Each winter, a cold, relentless wind blows over the northeastern Russian coast toward the sea. The wind pushes sea ice away from land, opening up pockets for new ice to form. The process repeats endlessly, bringing fresh crops of sea ice out to the Arctic Ocean and feeding a slow migration of ice westward toward Greenland.
But a study published in Scientific Reports on 2 April reveals that warming temperatures are melting Russia’s coastal “ice nurseries” faster than before. Some 80% of nursery ice melts before it joins the open ocean, compared to 50% before 2000.
Scientists worry that less nursery ice in the open Arctic Ocean could mean fewer nutrients for wildlife.
“Animals that rely on the food from sea ice will have trouble in the future,” said coauthor Eva-Maria Nöthig, a scientist at the Alfred Wegener Institute in Germany. Polar cod is one example of a species that could suffer, she said, although the exact implications are still unknown.
Don’t be fooled by the name: Sea ice nurseries are chaotic places.
“In the Russian shelf seas, [ice formation] takes place over very shallow water, and there is lots of turbulent mixing,” lead author Thomas Krumpen, a scientist at the Alfred Wegener Institute, told Eos. The mixing brings up sediment, dead organic matter, and pieces of tiny phytoplankton, all of which freeze inside the new sea ice.
The researchers wanted to know if sea ice formed in nurseries was changing with thinning ice coverage in the Arctic, so they followed nursery ice movement over 20 years using satellite images. They also looked at ice in the Fram Strait, situated between Greenland and Svalbard at the end of the large Transpolar Drift that sweeps ice across the Arctic, to see if any nursery ice reached there.
The data showed that ice leaving the nursery had a 15% lower survival rate in open waters with each passing decade. Nursery ice that reached the Fram Strait, a journey that often takes 2 or 3 years, fell by 17% each decade.
But Krumpen warns against making assumptions about ice nurseries. “Some media stated that there’s less ice being produced, but that’s actually not the case,” he noted.
Plenty of ice still freezes in the nurseries, but the sweltering summers melt the ice before it can travel far enough north to survive.
Eat Your Nutritious Sea Ice
The effects of fewer nutrients being transported offshore haven’t been studied in detail yet, according to Nöthig.
“Who’s winning and what this means for biodiversity, we don’t know yet,” she added.
Dorothea Bauch, a scientist at GEOMAR Helmholtz Centre for Ocean Research Kiel who was not involved in the study, said that less material transported by ice from the coastal regions could have “severe consequences” for biological systems. The latest study will allow researchers to “put a number to the projected changes,” she told Eos.
The findings offer another piece of evidence for declining sea ice in the Arctic, a phenomenon Krumpen said he can see firsthand not only from his data but also from aerial flights over the Arctic.
“The Arctic ocean is changing so rapidly, I can actually see it myself,” he said.
—Jenessa Duncombe (@jrdscience), News Writing and Production Intern