|[Muir Glacier, located in Glacier Bay, Alaska photographed in Aug. 1941 (left), Sep. 1976 (middle), and Aug. 2004 (right). You can actually see how the glacier has retreated over time and the way vegetation has replaced the rocky landscape.]|
A glacier is the result of compacted snow that has remained overtime. The snow eventually hardens into thick sheets of ice and slowly the glacier begins to grow larger. It usually takes between 4-10 years for compressed snow to turn into glacial ice. As snow falls annually, glaciers will thicken and spread over large distances. What is most interesting about glacial ice is that it actually moves much like a river. As snow falls on the highest point of a glacier, the weight pressing down onto the glacier itself increases. Due to the weight of all that compacted ice, glaciers begin to move at a very slow pace. This can be along valleys, mountains, fields, and even sometimes to the sea. Whether a glacier advances or retreats has to do with the climate and how much snow is accumulating or ablating (melting).
There are many different types of glaciers ranging from the ice sheets (continental masses of glacial ice) of Antarctica and Greenland to the ice caps (miniature ice sheets) of Iceland. There are also ice shelves which are glacial ice that has extended over the sea and ice streams which flow down channels. Alaska is home to ice fields, mountain glaciers, valley glaciers, piedmont glaciers, cirque glaciers, hanging glaciers, and tidewater glaciers. Check out more on the different types of glaciers here!
Glaciers not only offer interesting viewing opportunities, but actually make up 75% of the world’s freshwater, providing drinking water for communities when the glacial ice melts. Scientists have begun to test the use of glaciers for both irrigating crops and generating hydroelectric power. While not usually a threat, glaciers can result in both flooding and avalanches. Even more dangerous is the iceberg, which is really just a piece of an ice shelf that has broken off into the ocean. We all remember the titanic.
Repeat photography, like the pictures above, is a great way to document glacier change over time. We were fortunate enough to meet with Geologist Ron Karpilo, who has recently been repeating photos taken in Denali National Park by Stephen R. Capps in the early 20th century. Karpilo also photographed many of the glaciers in Glacier Bay. His photos showed an astounding decrease in the terminus of the glaciers signifying the apparent warming that has begun to affect the Earth's climate.
Glaciers also offer scientists a valuable record for studying climate change. Taking cores from deep inside glaciers has allowed scientists to accurately estimate both the age of glaciers and the reality that Earth has experienced numerous ice ages. “Since the beginning of the twentieth century, glaciers worldwide have been retreating slowly” (NSIDC). Many glaciers are said to have been retreating for the past 200 years. This is believed to be the result of an increase in carbon dioxide and greenhouse gasses being released into the atmosphere causing it to thicken. Thus the thicker atmosphere does not allow as much heat to escape Earth and creates a warming effect. To know how you can help go to savethearctic.org.
With the majority of Earth’s glaciers slowly melting away, it is up to humanity to try and solve the problems necessary to preserve these natural beauties. Most of these glaciers have been around for thousands of years, and play an important role in regulating the climate and stability of the Earth. “If all land ice melted, sea level would rise approximately…230 feet worldwide” (NSIDC). It is imperative that these places remain intact, not only for the sake of the wildlife that inhabit them, but for our sake as well.
-- Web-log written by Stephen St. Michael
For more information:
National Snow & Ice Data Center
Glaciers in Alaska
Worthington Glacier State Recreation Site
National Park Service - Kenai Fjords/ Exit Glacier
Exit Glacier and Harding Icefield