Erin Pettit explores glaciers to better understand and predict changing climate and rising seas. She is an assistant professor of geophysics and glaciology at the University of Alaska Fairbanks and creator of Girls on Ice, a wilderness science experience for high school girls.
Erin Pettit has conversations with glaciers. Mainly, she listens. As she translates their language, she'll tell the rest of us what they're saying about sea level rise, climate change, and how critical processes like ocean circulation may be transformed.
Pettit came up with the idea of using underwater listening instruments to record the noisy boundary of ice and sea. "Acoustic research has already contributed much of what we know about the ocean," she observes. "But no one had applied the technique to studying glaciers."
Glaciologists love to examine the ice-ocean boundary because its dynamic nature may reveal what triggers glacial change-warmer water, the atmosphere above, or as yet unknown forces. It's also a very dangerous place. Scientists have long looked for ways to safely make measurements amid disintegrating ice shelves and iceberg-jammed waters. Pettit's carefully placed hydrophones in Alaska and the Antarctic Peninsula could be one ingenious way.
Glaciers meet oceans in an explosion of sound. Calving ice slams into waves, water gushes out from below, and air bubbles pop as icebergs melt upon impact with sea. "This symphony comes from different sources within the glacier," says Pettit. "I'm dissecting our recordings to figure out what's generating flute sounds versus deep tuba notes versus midrange trumpets, so we can infer glacial changes from the sounds themselves. I'm especially interested in freshwater rushing out from underneath the glacier, because it directly contributes to sea level rise and signals major changes caused by ice-ocean-air interaction. The more water that spews out, the faster the glacier slides. These huge flushes of freshwater could alter circulation in a bay, then a gulf, and even further out."
Other fieldwork finds Pettit camped in a tent on an ice sheet in minus 20° weather. She discovers how ice sheets have grown and shrunk over hundreds of thousands of years by examining ice core samples that have been drilled and removed-yielding virtual frozen history books of our planet's year-by-year environment and climate.
"We know the last time Earth was this warm, about 130,000 years ago, sea level was six meters higher. That's a lot," she says.
The dynamic west Antarctica site Pettit studies would have been a major source of that high water in the past and could contribute to a rise that size again, faster than anyplace else. The impact on islands and coastlines globally could be huge.
"The core sample from this site will give us a more detailed look than ever before at the last ice age's coldest periods and how we emerged into our current modern climate," she explains. "That understanding can help us know where to focus efforts to mitigate problems today and in the near future."
Ice core layers are like tree rings, yet provide even richer details from long ago. Cores have exposed everything from snow that fell 800,000 years ago to carbon from car exhaust, painting a picture of not only polar regions but also tropical climes. As each annual snowfall compresses and turns to ice, snow captures impurities blown in by the wind. Analysis reveals yearly color differences between winter and summer snow, how much fell, dark layers caused by volcanic activity or global forest fires, specific carbon dioxide and nitrogen levels in the atmosphere, even radioactive isotopes from atomic bomb detonations.
Who will follow in Pettit's snowy boot prints? Perhaps one of the girls who participates in the free wilderness science program she created, Girls on Ice. Each summer, high school girls enter glacial landscapes, where they perform experiments exploring everything from how ice worms move or crevasses form to how fast meltwater flows or alpine vegetation grows-developing wilderness savvy and confidence as they scramble over rocks, hike off trails, cross streams, and rope up to traverse glaciers. Participants range from the scientifically passionate to the disinterested, from the outdoorsy to the fearful, yet all seem to emerge inspired and emboldened by their new physical and critical thinking skills gained on the ice.
"I think it's important for all of us, kids and adults, to push outside our comfort zone," Pettit says. "That's how you discover the most interesting things about yourself, other people, and the world around you. Curiosity and risk-taking drive many of the best scientific breakthroughs. You may feel scared, be questioned, or get cold before you learn how to keep warm, but the more you push yourself, the more discoveries you will make throughout life."