Those ice floes that the Transpolar Drift still carries to the Fram Strait are for the most part formed in the open sea, i.e., in regions of the Arctic Oceans far from the coasts. Consequently, compared to ice from the shelf seas, they contain significantly fewer particles like algae, sediments and nutrients – because waves, wind and tides stir up far more particles from the seafloor in shallow coastal zones than on the high seas. In addition, rivers like the Lena and the Yenisei carry major quantities of minerals and sediments to coastal areas; when the water freezes, they become trapped in the ice.
Whereas in the past, sea ice from the shelf seas transported this mineral load to the Fram Strait, today the melting floes release it on their way to the Central Arctic; what reaches the Fram Strait is less material, and with a different composition. This finding is a result e.g. of analysis of samples obtained by means of sediment traps that AWI biologists have been conducting in the Fram Strait for about two decades. “Instead of Siberian minerals, we’re now finding more remains of dead algae and microorganisms in our sediment traps,” says co-author Eva-Maria Nöthig. In the long term, this altered sea-ice-based particle transport is likely to produce lasting changes in the biogeochemical cycles and ecological processes of the central Arctic Ocean.
The evolution of sea ice and the ecological processes in the Arctic Ocean are also key research questions that will be addressed during the MOSAiC expedition, which will begin this September. The German research icebreaker Polarstern will journey to the Arctic and drift with the Transpolar Drift through the Arctic Ocean towards Fram Strait for an entire year, intentionally trapped in the ice. 600 people from 17 countries will take part in the expedition, which will be regularly resupplied by aircraft and other icebreakers; moreover, many times that number of experts will use the resulting data to take climate and ecosystem research to a new level. MOSAiC, the greatest Arctic research expedition in history, will be spearheaded by the Alfred Wegener Institute.