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Climate Changed

Researchers exploring the world’s polar oceans are witnessing major biological changes

Frazil ice and floes in the Southern Ocean © Kerry Steinberner/Australian Antarctic Division​

The oceans play a massive role in regulating the planet’s overall health. Tiny organisms that live in the ocean, called phytoplankton or microscopic algae, produce somewhere between 40 and 80 percent of the planet’s oxygen (depending on which scientist you ask). There’s a reason, after all, that many people call oceans “the lungs of Earth.” They’re also an essential planetary food source and a massive carbon sink. To date, oceans have absorbed about 40 percent of the planet’s human-generated carbon dioxide. That means they regulate our atmosphere and the concentrations of various gases in our air, and they transport carbon away from the surface, where it would otherwise contribute to climate change.

This complex web of interaction between the planetary system as a whole, the oceans’ chemistry, and the animals that live within it is even more complex in the polar regions, where sea ice adds another layer to the impact of climate change. Trying to understand how this all works is an enormous challenge. Biologist Jess Melbourne-Thomas, a research scientist at the Australian Antarctic Division and project leader at the Antarctic Climate and Ecosystems Cooperative Research Centre, is one of the field scientists and climate modelers attempting to put the pieces of this massive puzzle together.

The Ocean Isn’t Easy

When it comes to understanding all of this, science has certainly struggled. The oceans are some of the planet’s most complex systems, and they are remarkably difficult to study. “Thousands of species interacting over large areas and not really following any set of physical rules about the way they interact with each other” pose a challenge, Melbourne-Thomas says. And these interactions are all happening underwater, making them difficult to observe. “A saying around studying marine systems is it’s like observing forests, except you can’t see the trees and they move.”

That means predicting how the ocean will respond to future climate change is nearly impossible. “Often biologists are reticent to make definite statements about how life is responding, because the ability to adapt is difficult to measure. You have to see that things have adapted before you say they can adapt,” Melbourne-Thomas says. But by building computer models and gathering data based on observations, researchers can see that changes to the ocean are happening, often more quickly they anyone had predicted.

Heat and Acid in Polar Waters

Not all oceans are alike. The impact of climate change in tropical and warm-water regions are pretty well-known: Excess carbon produced by humans is being absorbed into the ocean. When that happens, a chemical reaction occurs that decreases the water’s pH and increases the amount of acid, which is now starting to kill the coral reef systems that house about 25 percent of the world’s marine life.

Acidification is happening in the polar oceans as well, but the impact is slightly different. While there are some corals in cold water, the biggest impact in the southern oceans will be on anything that builds an exoskeleton. Skeletons of Antarctic krill, for example, contain calcium carbonate, the same material that’s in coral composition. These tiny shrimp-like creatures exist in the Antarctic oceans in massive numbers; it’s estimated there is as much as 500 million tons of krill in the Southern Ocean. Krill is an essential food source for most the region’s animals — seals, whales, birds, fish, and penguins all depend on krill for survival. And humans have been getting in on this game as well. “The potential fisheries for them is huge,” Melbourne-Thomas says. “We think that’s going to be increasingly important,” especially as our access to fish in other parts of the ocean is dropping due to overfishing and the loss of corals.

Adult and larval krill compete for food (phytoplankton) during autumn in the Southern Ocean. This competition is thought to drive large variations in the Antarctic krill (Euphausia superba) population. Photo: Ulrich Freir/Alfred-Wegener Institut/Australian Antarctic Division

“Understanding what the capacity of the ocean is to support people into the future is important. If food resources are no longer available, what does that mean? Where can people go instead? The food security question is really important one,” she says.

And if the water’s acid content continues to grow in the Antarctic, there is going to be a much bigger burden on krill. “Organisms that are [building exoskeletons] need to put in more energy to make it happen, which has consequences. If the pH gets low enough, calcium carbonate will actually dissolve. We’re not there yet.”

But before the krill start to dissolve completely, researchers are witnessing a more immediate problem. Animals living in the southern and northern oceans are migrating. As the center of the planet heats more quickly, species that rely on cooler temperatures are traveling farther and farther away from the equator. That means they’re are flocking to the poles, which puts a burden on ecosystems that haven’t housed them in the past. But it’s also a finite migration. These species can move farther north or south in search of colder water, but eventually there will be nowhere left for them to run.

