Out of thin air

The history of the Earth's climate and atmosphere is one of the longest untold stories, a great puzzle in the overall picture of the planet's evolution. And Michael Bender, a University geosciences professor, has been working to put many of those puzzle pieces — past, present and future — into place.

When natural phenomena go unrecorded, it can be said that they vanish into thin air. And air is exactly where Bender is looking to find much of his information.

Every few days Bender receives a special delivery — packaged bottles of air from various locations around the world. These samples are sent, either weekly or biweekly, from 10 different sites, such as Antarctica, Tasmania, Samoa, the Indian Ocean, Alaska, Newfoundland and a ship that travels between Los Angeles and Australia, collecting samples intermittently.

"We measure the concentration of oxygen in that air," Bender said. From this measurement, he explained that he can learn how much carbon dioxide is being added to the atmosphere, how much is absorbed by trees on land and how much is absorbed by the ocean.

Plants take in carbon dioxide and give out oxygen in a process called photosynthesis and can convert carbon dioxide to organic material by reducing the gas to carbohydrates. Light provides the energy for the process. Electrons for this reaction ultimately come from water, which is then converted to oxygen and protons.

And by studying the amount of oxygen in the air, Bender is able to understand the broader picture of the planet's history.

Air, however, is only the beginning. Bender also collects similar forms of data from ice cores and ocean water around the globe.

"We learn different things from each of the different media," Bender explained.

The primary information extracted from the ice Bender collects is the concentration of oxygen isotopes.

In its natural form, oxygen is a molecule that always contains eight protons — or positively charged particles — at its center, the nucleus. Most oxygen will also have eight neutrons — particles with no charge — in the nucleus as well. This variety is called oxygen 16, which is named for the total number of protons and neutrons that the atom contains.

Some oxygen, however, may have either nine or 10 neutrons in its nucleus, making it oxygen 17 or oxygen 18, respectively. Isotopes refer to the atoms that have a varying number of neutrons in the nucleus. The different isotopes behave in different ways, and by determining the concentrations of each atom, Bender is able to determine the origin of the air, as well as understand the processes and reactions that the air has experienced.

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While most oxygen atoms have eight protons and eight neutrons, there is a small amount of oxygen 17 and oxygen 18 in air. According to Bender, these concentrations "give information about processes in biology and climate."

Because the relative composition of isotopes supposedly changes simultaneously across the Earth, the measurements in one area can be compared to those taken in another. By using samples from places where ice dates back the furthest — such as Greenland and Antarctica — and using the different depths of the ice there, Bender is able to determine what isotope level coincides with which ice cores in other places.

These findings ultimately help in fitting together the pieces of the overall geological puzzle.

By looking at the timing changes between Greenland and Antarctica for the last Ice Age — a cycle that should have lasted about 100,000 years — Bender can determine the cause of certain climate changes and see where and how they originated.

Bender also looks for the concentration of isotopes in the ocean water and the surrounding air. The different types of oxygen in the air and water represent oxygen from different places around the world.

Looking at this information, Bender can see whether the air is part of the lower atmosphere or part of the stratosphere. Air that originated in the stratosphere is consumed during photosynthesis and replaced with normal oxygen.

Compiling this information helps to determine the rate at which biological processes occur — which, in turn, sheds light on the total amount of food in the ocean and, consequently, the uptake of dissolved carbon dioxide.

Aside from its vast informative capabilities, Bender's data and his conclusions have an even greater significance. When combined with other types of data, "it has predictive capabilities in a couple of ways," he noted.

For example, Bender and his colleagues can use this information to predict the rates of carbon dioxide production, as well as the amount taken in by ocean waters and plants.

The mathematical models that calculate these estimations are developed using past data, he explained. The models are able to estimate the rates of production and absorption of the carbon dioxide. They are then tested using the current data, and pushed into the future to predict data ahead of time.

The main focus of Bender's research, he said, is to collect data that offers a better understanding of how the biosphere — the life-containing part of the atmosphere and the Earth's surface — and climate interact.

Specifically, Bender said he hopes to gain a better knowledge of the ocean and how it works as a physical, chemical and biological system. He also wants to learn what influences how fertile the land is and how climate and the biosphere affect each another.

Some of Bender's findings have recently been published in Scientific American and the Annual Reviews of Energy and Environmental Science.

Bender said he enjoys his work for several reasons. "I love the process of doing measurements in a laboratory," he said.

As an undergraduate, Bender studied at Carnegie Mellon University in Pittsburgh, Pa., which, at the time, was called the Carnegie Institute of Technology. After his junior year, he worked in geochemistry at Columbia University, and, upon graduating in 1965, studied at the Weizmann Institute in Israel. In 1970, Bender completed his doctorate work in geology at Columbia University.

Bender emphasized the importance of others who work in his field as well.

"This research just has value as part of what a lot of other people are doing," he said. "If people stop doing that, our work has a lot less value."

Laboratory technician Bruce Barnett and postdoctoral fellow Thomas Brunier work with Bender on the ice core project. Bob Mika is the lab technician for the oxygen measurements project and works with postdoctoral fellow Melissa Hendricks, who also helps to measure the photosynthetic rates in ocean water.

Much of Bender's work has been in collaboration with professor Ralph Keeling of the University of California. As a graduate student at Harvard University, Keeing created the first instrument to measure the concentration of oxygen in the air. The concentration is measured by making a ratio of oxygen to nitrogen. Measurements are very specific and require precision at about 3 or 4 parts per million.

Bender is also trying to determine how humans have changed the chemistry of the gases in the atmosphere during the past 100 years. He is performing this research by using gases inside of snow packs — which are often 100 years old — and measuring different gases. He has already proven that there were no freons in the air until the 1930s, when humans began using the chemical coolant for industrial purposes — adding yet another piece to the atmospheric puzzle that Bender is slowly putting together.