Glaciologist Looks To Ice For Clues About Global Warming

Glaciologists extract ice cores, analyze them and determine changes in climate over time.
Glaciologists extract ice cores, analyze them and determine changes in climate over time.

Once or twice a year Keith Mountain, chair of the Department of Geography and Geosciences at the University of Louisville, and colleagues from the Byrd Polar Research Center at Ohio State University spend months hunting for a disappearing treasure: ice.

They travel to a glacier in the mountains of Bolivia, Peru, China, Antarctica or Tanzania. The conditions can be brutal at elevations as high as 20,000 feet, but what they find might help save the planet.

Glacier ice contains thousands of years of the Earth’s climate history. It also provides clues as to how and why global warming is happening today, Mountain said.

The researchers use a portable drilling system to extract from the glaciers cylindrical ice cores about 13 centimeters in diameter and hundreds of meters long. They cut each core into 1-meter segments, then mark and pack it for later analyses.

Like the rings of trees, these ice cores are time capsules which can span tens of thousands of years.

Through mathematical models and other methods, including preliminary test drillings, the team can determine the amount of ice compression and come up with reliable ways to interpret these ice cores, he explained.

“We can reconstruct atmospheric temperatures and ascertain precipitation rates and how much dust there was in the atmosphere,” Mountain said. “We can find out the chemical composition of the atmosphere. You can pick up things like various nitrates-sea salt, for example-and figure out wind directions and the sources of moisture and how those may have changed over time.”

The team has determined from interpreting the ice records over time that, “yes, climate change is global and real,” he said.

Rising temperatures worldwide and local decreases in precipitation are contributing to the decline of the glaciers — which makes their work a race against time.

“When I started out in this field in the late ’70s I never would have thought that the photographs we took of this big ice sheet in southern Peru would become archival records of something lost,” Mountain said. “We photograph the changes there every year now, and the changes are occurring quickly. It’s retreating on the order of 50 meters a year.”

Ice is retreating not only in Peru, but worldwide. The famed white cap of Mt. Kilimanjaro in Tanzania soon will be no more. At its current rate of melting, he said, it will disappear by about 2015.

Glaciologists are just one scientific sector contributing to the mass of evidence on the reality of global climate change, Mountain said, noting that 95 percent of the scientific community believes that global climate change is happening and that humans are a significant causal factor.

Yet somehow, he said, a 95 to 5 percent ratio becomes a yes-no, either-or vote: “Some are trying to turn this into a debate, but there is no debate.”

In his native Australia where years of drought have led to bush fires and dying cattle, global warming is a real issue, Mountain said. That’s also true in other parts of the world.

“For the people in Peru, as the glaciers melt they are losing their irrigation water for farming. In Tibet, as the glaciers recede streams are evaporating and leaving big salt deposits that make the remaining water undrinkable,” he said.

The jury is no longer out on global warming, Mountain said.

“At some point, the jury has to come back and make a decision. What kind of policies are we going to develop to deal with this?”

Glaciers and Ice Caps to Dominate Sea Level Rise Through 21st Century

When a glacier with its “toe in the water” thins, a larger fraction of its weight is supported by water and it slides faster and calves more ice into the ocean at the glacier terminus. – Photo Credit: Nicolle Rager Fuller, National Science Foundation

Ice loss from glaciers and ice caps is expected to cause more global sea rise during this century than the massive Greenland and Antarctic ice sheets, according to a new University of Colorado at Boulder study.

The researcher, primarily funded by the National Science Foundation (NSF) and NASA, concluded that glaciers and ice caps are currently contributing about 60 percent of the world’s ice to the oceans and the rate has been markedly accelerating in the past decade, said Emeritus Professor Mark Meier of CU-Boulder’s Institute of Arctic and Alpine Research, lead study author. The contribution is presently about 100 cubic miles of ice annually — a volume nearly equal to the water in Lake Erie — and is rising by about three cubic miles per year.

In contrast, the CU-Boulder team estimated Greenland is now contributing about 28 percent of the total global sea rise from ice loss and Antarctica is contributing about 12 percent. Greenland is not expected to catch up to glaciers and ice caps in terms of sea level rise contributions until the end of the century, according to the study.

