Arctic sea ice is one of the most dramatic indicators of climate change. The ice cover on the Arctic Ocean is in a few months or so half of what it was decades ago, and its thickness has decreased, according to some estimates, 40%.
Changes in the ice can also mean a host of other changes, in the Arctic system and around the world. To better understand this, scientists have froze an icebreaker next to an Arctic pack ice that they will observe for a whole year.
The project is called MOSAiC, a multidisciplinary observatory drifting for the study of the Arctic climate. And what are the main questions they are trying to answer: what are the causes of the decline in Arctic ice and what are the consequences?
At about 5 degrees North Pole, ocean physicist Tim Stanton of the Naval Postgraduate School stands next to a hole in the ice, surrounded by boxes of tools and equipment.
"I just have to have the" hair dryer, "he says, eyeing two electrical connectors for a science buoy to be heated to a temperature of 18 degrees Fahrenheit.
A hair dryer? He says, "Well, it's a heat gun" what's it called "… he said." It's going to curl your hair, that's for sure! "
Stanton is in the midst of an exhausting eight-hour process to install the buoy about 15 miles from where the MOSAiC ship, the German icebreaker Polarstern, is docked.
This is part of a network of distributed equipment around the Polarstern and operating autonomously throughout next year. It will provide additional data on what is collected at the central research camp on the ice next to the ship.
The buoy is a big yellow banana gear, with a bunch of scientific bells and whistles hanging in the water.
"The flow pack goes up here," says Stanton, pointing to a cylindrical instrument with sensors that will pull up a metal rail suspended vertically in the water. "And that is what measures heat transport, salt and momentum in the water column."
Stanton wants to collect data on these attributes of the ocean as he thinks that this could help explain why sea ice is disappearing as fast as it is.
"At first glance, it must be obvious, no, you add heat, you melt the ice," he says. "But it's so complicated."
As the sea ice melts in the summer, it brings cooler water to the top of the ocean. The more salty seawater, which is lower because it is denser, can create a barrier preventing cooler water from getting off.
Stanton thinks that if this surface water stays trapped near the surface all summer, it can absorb much more heat from the sun and generate even more melting ice.
"You can get those cool, warm layers that, when a little wind blows, does a little mixing, really melts the devil on the ice," he says.
While Stanton asks questions about what's going on under the ice, other scientists are looking into the situation.
Jessie Creamean, from Colorado State University, for example, is on the ice trying out a device that collects and counts tiny particles in the atmosphere called aerosols.
"Alright, little aerosol sampler, is fine today," says Creamean, closing a pelican holster the size of a carry-on bag. She has already tested it in Colorado, but today 's experiment aims to check its effectiveness in cold weather.
People may be more familiar with aerosols created by pressurized cans like hairspray, but it's just a type. aerosols can also come from natural sources such as dust, pollen, mushrooms or sea salt, and they are actually seeds that clouds must form and grow.
In the Arctic, scientists believe that microbes in the ocean, such as bacteria and algae, can generate aerosols. And Creamean hypothesizes that less ice on the Arctic Ocean could mean that more aerosols would be blown from the water into the atmosphere and seed more clouds.
The mechanism for this could be twofold: more sunlight reaching the ocean as sea ice decreases and possibly causing increased growth of microbes, as well as increased contact between the ocean and the sea. 'atmosphere.
MOSAiC scientists are interested in clouds because they play an important role in regulating temperature, just like a thermostat. Depending on the season, whether the clouds cover the water or the ice, as well as their properties, they can cool down or warm the earth.
"It affects the amount of heat that can actually help melt the sea ice, or even reflect sunlight from the pack ice," says Creamean. "He therefore has an important role to play in controlling the amount of sea ice that we have here."
Creamean and Stanton are among hundreds of scientists from different disciplines who are trying to better understand this changing region.
"We're looking at interactions in the system," said Matthew Shupe, an atmospheric scientist at the University of Colorado and the National Oceanic and Atmospheric Administration, one of the expedition's coordinators.
"The way the atmosphere interacts with sea ice, how the ocean interacts with sea ice, ecosystem, biogeochemical processes," he said.
The main purpose of collecting all these data is to improve the way the Arctic is represented in climate models. These are computer simulations used by scientists to estimate things such as the amount of heat the Earth could heat in the next 50 years.
The better you reflect the functioning of reality in simulation, the better your prediction. But as little is known about the functioning of the Arctic Ocean system, Shupe explained that predictions about how the Arctic would react to climate change vary widely.
"The Arctic is a place where models are the least in agreement," he says. "So that tells us that we are missing something."
Projected changes in the Arctic – as when the Arctic Ocean will see its first summer without ice – are obviously important to the region. local ecosystem, for Arctic communities, and for anyone interested in doing commercial activity In the region.
But this research will also help scientists understand the impact of changes in the Arctic on other parts of the planet. For example, this could help scientists understand the possible links between global warming in the Arctic and extreme weather events at middle latitudes.
"We need to understand physics and, ultimately, improve our models that can help us answer these questions," said Shupe.
It will also help scientists anticipate how quickly the Greenland ice cap could melt, which would raise sea levels globally, and improve forecasts of global temperature rise over the next few years. years.
By traveling the Arctic Ocean for the next year and observing how all the smaller components of the Arctic system fit together, scientists hope to be able to clarify these big questions.
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