You’ll Never Guess What’s Shielding Antarctica’s Ice from Summer Heat

Sometimes, the tiniest things bring the biggest impacts

As a child, I used to suffer from respiratory viruses a lot. Those brought chest congestion and, with them, pneumonia. Sometimes, they were so severe that I needed hospitalization for weeks, waiting for antibiotics to clear the bacterial infection that followed.

But after a few of these episodes, something else started failing: my digestion. No matter what I ate, I felt terrible pain and gassy, which was hard for a kindergartener.

Panicking, my mother took me to the doctor again, who sent me home with a prescription for “lots of plain yogurt.” My mom didn’t buy it but agreed to give it a few weeks before exploring it further.

To our surprise, my belly issues cleared within a few days. The antibiotic overload had killed my gut bacteria. Without it, my digestion became sluggish. But yogurt, which has multiple beneficial bacteria for our guts, helped me recover.

But why am I telling you this? Isn’t this a story about Antarctic ice? It is, but it’s also a story about how sometimes the tiniest organisms make the most noise. Or, in his and my poor belly case, it brings the most benefits.

The icy waters of the Amundsen Sea in West Antarctica are home to a fascinating dynamic between marine life and melting ice shelves. While most of us associate algae blooms with warmer climates, the Antarctic’s phytoplankton blooms — tiny ocean-dwelling plants — play an important role in regulating heat. But how?

A new study by Dr. Andrew Twelves and colleagues reveals that these blooms might be providing a shield to nearby ice shelves, reducing melting during the critical summer months. Yes, you read that right. Algae are protecting the ice—tiny little algae.

Here’s the thing: as sea ice melts in the spring, patches of open water, called polynyas, form. These regions become fertile ground for phytoplankton blooms, turning the water a striking green. But as beautiful as this sight is, these tiny organisms are doing more than just adding a splash of color to the Southern Ocean.

The research team used advanced computer models to understand how phytoplankton affect heat distribution in the Amundsen Sea and its surrounding ice shelves, such as the Pine Island Glacier and the Getz Ice Shelf.

But how did they do it? You know I like explaining the methods too.

By coupling two sophisticated models — the MITgcm, which simulates ocean circulation, and BLING, which handles biogeochemical processes — the researchers dug into the interaction between these blooms and the ocean’s heat balance.

Their aim was to find out how chlorophyll, the pigment in phytoplankton that gives plants their green color, influences the way sunlight is absorbed and scattered in the ocean. Then, they set up two scenarios in their models: one with high levels of chlorophyll during the phytoplankton blooms and another without any chlorophyll. The results were fascinating!

In the scenario where phytoplankton blooms were present, heat from the sun was trapped near the ocean’s surface. But here’s where things get interesting. Instead of transferring this heat to the ice shelves, the ocean released it into the atmosphere over the summer.

This means that the deeper waters stayed cooler, and the amount of heat reaching the base of the ice shelves was reduced. According to Dr. Twelves, the presence of these blooms led to a 7% reduction in ice shelf melting. To put it simply, without the phytoplankton, those ice shelves would be melting faster.

As Dr. Saima May Sidik reported, the phytoplankton’s role in the ecosystem is complex. “Phytoplankton trap heat in the upper level of seawater,” she explained, but this heat doesn’t build up indefinitely. “This heat dissipates back into the atmosphere over the course of the summer.”

The deeper water, which plays a critical role in melting ice shelves from below, remains cooler because of the shading effect of the phytoplankton. This cooling limits the amount of sunlight reaching the water near the ice shelves, effectively slowing down the melting process.

One of the most interesting facts from this research is that the phytoplankton’s protective effect is a double-edged sword. While they slow the melting, they also rely on iron, which comes from melting ice shelves, to grow.

So, if they slow melting too much, they may reduce the iron supply they need for future blooms. It’s a self-regulating system that shows how intertwined biological and physical processes are in this fragile environment.

As Dr. Sidik put it, “Sediments released from melting ice provide iron that supports microbial growth; phytoplankton may stunt their own proliferation when they slow ice shelf melting.”

So, what does this mean for the future of Antarctica’s ice shelves?

Well, the interaction between marine life and melting ice highlights an essential feedback loop. The more ice melts, the more iron is released, supporting more phytoplankton growth, which in turn helps slow the melting — at least to a point.

But with climate change pushing temperatures higher and reducing sea ice cover, the ocean is likely to become more exposed to sunlight. This increased exposure could shift the balance, affecting both marine ecosystems and ice stability.

Another takeaway from the study is the importance of looking at biological processes when studying climate change. For years, scientists focused mainly on the physical dynamics of ice melt — rising ocean temperatures, changes in sea currents, and the role of warmer water from the deep reaching the ice shelves.

But now, we’re seeing that the biological side of things — tiny organisms like phytoplankton — also have a significant impact. Their ability to trap and release heat affects everything from sea surface temperatures to the melting of extensive ice shelves.

Looking ahead, the research team points out that more attention should be given to the relationship between phytoplankton blooms and ocean heat.

As Dr. Saima May Sidik emphasized, “As Antarctic waters lose their sea ice cover, larger areas of the sea surface will be exposed to sunlight. Microbes and other particles can influence how this sunlight affects the ocean, and they deserve additional attention in future studies.”

The balance between phytoplankton and the melting ice shelves of the Amundsen Sea shows just how interconnected life and climate are in this part of the world—and probably everywhere else, too.

It reminds us that even the smallest organisms can have a mighty impact on the biggest of environments. The takeaway is clear: these blooms are not just pretty patches of green on a cold ocean — they’re playing a key role in shaping the future of Antarctica’s ice shelves.