A paper on the subject appears in the July 19 issue of Science Express, the online edition of Science magazine. Co-authors include CU-Boulder INSTAAR researchers Mark Dyurgerov, Ursula Rick, Shad O’Neel, Tad Pfeffer, Robert Anderson and Suzanne Anderson, as well as Russian Academy of Sciences scientist Andrey Glazovsky.

“One reason for this study is the widely held view that the Greenland and Antarctic ice sheets will be the principal causes of sea-level rise,” said Meier, former INSTAAR director and professor in geological sciences. “But we show that it is the glaciers and ice caps, not the two large ice sheets, that will be the big players in sea rise for at least the next few generations.”

The accelerating contribution of glaciers and ice caps is due in part to rapid changes in the flow of tidewater glaciers that discharge icebergs directly into the ocean, said the study. Many tidewater glaciers are undergoing rapid thinning, stretching and retreat, which causes them to speed up and deliver increased amounts of ice into the world’s oceans, said CU-Boulder geology Professor Robert Anderson, study co-author.

Water controls how rapidly glaciers slide along their beds, said Anderson. When a glacier with its “toe in the water” thins, a larger fraction of its weight is supported by water and it slides faster and calves more ice into the ocean at the glacier terminus.

“While this is a dynamic, complex process and does not seem to be a direct result of climate warming, it is likely that climate acts as a trigger to set off this dramatic response,” said Anderson, also an INSTAAR researcher.

The human impact of this accelerated sea level rise could be dramatic. The team estimated accelerating melt of glaciers and ice caps could add from 4 inches to 9.5 inches of additional sea level rise globally by 2100. This does not include the expansion of warming ocean water, which could potentially double those numbers. A one-foot sea-level rise typically causes a shoreline retreat of 100 feet or more. The World Bank estimates that about 100 million people now live within about three feet of sea level.

“At the very least, our projections indicate that future sea-level rise may be larger than anticipated, and that the component due to glaciers and ice caps will continue to be substantial,” wrote the researchers in Science Express.

The team summarized satellite, aircraft and ground-based data from glaciers, ice caps, the Greenland ice sheet, the West Antarctic ice sheet and the East Antarctic ice sheet to calculate present and future rates of ice loss for the study.

Meier estimated there are several hundred thousand small glaciers and small, pancake-shaped ice caps in polar and temperate regions. They range from modest, high mountain glaciers to huge glaciers like the Bering Glacier in Alaska, which measures about 5,000 square miles in area and is nearly one-half mile thick in places.

The researchers used a mathematical “scaling” process to estimate more remote glacier volumes, thicknesses and trends by factoring in data like altitude, climate and geography. They used data gathered from around the world, including cold regions in Russia, Europe, China, Central Asia, Canada and South America.

While warming temperatures will likely cause many small high mountain glaciers in North America Europe to disappear by the end of the century, large ice fields and ice caps will continue to produce large amounts of melt water, Meier said. The scientists also believe many “cold” polar glaciers and ice caps will soon warm up enough to begin melting and contributing to sea rise.

The retreat of the Greenland and Antarctic ice sheets also is giving birth to new, smaller glaciers that are prime candidates for study by scientists. “It is incorrect to assume that the small glaciers will simply go away next century — they will continue to play a key role in the sea level story,” said Anderson.

Anderson also said that although the volume of ice locked up in Greenland is equal to roughly 23 feet in sea rise, only a small fraction is likely to be “pulled out” during the next century, most of it through outlet glaciers.

Many smaller “benchmark” glaciers around the world that have been under study for decades are expected to disappear by the end of the century, said Anderson. “We need to start gathering benchmark information on some of the larger glaciers that are unlikely to disappear, so that we can have a long-term record of their behavior.”

Anderson said outlet glaciers in Greenland behave much like tidewater glaciers in Canada and Alaska, making them very relevant for long-term study. “Since the world is becoming increasingly aware that sea-level rise is a very real problem, we need to acknowledge the role of all of the ice masses and understand the physical mechanisms by which they deliver water to the sea.”