Meteorologists have gotten better at predicting this week's weather. But as this ScienCentral News video reports, a worldwide system of ocean floats is on its way to helping scientists forecast potentially devastating events like floods or droughts months or even years in advance.
More sunlight hits the equator than the poles, making the atmosphere and oceans warmer in the tropics. Ocean currents move a lot of that heat to other parts of the world, where it warms the atmosphere and affects the weather.
"Nature doesn't like heat all in one place, so it tries to move it around, and the way it moves it around is our storms, is the wind that we see, and also the ocean currents," explains Breck Owens, a senior scientist at Woods Hole Oceanographic Institution.
In the past, scientists had no good means of globally measuring the oceans' role in the Earth's climate. Now, in an international effort called the Argo project, scientists are well on the way to establishing a worldwide network of ocean robots to help them do that. The first Argo float was dropped in the ocean in 2000. Now, there are over one thousand of the planned three thousand floats in the water. "It really will pepper the entire ocean with measurements from pole to pole and in all the different ocean basins," says Owens.
The probes are already giving scientists information they need to forecast the climate months or even years from now. "Basically, right now, they're measuring three things: the temperature and salinity profile, and from where they went down and where they came up, we actually get the average velocity over that time frame," explains Owens.
Each float has a hydraulic system that controls the amount of oil in a bladder at the bottom of the float. When the bladder is empty, the float sinks; when it is full, the float rises. Typically, the floats work on a ten-day cycle. Each float sinks to its target depth, which is about 1,000 meters. It drifts for ten days, and then sinks again to 1,500 or 2,000 meters (over one mile deep). Once it's down to its deepest depth, it rises, measuring temperature and salinity as it goes. When it reaches the surface, it radios its data and position by satellite back to shore, and then repeats the cycle over again.
|image: Scripps Institution of Oceanography|
"Internationally, there are over 20 countries that are actually involved in making floats and in deploying floats," says Owens, "and it's also funded by a number of different agencies. Then within the U.S., there are three research universities: Scripps [Institution of Oceanography], Woods Hole [Oceanographic Institution] and [the] University of Washington making floats." There are also some National Oceanographic and Atmospheric Administration (NOAA) laboratories that are helping in terms of analyzing and processing the data.
Owens says it's easy to put the floats in the Northern hemisphere. "We throw them off these volunteer ships, container ships." But he says it's a different situation in the Southern oceans. "In the southern ocean and particularly the South Pacific, it's much more difficult. And we're looking over the next years or so into ways of doing that—probably leasing a Russian or New Zealand ship and having it basically spend a year steaming around the South Pacific trying to launch floats—basically, one a day for the next year. That's one of the challenges in the Argo program, is in order to get this distribution, how do we get floats in remote places? We're working to have them to be deployed out of airplanes, from volunteer ships—any way we can think of to try to get them into these different places," says Owens. Regardless of the method of deployment, the goal is to have one float in roughly every 200 by 400 nautical mile area of the ocean.
Argo has counterparts that measure atmospheric conditions and some can measure the surface of the ocean, but they cannot measure within the ocean. "With the ocean, it's basically opaque," says Owens, "so things like satellite measurements can measure the height of the ocean, which allows us to estimate currents; it can measure the temperature, but really just the skin temperature, so what Argo does is it allows us to look into the ocean."
Scientists expect to use information from the floats to help them identify ocean phenomena like El Niño and La Niña that affect climate in large areas of the world in very predictable ways."The more we study these atmospheric phenomena that are coupled to the ocean, the more we realize they're global in nature, rather than just regional phenomena," says Robert Molinari, senior oceanographer at NOAA's Atlantic Oceanographic and Meteorological Laboratory. "So with Argo we'll get a global look at the ocean, and we'll be able to use that information and couple that with what we're finding out about the atmosphere to start trying to do predictions on these longer timescales."
"One of the unique things about Argo is it's actually data that's available to everyone, so as we collect it, it gets put basically on a network that's comparable to the internet and distributed in real time to centers all around the world," explains Owens. "It's actually available within a day or so of having been taken, which is actually a fundamental difference in the way we do science compared to the past. It used to be, if you were a scientist, you went out and made a measurement and that data belonged to you for a number of months or years in order to get first crack at analyzing it."
Scientists hope to have all 3,000 floats deployed by 2006. Studies using data from Argo were recently presented at the first Argo Science Workshop. The Argo project is co-sponsored by the World Climate Research Programme's Climate Variability and Predictability Project (CLIVAR) and the Global Ocean Data Assimilation Experiment (GODAE).