After Calving 50 Years’ Worth Of Ice, Scientists Get A Glimpse Of The Amazing Antarctic Seafloor

Nature, especially when left untouched, has a magical way of thriving on its own. Man doesn’t need to interfere. In fact, man should not.

Life goes on when it can, and because the ice in Antarctica has mostly remained untouched, life managed to happen.


Under the thick ice cover in an Antarctic iceberg, German scientists discovered an amazing seafloor that was finally exposed. Experts behind this has been calving of mega-iceberg A74 and what they found was an ecosystem teeming with amazing creatures. They had used video cameras that were able to track abundant filter-feeders that had been living prospering among the soft muds.

The fortunate team of RV Polarstern had gone through the narrow gap that existed between A74 and the Brunt Ice Shelf. The two produced the giant berg.

BBC

There had been several research groups from before and they had tried to probe waters below freshly calved ice shelves. Their goal was to study and understand these unique ecosystems, what animals were there, and how they operate. While many have attempted, many failed. The chances of success for this type of study are low.

BBC

It’s all about being at the right place, at the right time. And because it’s in Antarctica, it poses even more challenges. The sea-ice conditions just don’t allow research ships to get into position above the ideal site. But Polarstern, which is run by the Alfred Wegener Institute, was fortunate. The fates must have been on their side on that day.

The Polarstern was in the eastern Weddell Sea at that time. The ship had been on a pre-planned expedition. Just then, the large A74 coincidentally split from the Brunt. To help them even further, the weather decided to go easy on them. The calm day allowed the ship to slip behind the berg. The men in the ship had a clear glimpse of an area of seafloor that had been exposed for the first time after 50 years.

BBC

The Polarstern makes use of Ocean Floor Observation and Bathymetry System (OFOBS) as in instrument that needs to be towed behind the ship at depth because of its large size. It took them a total of five hours to collect a whopping 1,000 high-resolution images and long sequences of video. Dr. Atun Purser told BBC’s Science in Action Program, “There was quite a lot of life on every single rock that’s fallen out of this iceberg over time, as every single piece of hard substrate on the seafloor was colonized by slow-growing sponges, bryozoans – filter-feeding animals for the most part. That was immediately visible as soon as we put the camera sled down. But then there was also a lot of mobile animals down there. Lots of sea cucumbers had come into the area, or were living in the area; also fish and octopuses. There’s not much evidence of creatures living in the sediment – large creatures reworking the sediment. In the deep sea, you quite often see burrow structures. We didn’t see very much of that under the ice.”

Dr Huw Griffiths from the British Antarctic Survey was ecstatic when he took the pictures. He immediately sent these from the Polarstern. He explains, “What they have found isn’t shocking but it is amazing to get these images so soon after a calving event and it is definitely the largest area that will have been surveyed in this way. Finding this kind of community this far under the ice shelf is not surprising but it is a good indication that there is a rich supply of food reaching at least 30km under the ice shelf. This food is produced by plankton in the sunlit sea surface nearby, then dragged under the ice shelf by the currents of the Weddell Sea. These same currents will eventually move the iceberg westward around the Weddell Sea and then northwards to its doom.”

More research has to be made because they need to return at regular intervals to document and observe changes to the ecosystem, if there are any. The Polarstern is up to the task because AWI is conducting long-term studies in the Antarctic. 

The Weddell Sea’s eastern side is of great interest because it is not affected by the warming effects observed in its western side which is right beside the Antarctic Peninsula. This state may not be permanent because computerized models indicate a possibility of 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. This is the floating protrusion of glaciers that have drifted off the land into the Weddell Sea. When you look at its place on the map, the Weddell Sea is that portion directly to the south of the Atlantic Ocean.

The Brunt is on the eastern side and it acts like all other ice shelves because it is predicted to periodically calve icebergs. The last time this happened in the very same area was in 1971. No one knows when this will happen again.

 

Just how big is iceberg A74?

Satellite pictures show its measurements to be around 1,290 sq km. To put it into better perspective, Greater London is roughly 1,500 square kilometers and the Welsh county of Monmouthshire is about 1,300 square kilometers. This is large, but not quite like the humongous A68 berg that calved in July 2017 from the Larsen C Ice Shelf found on the western portion of the Weddell Sea. The first calving was around 5,800 square kilometers. Since this happened in 1971, the berg has dwindled into many smaller pieces since then.

 

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