After years of cracking and crumbling, a giant iceberg finally broke free from 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 sea floor full of life.
For five decades, the ocean has been shaded beneath this enormous stretch of ice – about twice the size of Chicago. Now the first rays of the sun penetrate the depth, about 30 kilometers down (18 miles). A German research vessel that happened to be nearby sat in the front row.
The icebreaker for a few weeks now Polarstern has been waiting for the gale-force winds and dangerous waves to die out so it can fly around this monstrous iceberg. This week the ship finally got its chance.
The large iceberg that split from the Antarctic ice shelf. (NASA Earth Observatory)
Despite being shrouded in darkness for half a century, the seabed turned out to be home to a surprising diversity of life in the silty landscape. By towing a camera platform under the ship with a long cable, researchers found many filter feeders and stationary species, including sponges, anemones, sea cucumbers, starfish, soft corals, mollusks, fish, and squid.
(OFOBS-Team PS124 / Alfred Wegener Institute)
Above: A sponge, almost 12 inches in diameter, attached to a small rock on the sea floor.
Many of the organisms huddled around rocks that would have fallen from the glaciers into the ocean.
(OFOBS-Team PS124 / Alfred Wegener Institute)
Above: Numerous tiny sponges, bryozoans, and corals cover rocks scattered across the sea floor, with a worm leaving a spiral of feces in between.
Particularly interesting is the presence of filterers. Phytoplankton are what creatures like these usually filter out of the water to eat, but these tiny organisms are thought to depend on sunlight; they are usually not found deep in the ocean.
(OFOBS-Team PS124 / Alfred Wegener Institute)
Above: A stone that supports countless filter feeders. The white curls are the arms of a brittle star used to capture food and prey.
But they may not be as scarce as we thought in the darkness of Antarctica. Or maybe there are other microscopic organisms or nutrients that filter these fixated creatures.
Last month, scientists drilled 900 meters deep into the Antarctic ice shelf above the western Weddell Sea, some 260 kilometers (162 miles) from the coast. But even here, in this incredibly isolated part of the sea, the team was shocked to find sponges and other filter feeders that were also attached to rocks.
“Our discovery raises so many more questions than it answers,” said British Antarctic Survey biogeographer Huw Griffiths at the time, “such as how did they get there? What are they eating? How long have they been there? How many times have they ended up there? “These boulders covered with life? Are these the same species that we see outside 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 has already shared numerous sediment samples from this newly revealed seabed, as well as an album of unique photos.
(OFOBS-Team PS124 / Alfred Wegener Institute)
Above: An anemone nearly 12 inches in diameter next to the remains of a worm’s stool pathway. Laser point for scale.
“It is extremely fortunate that we were able to respond flexibly and investigate calving on the Brunt Ice Shelf in such detail,” said physical oceanographer Hartmut Hellmer of the Helmholtz Center for Polar and Marine Research at the Alfred Wegener Institute.
“That said, I am even happier that we have successfully replaced a number of moorings, which will continue to record basic data on temperature, salinity, and ocean current directions and speeds once we take off.”
(Ralph Timmermann / Alfred Wegener Institute)
Above the Polarstern traversing the smallest gap between the iceberg and the Brunt Ice Shelf, also known as “foxhole” because it is so tight.
The data gathered 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 best protect these priceless ecosystems before it is too late.
“We need this knowledge to be able to take effective action against climate change,” said Hellmer.
“The effects of climate change on Antarctica, among others, are worrying.”