31/10/2016 Into the thinning ice of the Arctic Ocean

Polarstern in the Arctic Ice. Photo: Marcel Nicolaus/AWI

Research vessel Polarstern reached new and barely explored areas of the High Arctic Ocean this October. The scientists on board found spectacular fauna on a little known seamount at 87°N.

Text: Maja Sojtaric

German icebreaker, research vessel Polarstern docked in Tromsø on a sunny morning in September. It was loading up equipment and goods for a long leg towards an area of increasingly thinning sea ice in the High Arctic Ocean at 87°N.

46 scientists from various international research institutions were on board the Polarstern Expedition PS101, preparing laboratories and technical gear for work in the Arctic autumn, under challenging weather and ice conditions.

There are as many different stories as scientists on this ship and in the middle of it all is the leader of the expedition, marine biologist Antje Boetius. She is professor at the University Bremen, and a group leader at the Alfred Wegener Institute for Polar and Marine Research (AWI) in Germany. Professor Boetius acts as a member of the CAGE Advisory Board at UiT The Arctic University of Norway.

Robot with a hair-thin tether

“We are going to the Gakkel Ridge and specifically the Karasik seamount. Our aim is to find out if Arctic seamounts are hot spots of life in the Arctic as they are in other oceans. We will collect samples at the ocean floor and use a new type of robot to obtain information on the state of the deep-sea ecosystems. This area has, to our knowledge, never been ice free before and we have no images of the seafloor. So the robot provides a great opportunity for us to examine this extraordinary mountain under the sea.” Boetius told us during our visit to the Polarstern in Tromsø Port.

CAGE director Jürgen Wienert was shown around Polarstern in October, and got to take closer look at the impressive Nereid robot. The hybrid remote operating vehicle can travel great distances under the ice, while still remaining under real-time human control. Photo: Maja Sojtaric

CAGE director Jürgen Mienert with Antje Boetius on board RV Polarstern in September. Professor Mienert got to take a closer look at the impressive Nereid robot. The hybrid remote operating vehicle can travel great distances under the ice, while still remaining under real-time human control. Nereid Under-Ice (NUI) is built to travel up to 40 kilometers laterally underwater while collecting acoustic, chemical, and biological samples from the ocean environment. Photo: Maja Sojtaric

The robot that Prof. Boetius is talking about is an automated and remotely operated vehicle developed by Woods Hole Oceanographic Institution  and John Hopkins Whiting School of Engineering. Its recent upgrade to an under-ice deep-sea vehicle was funded by NASA’s PSTAR program.

The robot can film; take pictures and work under the sea ice tethered to the ship by a fine glass fiber as thin as hair. Should the tether sever, the robot can find its own way home. In harsh Arctic conditions that is no small feat.

Extraordinary mountain on the ocean floor

Karasik Seamount is a mountain on the ocean floor at 87°North and 60°E. It is some 4500 meters high, slightly higher than Matterhorn, and a part of one of the most isolated and least explored mid-ocean ridges on Earth – the Gakkel Ridge, a divergent tectonic plate boundary between the North American and Eurasian Plate. This ridge system extends all the way through the Arctic basin from Greenland to Siberia and is known to have the slowest spreading rate of all mid-ocean ridges.

“The Karasik Seamount belongs to a chain of seamounts rising from 5000 m to 500 m water depth. It makes it one of the steepest mounts that we know of in the Arctic. Close by, chemical plume signatures were detected during previous missions, and some seafloor sampling indicated the presence of active fauna in the water and at the seafloor.” Boetius told us.

A spectacular discovery

When she spoke to us in September Prof. Boetius suggested that it was possible that Karasik hosts a completely new biogeographic province, inhabited by a fauna previously unknown to science and associated with methane release. The results at the end of the expedition in October proved her right.

“With the first pictures of the summit of the Karasik seamount we did not believe our eyes: It is overgrown with huge globular sponges. Between the sponges lie centimetre-thick mats of needles and worm-burrows. We were able to observe different species of fish, which were not to be expected here, and caught a glimpse of the northernmost corals discovered so far. There are huge white starfish, blue snails, red crabs and white and brown clams between the sponges” Boetius said in a press release posted by AWI. 

Life on ocean floor sheds light on life in space

The methane plume signatures, and the robot’s ability to detect them, are of specific interest for NASAs scientists who are involved in the project. The area in the Arctic will be used as an analogue to understand how the hydrocarbon signals might present themselves on Europa, Jupiter’s ice-covered moon. Hydrocarbon signatures are important in determining viability for life in space.

Antje Boetius is fascinated by the abundance and biomass of life in the ice-covered Arctic deep-sea. She has previously retrieved large bacterial sponges from the area, but nothing could compare to the view she and her colleagues got of the sea floor so close to the North Pole.

“The moment we saw this oasis of life on the ocean floor, was a reward in itself for me.” says Boetius.

Thinning ice made expedition possible

One thing that made this expedition such a success was ironically the immense thinning of sea ice in recent years. Just a few years ago Polarstern had to navigate up to three meter thick ice floes in this area. But the ice thickness has been reducing steadily and dramatically in recent years making the area more accessible for scientists.

Newly grown sea ice (greyish areas) forming between old floes, which survived the previous summer melt. Photo: M. Nicolaus/AWI

Newly grown sea ice (greyish areas) forming between old floes, which survived the previous summer melt. Photo: M. Nicolaus/AWI

The scientists have measured average sea ice thickness to less than a meter in the area, and observed a late start of the freeze up period. The results of their mission confirm the predicted trend of the decreasing sea ice volume in the Arctic basin.

“The Arctic Ocean holds an unknown diversity of ecosystems and life. We should recognize how little we know, and yet how urgent it is to think about how to map and protect some of the pristine habitats of the central Arctic basins.” concludes Antje Boetius.

Read more about Polarstern  expedition PS101: Weekly reports – AWI


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