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Updated: Jul 2, 2026

Continuous Hydrologic and Water Quality Monitoring of Vernal Ponds
Published on: November 13, 2017
Historical trends in lake and river ice cover in the northern hemisphere
1Center for Limnology, University of Wisconsin-Madison, Madison, WI 53706, USA. U.S. Geological Survey, Water Resources Division, 8505 Research Way, Middleton, WI 53562, USA. Department of Forestry, Virginia Polytechnic Institute and State Unive.
Abstract:
Freeze and breakup dates of ice on lakes and rivers provide consistent evidence of later freezing and earlier breakup around the Northern Hemisphere from 1846 to 1995. Over these 150 years, changes in freeze dates averaged 5.8 days per 100 years later, and changes in breakup dates averaged 6.5 days per 100 years earlier; these translate to increasing air temperatures of about 1.2 degrees C per 100 years. Interannual variability in both freeze and breakup dates has increased since 1950. A few longer time series reveal reduced ice cover (a warming trend) beginning as early as the 16th century, with increasing rates of change after about 1850.
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