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Rivers of Ice

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Deep inside the Tracy Arm, we had the opportunity to witness a tidewater glacier up close. Steep rock walls enveloped us. A cool breeze wafted off the mass of ice and snow. Icebergs drifted lazily in the bay. Countless Harbor Seals lounged on top of those icebergs, nursing their pups. Occasionally a rumble could be heard, and if we looked fast enough, we could see chunks of ice calving from the face of the glacier, revealing a cliff of deep blue. Freshly calved icebergs, with only 10% of their mass exposed above the water, had that same blue glow. Welcome to the South Sawyer Glacier.

In the past two weeks we have paddled past many glaciers, so we figure that it is high time we provide you with some basic information about glaciers, our own observations, and how they are affected by global climate change.6_29_10fjord

What is a glacier?

A glacier is basically a river of compressed snow. Glaciers move very slowly through the landscape, shaping it as they move. Not many people realize that glaciers are actually the Earth's largest freshwater reservoir (according to the World Wildlife Federation). If you were to combine all of the glaciers on Earth, they would cover an area the size of South America.

The climate and topography of Alaska have been favorable for the formation of glaciers for the last 12.5 million years (according to the U.S. Forest Service). The combination of a maritime climate and coastal mountains of Southeast Alaska are prime conditions for glaciation. Moist air from the Pacific Ocean flows toward the mountains, where it rises, cools and releases snow and rain. The Juneau Icefield receives over 100 feet of snow every year. Mild temperatures in the summer mean that the winter snow accumulation is greater than the summer snow-melt at higher elevations.

This snow accumulates year after year. Newer layers of snow weigh down on older layers of snow, compacting it into solid ice. This ice appears blue thanks to its crystal structure. It absorbs all colors of visible light except for blue, which it transmits. Some glacial ice may appear white because it is fractured or contains air pockets; it transmits all colors of the light spectrum.

6_29_10sealicebergs Why are glaciers retreating?

Almost all of the glaciers that have been studied in Alaska are retreating, or shrinking. The melt-water of Alaskan glaciers comprises about half of the water that comes from melting glaciers around the globe. In general, glaciers have been retreating since the end of the Little Ice Age, which happened around 1850. However, historic trends can not explain the increased rate of glacial retreat in recent decades. As the Earth warms up, glaciers will retreat at faster and faster rates. We found out that the Alaskan glaciers have been melting almost twice as fast in the past 5 to 7 years as they had previously. According to the World Wildlife Federation, the Earth is projected to warm up by 1.4 to 5.8 degrees Celsius by the end of the 21st Century. If the Earth warms as much as 4 degrees Celsius, almost all of the Earth's glaciers would melt.

What glaciers did the expedition team see?6_26_10icebergAmy

The Juneau Icefield is home to 38 glaciers, covering a 1,500 square mile expanse of land. We saw just a few of the glaciers that this amazing area has to offer. We have been fortunate enough to see a couple tidewater glaciers, dropping all the way down to the ocean. Many of the glaciers we have seen are hanging glaciers, where the terminus or bottom of the glacier no longer reaches the ocean. Oftentimes we paddled past a large moraine, which is a pile of silt and rock deposited by the glacier.

We passed Le Conte Glacier, just north of Wrangell, watching icebergs drift out of Le Conte Bay. This is North America's southernmost tidewater glacier on the Pacific Coast. Recently, we visited the South Sawyer Glacier in Tracy Arm and observed Harbor Seals raising their young among the floating icebergs at the glacier's terminus. We paddled past the Taku Glacier, which is one of few glaciers that is still advancing.

Near Juneau, we had the opportunity to get a close look at the Mendenhall Glacier. This glacier has a 13 mile journey down from the Juneau Icefield to Mendenhall Lake. Paddling into Haines, we chose to paddle in the Chilkat Inlet, observing the Davidson and Rainbow Glaciers. The Davidson Glacier is in a state of ablation,with a huge moraine that forms Glacier Point, sticking out into the inlet. The Rainbow Glacier was a prime example of a hanging glacier, with cliff face and waterfall dropping below the mass of ice and snow.

6_29_10nurse Paddling past these glaciers was chilly, humbling, breath-taking, and saddening. As we approached Holkom Bay, a cold breeze wafted down from the Sumdum Glacier and the temperature dropped by about 10 degrees in two minutes. I felt small and insignificant in the presence of these massive rivers of ice that shape the landscape. The deep blue of freshly calved icebergs was a stunning sight and we all loved studying the sculptural forms of drifting icebergs. I also enjoyed seeing how the calving of the South Sawyer Glacier supported the early stage of life for so many seal pups.

I could say that I was glad to see so many glaciers before they're gone, but I won't. I won't say it because I remain hopeful that we will all work to stop global climate change. If we reduce our carbon footprints by living more simply and using alternative energy sources, maybe we'll prevent that 4 degree temperature rise from happening and glaciers will still be around for future generations to see. For this, and many other reasons, I will keep on trying live a greener life. Will you?

 

Want to learn more?

http://wwf.panda.org/about_our_earth/aboutcc/problems/impacts/glaciers/

http://www.fs.fed.us/r10/tongass/districts/mendenhall/

http://earthobservatory.nasa.gov/IOTD/view.php?id=5668

http://www.fs.fed.us/r10/tongass/districts/mendenhall/faq.shtml

http://www.fs.fed.us/r10/tongass/forest_facts/resources/geology/icefields.htm

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