The Calved Brunt ice shelf reveals a seabed teeming with life hidden for 50 years – tech2.org

The Calved Brunt ice shelf reveals a seabed teeming with life hidden for 50 years


After years of cracking and crumbling, a huge iceberg finally broke off Antarctica’s Brunt Ice Shelf last month and began drifting out to sea. Like a retractable skylight, the event gave us a rare glimpse of a previously unreachable seabed absolutely teeming with life.

For five decades, the ocean below this huge chunk of ice, roughly twice the size of Chicago, has been kept in the shadows. Now the first rays of sunlight are penetrating the depths, about 30 kilometers deep (18 miles). A nearby German research ship had a front row seat.

For several weeks the icebreaker Polarstern He has been waiting for the hurricane-force winds and dangerous waves to subside so he can circumnavigate this monstrous iceberg. This week, the ship finally had its chance.

brunt oli 2021059 1The great iceberg that broke off the Antarctic ice shelf. (NASA Earth Observatory)

Despite being shrouded in darkness for half a century, the seafloor turned out to be home to a surprising diversity of life in its silty landscape. By towing a camera rig under the ship with a long cable, the researchers found many filter feeders and stationary species, including sponges, anemones, sea cucumbers, starfish, soft corals, mollusks, fish, and squid.

CSM 20210314 A74 seabed 2 AWI OFOBS equipment PS124 010 3c8b0802ca(OFOBS Team PS124 / Alfred Wegener Institute)

On: A sponge almost 30 centimeters (almost 12 inches) in diameter stuck to a small stone on the seabed.

Many of the organisms were huddled around rocks, which would have fallen from glaciers into the ocean.

CSM 20210314 A74 seabed 1 AWI OFOBS equipment PS124 009 ae4bf9e1f5 (OFOBS Team PS124 / Alfred Wegener Institute)

On: Numerous small sponges, bryozoans and corals embed stones strewn across the seafloor, with a worm leaving a spiral of feces in the middle.

The presence of filters is particularly interesting. Phytoplankton are what creatures like this often filter out of water to eat, but these tiny organisms are thought to depend on sunlight; they are generally not found in the depths of the ocean.

csm 20210314 A74 image12 AWI OFOBS equipment PS124 008 6a7aae3f70 (OFOBS Team PS124 / Alfred Wegener Institute)

On: A stone that supports numerous power filters. The white curls are the arms of a brittle star that is used to capture food and prey.

But perhaps in the darkness of Antarctica, they are not as rare as we thought. Or perhaps there are other microscopic organisms or nutrients that these fixed-in-place creatures are filtering out.

Last month, scientists drilled 900 meters (0.6 miles) deep into the Antarctic ice shelf over the western Weddell Sea, about 260 kilometers (162 miles) off the coast. Yet even here, in this incredibly isolated stretch of sea, the team was surprised to find sponges and other filter feeders also attached to rocks.

“Our discovery raises a lot more questions than it answers,” said biogeographer Huw Griffiths of the British Antarctic Survey at the time, “like how did they get there? What are they eating? How long have they been there? How common are they? ? ” These boulders covered in life? Are they the same species we see off the ice shelf or are they new species? And what would happen to these communities if the ice shelf collapsed?

The team on board the Polarstern He has already shared numerous sediment samples from this recently revealed seafloor, as well as a once-in-a-lifetime photo album.

csm 20210314 A74 image11 AWI OFOBS kit PS124 007 4cd82c9f39(OFOBS Team PS124 / Alfred Wegener Institute)

On: An anemone almost 30 centimeters in diameter next to the remains of a worm’s fecal trail. Laser point for scale.

“It is very fortunate that we were able to respond flexibly and explore the calving event on the Brunt Ice Shelf in such detail,” says physical oceanographer Hartmut Hellmer of the Alfred Wegener Institute’s Helmholtz Center for Polar and Marine Research.

“Having said that, I am even happier that we have successfully replaced a series of moorings, which will continue to record elemental data on temperature, salinity, and ocean current directions and speeds once we are gone.”

csm 20210314 Polarstern between Brunt and A74 RalphTimmermann 004 5f2374f62d 1(Ralph Timmermann / Alfred Wegener Institute)

About him Polarstern traversing the smallest gap between the iceberg and the Brunt Ice Shelf, known as a “trench” because it is such a tight squeeze.

The data collected from this risky endeavor will be used to better understand how the Antarctic Ice Sheet will respond to climate change in the future and what we can do to better protect these invaluable ecosystems before it is too late.

“We need this knowledge to be able to take effective countermeasures against climate change,” Hellmer argues.

“The effects of climate change in Antarctica, among others, are worrisome.”

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