“The caveat is that, for a lot of animals, we’re not sure how adaptable they can be. How well can they tolerate warmer water without needing to move? Will they adapt physiology to deal with new conditions, and how long might it take them to do this? There’s more and more evidence that the rate of change is going to be too fast for adaptation to happen,” Melbourne-Thomas says.

The Enduring Importance of Ice

Sea ice breakout © Australian Antarctic Division​

Nearly every living being in the northern and southern oceans relies on ice in some way for survival. It’s not just polar bears and penguins. “There’s so much going on under the ice in terms of the biology,” Melbourne-Thomas says. Though sea ice looks flat from above, underneath are craggy, sharp ice peaks that crash into each other and break into pieces. They create caves that animals can live in, and algae grows along all the underwater surfaces. “Krill hover underneath and feed on the algae. That will attract bigger things like fish and penguins. It’s much more mountainous on the underside,” she says.

The algae or phytoplankton — which produce the planet’s oxygen — that live on the ice are at the center of what scientists call the “microbial loop.” They eat each other and they are eaten, all the while absorbing carbon dioxide gases and recycling nutrients in the water, and when they die they take the carbon they’ve absorbed with them as they sink to the ocean floor. This means they also protect the planet from carbon that would otherwise contribute to climate change. “Bacteria and the phytoplankton drive productivity in marine food webs. They’re the smallest things and have quite complex relationships to the ocean,” Melbourne-Thomas says.

Diverse sea bed life © Australian Antarctic Division​

Loss of these ice habitats has already been well documented, and it’s accelerating, especially around the North Pole. “A lot of the change that we’re seeing already in response to climate change in the polar environments is to do with changes to sea ice,” Melbourne-Thomas says. And because of the connectedness of everything — because of the way each individual life on the planet relies on the systems and processes that happens around it—the rapid loss of even one aspect of the system can change the entire ecosystem. It’s a shift that’s happening quickly, and when entire ecosystems shift at a fast rate, it’s very difficult to predict how the life in that system will react.

Modeling the Future

Thanks to technological advances, it’s becoming slightly easier to study the ocean and understand if and how the animals living in it can adapt to climate change. Melbourne-Thomas and others are currently working on building predictive models that will tell scientists what the potential outcome of planetary change could look like. “Mathematical modeling allows us to try and simplify some of those complex connections and make statements about the likelihood of changes occurring in the future,” Melbourne-Thomas says. “The crux of it is that we don’t have any other tools. Models are the only means we have to make any kinds of statements about what the future might look like. There’s no crystal ball.”

Climate scientists have been making models for a long time, but the biological models are just now starting to be built by plugging in data gathered by a variety of sources: from satellites trained on the southern oceans that measure temperatures, observe phytoplankton blooms, and photograph penguin and whale populations to data gathered from sampling schools of krill and underwater acoustic technologies that identify animal populations.

“Taking samples costs a lot of money, and you have to get them back to where they came from. So we have to be strategic about what we measure, how we measure, and how often,” Melbourne-Thomas says. “We’re a bit slower with biological models, partly because, unlike in physical systems, there’s no set of underlying rules you can put in your models as equations that don’t change. Models for physical systems are based on an underlying set of basic equations — unfortunately we don’t really have these (yet!) for biology.”

The key, Melbourne-Thomas says, is to build several models that all utilize different aspects of the data collected and then compare them to each other. “Each model will have its own idiosyncrasies, biases, and things it does particularly well on its own. When you combine models, you get a more reliable picture.”

The Antarctic Belongs to Everyone

Modeling, research, and data gathering aside, Melbourne-Thomas says education and outreach are essential elements to protecting the polar oceans. If you’re interested in helping scientists better understand how these systems work — and preserving them — there are several active NGOs that work directly with managing marine environments. “Marine and polar NGOs are very vocal and play an important role in influencing change and supporting research.” Melbourne-Thomas says.

Additionally, Melbourne-Thomas is the co-founder of the Homeward Bound project, which brings international teams of women with science and leadership backgrounds to Antarctica every year. The program’s goal is to inform these women on how to use their knowledge and leadership skills to drive change in climate policy around the world.

“Being educated is an important element [in protecting the planet],” Melbourne-Thomas says. “We need to make good information easily available to people. If you know what the issues are, you’re more likely to speak up. If enough people speak up, we’re more likely to see change.”

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