Aboard MOSAiC: Hardy fish, powerful waves, shrinking ice floes

This is a re-post from Yale Climate Connections by Kristen Pope

Hundreds of researchers from around the globe took turns collecting data in the Arctic aboard the German icebreaker RV Polarstern on an expedition that lasted over a year. Now, this data is rewarding the researchers with important and surprising insights about this vast, mysterious region that is warming more than twice as fast as Earth as a whole.

They found Atlantic cod and squid swimming much farther north than thought possible. They saw powerful waves smash the Arctic ice with a force that carried the water into the floes for miles. And they were surprised by how quickly their ship made its transit through the receding Arctic ice.

More surprises and valuable insights about the little-studied Arctic region should become available as some 442 experts pore through their data and begin to publish their findings after their stints on various legs of the MOSAiC expedition (Multidisciplinary drifting Observatory for the Study of Arctic Climate). Still another 300 additional researchers and others assisted without traveling to the Arctic.  The researchers on the first leg of the expedition set out in September 2019 and drifted with a floe of ice. For 389 days, researchers and crew endured vicious storms, temperatures that dropped to -42 degrees Celsius, and the logistical nightmare of COVID. They successfully completed the voyage in October 2020.

Research topics range from sea ice and snow, to the ocean, atmosphere, ecosystem, biogeochemistry, and more. Elementa, an open access scientific journal, published a Special Feature about the expedition, with overviews by the atmospherephysical oceanography, and snow and sea ice teams. Researchers also have published numerous other papers, and many more are in various stages of development.

The discovery of fish in the Central Arctic Ocean, detailed by researchers in an article for Science Advances, could benefit Arctic mammals, according to the researchers.  They found squid and cod, which could potentially serve as a food source for seals and walruses in the region. However, the researchers warned these fish populations are not large enough to expand commercial fisheries.

Data gathered over a year … but was it a representative year?

One of the expedition’s principal objectives involved collecting baseline data to thoroughly document conditions during a one-year period. However, to be able to fully use the data they collected, the researchers needed to determine whether the year they observed was typical or whether it was an anomaly.

“The big picture part is how does the MOSAiC year fit into other years? How is it representative or not of other years?” said Matthew Shupe, MOSAiC expedition co-coordinator and atmospheric scientist with CIRES at the University of Colorado and the National Oceanic and Atmospheric Administration (NOAA).

Shupe says the researchers found their summer in the Arctic warmer and wetter than normal, which he said may be related to the retreating ice edge and closer proximity to the open ocean water. He also noted circulation was very strong during the year – particularly in January, February, and March – relative to previous patterns.

“What we found is that a lot of the times the conditions we observed were pretty typical, but there were definitely some periods that were kind of outside of what we’ll call the norm,” Shupe said, and some storms were stronger than normal.

Packing up instrumentsPacking up Met City instruments at met City proper. (Alfred-Wegener-Institut, Lianna Nixon / CC BY 4.0)

Dancing with the ice edge

One of the most surprising things the expedition observed was how quickly the ship ended up transiting the Arctic. They had expected to be in the ice until at least September, but emerged in July.

“We didn’t really expect the ship to come out as fast as it did,” says Donald Perovich, co-lead of MOSAiC’s ice team and professor at Dartmouth’s Thayer School of Engineering. They needed the ship to move quickly enough to collect as much data as possible during the year, but Perovich says he was surprised by how quickly the ship and the floe it was drifting with moved across the Arctic, and also by how dynamic the ice cover was.

As they approached the ice edge, the team discussed how far beyond it they thought the powerful ocean swells could go. They estimated the waves could travel many miles past the ice edge. As they approached the ice edge, they tried to collect as much data as possible without losing any equipment to crumbling ice. Finally, they decided it was time to pack up, and the team took two days to remove the extensive array of equipment. They got off the ice floe just in time.

“We go to bed that night and wake up in the morning and look out and the ice floe is gone,” Shupe says. “It was totally gone – it disintegrated into a thousand pieces, all these little chunks.”

After their earlier-than-expected emergence from the ice in July, the team routed the ship back up north, repositioning it near the same general floe where they had had affixed the ship to the original floe the previous fall. Returning to a similar location allowed them to continue collecting data from within the ice.

Perovich’s team now is working through data sets and analyzing topics like albedo, melt ponds, snow, heat fluxes, ice mass balance, and energy budgets.

“It was truly an interdisciplinary look at the Arctic Ocean as a system with the atmosphere, sea ice, the ocean, ecosystem, and biogeochemistry,” Perovich says.

“The field experiment is over, but in some ways the adventure continues,” said Perovich, excited about the connections and discoveries to come as teams analyze more data about the Arctic.

Filling in data gaps

“The ecosystem in the Arctic is fragile,” said Céline Heuzé, associate professor at the University of Gothenburg, Sweden, co-lead of the MOSAiC physical oceanography team. She noted that the expedition collected an enormous amount of oceanographic data, which had always been very difficult to obtain. The team’s Elementa overview says, “fewer than 700 full-depth temperature/salinity profiles existed in the whole deep Arctic north of 82°N prior to 2019,” noting only 40 were winter samples.

“We have been trying to create models that represent the entire seasonal cycle with only measurements from the summer,” Heuzé says. “So it’s like trying to predict the weather in New York all year round, knowing only what happens in August.”

Collecting samplesDaniela Krampe (Team Ice) and Lasse Mork Olsen (Team Eco) take a water sample which was collected under the ice by the remotely operated vehicle ROV Beast. (Alfred-Wegener-Institut, Matthias Jaggi / CC BY 4.0)

MOSAiC allowed much more detailed and in-depth data collection from the full water column. Researchers could take the time to sample all the way down to the sea floor. The facilities set up on the ice also allowed for additional measurements, including some from a distributed network of autonomous sensors placed up to 50 kilometers (31 miles) around the ship. This approach allowed data collection that showed the bigger picture.

MOSAiC is also key in filling data gaps to study things like Central Arctic aerosols such as fogs and mist. “Now we’ve really established a baseline, and we can use that baseline going forward to understand change,” Shupe says.

SensorRemote sensing (RS) instruments carry the same sensors that are used on satellites. MOSAiC offers the chance for direct measurements of e.g. ice and snow thickness and composition to better interpret RS data. (Alfred-Wegener-Institut, Steffen Graupner / CC BY 4.0)

Heuzé noted that some ocean data sample processing was delayed as a result of COVID backlogs, yet researchers already noticed some trends in the data they have, including Atlantification, which is when warmer and saltier water from the Atlantic moves into the Arctic. They also found a level of vertical mixing, which models had predicted, perhaps caused by thin sea ice allowing water and waves to move more easily. Additionally, they observed a thin layer of meltwater that may help to protect sea ice and stabilize the water column, though large storms seemed to disrupt this effect.

Heuzé is still collecting data from autonomous sensors that were deployed during the expedition. When the sensors surface, they send her data via satellite.

Expedition members believe MOSAiC’s data will help improve climate models by providing year-round data to help create better models. Teams are poring over details of their data to ensure it is of the highest quality before making it publicly available in January 2023.

“From the very beginning with MOSAiC, we’ve always felt that the data are the legacy for MOSAiC,” Perovich says. “The hope is that the data will be used for decades to come.”

Posted by Guest Author on Monday, 18 April, 2022

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