Alaska's Capital City of Juneau Braces for Record Flooding Amid Climate Change

The city of Juneau is urging residents to evacuate as it prepares for record floodwaters flowing downstream from the Mendenhall Glacier, which is being driven by climate change amid glacial retreat. Summer glacial flooding, known as a glacial lake outburst flood, threatens parts of the city due to a combination of rainwater and snowmelt. Authorities say flooding from the Mendenhall River will probably crest around 4pm Alaska time, or 8pm ET on Wednesday.

Key Takeaways:

• The Mendenhall Glacier is expected to experience a record flood, with water levels anticipated to crest at over 16ft on Wednesday morning, according to the National Weather Service (NWS) in Juneau.
• The flood warning was issued after "a lot of analysis" by local hydrologists, who confirmed that a sub-glacial release had occurred, causing the lake and river to rise significantly.
• Climate change is being blamed for the intensification of the annual Mendenhall glacial lake outburst flood, with Alaska's glaciers being among the fastest-melting glaciers on Earth and having been in steep decline since the late 1980s.
• The retreat of smaller glaciers in the area has created a basin that fills with rainwater and snowmelt each spring and summer, leading to the formation of an ice dam and the subsequent flood.
• The Mendenhall Glacier fills a large valley north of Juneau, creating an ice dam for a meltwater lake that fills Suicide Basin, and has been responsible for the annual Mendenhall glacial lake outburst flood since 2011.
• Alaska has warmed twice as fast as the rest of the US over the last several decades, with an average annual temperature rise of 3.1 degrees Fahrenheit over the last century.
• Rick Thoman, Alaska climate specialist at the Alaska Center for Climate Assessment and Policy, stated that "without climate change, there is no reason to think that this would be happening on the Mendenhall Glacier, then in the lake, and downriver."
• The Mendenhall Glacier has been a popular tourist attraction and has experienced significant erosion and flooding in recent years, with the August 2023 outburst sending record amounts of water into Mendenhall Lake and down Mendenhall River toward Juneau.

Statistics:

• The Mendenhall River is expected to crest at over 16ft on Wednesday morning.
• Alaska's glaciers are among the fastest-melting glaciers on Earth and have been in steep decline since the late 1980s.
• The state of Alaska has warmed twice as fast as the rest of the US over the last several decades.
• The average annual temperature in Alaska has risen 3.1 degrees Fahrenheit over the last century.
• The Mendenhall Glacier recedes at a rate of 100 to 150 feet per year.
• The annual Mendenhall glacial lake outburst flood has been occurring since 2011.

Sources:

• National Weather Service (NWS) in Juneau
• The Juneau Empire
• National Oceanic and Atmospheric Association (Noaa)
• Alaska Climate Science Center
• The Alaska Center for Climate Assessment and Policy
• Climate.gov
• Associated Press