A small group of scientists and doctoral students from the University of California at Davis recently returned from Antarctica, where they were the first group to collect turbulence measurements of an underwater glider located under an ice floe.
This multinational collaboration led by the Korean Polar Research Institute, KOPRI, was only the second time a glider was successfully deployed under an ice platform.
With these data, scientists will be able to better understand the speed with which ice packs melt and predict how these rates will change in future climate scenarios.
The glider, named Storm Petrel, is a type of autonomous underwater vehicle equipped with wings. It was deployed under the Nansen pack ice on 7 January and resurfaced 20 hours later on 8 January. Its sensor set allowed scientists to quantify the flow of heat and energy using a relatively common open water system, but never used before. way under an ice cream.
"It took us three years of development to get to those 20 hours, and we did it," said principal investigator Alexander Forrest, an assistant professor at UC Davis College of Engineering, who said: He was not able to participate himself in this trip, but participated with his remote Davis team. "I am quite satisfied with the success of the vehicle, but above all with the incredible feat of our UC Davis students at the helm of operations."
The frozen border
Sending an underwater glider under the ice of Antarctica is not so different from sending a scientific instrument in the space. After careful planning and calculations, everything is fine, in the dark, with blackout communications until it re-emerges. In these environments, he comes back or does not come back at all.
Under the pack ice, the glider did not send any signal to the team for 20 hours. When it surfaced, the shipboard researchers were temporarily disconnected from the Internet. That left Forrest, alone in Davis and watching on his computer screen, to be the only one to see when he got up and shouted "Yes!"
In addition to the challenge of operating in this extreme environment, the glider had to be deployed very precisely in a "super cold" water plume – a delicate task, which Forrest equates to Luke Skywalker's flight into the narrow trenches of the Death Star – so that it could fly up, down, in and out without hitting the surface or the bottom of the ocean.
Fun fact: when the water is cooled very slowly, it can remain a liquid beyond its freezing point. For this to happen, it must be so pure that there is no surface on which ice crystals can develop. This is called supercooled water. Scientists were continuing this plume because it indicates the location of the melt water.
"We are trying to understand the dynamics of this system and what that panache is doing," said Forrest. "This plume was much higher in the water column in 2019 compared to 2017, which indicates that a greater amount of meltwater could occur, which is certainly a source of concern and should be the subject of further investigation. "
Glaciers, glaciers and sea level rise
The ice has always melted, but at a time of warming polar environments, things happen faster. Ice melting usually occurs where the ice meets the ocean and goes largely unnoticed – until an ice floe collapses, a phenomenon that is becoming more and more common in the ice. during the last ten years.
Unlike ice floes, glaciers are located on land. In all polar landscapes, glaciers advance, directly contributing to the rise of sea level. The ice plateaus are already part of the ocean and are constantly passing from a solid state to a state. liquid. Ice trays do not directly raise the sea level, but serve to reinforce the ice on the mainland. When ice trays come off, from the Arctic to the Antarctic, this stabilizing effect is lost, releasing glacial ice to accelerate its passage from land to the ocean.
"Changes to the surface of the ice are sometimes easily identifiable, but it's often difficult to fully understand the changes that occur under the ice," said Jasmin McInerney, PhD candidate at UC Davis. "There is a lot of speculation about this, unless robotics teams such as ours can physically reach these places.With all the consequences of the disappearance of the pack ice, it is important to get rid of as many unknowns as possible. possible to estimate when this could happen. "
The Nansen pack ice is relatively small compared to larger systems such as the Ronne-Filchner, Ross or Thwaites pack ice. The international team, led by KOPRI, plans to apply the same techniques as those developed in this project on the Thwaites ice floe. Forrest and his team plan to partner to continue developing robotic observation tools and techniques.
Underwater robots help predict when and how ice platforms collapse