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NSF Press Release


Embargoed until 2 P.M., EDT
NSF PR 00-56 - September 7, 2000

Media contacts:

 Cheryl Dybas, NSF

 (703) 292-8070


 Brian Mattmiller,
 University of Wisconsin-

 (608) 262-9772

Program contact:

 Scott Collins, NSF

 (703) 292-8481

This material is available primarily for archival purposes. Telephone numbers or other contact information may be out of date; please see current contact information at media contacts.

Tale of the Ice, Revealed
Records of lake, river, ice across globe reveal major warming trend

Scientists funded by the National Science Foundation (NSF) have amassed lake and river ice records spanning the Northern Hemisphere that show a steady 150-year warming trend. The records come from sources as diverse as newspaper archives, transportation ledgers and religious observances.

The study, which includes 39 records of either freeze dates or breakup dates from 1846 to 1995, represents one of the largest and longest records of observable climate data ever assembled. University of Wisconsin-Madison limnologist John Magnuson led a team of 13 co-authors who contributed to the report, published in the September 8 issue of the journal Science.

"This research is important because it humanizes the impacts of global environmental change by using a simple measurement that is relevant and meaningful to the public," says Scott Collins, director of NSF's long-term ecological research program, which funded the work.

All but one of the 39 ice records, which come from sites ranging from Canada, Europe, Russia and Japan, indicate a consistent warming pattern. The average rate of change over the 150-year period was 8.7 days later for freeze dates, and 9.8 days earlier for breakup dates. A smaller collection of records going well past 150 years also shows a warming trend, but at a slower rate.

The findings also correspond to an increase in air temperature over the past 150 years of plus-1.8 degrees Celsius. A temperature change of 0.2C typically translates to a one-day change in ice-on and ice-off dates. Freeze dates were defined in the study as the observed period the lake or river was completely ice covered; the breakup date was defined as the last ice breakup observed before the summer open-water phase.

The records in this study are the longest and most intact of 746 overall records collected through the project. Some individual records are of astonishing lengths, with one dating back to the 9th century. Another is from the 15th century, and two more date to the early 1700s. For example, Lake Suwa in Japan has a record dating back to 1443 that was kept by holy people of the Shinto religion. The religion had shrines on either side of the lake. Ice cover was recorded because of the belief that ice allowed deities on either side of the lake -- one male, one female -- to get together.

Lake Constance, a large lake on the border of Germany and Switzerland, has a peculiar record dating back to the 9th century, also for religious regions. Two churches, one in either country, had a tradition of carrying a Madonna figure across the lake to the alternate church, each year the lake froze. Two other long-running records come from Canada's Red and McKenzie Rivers, which date back to the early 1700s and were kept because ice cover and open water were critical to the fur trade. Records from Grand Traverse Bay and Toronto Harbor, both on the shores of the Great Lakes, reflect their prominence as shipping ports.

Another finding in the study, based on 184 ice records from 1950 to 1995, showed that variability in freeze and breakup dates increased in the last three decades. Magnuson says that may be related to intensification of global climate drivers such as the El Nino/La Nina effects in the Pacific Ocean. The ecological effects of global warming are only beginning to be studied. But research has already been done that shows ranges of some butterflies and birds extending northward.




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