Reining in estimates of sea level rise.An error in satellite measurements of global sea level has inflated recent estimates of how quickly the oceans are swelling, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. scientists. Their revised calculations of 1 to 3 millimeters per year bring the satellite measurements more in line with data compiled over the last half century by coastal stations set up to gauge tides around the world. A U.S. and French satellite called TOPEX/Poseidon tracks the height of the seas with altimeters that emit radar pulses which bounce off the ocean surface and return to the satellite. Launched in 1992, TOPEX/Poseidon was designed to track ocean currents, but the altimeters proved more accurate than planned, and scientists found they could use the satellite data to monitor global sea levels. One of the scientists involved in the satellite mission, R. Steven Nerem of the University of Texas at Austin “University of Texas” redirects here. For other system schools, see University of Texas System. The University of Texas at Austin (often referred to as The University of Texas, UT Austin, UT, or Texas , reported in the Dec. 15, 1995 Journal of Geophysical Research Journal of Geophysical Research is a publication of the American Geophysical Union. JGR was formerly titled Terrestrial Magnetism from its founding by the AGU's president Louis A. that the satellite data show sea levels rising at a rate of 5.8 millimeters per year over the satellite's first 2.5 years. That rate greatly exceeded values suggested by the global network of tide gauges, which showed sea levels rising at an average rate of less than 2 mm per year over a 50-year period. Early this year, the satellite numbers crept even higher, into the range of 8 mm per year. After Nerem and others questioned the accuracy of the data, engineers discovered an error in the software that corrects the clock keeping time on the satellite. NASA engineers have since corrected the problem. "It was very small, almost unnoticeable in all other uses of the TOPEX TOPEX Topography Experiment TOPEX Ocean Topography Experiment TOPEX Typhoon Operational Experiment TOPEX The Ocean Topography Experiment POSEIDON TOPEX Topology Ocean Experiment data," says Nerem. The error showed up in the sea level calculations because these track smaller changes and require more accuracy. Even before the error surfaced, Nerem and his colleagues cautioned that the TOPEX/Poseidon measurements represent only snapshots of sea level changes. With this short period of observations, it is impossible to tell whether the current rise is part of a long-term climate trend or just a minor fluctuation. Scientists expect sea level to be rising, in part because global warming global warming, the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. over the last century has melted mountain glaciers and expanded seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. volume. But researchers say they need at least a decade of satellite measurements to determine how sea level is actually responding to climate change. |
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