August 7, 2020

The surface of thousands of lakes freezes intermittently in winter due to climate change | Science

Meltwater pools on the summit of the Helheim Glacier, on June 19, 2018.

Scientists continue to show that the effects of climate change not only will they be a calamity for future generations. Scholars from Canada, the United States, Germany, Sweden and Great Britain published a study a few days ago stating that the surface of thousands of lakes located in the northern hemisphere freezes intermittently during the winter, due to the increase in temperature . According to experts, the situation could seriously worsen in the coming decades.

The research, published a few days ago in the magazine Nature Climate Change, It was directed by Sapna Sharma, professor of biology at the University of York (Canada). The study was based on information collected since 1970 in 514 lakes in the northern hemisphere. "With this data, we developed a classification model to identify which features were most significant in lakes with intermittent ice surfaces," Sharma tells EL PAÍS. To do this, they took into account factors such as altitude, depth, shape of the coasts, wind and rainfall.

The surface of thousands of lakes freezes intermittently in winter due to climate change

"The model had a success rate of 95% and identified that the average annual air temperature was the most important variable," says Sharma. "Since the model worked very well, we extrapolated it to the database of Hydrolakes, which has about 1.4 million lakes, "says the researcher. Thus, the experts calculated that, due to the increase in temperature, some 14,800 lakes currently have an intermittent freezing of their surface.

In the article that presents the study, the authors highlight the negative impact of this phenomenon in two aspects. The ice on the surface allows the water in the lakes to remain cool and calm. Otherwise, the feeding and spawning of different aquatic species is put at risk. In turn, lakes that do not freeze cut access to a significant number of human groups, since they are used as a means of transportation. Also, the protein sources of these communities are reduced by the problems of fish reproduction. Even experts stress the difficulty of outdoor sports activities in the winter months, an issue that is not minor in several areas of the world.

Map of northern hemisphere lakes that may experience intermittent thaws due to climate change.
Map of northern hemisphere lakes that may experience intermittent thaws due to climate change.

According to the forecasts of these scientists, some 35,000 lakes -parties in 50 countries- can run with the same luck at the end of this century if the climate increases two degrees centigrade; if the increase reaches eight, the affected lakes would be more than 230,000. Reading the figure of eight degrees Celsius can cause surprise. Sapna Sharma comments: "Some models predict increases in global air temperature of up to nine degrees centigrade at the end of this century. Even if the air temperatures are increased by 4.5 degrees Celsius, the northern latitudes can experience twice this warming due to Arctic amplification. "

Experts say in one part of the study: "One of the first observed impacts of climate change has been the loss of fresh water ice" In this sense, they justify their investigation by ensuring that there was "no comprehensive, large-scale evaluation of ice loss in the lakes." In 2014, a investigation published by experts from the University of Waterloo (Canada) -in collaboration with the European Space Agency- in 400 lakes of Alaska showed that, on average, these freshwater deposits remain frozen 24 days less than in 1950. Also, lake cooling it was reduced by 22% between 1991 and 2011.

"We have found in our work that a slight increase in temperature already has a significant impact on the surface of many lakes. This can get worse in the same generation. Let's think about our children and grandchildren now: they will not experience winter the same way we do, "says Sharma.


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