Quarterdeck 3.3

Part 3
Captain Climate
Achim Stössel brings an ocean of experience to Texas A&M

By Rahilla C.A. Shatto

. . .Continued from part 2

Westward, Ho!

By 1994 the Stössel family was ready for another challenge, and that fall Stössel joined the physical oceano-graphy faculty at Texas A&M University. He had grown tired of interacting almost exclusively with computers, and looking around he felt that some of his colleagues developed problems communicating in ordinary language with people outside their field. Stössel did not want this to happen to him.

Marion had put her career on hold three years earlier with the birth of their first child, Ingo. Like Achim, she was raised abroad, primarily in Bogotá, Colombia but also in Pittsburgh, Pennsylvania. After twelve years together in Hamburg the two were ready to go international again.

[207K] Stössel with his wife, Marion, an dtwo children, Ingo (left) and Tinka (right), at their Bryan (Texas) home. (Photo by Donald P. Shatto)

At Texas A&M Stössel continues to refine our understanding of global climate using computer models, and teaches modeling techniques to students in specialized graduate courses such as Computational Fluid Dynamics and Ocean Modeling. He finds that teaching offers the communication challenge he sought, but is surprised that he and his students will often judge the same lecture quite differently. With practice he hopes to identify and consistently reproduce the elements of good teaching in all his classes. Stössel also works for the newly-formed, interdisciplinary Texas Center for Climate Studies, which now offers a seminar series designed to confront scientists and students across disciplines with climate issues.

Although he and Marion miss the lengthy vacations that most German employers offer, they enjoy their new situation in Texas. They recently had a second child, Tinka. Ingo, now four years old, especially prefers the wide open spaces in Bryan/College Station to Hamburg's crowded streets which lack space for playing!

The Earth's poles-where the action is

In keeping with his previous research on sea-ice formation and dynamics, Stössel's current work primarily concerns modeling the role of the Earth's poles in global climate. Although many of us may think of the poles as static regions, largely isolated from mankind's activity, the polar ice caps can be viewed as highly interactive components of our climate and sensitive indicators of global change.

[69K] Graphics generated by a computer model of sea ice formation show how sea-ice coverage and thickness vary from season to season.

Sea ice is an important player in determining climate for two reasons. First, the shining white icecaps reflect most of the sun's short-wave radiation back into space after it enters the atmosphere. If this reflectivity decreases, for example due to human-induced increases in greenhouse gases, more radiation will remain trapped at the Earth's surface. In places where sea ice has melted the air temperature, normally -30° to -40°C, would increase to match the surface temperature of the ocean, a comparatively steamy -2°C. This increase would be large enough to significantly influence the way air circulates in our atmosphere.

Second, when seawater cools and ice forms at the poles, masses of dense, cool water with high salinity are created. When seawater freezes it pushes excess salt out of the resulting ice and into the surrounding water. The salty, dense water may eventually sink to the ocean floor, displacing saltier, albeit warmer water to the surface to take its place. As more ice forms and more dense water sinks, the "bottom water" is forced to flow slowly toward the equator. Long and complicated mixing processes eventually push the water to the surface at lower latitudes. On the surface, the water flows poleward again, simultaneously pulled by the ever-sinking dense water in the regions where bottom water forms and pushed and prodded by other global forces.

Stössel cautions that the role of sea ice on global climate is still not well assessed. In one extreme scenario, any reduction in surface cooling and decline of new ice formation in the critical regions where "bottom water" is formed would mean that no dense water could form there. A lens of fresh water could form on the surface in those regions, such as the northern North Atlantic, enhanced by increased freshwater runoff from glaciers melting in the continually warming atmosphere. No dense water would sink and no warm water would be pulled in to replace it. The North Atlantic Current, a northern branch of the Gulf Stream, might slowly deflect eastward toward the Iberian Peninsula rather than blaze into the northern North Atlantic as it does today. Without the tremendous influx of warm water provided by the Gulf Stream, water and air temperatures in the northern North Atlantic would decrease dramatically and cause cold, inclement weather throughout Europe.

Continued . . .

URL=http://oceanography.tamu.edu/Quarterdeck/QD3.3/Shatto/shatto-c.html
Updated January 8, 1996