Ice Breakup in Three Alaskan Rivers

2023-03-23

Table of contents

Communities Connecting: Ice Breakup in Three Alaskan Rivers
Key Points
Background
About the Data
- Notes
- Data Sources

Ice Breakup

Ice breakup is when ice cover, found on rivers, lakes, and seas, breaks up and melts in the spring or summer.

This process is a natural occurrence that occurs yearly as the weather warms and the sun shines for extended periods. Ice breakup is an important event for many ecosystems, as it can affect the availability of food and habitat for animals.

It can also significantly impact human activities, such as transportation and agriculture. In some areas, ice breakup is also accompanied by flooding, as the melting ice releases water that was previously trapped under the ice.

Communities Connecting: Ice Breakup in Three Alaskan Rivers

This feature examines spring river ice breakup in three communities that have kept detailed records for more than 100 years.

Figure 1. Ice Breakup Dates for Three Alaskan Rivers, 1896–2022

This figure shows annual ice melt dates at three locations: the town of Nenana on the Tanana River, Dawson City on the Yukon River, and Bethel on the Kuskokwim River. Annual data for each river have been plotted with a nine-year moving average.

Year	Yukon River	Tanana River	Kuskokwim River
1896	134
1897	134
1898	133.6667
1899	133.5556
1900	132.8889
1901	131.7778
1902	131.1111
1903	130.7778
1904	129.7778
1905	130.1111
1906	129.7778
1907	129.3333
1908	129
1909	129.6667
1910	129.6667
1911	128.7778
1912	128.6667
1913	129.4444
1914	129.4444
1915	129.4444
1916	130.7778
1917	131	127.4
1918	131	127.9111
1919	131	128.0889
1920	131.6667	128.6
1921	132.2222	128.5556
1922	130.8889	128.1111
1923	131.1111	128.3333
1924	131	128.7778	131.4
1925	129.6667	128	131.6889
1926	129.4444	127.6667	132.3111
1927	129.1111	127.4444	132.7111
1928	128.3333	126.6667	132.8889
1929	128.3333	126.2222	131.5
1930	127.5556	125.4444	129.125
1931	129	127.5556	131.375
1932	128.2222	126.2222	133.25
1933	128.2222	126.7778	134.25
1934	128.7778	126.8889	132.875
1935	129	125.8889	132.2857
1936	127.6667	123.7778	129.4286
1937	127.3333	123.8889	128.4286
1938	127	123	128.875
1939	127	122.7778	130.375
1940	125.8889	121.6667	130.25
1941	127	123.3333	130.875
1942	126.8889	122.5556	131.5
1943	126.5556	122.2222	133.25
1944	126.6667	123.8889	133.8889
1945	128.2222	126.4444	137.2222
1946	129.3333	126.7778	138.5556
1947	129.5556	126.7778	138
1948	130.7778	128.4444	139.4444
1949	130.6667	127.7778	138.6667
1950	130.2222	126.6667	137
1951	130.6667	127.1111	136.3333
1952	130.5556	127	136.1111
1953	130.1111	126	134.7778
1954	129.1111	124.3333	133.2222
1955	129.6667	124.5556	133.5556
1956	129.3333	124.8889	134.8889
1957	128.8889	124	131.7778
1958	130.1111	125.4444	134.2222
1959	129.3333	125.3333	134.7778
1960	131.1111	126.6667	136.4444
1961	132.2222	127.2222	136.625
1962	132.4444	127.5556	139.75
1963	133.3333	128.1111	139.125
1964	132.7778	128.2222	138.375
1965	132.7778	127.6667	136.75
1966	133	127.5556	138.125
1967	132.5556	127.1111	137.625
1968	133.3333	127.7778	139.125
1969	131	125.8889	136.625
1970	130.1111	125.7778	135.5556
1971	129.8889	126	134
1972	129.2222	125.8889	135.4444
1973	128.8889	125.5556	136.3333
1974	129	125.7778	136.6667
1975	128	125.3333	135.7778
1976	127.4444	124.4444	134.1111
1977	127	123.2222	132.3333
1978	127.5556	123.8889	132.7778
1979	126.5556	123.1111	133.2222
1980	126.5556	123.1111	132.7778
1981	127.6667	124	133.4444
1982	128.2222	124.2222	132.4444
1983	128.5556	124.7778	133.4444
1984	128.5556	124.5556	134.3333
1985	127.6667	124.6667	134.5556
1986	126.7778	124	134.3333
1987	125.3333	123	133.2222
1988	126.2222	124.7778	134.7778
1989	125.1111	122.8889	133.4444
1990	123.4444	121.5556	131.4444
1991	122.1111	120.2222	130.5556
1992	122	120.3333	129.6667
1993	122.2222	120.5556	128.5556
1994	122.7778	119.3333	128
1995	123.6667	119.8889	129.3333
1996	124.3333	120	129.6667
1997	124.2222	119.2222	128.6667
1998	125.6667	120.7778	130
1999	126.3333	120.7778	129.4444
2000	126.8889	120.6667	129.1111
2001	125.8889	119.7778	129
2002	126.6667	120	131.3333
2003	126.6667	120.7778	131
2004	126.3333	121.6667	130.5556
2005	126	121.5556	130.3333
2006	125.1111	120.5556	130.4444
2007	124.5556	120.2222	130.1111
2008	124	119.6667	131.6667
2009	125.1111	122.4444	134.5556
2010	125.4444	122.1111	133.7778
2011	124.6667	121.2222	131.6667
2012	123.5556	120.8889	130.3333
2013	123.3333	120.2222	129.4444
2014	123.8889	120.2222	128.6667
2015	123.1111	118.5556	124.7778
2016	122.7778	117.8889	124
2017	123.2222	118.5556	122.8889
2018	122.3333	116.5556	120.2222
2019	122.5111	116.7778	119.9778
2020	122.4667	117.1111	119.5111
2021	123.5333	117.4444	120.4889
2022	123.6	117	119.8

