Antarctica’s majestic underwater world is trying to adapt to a warmer planet
By Allison Chinchar, CNN Meteorologist
Icebergs surrounded a team of researchers in January as they cruised toward Antarctica. The team had been studying a thriving underwater ecosystem near the continent for years, but thanks to new modeling and powerful instrumentation they were able to navigate through a crumbling landscape of ice to their destination.
“We saw a lot of icebergs and they were impressive — the size of buildings,” Patricia Yager, a professor at the Department of Marine Sciences at the University of Georgia, told CNN. “Some are as tall as the Statue of Liberty, up to 300 feet above the waterline.”
“There’s a lot of melting going on,” Yager said. “Lots more than I expected. There was more meltwater and more heat in that ocean than I imagined.”
The Thwaites Glacier in Antarctica, roughly the size of Florida, is melting at a rapid rate. In fact, most of the ice in western Antarctica is melting. But the Thwaites Glacier — also known as Doomsday Glacier — is one of the most unstable in Antarctica. This is very worrisome because of the sea level rise it could cause.
But it’s more than that.
“What we realized as biologists and chemists and ecosystems scientists was, our ecosystem was also being impacted,” Yager said.
Scientists believe this ecosystem is pivotal to climate research, and years of extraordinary warming has allowed them to finally see it with their own eyes. Everything in this ecosystem — from the small phytoplankton to the larger seals and penguins — is being impacted.
Yager and her fellow researchers want to know what will happen to the surrounding ocean salt water if the glaciers melt, particularly what happens to the ecosystems that live in it — or under it.
The entire food chain is being impacted
While Yager and her team were in Antarctica, they found an elephant seal in the polynya — an oasis of open water where sea ice would normally exist — that they were studying.
“Nobody’s reported seeing an elephant seal there before,” she said. “What we see is if there’s a shift in the ecosystem, the animals respond. The problem is they’re not just responding to the food. They’re also responding to change in habitat and ocean currents.”
But how did that elephant seal get there? Well, that is where these important microorganisms called phytoplankton come in.
Phytoplankton are vital to the Antarctic food chain. Krill eat the phytoplankton, and animals like seals, fish, and penguins eat the krill.
Certain coastal regions of Antarctica have the highest abundances of phytoplankton in the world.
“The Amundsen Sea Polynya is about half the size of the state of Georgia,” Yager said. “So it’s a big feature. On a per meter squared basis, it is more productive [than other polynyas] for reasons we think that are related to this melting glacier.”
It was discovered about a decade ago that this meltwater was providing iron-rich water to the polynya. So much iron that it was providing beneficial fertilizer to the local ecosystem.
However, high amounts of iron are not usually found in the coastal Antarctic because there is so little exposed rock there.
“The Southern Ocean is famously known for being a high-nutrient, low-chlorophyll zone,” Yager said. “We figured out that this ocean, for the most part, has plenty of nitrogen but it is missing another important fertilizer, which is iron.”
Where there’s iron, there are phytoplankton blooms.
This ecosystem may have adapted to climate change in some ways, but it will need to change in many more ways to survive rising temperatures.
“We knew from the satellites that there was a big phytoplankton bloom in this area. It’s why we went to first explore this region back in 2007. Rob Sherrell, a trace metal geochemist from Rutgers University, pointed out that if there are algae blooming, then there must be iron. The question was, where was the iron coming from?”
What the researchers didn’t understand was why meltwater was coming out from where it was, and why it was so rich in iron, Yager said.
“So we went down there thinking, okay, well, the glacier has iron in it, and the melting glacier is dribbling iron into the ocean, which is a perfectly reasonable hypothesis. That’s what’s happening in parts of Greenland,” Yager said. “However, turns out, that’s not what’s happening. It’s more interesting than that.”
Back home, the science team set out to build a computer model to explore how the iron delivery worked.
“That’s what we went down to test this year,” Yager said. “The model suggested that the iron is actually coming mostly from the deep ocean water responsible for melting the glacier, but the delivery of iron to the surface is because of the added buoyancy from the melt.”
That upwelling of iron is fueling thriving ecosystem communities with species of algae, icefish, seals and jellyfish.
It may seem hard to believe that organisms could thrive in such cold environments, but there is life down there. And when you change that environment, it can have dire consequences.
“That life loves being down there,” Yager said. “If you take them away from that cold environment, they don’t survive. If you take the bacteria or the organisms that live down there and you put them in warm water, they often die.”
So while on the surface it may seem like a good thing that parts of these ecosystems are thriving — such as the phytoplankton, zooplankton — other aspects of the ecosystem can’t adapt as easily.
“For example, the Adelie penguins really depend on sea ice, and as the sea ice has disappeared from the peninsula in western Antarctica, the Adelies have declined dramatically because their habitat is gone,” Yager said. “What we’re seeing is an ecosystem shift. Adelie penguins are moving to new areas where there is more sea ice, and other penguins that don’t need the sea ice are moving in.”
