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The retreat of glaciers in the American West is dramatic. But the changes happening at the North and South poles are even more alarming.

Christina Hulbe, assistant professor of geology at Portland State, says the highest rate of warming on the planet is happening on the Antarctic Peninsula, nearly a thousand miles south of the tip of South America. In March 2002, a chunk of ice about the size of Rhode Island broke off the Larsen Ice Shelf following one of the warmest summers on record.

The shelf, approximately 12,000 years old, had survived many fluctuations in the Earth’s climate. Hulbe and colleagues from University of Maryland and the National Snow and Ice Data Center in Boulder, Colorado, concluded that summer melt-water had filled pre-existing crevasses. Because water is more dense than the ice around it, it caused those crevasses to propagate downward through the full thickness of the ice, shattering the entire shelf.

The melt-water was created over years of warmer-than-usual summers; the mean annual temperature in Antarctica has been rising steadily since the late 1940s.

Hulbe uses computer models to study this phenomenon, and in 2002 was awarded a grant from the National Science Foundation that, along with an ongoing grant from NASA, will support her efforts to see whether such massive breakup events could take place on the larger ice shelves farther south on the continent.

“These ice shelves—the floating extensions of mountain glaciers—are catastrophically disintegrating,” she says.

At the other end of the planet, Hulbe is studying Heinrich events: the depositing of debris onto the ocean floor from floating icebergs. Scientists have found this debris as far south as Portugal, and Hulbe is studying what this sediment record might tell us about cooling and warming periods throughout history.

“It allows us to connect present day observations to events tens of thousands of years ago,” she says.

The projects Hulbe works on are mostly done from the comfort of the PSU campus, where she receives numerical data from thousands of miles away. When she visits glaciers these days, it’s on summer hikes in the Cascades. Hulbe loves being in the mountains, a carry-over from her childhood when she lived in tent camps for weeks at a time in Northern California with her geologist father.

Hulbe is quick to point out that there are hundreds of variables that account for changes in the Antarctic landscape, and a lot of them have nothing to do with global warming. In fact, science has shown that some parts of Antarctica have actually gotten a little cooler in recent decades, although within a normal range if you look at the big picture, she says. But the catastrophic events such as on the Larsen Ice Shelf are definitely climate-related.

Why is the ice in Antarctica important? It could be a sign of things to come. Hulbe says breakups of old ice shelves could trigger runaway erosion of the ice sheets they’re connected to. If all the ice in Western Antarctica were to slide into the ocean, sea levels worldwide would rise as much as five meters. By contrast, if all the world’s mountain glaciers melted, sea levels would rise only about half a meter, she says.