Life gets busy where it can, even under a thick layer of ice in Antarctica.
German scientists inspected an area of the seafloor newly uncovered by the calving of mega iceberg A74 and found it teeming with animals.
Video cameras followed copious filter feeders that bloomed among the soft mud.
It was a remarkable opportunity for the team when their ship, RV Polarstern, cut the still narrow gap between the A74 and the Brunt Ice Shelf that spawned the gigantic mountain.
Research groups regularly try to survey waters under freshly calved ice shelves to better understand how these unique ecosystems work. But success is not easy to achieve.
You have to be in the right place in Antarctica at the right time, and often the sea ice conditions just won’t let a research vessel get into position over the target location.
But Polarstern, run by the Alfred Wegener Institute, was lucky. It was already in the eastern Weddell Sea on a pre-planned expedition when the city-sized A74 split off from the Brunt.
And when the weather calmed down last weekend, the ship slipped in behind the mountain to take a look at a patch of seabed that is now free of ice for the first time in five decades.
Polarstern uses an Ocean Floor Observation and Bathymetry System (OFOBS). This is an advanced instrument package that is towed at depth behind the ship.
In five hours, the system collected nearly 1,000 high-resolution images and long video images.
“Despite years of continuous ice cover, a developed and diverse seabed community has been observed,” said OFOBS team members Dr. Autun Purser and Dr. Frank Wenzhoefer.
The images show numerous unstalked animals attached to several small stones that are abundantly scattered across the soft sea bed.
“Most of these are filter-feeding organisms, believed to consist of fine material that has been transported under the ice over the past few decades.
“Some mobile fauna, such as holothurians, ophiuroids, several molluscs, as well as at least five fish species and two octopus species, were also observed.”
Dr. Huw Griffiths of the British Antarctic Survey was delighted to see the photos returned from the Polarstern.
“What they found is not shocking, but it is amazing to get these images so soon after calving and it is definitely the largest area that will have been explored in this way,” he said.
“It is not surprising to find this kind of community so far below the ice shelf, but it is a good indication that there is a rich food supply extending at least 30 km below the ice shelf.
“This food is produced by plankton in the nearby sunlit sea surface, then dragged beneath the ice shelf by the Weddell Sea currents. These same currents will eventually move the iceberg west around the Weddell Sea and then north to its setting”, he says. told BBC News.
From a research perspective, the idea would be to go back at regular intervals to document any changes in the ecosystem.
This is something Polarstern could do as AWI is conducting long-term surveys in the region.
The east side of the Weddell Sea is interesting because it has not witnessed the warming effects seen in the western sector, next to the Antarctic Peninsula.
This situation won’t last long, however, with computer models suggesting that warm ocean water from the north could enter regularly by the end of the century.
Where is this in Antarctica?
A74 broke off the Brunt Ice Shelf, the floating spur of glaciers that flowed off land into the Weddell Sea. On a map, the Weddell Sea is that sector of Antarctica immediately south of the Atlantic Ocean. De Brunt is located on the east side of the sea. Like all ice shelves, it will periodically calve icebergs. A large mountain last calved from this particular area in 1971.
How big is Iceberg A74 really?
Satellite measurement puts it at about 1,290 square kilometers (500 square miles). Greater London is approximately 1,500 square kilometers; the Welsh county of Monmouthshire is approximately 1,300 square kilometers. That’s big anyway, although not as big as the monster mountain A68 that calved from the Larsen C Ice Shelf on the west side of the Weddell Sea in July 2017. That was originally about 5,800 square kilometers, but has since broken into many small pieces.
