Monday, March 23, 2015

Alaska's Glaciers

© Lynn Wegener / Alaska Stock

With thousands of miles of coastline, an abundant amount of lakes, rivers, and mountains, perhaps one of the most unique features of Alaska are the Glaciers. At Alaska Stock Images, you will find a wide variety of Alaska photos including the most pristine and beautiful Alaska Glacier Photos. To find more pictures of Alaska or photos of glaciers and icebergs, visit our search page.
The United States has close to 75,000 square kilometers of Glaciers, and the majority of that ice is located in Alaska. There are an estimated 100,000 glaciers in Alaska but only about 616 are actually named. Glaciers can be as much as 4500 feet in thickness. A good way to estimate the thickness of a glacier is that the ice thickness is about one-half of the surface width of the glacier. The largest glacier in Alaska is the Bering Glacier, located in Glacier Bay, which stretches 122 miles long.

Glaciers form where more snow falls than melts over a period years, compacts to ice, and becomes thick enough to begin to move. Snow becomes a glacier when the bottom layers become so compacted and heavy that they begin to deform, lose traction on the earth’s surface and begin to “slide” or move.
Glacier crevasses and holes are often seen as blue because the red (long wavelengths) of white light is absorbed by ice and the blue (short wavelengths) are transmitted and reflected back to the eye. The longer the path that light is able to travel in the ice, the bluer it appears.

The age of a glacier is often perceived of as being very old…even ancient. However, like the difference between rivers and the water in rivers, it takes a few weeks for water to travel the full length of a river even though the “river” may have been in existence for thousands of years. Likewise, glaciers have existed in the mountains ever since the ice age, but the glacier ice moves through the entire length of the glacier in 100 years or less. So, most of the glacier ice in Alaska is less than 100 years old! Therefore, most of the glacier ice is not ice-age leftovers.

The Hubbard Glacier, found in the Russell Fjord of Glacier Bay, is the largest tidewater glacier on the North American continent. It has been advancing toward the Gulf of Alaska since it was first discovered in 1895. In fact, the Hubbard Glacier has caused concerns for the residents of Yakutat. Due to the advancement of the glacier, there have been short-term blockages of the seaward entrance of Russell Fjord, which created the largest glacier-dammed lake in North America. At the time of blockage, the new “lake” rises in level at a rate of nearly a ½ foot a day! If the Fjord ever becomes permanently blocked, the back up of water from the glacier could have catastrophic results for the people and city of Yakutat, wildlife, and ecosystem of the area.

It is estimated that during any given summer glaciers melt off produces over 50,000 billion gallons of water. The Mendenhall Glacier started retreating in the mid-1700's because its annual rate of melt began to exceed its annual total accumulation. The glacier's terminus currently calves into Mendenhall Lake, where the water is 220 feet deep. The ice is retreating at a rate of 100 to 150 feet a year. While most glaciers are retreating, there are a few that continue to grow. For example, the Taku Glacier is the only advancing glacier of the Juneau Icefield. It has been advancing since 1890 at a rate of a few hundred feet per year. The US government observes and reports on the status of glaciers overall through a series of “benchmark glaciers” as identified by the US Geological Society. The data collected will “improve the quantitative prediction of water resources, glacier-related hazards, and the consequences of climate change.”

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