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Alaska's Changing Environment
Documenting Alaska's physical and biological changes through observations
Alaska has recently experienced profound environmental change related to extreme weather events and deviations from the historical climate. Sustained warmth, sea ice loss, coastal flooding, river flooding, and major ecosystem changes have impacted the daily lives of Alaskans around the state.
Temperatures have been consistently warmer than at any time in the past century. This warming varies greatly across the state, with northern and western regions warming at twice the rate of southeastern Alaska. The growing season has increased substantially in most areas, and the snow cover season has shortened.
Precipitation overall has increased, and like temperature, the changes vary regionally. The ocean around Alaska is now regularly warmer than at any time in the past 150 years, affecting everything from algae to fisheries and human health.
Coastal flooding during the autumn storm season has occurred on the Bering Sea coast throughout history, but recent winters have brought record low ice, which in the past has served as a buffer to big Bering Sea storms. This has resulted in out-of-season flooding occurring in places expecting stable sea ice.
We have compiled observations through August 2019 about the major changes currently affecting Alaska's physical and biological systems. We focus on the past five years, though we also provide information from earlier decades for historical context. This effort is by no means comprehensive, but serves to highlight the monumental shifts occurring in our state.
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Many factors in Alaska's environment are specific to certain times of year: ice break-up of Alaska’s big rivers is a sure sign of spring; wildfires are a summer issue, and the season is lengthening; costly coastal flooding along the Bering and Chukchi Seas has historically been an autumn concern.
While powerful storms impacting maritime operations near the Aleutians and Gulf of Alaska can occur any time of year, the strongest storms nearly always happen in the fall and winter months. Many of these seasonal events have experienced profound changes in recent years.
Big fire seasons more frequent
Warmer springs and earlier snow melt had lengthened the wildfire season to the point in 2006 when Alaska’s interagency fire management organization changed the “start date” for wildfire response from May 1 to April 1. While the year-to-year variability of acreage burned has changed little, the frequency of large wildfire seasons has increased dramatically. Wildfire seasons with more than one million acres (red bars in graph) burned have increased by 50% since 1990, compared to the 1950–1989 period.
Dramatically more smoky days
As the frequency of big (1+ million acres) wildfire seasons has increased, so has the frequency of smoky days, posing a significant health hazard. Prior to 2004, Fairbanks had only one summer (1957) in the previous half century when there were more than three weeks of significant smoke. Since 2004, it has occurred five times, including twice since 2014.
Storminess not increasing
Storminess, related to the frequency, duration, and intensity of wind, is one of the most important aspects of day-to-day weather for Alaskans. In and around Alaska there has been a slight overall decline in autumn (September–November) storminess over the past 40 years. Winter (December–February) storminess has shown no clear trend since 1990. There has also been no detectable trend in the number of moderate and strong storms during the past 70 years over the Bering and Chukchi Seas, where sea ice has retreated. However, even without an increase in storms, coastal flooding and erosion in these waters are increasing as the sea ice-free open water season lengthens.
River break-up happening earlier
Alaskans have closely watched spring river ice break-up for millennia, and for generations have monitored the timing of the break-up of the Tanana River at Nenana. Break-up has trended earlier, especially in recent years. Four of the past six years have seen break-up earlier than all but one year prior to 1990. The earliest break-up in the history of the Nenana Ice Classic, by six days, was in 2019.