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Argo Will Explore Our Climate's Future

Thousands of probes will serve as underwater weather stations

by Ric Getter

PALACE probe
University of Washington researcher Dana Swift with one of the PALACE probes to be used in the Argo Projectr. (Photo: University of Washington)

It's hard enough to predict what tomorrow's weather will be. But, have you ever wondered how scientists can talk about how the climate may change in the next century? The answer is all around us. In fact, it covers about 70% of the Earth's surface.

Scientists are beginning to learn that the temperature, movement (currents) and the saltiness ("salinity") of the great oceans that cover our planet have a very big impact on our climate. Even though we've explored the entire surface of the ocean, what goes on in its dark depths has remained a mystery. But, with a combination of new underwater and space technology, scientists are beginning to learn more about the turbulent, undersea world.

The Argo Project (named after the ship used by the mythical Greek hero, Jason) is an international effort that will be setting 3,000 sensor-equipped floats adrift in the world's oceans. They are designed to submerge up to 2 kilometers (1.25 miles) beneath the surface, riding with the current for ten days, taking measurements of temperature and salinity. Then, they will automatically resurface to report their findings and position to NASA's aptly-named Jason-1 satellite before submerging, once again, to continue their research. The floats will carry enough power to last for about four years and will sink to the ocean's bottom when their batteries are exhausted.

Weather vs. Climate

As you well know, the weather can change from moment to moment. Weather stations and remote sensors all over the world monitor the weather, relaying their data to huge, super-computers that process the information and help meteorologists produce the local forecasts that we're all familiar with. On the other hand, changes in climate span years, decades and centuries. They can be as brief as an El Niño or as long as an Ice Age. According to Prof. Stephen C. Riser, an Oceanographer from the University of Washington who is participating in the Argo Project, the network of sensors will develop into a system to understand and predict changes in climate. "We would like to do the same thing for the ocean so that in the long term you can put the two together and really say what will happen with the climate on scales of five, ten, twenty or a hundred years," he told NetSchools.

Why are the oceans so important for predicting climatic change? For the answer, Professor Riser asks us to imagine a pan on a stove. "Suppose you start off with a pan of air and heat it up. Turn the burner off and what happens? The air inside is going to cool off pretty quickly. Suppose you had a pan of water and heated it up. It's going to cool off a lot slower. That's the difference between the ocean and the atmosphere. The ocean can store a lot of heat and it's going to have the effect of slowing down whatever kind of climate change you might see."

The S-PALACE probe will drift underwater for about a week and then rise to the surface while recording the temperature and salinity of the water. It will then send its data to an orbiting satellite and sink back down. (Graphic: Woods Hole Oceanographic Institute)

A New Branch of Oceanography

Understanding the relationship between the ocean's currents and the climate is a very new branch of oceanography (called "dynamical oceanography"). Henry Stommel (1920-1992), considered by some to be one of the most important oceanographers of all time, had a knack for coming up with original ideas and made some of the most important advances in this new field. He was the first to show how the familiar current known as the Gulf Stream could be explained by forces caused by the Earth's rotation. In the 1940's, he began to understand how the salinity of ocean water could effect the movement and mixing of ocean currents. This is something he discovered by experimenting with buckets of salty water and chopped-up parsnips.

Stommel's work provided the basis for understanding events like El Niño (referred to by oceanographers as the "El Niño Southern Oscillation" or ENSO) and other less well-known occurrences such as the Pacific Decadal Oscillation, North Atlantic Oscillation and the Arctic Oscillation. Their impact on our climate and weather are still a puzzle scientists are trying to solve.

The network of S-PALACE (Salinity Profiling Autonomous Lagrangian Circulation Explorer) sensors used by the Argo project will also help scientists understand the effect that humans have had on the environment. Researchers now generally agree that there is evidence of global warming from the "greenhouse effect" caused, in part, by burning fossil fuels. Prof. Riser believes that these changes can also be monitored and, perhaps, predicted with the data gathered by Argo's sensors.

"People thinking about climate change generally don't take the ocean into account, mainly because it's too hard and there are no good observations," Prof. Riser explained. "What we are doing with Argo is trying to have an observing network in the ocean that is comparable to the one we have in the atmosphere." As Argo's sensors are deployed around the world over the next few years, scientists may be able to understand the inner workings of the oceans well enough to get a look at our planet's climatic future.

Follow That Float!

The data being sent back from the Argo floats is being is being made available in real time via the Web. Professor Riser told us about a number of students who have "adopted" a float and are following its progress and learning about the mysterious ways of deep ocean currents. The data is available on Prof. Riser's web site. Teachers can find out how to use the Argo Project in the classroom at NASA's Jason-1 site. If you or your class starts tracking a float, write to us at letters@netschools.net and we will share your discoveries here.

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