Story last updated at 9/18/2013 - 1:52 pm
Flowing through the Alaska Coastal Range near Petersburg, LeConte Glacier has slowly edged its way to salt water for thousands of years. Geologists have determined there was an advance that lasted from 1300 AD to about 200 years ago during the Little Ice Age.
It is now the southernmost active tidewater glacier in North America. Nearby Shakes Glacier terminates in Shakes Lake, and the outlet flows into the Stikine River so it doesn't qualify for that distinction.
Twice this summer we took visiting friends to experience seeing this glacier close-up. Our charter boat slowly moved among clear, aquamarine blue, snow white, and gravel sandy-covered icebergs bobbing in LeConte Bay. Eventually the face of the glacier came into view. A wall of fractured white and blue ice terminates the fjord. Before us were spiky surfaces and crevasses that marched upward and swung to the left to disappear into the barren mountains. Occasionally icebergs calved into the sea creating explosive booms and sending small waves down the bay.
This crash of bergs accounts for the Tlingit name for the bay. It is said to have been "hutli" for the mysterious thunderbird, however anthropologist R. L. Olson was told years ago that the name was "Xattlai." Oral history tells us that the Stikine people heard the rumblings: it was the home of the Thunder Bird who produced the sounds by flapping of its wings.
Of course, LeConte is not a Tlingit word. It was named in 1887 by Navy Commander C. M. Thomas who conducted the first surveys of the area for the U.S. Coast and Geodetic Survey. Joseph LeConte was a professor of geology at the University of California.
A number of years ago I located Thomas' original report. He wrote that the bay was inaccessible for vessels because of the immense quantities of floating ice that was continually breaking off in big masses. Fortunately his ship carried small boats for situations such as this. Thomas' staff collected information for what became the first topographic map of the area. He wrote "The running of the shore line was executed by Mr. J. R. Stone with great labor, physical discomfort and danger." Stone must have been the one to determine the exact position of the glacier front at that time.
I could barely imagine how Stone negotiated the steep fjord walls. LeConte Bay was once filled with the glacier, and it ground its way through bedrock picking up boulders, gravel and sand. As the glacier has moved forward, it sculpted the exposed bedrock. Mr. Stone navigated steep rock mountains with few handholds. "I cannot," Thomas wrote, "commend too highly his perseverance and skill in overcoming great obstacles in the performance of his task."
Thomas also noted that in 1887 the glacier was retreating: "The line of its former height above the present level is easily observed against the face of the bluff."
Since then glaciologists have studied LeConte Glacier. We learn that once the glacier retreated from the ocean bottom, it began to hang over deep ocean water. This continues to cause a retreat because of increased calving and melting ice beneath the ocean. The weight of the suspended ice accelerates the calving. The glacier terminus in 2001 floated in 885 feet of water. Unfortunately the boat we were in did not have a depth sounder.
As for the land-based portion, scientists reported that the glacier eroded its bed down to 2,000 feet below sea level at a point five miles from where it enters salt water. In the far distant future the fjord will reach that depth as the glacier continues to retreat.
In 1962 the glacier stabilized at a narrows near what was then almost the head of the bay. It remained stable until the early 1990s. In 1991 the glacier made a large advance, and then in fall 1994, it began an extensive calving retreat. It retreated a mile by September 1996 and continued at a slower pace until 1998. That year it was reportedly the fastest retreating glacier in the world. The forward flow was 81 feet per day with extreme calving from the 100- to 200-foot face. University of Alaska Fairbanks reported this was at least as fast or faster than other historic calving glacier retreats in Alaska.
We could see only a small portion of the glacier. In 2002, 90 percent of the glacier extended 22 miles back into the higher, northern mountains on the Alaska side of the U.S./Canada boundary.
Much of the floating icebergs when we visited in August had begun to melt, and the wind had blown them down the bay into a nook in the shoreline. Some icebergs had floated out into Frederick Sound, and one grounded at the mouth of Wrangell Narrows. Often during the summer months, icebergs can be seen from Alaska Airlines as it flies overhead. Sometimes, I'm told, the bergs float in front of Petersburg.
On our second trip, our guides, owners of Alaska Vistas, Sylvia Ettefagh and John Verhey were able to weave their way between smaller bergs toward the face of the glacier. Those beautiful pinnacles I admire can fall off the face and cause big waves. Another hazard is massive bergs emerging from below the water surface in front of the face bursting up to fall back into the sea. It is comforting to know the guides from both Petersburg and Wrangell are well aware of these navigational hazards.
No one wants to be in the bay when extensive calving occurs. Years ago researchers watched the entire face of the glacier disintegrate over a distance of 300 feet. The more than 900-foot tall wall of ice thundered to the sea filling the entire bay with icebergs and waves.
LeConte Glacier has been extensively studied in recent years. A survey of the glacier was started by Petersburg High School instructor Paul Bowen in 1983. He took his students yearly to locate the terminus. In 1997, Victor Trautman joined Bowen, and in 2005 he took over the project that continues today. Students fly in on Temsco's helicopters to do the survey work. Research is current. On a website is the students' map dated June 3, 2013. There are other maps that show the retreat of the glacier from 1904 to 1996. Photographs are also included. Check out lecontewebs.com and click on Trautman's website that appears above the glacier's photograph!
LeConte Glacier has retreated 2.5 miles since Thomas' visit in 1887. No wonder cliffs are so steep in the 12-mile long fjord. We could tell the most recent retreat because there is no vegetation on the rocks.
In addition to the glacier, LeConte Bay is a major harbor seal pupping, feeding, and resting area. This is a refuge from predators. There were still many seals and a few pups on the icebergs when we visited. In the spring mountain goats are common within a hundred feet of salt water. They were all high in the mountains outside of sight to us.
With all these experiences, LeConte Bay is a popular destination for charter boats, kayakers and personal water craft. We saw a large yacht anchored near Camp Island. Watch out for the shallow, submerged moraine at the mouth of the bay that was left from the glacier thousands of years ago. This captain knew to send the people in the tender. Another charter boat came in just as we left. It is often possible to be in the bay near the glacier alone with family and friends. An awe inspiring experience!
Pat Roppel is the author of numerous books about mining, fishing, and man's use of the land. She lives in Wrangell. She may be reached at firstname.lastname@example.org.