The Antarctic Ocean Seafloor Bared After 50 Years Since Last Iceberg Calving

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A group of scientists have recently released images of the Antarctic seafloor after being hidden by a giant and thick sheet of ice.


The iceberg, known as A74, broke away from the Brunt Ice Shelf in the Antarctic, revealing some very interesting things lurking on the ocean floor. A74 is said to be about one-and-a-third the size of Houston, Texas, measuring around 790-square miles. And according to the Alfred Wegener Institute (AWI) polar research organization, having an iceberg that large split is incredibly rare. In fact, they explain that something like this only happens in the Antarctic once every decade.

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What was even more surprising is that the break has exposed the ocean floor to have loads of sea animals. Scientists used video cameras to track the various filter feeders that were living in the soft mud below the ice. As for the research group, their ship RV Polarstern, managed to fit through the narrow gap in between the A74 and the Brunt Ice Shelf that had made the giant iceberg in the first place.

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It’s nothing new for research teams to attempt to search deep waters after ice shelves have calved. This is how they get to know and understand the unparalleled ecosystems that exist below the ocean’s surface. History has proven that this is not an easy feat.

BBC

For those that have managed to capture such extraordinary images, a lot of it has to do with pure luck and being in the right place within Antarctica at the right time. Moreover, it also depends on the actual sea-ice conditions, since more often than not, the ice is so thick that there’s simply no way for a research vessel to even position itself in the right area.

Yet for the research group on the Polarstern that happens to be run by a team from the Alfred Wegener Institute, it seemed that the gods were smiling down on them that day. The ship was on a pre-planned expedition in the eastern Weddell Sea when the A74 iceberg happened to split away from the Brunt ice shelf.

By the weekend, the weather had relaxed enough to allow the ship to literally get through the cracks, and get a closer look at the ocean’s bottom which had finally come exposed for the first time in five decades. And what they managed to photograph was both breathtaking and exceptional.

BBC

The RV Polatstern uses the Ocean Floor Observation and Bathymetry System (OFOBS), which is simply described as a sophisticated instrument that’s towed behind the ship at particular depth in order to take photographs. It was utilized for more than five hours as it managed to capture almost 1,000 high-resolution images, as well as considerably lengthy video sequences.

BBC

OFOBS team-member, Dr. Autun 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.”

Dr. Purser added, “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.”


For one, Dr. Huw Griffiths – of the British Antarctic Survey – was incredibly ecstatic when he saw the images taken on the Polarstern. He shared with BBC News, “What they have found isn’t shocking but it is amazing to get these images so soon after a calving even and it is definitely the largest area that will have been surveyed in this way.”

He added, “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.”

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For those in the research field, ideally they need to go back in regular intervals to be able to properly document any changes that occur in the ecosystem. As for the RV Polarstern, this would be doable considering the AWI wants to continually conduct long-term studies in that area of the Antarctic.

Notably, the eastern side of the Weddell Sea is reportedly one of the best to investigate since it’s seemingly immune to the appalling effects of global warming seen further west in the Antarctic Peninsula. But of course, things could shift quickly considering computer models show that it could soon be affected by warm ocean waters coming from the north in the next few decades.

Although the calving of the A74 from the Brunt Ice Shelf is not exactly surprising, the fact that it’s been 50 years, 1971 to be exact, since the last time that happened, it’s still astonishing to say the least and researchers hope that they can make the most of the ocean’s floor exposure before it gets covered up once again.

 

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