Figure 1. Ice Breakup Dates for Three Alaskan Rivers, 1896-2022
Data source: Nenana Ice Classic, 2022; Yukon River Breakup, 2022; Kuskokwim Ice Classic, 2022; National Weather Service, 2022.
Web update: July 2022
Units: Days from January 1

Key Points

The Tanana, Yukon, and Kuskokwim rivers show a long-term trend of melting ice earlier in the spring. The ice break dates for all three rivers shifted eight to nine days earlier than their respective record periods.
The earliest recorded breakup date occurred within the past four years at all three locations.
Although the general trend is to disintegrate earlier, the most recent river split dates are within historical variability.

Background

Areas in the extreme north, such as Alaska, are warming faster than other parts of the world, and this trend is expected to continue. The Tanana, Yukon, and Kuskokwim rivers in Alaska provide an especially remarkable record of a northern climate.

For more than a century, locals have recorded the day the ice in these rivers begins to move or melt each spring. Some towns hold annual competitions to guess when the ice will melt.

Since 1917, the Nenana Ice Classic on the Tanana River in central Alaska has paid out several million dollars in winnings to those who came closest to correctly guessing the date and time the glaciers will melt.

Similar traditions exist in Dawson City on the Yukon River, just across the Canadian border, where the date of parting is recorded since 1896, as well as in the Kuskokwim River in Bethel, where the date of departure is documented since 1924.

However, breaking the ice on the river was more than just a friendly competition. The thaw is a critical transition time for the communities that rely on these relatively remote and free-flowing wild rivers for transportation, hunting, and fishing for subsistence and other needs other demand.

In addition, early thaw can lead to severe ice migration, congestion, infrastructure damage, and devastating flooding.

The data collected by these communities clearly shows how the dates of river thaws in Nenana, Dawson City, and Bethel have changed over time. The towns all use the same method to measure the date and time when the ice melts in the river.

Residents place tripods on the ice in the middle of the river. This tripod is attached by cable to the meter on the shore.

When the ice under the tripod breaks or starts to move, the tripod moves, pulling the thread, and the clock stops.

About the Data

Notes

Besides climate change, annual natural variations and other factors, such as local land use and development patterns, can influence ice break dates. The three main sites here are relatively remote and undeveloped, so melting dates are more likely to reflect natural changes in weather and climate conditions.

However, corresponding measurements of water conditions and air temperature help understand the link between changes in river thaw and climate changes.

A recent comparison with satellite measurements of ground freeze/thaw conditions shows a strong correlation between regional temperature conditions and the actual Tanana River rupture date.

Data Sources

The ice-breaking dates of the Tanana River at Nenana, the Yukon River at Dawson City, and the Kuskokwim River at Bethel were recorded and widely publicized as part of three lengthy community competitions: the Nenana Ice Classics, Yukon River Ice Break, and Kuskokwim Ice Classic.