Imagine having your own personal atlas, with just the maps you're interested in, maps you can change any time you want to look at the world from a different perspective. Texas A&M oceanographer Tom Whitworth is designing just such a customized atlas for the Southern Ocean, the seas ringing Antarctica.
"My colleague Alex Orsi and I are half done with our four year atlas project, comparing data for the ocean south of 30 degrees latitude gathered by the World Ocean Circulation Experiment (WOCE) with data gathered over the last 75 years," said Whitworth, a research scientist with Texas A&M's Department of Oceanography.
Whitworth and Orsi will combine all the "good" information into computer databases for a cyber atlas of the Southern Ocean. Internet users will be able to access the data and select information relevant to their interests; software will then generate customized maps.
"Scientists subjectively assess data quality every time they make a new map," Whitworth said. "But this time we want to establish a standard, made possible by technological advances in measurement and the global coverage of the WOCE program. We can decide once and for all which data points to keep and which to ignore."
WOCE, an international scientific initiative whose U.S. component is headquartered at Texas A&M, has spent the last 10 years collecting data to help establish a global ocean baseline for the study and modeling of the oceans' decadal variability. Where once all measurement was done with analog instruments read by humans - thermometers, for instance - many readings are now taken electronically. All the WOCE data readings have made using the same techniques and with the same precision. However, there are large areas where no data was collected by WOCE, so Whitworth and Orsi will have to rely on historical observations to fill in those gaps.
"Scientists still measure the same ocean characteristics - temperature and salinity, for example - but advances in technology yield a consistent database," Whitworth said. "In addition, WOCE has collected data on things we've only recently begun to measure, such as CFC's (freons), which is a pollutant in the atmosphere but which, once in the sea, can be used as a tracer by oceanographers.
"CFC's can be introduced to water at the surface in the North Atlantic, and then sink and flow southward, eventually ending up at a depth of 2000 meters near Antarctica," he observed. "Water with CFC's which sank in the Arctic is just now crossing the equator in the Atlantic."
Seawater characteristics are determined by atmospheric conditions at the sea surface but also by biological and chemical conditions there. When seawater sinks, the signals imparted at the surface remain detectable for great distances despite the mixing and stirring that occurs in deep water.
"When we sample the composition of deeper water, we can tell where it came from and guess how long it took to get to where we obtained the sample," Whitworth said. "For example, we're sampling water in the mid-Pacific from 2000 to 3000 meters down that probably sank over 1000 years ago."
Because the surface water around Antarctica is cold and very dense, it sinks and spreads throughout the world's oceans. Thus, the Southern Ocean is the source of much deep and bottom water through the world, although it takes many decades for water from the south polar regions to reach the North Atlantic.
"You can easily see how if we influence the world's climate today, the effects could linger for hundreds of years," Whitworth said. "The ocean has a memory."
Contact Judith M. White, 979-862-2694, jw@univrel.tamu.edu; Tom Whitworth, 979-845-5872, twhitworth@tamu.edu.