But when the ecosystem shifts, so too does the food web.
If the varieties of phytoplankton and krill shift, for example, then the fish, seals and penguins must shift, too, out of necessity.
“There’s going to be winners and losers with climate change,” Yager said. “Life will find a way and somebody will come in and take advantage of whatever food is available. It just might not be the thing that used to live there.”
Why this location is so unique
Yager has been traveling to Antarctica for research since 2007, but thanks to a very high-resolution model created by Pierre St-Laurent, a research scientist at the Virginia Institute of Marine Science, the crew think they found the ideal spot.
“It’s an interesting experience to be quietly sitting at your desk in the US and suddenly receive an email request from a colleague in Antarctica who is on the field and who would need guidance,” St-Laurent told CNN.
He worked out codes to predict the ocean currents using basic ingredients like water temperature, salinity, winds, the depth of the ocean and sea ice arrangements along coastlines of the Amundsen Sea. These predictions help the team — funded by the National Science Foundation and the UK Natural Environment Research Council — understand what’s going on below the surface.
The problem was getting there.
“This year, unusually strong winds blew the sea ice into a big pile that blocked us from getting to the Thwaites,” Yager said. “We tried to go around, but all the icebergs also made it tricky to navigate through.”
Those icebergs falling from the Thwaites glacier had now drifted farther apart to essentially clear a path, albeit a windy one, for their crew to investigate the Eastern Notch area between the Thwaites and Dotson. The researchers wanted to verify what the models had predicted for a coastal current delivering meltwater and iron from the Thwaites.
“So this part of Antarctica, according to satellites, is one of the most productive in terms of biology,” Yager said. “It’s the greenest place in Antarctica and has the densest chlorophyll per meter squared. But it’s very hard to get there as you might notice. It’s pretty far away from everywhere.”
Whether you travel from New Zealand or the southern tip of Chile, it’s a two-week trip by ship — about as far away from anywhere as you can get.
“We know that the sea ice is integral to the ecosystem in this area — they’re called marginal ice zones,” Yager said. “In the wintertime, the sea ice in these zones covers up the ecosystem. But then in the spring and summer, when it melts to make a polynya, it provides some layering of the ocean, and tend to be quite productive.”
The ocean has three primary layers — the surface layer (sometimes referred to as the mixed layer), the thermocline layer and the deep ocean.
The surface layer is the top layer of the water, and is well stirred from the wind and other forces. This top ocean layer also tends to be the warmest layer due to heating from the sun. And the phytoplankton also live in the surface layer.
“Because it’s not just the iron — it’s the iron and light together that the phytoplankton need,” Yager said.
She collaborated with a group called TARSAN, a ship-based project studying how atmospheric and oceanic processes are influencing the behavior of the Thwaites and Dotson Ice Shelves. Their research helps identify how variations in atmospheric or oceanic conditions may influence the behavior and stability of ice shelves in the region in the future.
“If you bring iron up from below, disappearing sea ice and stronger winds could take away some of the stratification of the ocean, and now you’ve got less light for the phytoplankton,” Yager said.
This is why having multiple teams working together is so important, because each group can see something from a different angle.
If we catch it early, can we fix it?
The concern is that eventually, when the sea ice goes away and the polynyas disappear, this ecosystem will be destroyed.
“That has actually happened off the northeast coast of Greenland, there is no longer a polynya there, it’s gone completely,” Yager said.
“There’s two things happening in Antarctica,” she said. “The sea ice melts seasonally to make a polynya and the glaciers are melting and adding iron. So in this immediate time period, it’s all working together pretty well. We have this wonderful bloom.”
But too much of a good thing can be a bad thing in the long term.
Yager says it’s just like the food pyramid — it’s all about balance. As humans we need protein, grains, vegetables and fruit. If you eat a diet focused highly on fruits, your balance is off.
If this area becomes too high in iron, the balance will eventually tip.
“If we keep pushing in the same direction, and the sea ice goes away, the whole setup may collapse. And then we’re just pumping high carbon and high iron deep water into the surface of the Southern Ocean, and we don’t really know what the effect of that is going to be,” Yager said.
“That’s why we’re testing and improving this model to help us predict forward,” she said. “It’s giving us a clue of what might happen in the future, before it actually happens.”
St-Laurent also had a chance to travel to Antarctica, though in a different region called the Ross Sea.
“The remoteness of Antarctica is what struck me the most; in many ways the research expedition felt like taking a trip to the moon,” St-Laurent said.
“And yet, we know that this remote part of Earth has the potential to impact all coastal communities greatly as the Antarctic ice sheet continues to lose mass over the next decades and contributes to global sea level rise. Despite the scale of the planet, we’re in many ways interconnected, for better or for worse.”
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