The photo is sourced from rscf.ru
Melting of the Antarctic glaciers may, in theory, lead to rising sea levels in the world’s oceans and, as a result, flooding of many coastal areas. To assess this risk accurately, we should take into account not only the melting of glaciers on the Antarctic coastal area but also the temperature increase in the continent’s central, which leads to warm air transfer and snowfall. Together with precipitation, part of the water released into the world’s oceans by melting glaciers returns to Antarctica, which can compensate for the rate of water level rise.
To assess this effect, the scientists of the Arctic and Antarctic Research Institute (AARI) and Shandong Pedagogical University went on an expedition to the Antarctic Vostok station, where they extracted three cores – vertical ice columns, each about 70 metres long – from under the glacier surface. Such samples make it possible to determine the properties of the ice deposited over millennia and its formation conditions.
“When snow falls in Antarctica, it deposits on the glacier surface and accumulates for hundreds of thousands of years. Over time, this snow compacts and turns into ice. Analysis of the thickness, chemical and isotopic composition of the resulting ice layers, provides us with information about the rate of snow accumulation on the continent and allows us even to determine the way the air temperature changed over the continent in different periods,” the Russian Science Foundation quotes Alexei Ekaykin, PhD in geographical sciences.
First, the scientists identified the layers containing the compounds specific to large volcanic eruptions, including sulfates. For example, the Philippine volcano Pinatubo erupted in 1992, and the Agung volcano in Indonesia erupted in 1964. The core layers corresponding to these years contained higher concentrations of sulfates than the neighbouring ones. So the researchers used them to determine the age of the other ice layers.
Then the authors compared the thickness of the core layers and their age, and calculated how much snow had accumulated in Antarctica in different periods of time over the past 2200 years. It turned out that from 168 BC up to the XIX century, the snow accumulation rate in Antarctica decreased by 1%, whereas with the beginning of the industrial period in the first half of the XIX century, it seriously increased: now snow accumulates in central Antarctica 24% faster than 200 years ago.
To prove that such changes relate to the temperature increase at the surface of the Earth, the authors determined in various sections of the cores the amount of heavy water – molecules containing heavy hydrogen (deuterium) and heavy oxygen (oxygen-18). The point is that the higher the temperature of the atmosphere, the larger number of heavy isotopes with clouds reach high latitudes – to the South and North Poles. So, as the weather warms, more and more of these particles available in the ice.
Having compared the number of isotopes in different layers of the cores, the authors mathematically calculated that since 1816 the air temperature over the studied area increased by about 1-2 degrees Celsius. As a result, with warming by 1 degree Celsius, the snow accumulation rate in Antarctica increases by an average of 11%. These data will be useful in climate modelling and ocean level forecasting.
“The obtained data allow us to adjust the available projection, taking into account that more and more water returns to Antarctica as precipitation as the weather warms. In the future, we plan to expand our observations by conducting measurements at other Antarctic stations,” the Russian Science Foundation quotes Alexei Yekaikin.
