German research vessel Polarstern, operated by the Alfred Wegener
Institute for Polar and Marine Research, transits the Northwest Passage for the
first time. A 17,300-ton polar icebreaker, Polarstern left the port of
Reykjavik in mid-August, sailed around Greenland on a southern course, and is
crossing the Northwest Passage. Its destination is the East Siberian Sea where
geoscientific measurements at the junction between the Mendeleev Ridge and the
East Siberian Shelf are the focus of this expedition. The measurements sought
within the framework of the International Polar Year will help to understand
how undersea ridges and basins were built. This expedition takes the
researchers around the North Pole in 68 days.
Following in the tracks of Alfred Wegener, who founded the theory of
continental drift in 1915, researchers want to clarify the tectonic
interrelations on the bottom of the Arctic Ocean. They employ seismic
measurement methods that will allow a look at the geological units and
sediments. “At the bottom of the sea, we find mountains which are about the
same height as the Alps,” explains chief scientist Wilfried Jokat. “These are
partially overlaid by sediments, so that we have to look beneath the surface to
find clues hinting at the geological history of the Mendeleev Ridge,” he
further notes.
Where the Mendeleev Ridge meets the East Siberian Shelf, very old layers can be
found at the surface of the ocean floor. If the researchers find such places by
means of the equipment on board Polarstern, they will try to retrieve cores
with a gravity corer. Rocks 50 million years old crop out at these places;
usually, only layers of the upper 33 feet to 49 feet can be cored with a
gravity corer, which only shows layers about 1 million years old. Both sediment
cores and sediment profiles will be used to further a proposal for future
Arctic depth drilling. Within the framework of the International Ocean Drilling
Program (IODP), a long drilling core will be obtained to give new insights into
Arctic geological history of the last 100 million years.
There are areas with a high rate of sedimentation in the East Siberian Sea. If
the researchers manage to retrieve cores from these sediments, it will help to
conclude climate history of the more recent geological past. For example, the
rate of organic carbon in sediment cores hints at biological activity, and
researchers can reconstruct temperature and ice cover up to one million years
ago.
