Massive ice loss in the Bering Strait | Polarjournal

Crab fisherman in Chukotka, the Russian side of the Bering Strait. In the future, there will be restrictions to the Russian favourite activity: ice fishing. (Foto: Heiner Kubny)

The ice cover of the Bering Sea has reached new lows in the winters of 2018 and 2019, which have not been seen in the past thousands of years. This was reported by scientists, which heightened concerns about the accelerating effects of climate change in the Arctic.

On Saint Matthew Island, the organic compounds of plants were studied. Thereby, researchers could reconstruct how rainfall and ice have affected the Bering Sea. (Photo: Heiner Kubny/Google)

Satellite data provides a clear picture of how sea ice in the region between the Arctic and northern Pacific has changed over the past four decades. Therefore, the scientists turned to the peatlands on the remote island of Saint Matthew south of the Bering Strait. The organic compounds of plants that are thousands of years old were investigated.

By studying various forms of oxygen molecules trapped in the sediment, the scientists were able to estimate the atmospheric and oceanic conditions that would have affected rainfall and sea ice over about 5,500 years, according to the study published in the journal Science Advances.

“The island itself has acted as its own weather station,” said the study’s co-author, Matthew Wooller, director of the Alaska Stable Isotope Facility at the University of Alaska Fairbanks. The sediment layers in the peat cores serve as a “book that goes back in time”.

With the rapid warming of the Arctic in recent decades, the extent of sea ice over the northern polar region has steadily decreased. In July 2020, Arctic summer ice reached its lowest level in 40 years for this month. In winter, sea ice builds up every year. However, the new study suggests that even in the Bering Sea, the ice maxima of the cold season could decline.

On April 29, 2013, the Bering Sea still had quite a lot of ice. (Photo: NOAA)

The loss of sea ice is already affecting Arctic wildlife, including walruses, polar bears and seals, with consequences for indigenous communities that rely on hunting for their livelihoods.

“If we lose more sea ice, of course, the Arctic’s temperatures will change completely,” said Julienne Stroeve, a climatologist with the National Snow and Ice Data Center at the University of Boulder Colorado.

Just five years later, on April 29, 2018, the Bering Sea was completely ice-free. There was also no ice in sight along Alaska’s northern coastlines. (Photo: NOAA)

However, air temperature was not the only factor affecting sea ice. Shifts in ocean and atmospheric circulation associated with climate change have an even greater impact, said lead author Miriam Jones, a geologist with the U.S. Geological Survey.

The study found that changes in sea ice were at least several decades behind changes in atmospheric greenhouse gases. This suggests that the recent lows of winter sea ice were a reaction to greenhouse gas levels decades ago.

Researchers reviewed their results using satellite data on sea ice from four decades ago. Stroeve suggested that the study could have been reinforced by more comparisons with observational data collected by ships and whaling expeditions from the mid-nineteenth century.

Heiner Kubny, PolarJournal

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