Tracking the ice on the Arctic

THIRUVANANTHAPURAM: This September, when the winters begin, the research icebreaker 'Polarstern' will set sail from Norway towards the North Pole, and intentionally get stuck in the ice of the Central Arctic. For one whole year, it will glide across the Arctic Ocean, the longest expedition ever to be undertaken in the Arctic. The Polarstern will have 600 researchers from 17 countries, collecting field data to learn more about the Arctic. And on board will be Vishnu Nandan, a polar researcher who belongs to the city, the only Indian till date.

The mammoth expedition will have researchers working on various aspects of the Arctic and is expected to provide us a better understanding of the climatic system in the Arctic. “This will help us get more answers on what is happening and also with the mid-latitudes, on how the Arctic is actually influencing the global climatic conditions. It is a data for generations to come in,” says Vishnu, who is part of the seven-member team which will work on providing accurate estimates of sea ice thickness. “The last such expedition was SHEBA, and it was in the 1970s. It has been over forty years and we are still using that data. So from that perspective, we will be using the MOSAiC data for the next 50 to 100 years,” says Vishnu.

“It will also help us determine how the ice changes in one year. We are using multiple radar frequencies and this will help in getting better estimates of sea ice thickness,” says Vishnu, whose study report on the Arctic sea ice provided a crucial turning point in the estimation of sea ice thickness in the Arctic. It was in 2017 that Vishnu published his findings on the overestimation of Arctic sea ice thickness due to the presence of salty snow over the sea ice.

It was during an expedition to the Arctic, while working on sea ice climate modelling, that Vishnu placed a bit of snow in his mouth. “The snow was very saline. After tasting it, I was struck by its intensity. When salinity increases, the absorption of radar waves increases and penetration decreases which means that the radar satellite estimation of sea-ice thickness is very flawed. We had till then not estimated the error that comes with salinity,” says Vishnu. The study was published in the Geophysical Research Letters of the American Geophysical Union. “The error of overestimation is close to 25 percent.

The Arctic sea ice may be much more thinner than we ever expected. After my study report was published, the saline snow factor has been incorporated by the other research organisations,” says Vishnu, a postdoctoral research scholar with the University of Victoria, working on Arctic and Antarctic sea ice. For someone who has undertaken 16 expeditions to the Polar regions, Vishnu is able to decipher the changes in the Arctic due to global warming. “There is substantial warming even during the winters and it is severely affecting the mid-latitudes,” he says. “The sea ice thickness is also showing a downward trend. Over the next 50 years, we will witness a sea ice-free Arctic during the summers,” he adds.

The landscapes have changed him considerably, he says. "You get this profound silence if you go there if it is not windy. You are at peace there. I get excited to go to the Arctic so I can be silent,” he smiles.