[su_dropcap]L[/su_dropcap]ocated in Kenai Fjords National Park, Alaska, Exit Glacier is one of 38 interconnected valley glaciers in the Harding Icefield, the largest ice field contained completely within the United States. In the spring of 1968, the first documented mountaineering party succeeded in crossing the Harding Icefield, and Exit Glacier was given its name for serving as the exit off the ice field during the expedition.
Exit Glacier is one of Harding Icefield’s smaller glaciers, but is one of the most visited because of year-round, easy access by a roadway and hiking trails around and above the glacier. When snow arrives in the area (usually mid-November) until early May each year, the access road is closed to cars but open to a wide range of winter sports and recreation, including snowmobiles, dogsleds, fat-tire bicycles, cross-country skiing and snowshoeing.
According to park research studies and recent enhanced monitoring and mapping, Exit Glacier has retreated about a mile in the past 100 years, and shrinking has escalated during the last few years with 187 feet (57 meters) lost from 2013-14 and another 136 feet (41.5 meters) in 2015.
Filmakers, Raphael Rogers, Kristin Gerhart and Paul Rennick, traveled to Alaska to explore Exit Glacier, but along with stunningly beautiful mountain views and amazing blue ice, they saw melting. Local guide, Rick Brown, explained what they were seeing and what’s been happening at Exit Glacier in this short video documentary, Glacier Exit.
Understanding Valley Glaciers
In order to understand why glaciers are considered a visual indicator of climate change, it helps to understand some basics about glacier formation, movement and their sensitivity to fluctuations in temperature.
Exit Glacier is what is known as a valley glacier (aka alpine glacier) that forms when more snow falls on mountain peaks during a year than melts during the summer, creating a snow pack that builds up and thickens. Over time, the weight of the snow causes the snow pack to compress and turn into ice, and the glacier grows as more and more snow and ice accumulate. Then, the weight of the ice starts to slowly push down the mountain through the valley. This downward movement of the glacier is hardly noticeable to the observer, but it’s a powerful force of nature that erodes the ground beneath it, stripping the valley floor and knocking loose rocks and debris. Along the way down, the glacier becomes a mixture of rock, dirt and ice.
While snow falls in the cold, higher elevation temperatures at the top of the glacier (the ‘accumulation zone’) during valley glacier formation, the ice is continually melting in the warmer area at the bottom of the glacier (the ‘ablation zone’). If the accumulation at the top pushes ice down the valley faster than the ice melts at the bottom, the glacier advances. When ice at the bottom melts faster than ice accumulates and moves down from the top, the glacier recedes.
During a glacier recession, ice and rock continue to flow downhill to the toe of the glacier (the end of the glacier at any given point in time, aka ‘terminus’ or ‘snout’), and the rocks are then continuously deposited on the ground at the front edge of the glacier as the ice melts. During periods of ‘stagnation’, the ice at the front of the glacier melts at essentially the same rate as the ice flows down, resulting in the toe of the glacier staying in one place. Rock and debris, however, continue to be pushed downward to the front edge of the glacier where it is deposited as the ice melts away.
Information/Resources:
Exit Glacier – visitor information. How to get up close to the glacier and explore the area.
The Retreat of Exit Glacier by Susan Huse
Kenai Fjords National Park (Where Mountains, Ice and Ocean Meet) – learn more, plan your visit, get involved
Physical Science in Kenai Fjords, by Virginia Valentine, Keith Echelmeyer, Susan Campbell, Sandra Zirnheld (Alaska Park Science: Volume 3 / Issue 1, 2004)
⇒ Exit Glacier conditions (May 28, 2018 update), an ice fall hazard zone was identified by Kenai Fjords park officials at the toe and sides of Exit Glacier. The condition is dangerous due to tall blocks and slabs of ice, and entry into the ice fall hazard zone is prohibited; however, the road to Exit Glacier and hiking trails remain open.
Located above the Chamonix valley within the Mont Blanc massif mountain range of the French Alps, the valley glacier, Mer de Glace (‘Sea of Ice’), is the largest and longest glacier in France and a popular tourist attraction as it offers spectacular mountain views as well as tours, exhibits, off-piste ski runs, and restaurant/hotel. Unfortunately, it has also been retreating during the last 30 years.
Feature image “Toe of Exit Glacier” is courtesy of the US National Park Service/Paige Calamari, PD. The 2011 photo of the toe of Exit Glacier was taken from the Outwash Plain below. Since that time, warmer temperatures have reduced the glacier mass of Exit Glacier, and it will likely never look like this photo again.
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