sea level in the near future.