Life gets busy where it can, even under thick ice in Antarctica.
German scientists have inspected an area of the seafloor recently exposed by the detachment of the mega-iceberg A74 and have discovered that it is teeming with animals.
Video cameras tracked abundant filter feeders that thrived amid the soft mud.
It was an extraordinary opportunity for the team, as their ship, RV Polarstern, crossed the still narrow gap between A74 and the Brunt Ice Shelf, which produced the giant iceberg.
Research groups frequently attempt to probe the waters below newly calved ice shelves to better understand how these unique ecosystems operate. But success is not easily earned.
You have to be in the right place in Antarctica at the right time, and often sea ice conditions simply do not allow a research vessel to hover over the target site.
But Polarstern, run by the Alfred Wegener Institute, was lucky. I was already in the eastern Weddell Sea on a pre-planned expedition when the city-sized A74 parted ways with the Brunt.
And when the weather calmed down last weekend, the ship slid behind the iceberg to get a glimpse of an area of the seafloor that is now ice-free for the first time in five decades.
Polarstern employs an Ocean Floor Bathymetry and Observation System (OFOBS). This is a sophisticated instrument package that is towed behind the boat at depth.
Over five hours, the system collected nearly 1,000 high-resolution images and long video sequences.
“Despite years of continuous ice cover, a developed and diverse seafloor community was observed,” said OFOBS team members Dr. Autun Purser and Dr. Frank Wenzhoefer.
“In the images, you can see numerous sessile animals attached to several small stones spread generously across the smooth seabed.
“Most of these are filter-feeding organisms, presumably subsisting on fine material carried under the ice over the past few decades.
“Certain mobile fauna were also observed, such as holothurians, ophiuroids, several mollusks, as well as at least five species of fish and two species of octopus.”
Dr Huw Griffiths from the British Antarctic Survey was thrilled to see the images sent from Polarstern.
“What they have found is not shocking, but it is surprising to get these images so soon after delivery and it is definitely the largest area that will have been studied in this way,” she said.
“Finding this type of community so far below the ice shelf is not surprising, but it is a good indication that there is a lot of food reaching at least 30 km below the ice shelf.”
“This food is produced by plankton on the surface of the nearby sunlit sea, then washed under the ice shelf by the currents of the Weddell Sea. These same currents will eventually move the iceberg west around the Weddell Sea and then north to their doom, “he said. he told BBC News.
From a research perspective, the idea would be to return at regular intervals to document any changes in the ecosystem.
This is something Polarstern could do because AWI is conducting long-term studies in the region.
The eastern side of the Weddell Sea is interesting because it has not witnessed the warming effects that have been observed in its western sector, near the Antarctic Peninsula.
However, this situation may not last, as computer models suggest that there could be regular incursions of warm ocean water from the north by the end of the century.
Where is this in Antarctica?
A74 broke away from the Brunt Ice Shelf, which is the floating bulge of glaciers that flowed from land into the Weddell Sea. On a map, the Weddell Sea is that sector of Antarctica directly south of the Atlantic Ocean. The Brunt is on the east side of the sea. Like all ice shelves, it will periodically give birth to icebergs. A large iceberg last gave birth in this particular area in 1971.
How big is iceberg A74?
Satellite measurement places it at around 1,290 square kilometers (500 square miles). Greater London is approximately 1,500 square kilometers; the Welsh county of Monmouthshire is about 1,300 square kilometers. That’s big by any measure, though not nearly as big as the A68 iceberg monster that spawned in July 2017 from the Larsen C Ice Shelf on the western side of the Weddell Sea. It was originally about 5,800 square kilometers, but it has since been broken into many small pieces.
