Alaska’s Disappearing Glaciers: A Century of Change
Historical Documentation of Glacial Retreat
Bruce Molnia, a geologist with the U.S. Geological Survey, has spent decades collecting and studying historical photographs of Alaskan glaciers. These images provide a unique glimpse into the dramatic changes that have occurred over the past century due to global warming.
Molnia’s before-and-after photographs offer compelling evidence of the melting glaciers in Glacier Bay National Park, Denali and Kenai Fjords National Parks, and the Chugach National Forest. By revisiting the exact locations where the original photographs were taken, Molnia has captured the stark contrast between the once-towering ice giants and the receding glaciers of today.
Impacts of Global Warming on Alaskan Glaciers
Over the past 75 to 100 years, average annual temperatures in Alaska have risen by about 5 degrees Fahrenheit, leading to a significant retreat of glaciers. Of the glaciers studied by Molnia, only 1 to 2 percent have grown, likely due to increased snowfall at higher elevations. The vast majority are visibly shrinking, with some losing up to 20 miles in length over the past 95 years.
This glacial melting has severe consequences for Alaska’s environment and infrastructure. A 2003 study by the Government Accountability Office found that 86 percent of Alaska’s villages are threatened by flooding and erosion due to melting glaciers and sea ice.
Global Extent of Glacial Melting
The decline of glaciers is not limited to Alaska. Glaciers are shrinking almost everywhere, including in the Arctic National Wildlife Refuge, Antarctica, and atop mountains in China, Peru, and Argentina. Even the iconic icy cap of Mount Kilimanjaro is rapidly melting.
Glaciologist Lonnie Thompson of Ohio State University predicts that Glacier National Park on the Montana-Canada border will lose all of its glaciers within 30 years if the current trend continues.
Natural and Human-Induced Causes of Glacial Melting
While natural variations in the earth’s climate have caused ice ages to come and go, scientists agree that the recent surge in carbon dioxide levels in the atmosphere has significantly accelerated glacial melting. Carbon dioxide traps heat in the atmosphere, leading to the greenhouse effect.
Human activities, such as burning fossil fuels, release large amounts of carbon dioxide into the air. This buildup of greenhouse gases is exacerbating the effects of global warming and driving the rapid melting of glaciers.
The Science of Glacial Melting
Glaciers are formed by the accumulation and compaction of snow over time. The weight of the snow compresses the flakes into ice crystals, which can grow as large as a human head.
When light penetrates the compacted ice, red wavelengths are absorbed, leaving a haunting blue glow. This glacier blue is a unique and mesmerizing sight, best observed at the bottom of crevasses or where glaciers are melting.
The Beauty and Significance of Glaciers
Glaciers are not only awe-inspiring natural wonders but also vital components of the earth’s ecosystem. They provide habitat for wildlife, regulate water flow, and contribute to the planet’s cooling system.
The loss of glaciers due to global warming is a serious threat to the environment and human civilization. It is essential to understand the causes and impacts of glacial melting and to take action to mitigate its devastating consequences.
