Researchers find less thick, multi-year ice and show that the dwindling ice pack will have impacts deep in the sea, and not just at the surface
By Summit Voice
SUMMIT COUNTY — Researchers aboard the Polarstern say findings from their two-month Arctic cruise helps confirm satellite data showing that Arctic sea ice is not only shrinking, but quickly growing thinner.
The research also helps show how the seasonal changes in Arctic ice extent are not restricted to the visible surface, but have impacts to Arctic Ocean biological communities all the way to the sea floor.
Using high-tech equipment, including a new under-ice trawl, the scientists determined that thick multi-year sea ice has further declined in extent. The survey covered about 3,500 kilometers of sea ice. Some parts of the Laptev Sea were free of ice as early as July in an area where the Polarstern encountered thick multi-year ice just one year earlier. The fresh water content of the sea surface has increased accordingly as a result of the melting ice.
“The Arctic of the future will consist of thinner sea ice which will therefore survive the summer less frequently, will drift more quickly and permit more light to penetrate the ocean. This will lead to great changes in the composition of sea life“, said research leader Prof. Dr. Antje Boetius, who manages the Helmholtz-Max-Planck Research Group for Deep-sea Ecology and Technology at the Alfred Wegener Institute.
The Polarstern returned to port in Bremerhaven Oct. 8. More than 50 scientists and technicians from 12 countries conducted research on the retreat of the sea ice and the consequences for the Arctic Ocean.
A number of new technologies were used for to film and photograph life in and below the ice down to a depth of 4400 metres. Since its departure from Tromsø, Norway on August 2, Polarstern has travelled some 12,000 kilometers and conducted research at 306 stations. These included nine ice stations where the ship moored to an ice floe for several days to examine the ice, the water beneath it and the bottom of the sea.
The new under-ice trawl helped scientists for the first time take a close look at biological communities living on the underside of the Arctic pack ice.
“We had a polar cod in our net almost every time. This species is particularly adapted to life below the ice; it does not occur without ice,” said Dr. Hauke Flores, with the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association.
The sea ice physicists from the Alfred Wegener Institute also used an under-ice robot to record the light incidence and distribution of algae on the lower side of the ice. They were able to detect the diatom Melosira artica in high concentrations also under the first-year ice in the central basin of the Arctic. These single cell algae can produce metre-long chains and form dense accumulations beneath the ice. Photos from the deep sea have shown that the algae largely dropped to the bottom of the sea as a result of the melting ice.
The findings suggest that rapid changes in the Arctic are not restricted to the sea surface. Atlantic water flowing into the Arctic at a depth of several hundred meters had an elevated temperature and salinity which could be measured down to a depth of several thousands of metres in the Arctic Basins.
Images and measurements of the bottom of the sea showed for the first time that the deep sea of the Central Arctic is not a desert, but that frequently accumulations of sea cucumbers, sponges, feather stars and sea anemones gather to feed on the sea algae.
The warm temperatures, the retreat of the ice and the greater light availability beneath the ice causes the seasonality of the Central Arctic to shift. The production and the export of algae is taking place earlier compared with previous years, as the results of annually anchored sediment traps show.
As a result of the extremely thin ice cover, Polarstern was able to navigate far into the North later in the year than usual. The sea ice physicists were therefore able to collect important data at the start of the freezing period. The measurements on the new thin ice are important, because this sea ice will occur more frequently in the future.
Filed under: Arctic, biodiversity, climate and weather, Environment, global warming Tagged: | Alfred Wegener Institute, Alfred Wegener Institute for Polar and Marine Research, Arctic, Arctic sea ice, climate, global warming, Polarstern