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Clarkson University Professor Presents Findings On Sea Ice At Two International Conferences
[A photograph for newspaper use is available at http://www.clarkson.edu/news/photos/knuth.jpg]
Sea ice covers over 10 percent of the earth’s surface. Dr. Shen’s research investigates pancake ice which occurs in many polar and sub polar areas in both the Northern and Southern hemispheres. Pancake ice covers have been estimated at six million square kilometers in the Southern Ocean alone. In turbulent seas the first ice to form are tiny discs. As the discs accumulate they form a suspension known as grease ice. In quiet conditions these ice shapes become a sheet of thin ice. In wave dominated seas, waves and wind compress ice particles into large plates called pancake ice. These plates can then raft and form large, dense pancake ice. Different types of waves create different sizes of pancake ice.
Dr. Shen explains that changes in sea ice affect the polar seas and create feedbacks to the climate. With the presence of ice, global climate is affected because the water drastically reduces interaction with the atmosphere. Heat, humidity and wind transfer essentially stop with the pack ice cover. As saltwater freezes, the salt in the water becomes too dense and sinks to the sea floor taking with it oxygen, carbon dioxide, and organic material. These changes affect the Antarctic Circumpolar Current which affects global ocean circulation, climate changes, rainfall and temperature.
Sea ice exploration in both the Artic and Antarctic has changed a great deal over the last 20 years from how research is done to how the knowledge acquired is represented. “Since pancake ice formation is very wave dependent it is hard to find a particular wave occurring at a particular time and then get a ship there in time to spot it. Field experiments are very difficult but you have to be in the field to do work relevant to nature,” Dr. Shen said. Today, indoor labs are more accessible and oftentimes more practical. Lab simulation of the formation of pancake ice involves working in -20 C or -4 F, similar to a cold February night in the artic sea, in a swimming pool sized pond. Ice tank air temperature and water temperature can be easily monitored and controlled and experiments can be repeated. Depending on the type of lab, researchers can look at multiple wave patterns side by side in one day.
A great deal of information has been gained by polar orbiting satellites that take photographs to show the distribution of pack ice. The information can be graphically rendered with computer simulations. Dr. Shen explained, “Before computers, researchers could only study the process and theories and could not do a global interactive study. The technology really developed in the 80’s but the computers were so slow. We had no idea then how things would progress to today and the detail of the graphic models.”
The research presented was funded by a grant from the National Science Foundation (NSF) Office of Polar Programs as part of a project to study the formation of pancake ice with Clarkson University. The funding from NSF was used to pay for equipment, graduate research students, summer salary, and travel.
PHOTO CAPTION: Margaret A. Knuth, second year master’s student in the Department of Civil and Environmental Engineering, uses a transducer to measure wave action in a wave tank located in the William J. Rowley Science and Engineering Laboratories at Clarkson University. Knuth does research with Hayley H. Shen, professor of Civil and Environmental Engineering and associate director of Clarkson University’s Honors Program. Shen recently presented research on the freeze-up of sea water into pancake ice fields at the 20th International Symposium on Okhotsk Sea and Sea Ice in Mombetsu-City, Hokkaido, Japan.