Climate Change Indicators in the United States: Community Connection: Ice Breakup in
Two Alaskan Rivers - www.epa.gov/climate-indicators - Updated August 2016
Community Connection: Ice Breakup in Two Alaskan Rivers
Regions in the far north are warming more quickly than other parts of the world, and this pattern is
expected to continue1,2 (see the Arctic Sea Ice indicator; for more information about regional
temperature changes, see the U.S. and Global Temperature indicator). The Tanana and Yukon rivers in
Alaska provide a particularly noteworthy record of northern climate because, for a century or more,
local citizens have recorded the date when the ice on these rivers starts to move or break up each
spring. In fact, some towns have annual competitions to guess when ice breakup will occur.
Since 1917, the Nenana Ice Classic competition on the Tanana River in central Alaska has paid several
million dollars in winnings to the people who come closest to guessing the exact date and time of day
when the river ice will break up. A similar tradition exists in Dawson City on the Yukon River, just across
the border in Canada, where breakup dates have been recorded since 1896.
(River ice breakup is more than just a friendly
competition, though. Ice breakup is an
important time of transition for communities
that rely on these relatively remote and free-
severe ice movement, jamming, damage to
infrastructure, and destructive floods.3
The data collected by these communities
highlights how the river ice breakup dates in
Nenana and Dawson City have changed over
time. Both towns use the same method to
measure the exact time of river ice breakup.
Residents place a tripod on the ice in the center of the river. This tripod is attached by a cable to a clock
on the shore. When the ice under the tripod breaks or starts to move, the tripod moves, pulling the
cable and stopping the clock.
Key Points
• The Tanana and Yukon rivers both demonstrate long-term trends toward earlier ice breakup in
the spring. The ice breakup dates for both the Tanana and Yukon rivers have shifted earlier by
approximately seven days over their respective periods of record.
• The 2016 breakup date recorded at Dawson City was the earliest on record.
• Despite the overall trend toward earlier breakup, recent breakup dates for both rivers are
largely within the range of historical variation.
flowing wild rivers for transportation,
subsistence hunting and fishing, and other
needs. In addition, early thawing can lead to
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Climate Change Indicators in the United States: Community Connection: Ice Breakup in
Two Alaskan Rivers - www.epa.gov/climate-indicators - Updated August 2016
Figure 1. Ice Breakup Dates for Two Alaskan Rivers, 1896-2016
April 1
April 16
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Climate Change Indicators in the United States: Community Connection: Ice Breakup in
Two Alaskan Rivers - www.epa.gov/climate-indicators - Updated August 2016
ice breakup dates for these two rivers are also archived by the National Snow and Ice Data Center at:
http://nsidc.org/data/lake river ice.
1 Melillo, J.M., T.C. Richmond, and G.W. Yohe (eds.). 2014. Climate change impacts in the United States: The third
National Climate Assessment. U.S. Global Change Research Program, http://nca2014.globalchange.gov.
2 IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis.
Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge
University Press, www.ipcc.ch/report/ar5/wgl.
3 Beltaos, S., and B.C. Burrell. 2003. Climatic change and river ice breakup. Can. J. Civil Eng. 30:145-155.
4 Nenana Ice Classic. 2016. Accessed May 2016. www.nenanaakiceclassic.com.
5 Yukon River Breakup. 2016. Accessed May 2016. www.vukonriverbreakup.com.
oEPA
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