Science News Online

• Main Author: Sid Perkins
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Antarc*; Antarctica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.548.8731; http://sprint.clivar.org/soes/staff/ejr/Rohling-papers/Science NEWS Online.pdf

The gargantuan volumes of meltwater that boosted sea levels during the most recent round of ice ages derived equally from ice sheets in the Northern and Southern Hemispheres, according to new simulations of ocean currents. Between 65,000 and 35,000 years ago, the planet's climate was much colder and more variable than it is now. For example, global average temperatures warmed significantly at least four times, melting land-based ice sheets and raising sea levels by dozens of meters before cooling set in again, says Mark Siddall, an oceanographer at the University of Bern in Switzerland. Many scientists assumed that most of the meltwater released in the 30,000-year period came from ice sheets in the Northern Hemisphere. During the cold times, ice masses could readily spread across continental land areas, thereby storing water as ice at heights above sea level. That seemed an unlikely scenario for the Southern Hemisphere, where Antarctica is surrounded by ocean. Growing ice sheets on that small land mass would simply flow off the edge of the continent. Siddall and his colleagues used a computer model of ocean currents to analyze various meltwater scenarios during an average, theoretical warming spell in which sea level rose about 30 m over about 1,500 years. According to the model, if all the fresh water came from ice sheets in the Northern Hemisphere, the salt- and