Glaciers as “global thermometers” show the fast pace of melting in a warming world

By Madhurita Goswami
Medill Reports

Glaciers across the globe behave in a synchronized manner, said geologist Thomas Lowell at the recent Comer Climate Conference, an annual national conference held in southwestern Wisconsin. Not only does he study glaciers around the world to reach this conclusion but also compared data obtained by separate dating techniques.

Sounding the alarm, as we warm temperatures the glaciers retreat faster, he said. This, in turn, would change the sea levels in coming years by a greater extent than people imagine now, Lowell added.

The results show that incoming solar radiation, which varies seasonally in the two hemispheres, is not the major factor affecting climate change and has implications for identifying other factors.
“I have looked at glaciers from central-northern Greenland to Antarctica,” said Lowell, a professor of geology at the University of Cincinnati. “They were universally behaving in the same way during the last glacial maximum. They were out, bounced around a little bit and receded at the same time.”

 

Thomas Lowell gives his presentation on comparing data from glaciers around the world (Abigail Foerstner)

The maximum reach of the ice age, or glacial maximum, left its mark on the Earth’s landforms some 18,000 years ago.

Glaciers are “global thermometers” which track temperatures and can be used for reconstruction of our past climate. However, they don’t leave a continuous record. “We get different pieces from different places and try to match them. They might not match because there are some missing pieces,” Lowell said. There is, however, substantial correlation in the data that he is trying to quantify.

The pattern of glacial movement also shows how sensitive they are. Lowell said, “The zigs are around a thousand years apart. It shows, in my opinion, that a temperature pattern was superimposed on the glaciers. It was generally cold but there were warmer and colder times.”

Of the two techniques used to obtain glacial data, radiocarbon dating is the traditional one. It requires accumulation of organic material around the periphery of a retreating glacier. Scientists study the decay of carbon-14 in this organic matter. The other dating technique relies on moraines, a chain of boulders tossed behind by retreating glaciers.

When particles produced by galactic cosmic rays strike the rock surface, beryllium-10, a radioactive isotope of beryllium, is produced. Scientists can analyze beryllium-10 decay to find out when it was generated, which corresponds with moraines losing their ice cover.

“Each technique has its advantages and limitations. Lowell’s emphasis on observing both the chronologies and finding a correlation between them is a more compelling reconstruction of what happened in the past,” said Jerry McManus, a climate scientist and professor at the Lamont-Doherty Earth Observatory of Columbia University.

“In cases where organic matter is available, it is relatively easier to take measurements and more data can be quickly produced. However, the amount of carbon-14 in the earth’s atmosphere changes over time and it is a bit of a moving target,” he said. On the other hand, many glacial sites don’t have moraines and so beryllium-10 dating is not an option there.

Photo at top: Huge icebergs are breaking off the Greenland glaciers. (Gary Comer/Comer Family Foundation)