By Sara Cooper
Medill News Service, Dec. 18, 2024
In the span of minutes, a cliff of ice has fractured on Antarctica’s western coast, expelling a monolith into the sea. An iceberg was just born, and many more will follow into the South Atlantic Ocean waters.
At the University of Michigan in Ann Arbor, this scene plays out in parallel within the numerical simulations of physicist Samuel Kachuck.
This fracture event, called iceberg calving, is part of the Antarctic ice sheet’s routine maintenance. Snowfall builds up the ice and icebergs trim it down. Under stable climate conditions, this process keeps the ice sheet at equilibrium. As temperatures rise, however, the thousands of icebergs that chip away from its coast each year carry away more and more of the Antarctica’s ice.
Kachuck wants to understand the physics behind this behavior. Using computer models, he reenacts calving scenarios to determine how an ice shelf can pivot from stability to collapse.
“I think about simulations as being narrative devices,” said Kachuck at the annual Comer Climate Conference in southwestern Wisconsin this fall. “It’s just another way of telling the story of our experiences.”
The story he’s currently working on: the future of Antarctica.
By studying ice sheet dynamics Kachuck is trying to understand how Antarctica is evolving with the warming climate. With accurate models of this behavior Kachuck hopes to predict how much and how fast ice will be shed from the continent.
This is urgent work as a shrinking Antarctica heralds some of the most extreme consequences of climate change. If all the ice on the continent were to melt the global average sea level would rise an astounding 57 meters, or 187 feet.
In Kachuck’s words, this outcome is currently not a “serious proposal.” The United Nations Intergovernmental Panel on Climate Change gauges global sea level rise somewhere between 30 centimeters (1 foot) to 1 meter (3.28 feet) by 2100, while some scenarios go as high as 1.8 meters (5.9 feet) based on continued high carbon dioxide emissions from burning fossil fuels. To Kachuck, however, those estimates miss the point.
“I don’t like the global average sea level number,” he said. “It’s a fine shorthand, but that number is going to be different for every locality depending on their circumstances.”
Instead, he advocates for scientific communications that emphasize the impact in local arenas. Invoking the wisdom of folk singer and activist Pete Seeger, he urges the need to “think globally, sing locally.” Islands and coastal lands near sea level would be inundated, for instance.
For Kachuck’s part, he hopes his simulations will help draw the battlefield lines of sea level rise that each community faces. To succeed, his work takes trial, error and lots of data.
“The biggest uncertainties arise from our models,” said noted geologist and climate activist Richard Alley. “The imperative to improve our models, to get more data and test these ideas, has never been higher.”
According to the data we do have, the Antarctic ice sheet may be in a precarious position, scientists contend.
Yuxin Zhou, a paleoclimatologist at UC Santa Barbara, believes this may be the case. His research indicates that during the last interglacial period, when temperatures were just 1 degree Celsius warmer than the pre-industrial era, the Antarctic ice sheet may have been much smaller than previously thought.
According to the European Union’s Copernicus Climate Change Service, the average global temperature for 2024 will exceed 1.5 degrees Celsius of warming compared to pre-industrial times.
“Even during a time that’s not that hot, Antarctica might be very sensitive to a small amount of warmth,” Zhou said. “Projecting that into the future, a small amount of warming may cause the Antarctic ice sheet to very quickly melt away.”
We have, in fact, already seen this play out.
The Larsen B ice shelf sat on Antarctica’s western peninsula for 10,000 years. This floating mass covered over 1,200 square miles of the Weddell Sea. In the early months of 2002, it almost completely disappeared.
Several unusually warm years thawed the ice on Larsen B’s surface. Meltwater pooled, seeping down and weakening its interior. An invisible scar cut across the ice shelf, and when the damage reached a critical threshold a mass the size of Rhode Island fell into the ocean.
The Larsen B ice sheet fell apart within the span of 4 months in 2002. This event demonstrates how sensitive the Antarctic ice sheet can be to climate disruption. (Photo/NASA)
To an observer, Larsen B collapsed in a flash. In truth, it was an exasperated surrender to years of climate abuse.
For Kachuck, this event illustrates his theory of change. To explain, he again invoked the words of Pete Seeger.
“Seeger used to tell this story of buckets on a seesaw,” Kachuck said. “One of them is filled with rocks and the other is empty. There’s a line of folks carrying sand and they’re filling it up, one person at a time taking a teaspoon to the bucket. All of a sudden one day it goes “zoop!” and everyone looks and says, ‘Gee, how’d it happen so fast?’”
Ice shelves collapse, fires rage, floods overtake communities – while these events can feel sudden, each is built up gradually. To Kachuck, progress will take the same shape.
“It’ll take a lot of us working together to get that bucket to go “zoop” in a positive direction,” he said, “we can’t lose sight of that fact, but working together we can enact real change.”
Illustration of Antarctica at top by Sara Cooper/Medill News Service
