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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 External Non-U.S.
government site.
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 External Non-U.S.
government site. 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. (For more about Lonnie
Thompson's research, see related story: Science goes to
new heights.)
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 External Non-U.S.
government site, 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 External Non-U.S. government
site, Ted Scambos at the National Snow and Ice Data Center
in Boulder, Colo. External Non-U.S. government site, and
Maria Vernet with Scripps Institution of Oceanography
External Non-U.S. government site, 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.”
Project along peninsula will take ice core to bedrock
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. (See related story: Winter
no relief.)
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.”
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