Mosley-Thompson helped pioneer ice core research in polar regions
Posted July 11, 2008
It’s strangely dusty in the polar regions, if you know where to look. For more than three decades, Ellen Mosley-Thompson has followed the dusty trail through ice cores taken from Antarctica and Greenland, learning much about the past climate of the planet — and possibly something of its future.
She and her colleague, Lonnie Thompson, are among the world’s leading experts on dust in ice cores, pioneering the field in the 1970s while still graduate students at The Ohio State University in Columbus, Ohio.
At the time, such research focused on deep cores with climate histories of tens of thousands of years, according to Mosley-Thompson. No one really thought that dust could be a key narrator in the climate story, particularly in the most recent epoch, the Holocene, which began about 11,500 years ago.
Why dust? When snow forms, it crystallizes around tiny, atmospheric particles, which fall to the ground with the snow. The type and amount of trapped particles, such as dust or volcanic ash, tell scientists about the climate and environmental conditions when the snow formed. They can chemically analyze the dust to find out where it came from, so that the amount and location of the particulate reveal information about wind patterns and strength at the time the particles fell with the snow.
The Thompsons, using ice cores from Greenland and Antarctica, demonstrated that elevated dust found in ice sheets was a key indicator of glacial stage ice versus interglacial stage ice, because the former is quite dusty while the latter much cleaner.
A glacial period involves colder temperatures and advancing glaciers, while interglacials, such as the current Holocene, are periods of warmer temperatures and less ice. During an ice age, the climate alternates between glacial and interglacial stages as Earth’s ice cover advances and recedes.
“That was the early focus of our work. That was really our first contribution,” said Mosley-Thompson, who hasn’t lost her West Virginia accent all these years later as she discusses her career and future projects. “That dust has to come from somewhere. ... That dust isn’t coming from Antarctica; it’s coming from other places.”
For her PhD at OSU, Mosley-Thompson interpreted the physical and chemical characteristics of a 100-meter-long ice core drilled at the South Pole in 1974 where the iconic dome now sits, though operations have moved to a new building. Analyzing the dust content and comparing oxygen isotope ratios, she reconstructed a 900-year record that revealed increased dust deposition — meaning a colder glacial period — during the so-called “Little Ice Age” period from about 1450 to about 1880.
Then, integrating the South Pole data with more recent ice cores from Siple Station in West Antarctica, the Dyer Plateau in the Antarctic Peninsula and from Plateau Remote in East Antarctica, Mosley-Thompson found that an inverse relationship exists climatologically between different parts of the continent.
Essentially, the cores told her and colleagues that when atmospheric conditions were cold and dusty over East Antarctica, the Antarctic Peninsula was warmer. Scientists are still studying that relationship, especially considering the rapid warming under way in the peninsula area.
“This is a pattern that we find existed pre-anthropogenically,” Mosley-Thompson said, meaning before human-induced activities began warming up the planet. “It’s what you expect from a meteorological perspective.”
Today, the Thompsons lead the ice core paleoclimate team at OSU’s Byrd Polar Research Center. Thompson mostly tackles mountainous areas in the tropics and subtropics to collect ice cores, while Mosley-Thompson usually spends her time swinging between the polar regions for her research.
Mosley-Thompson’s interests continue to be on atmospheric dust and volcanic ash, but have expanded to included atmospheric chemical composition, and evidence for past, abrupt environmental changes — and their possible effects on human civilization. At age 60, she shows no signs of slowing down, with two field expeditions planned for next year: one to Greenland and the second to the Antarctic Peninsula for the first science cruise of her career.
The latter project is called LARISSA, for LARsen Ice Shelf System Antarctica, which will bring together some of the premiere polar researchers of the day, including Mosley-Thompson, Eugene Domack with Hamilton College in New York, Ted Scambos at the National Snow and Ice Data Center in Boulder, Colo., and Maria Vernet with Scripps Institution of Oceanography, among others.
“The thing that’s really exciting is that it’s real interdisciplinary,” Mosley-Thompson said of the collaborative project. “The idea is we’re going to bring all of our knowledge and tools to bear on the Antarctic Peninsula.”
The peninsula, most polar scientists will tell you, is warming more rapidly than just about anywhere else on the planet. The total increase in mean annual air temperatures is about 2.8 degrees in the last 50 years, while mean winter temperatures have risen even more — 6.5 degrees Celsius during that same time.
The Larsen Ice Shelf is a long ice shelf in the northwest tip of the Antarctic Peninsula on the Weddell Sea side. The Larsen is actually — more accurately, was — a series of three shelves. The Larsen A disintegrated in 1995 and the Larsen B fell away in 2002 in spectacular fashion. The Larsen C, the largest of the trio, is still holding on.
“Since then, the glaciers that were buttressed by this shelf are now discharging ice four, five, six, seven, eight times faster to the ocean,” Mosley-Thompson explained. “The concern is that they contribute to sea level rise.”
In fact, ice loss in Antarctica increased by 75 percent in the last 10 years, as glaciers sped up, and is now nearly as great as that observed in Greenland, according to a study by NASA and university scientists released earlier this year.
LARISSA seeks to get a “big picture” view of the Larsen area using a variety of tools, including GPS to learn more about the ice dynamics, and drilling ice cores to study the climate history. Mosley-Thompson said the cryosphere team hopes to drill at least one ice core down to bedrock, about 500 meters.
Sediment cores previously drilled in the area by Domack and his colleagues show that the Larsen B had been in place for at least 10,000 years, according to Mosley-Thompson. “If that’s true, then it’s very likely that ice shelf was in place for a much longer time.”
That means there’s a possibility of drilling into glacial stage ice, before the beginning of the Holocene, which would represent one of the oldest ice core records from the Antarctica Peninsula, according to Mosley-Thompson.
“Because ice layers thin rapidly near the glacier bed and the ice where we plan to drill is about 500 meters thick, the team will be thrilled to extract a history reaching back about 25,000 years — although a longer record is always possible,” she said. In comparison, ice cores in East Antarctica, where the ice is nearly 4 kilometers thick, the longest record goes back much further in time, about 800,000 years.
The snow accumulation rate should be high enough that the team will get what’s called annual resolution in the upper sections of the core, which allows them to tease out details about climate year to year.
Think of it a bit like a digital camera: A high-resolution image provides much greater detail in each pixel, allowing you to enlarge the picture. A low-resolution shot loses detail and begins to blur as the photo expands in size.
The data the researchers collect will add to our understanding of climate change, particularly in a rapidly changing area, with the Larsen B the poster child of abrupt environmental collapse. The Wilkins Ice Shelf, a much younger ice shelf on the other side of the Antarctic Peninsula, began to break up late in the austral summer, and European scientists reported in June that it’s continuing to collapse, despite the onset of winter.
Many scientists expect ice in West Antarctica and Greenland to continue to recede significantly in the next century if temperatures continue to rise, with more collapses like that of the Larsen and Wilkins ice shelves.
Mosley-Thompson said she often lectures about the changes under way on the planet, connecting ice core science with how a warming world transforms both human systems and ecosystems, resulting in more extreme weather events, such as alternating droughts and floods, which destroys arable land and reduces water supplies.
“The impacts will be variable — there will be winners and losers — probably more losers than winners though. Some areas will likely experience high prices for food and energy while other areas may experience widespread devastation, producing a generation of environmental refugees,” she said.
“All of that is tied to climate change.”
NSF-funded research in this story: Ellen Mosley-Thompson, The Ohio State University.
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