Quarterdeck 3.3

Part 4 (conclusion)
Captain Climate
Achim Stössel brings an ocean of experience to Texas A&M

By Rahilla C.A. Shatto

. . .Continued from part 3

Get higher-forcing from the atmosphere's interior

Stössel points out that despite the fact that characteristics of sea ice are well-documented, it remains difficult to include all the processes associated with them in climate models. He says that people simulating regional or small-scale environmental change "tend to have all kinds of sophisticated sea-ice related features included [in their models], specifically regarding snow on top of the icerealistic ridging characteristics of ice and things like that." But "when you talk about global climate models you want to restrict the physical processes to the most important ones in order to retain a reasonably computable program, and to maintain an overview of the various complex interactions in your model. The biggest challenge is to find the compromise among the models of each climate component, keeping in mind that they will compete with one another for the computer's resources."

The aspects of sea ice which are least understood have to do with its interaction with both the ocean and the atmosphere. Stössel notes that this involves atmospheric and oceanic boundary-layer physics, which must be carefully treated in a good simulation. The traditional method for studying global climate consists of linking an existing model of ocean circulation to one of its atmospheric counterpart. Conditions at the interface between the ocean and the atmosphere, which consist of specified boundary conditions in an uncoupled simulation, form the input for each other in the coupled model. Stössel is quick to point out that this type of model is regarded as the most reliable tool for climate prediction and probably will remain so well into the future. The boundary between the ocean and atmosphere is still manipulated, however, in order to prevent a coupled model from drifting into an unrealistic climate state.

Stössel has applied for funding to surmount this problem. He wants to create a model in which conditions in the interior atmosphere, far from the sea surface, drive a global sea-ice­p;ocean model. This should result in a simulation of both the atmospheric and oceanic boundary layers, and thus a true representation of the atmosphere­p;sea-ice­p;ocean interface. Stössel hopes this kind of configuration will finally avoid predetermination of or correction toward known conditions.

The need for speed

To date, the computer models that scientists use can reflect only the outlines of the complexity of Earth's climate. Even a fairly small model including a limited number of climate variables requires days of computer time on the fastest workstations.

Fortunately, current satellite surveys do not show significant reduction in polar ice coverage due to global warming-yet. It may not be too late to learn as much as possible about the role of sea ice and try to predict how much change the Earth's poles can tolerate before our ice starts to melt.

In the upcoming years, Achim Stössel will dedicate his research to the development of more meaningful climate models using increasingly powerful computers and networks, while he trains new scientists in that endeavor. Stössel would like to make sure that the role of the Earth's polar regions is reflected in climate models accurately enough for the models to lend more credibility to climate change prediction.

URL=http://oceanography.tamu.edu/Quarterdeck/QD3.3/Shatto/shatto-d.html