Llewellyn Glacier, BC: Recession and Recent “Disappearance of Glacial River”

4 Comments

In early-September a story broke regarding a so-called disappearance of a glacial river in northern British Columbia.

A couple of these stories can be found here and here.

The purpose of this post is to show a bit of visual evidence of, and context for, what happened and why.

First, a few bits of information regarding Llewellyn Glacier, British Columbia:

Llewellyn Glacier is one of the largest glaciers in British Columbia at 458 km2 (as of 2011-08-03). It is an outlet glacier of the Juneau Icefield, which sits along the northern end of the Coast Mountains of Alaska and British Columbia (Fig. 1).

Figure 1: This 2001-08-15 Landsat ETM+ satellite image (panchromatic band, 15 m resolution) shows the Juneau Icefield with Llewellyn Glacier outlined in blue. Each gray grid cell is 10 km by 10 km. Downtown Juneau, Alaska is located at approximately 535000 E., 6462000 N. (information on the UTM geographic coordinate system here).

Llewellyn Glacier has been receding rapidly, particularly during the past two decades.  Of the 53 outlet glaciers of the Juneau Icefield, Llewellyn Glacier has receded the most – in terms of surface area – in recent years (Beedle and Raup, 2008).  From 1991 to 2011 Llewellyn Glacier shrunk from 471 km2 to 458 km2, a loss of 13 km2, or nearly 3% of the 1991 surface area (Fig. 2).

Figure 2:  This 2011-08-03 Landsat TM satellite image (false-color composite of bands 4, 3, and 2 – vegetation appears red) shows the terminus of Llewellyn Glacier with outlines from 1991, 2001, and 2011 showing recent recession.  Gray grid cells in this image are 1 km by 1 km.

Prior to late-summer 2011 two rivers drained from two lakes at the terminus of Llewellyn Glacier to Atlin Lake.  One drained to the north into Llewellyn Inlet, and the other drained northeast into Sloko Inlet.  Both inlets are portions of much larger Atlin Lake (Fig. 3).

Figure 3:  This 2011-08-03 Landsat TM satellite image (false-color composite of bands 4, 3, and 2 – vegetation appears red) shows the terminus of Llewellyn Glacier, the two terminal lakes, the two rivers – one draining into Llewellyn Inlet and the other draining into Sloko Inlet, and a portion of Atlin Lake.  Gray grid cells in this image are 1 km by 1 km.

On August 11th, at the end of their 2011 field season, Juneau Icefield Research Program (JIRP) students and scientists hiked down Llewellyn Glacier to Llewellyn Inlet.  On a portion of the usually high-and-dry trail they found themselves wading through what was at times chest-deep water.  In late-August, Atlin, British Columbia locals Diana Thayer, followed by John Lyons, noted the disappearance of the river that had previously drained into Sloko Inlet.  The assessment of the cause of this rerouting of a significant amount of water by John Lyons after visiting the site and flying over the glacier (see John’s comments on the CBC story here), is the same that we show here (Fig. 4).

Figure 4:  This image shows a Landsat TM satellite image from 2011-08-03 (left) and a Landsat ETM+ satellite image from 2011-09-12 (right), both freely available from the USGS Global Visualization Viewer.  The black ‘striping’ in the ETM+ image is due to a malfunction that occurred on board the satellite in May 2003, see here for more information.  The gray grid cells in this image are 1 km by 1 km.  Numbers correspond to descriptions below.  Names in italics refer to place names that do not have official names (to the best of our knowledge), and are used here to describe the events that occurred.

Sometime in early August the receding Llewellyn Glacier rerouted water that once flowed into Sloko Inlet.  Refer to the image above for the following descriptions:

1.  After August 3rd (Fig. 4, left image), but before August 11th, when JIRP students and scientists encountered abnormal water levels, the receding Llewellyn  Glacier separated from a bedrock ridge, allowing water from “Lake 1” to flow into “Lake 2” through a previously-ice-dammed channel.

2.  Subsequently, the water level of “Lake 1” dropped below the outlet into “Sloko Inlet River”, separating the river’s bed from its source.  Note the large area that was once covered by waters of “Lake 1”, just below (south) of the number ‘2.’ in the image on the right.

3.  “Sloko Inlet River” ‘disappears’.

4.  “Llewellyn Inlet River”, now with the extra water diverted from “Lake 1” to “Lake 2”, swells and – in some areas – changes course.  Note the area just above (north of) the number ‘4.’, where the river swelled significantly between the two images.  This area is pictured in figures 5 and 6, below.  Both images are taken facing south (roughly) – the terminus of Llewellyn Glacier visible in the background.  Thanks to JIRP student/scientist Kent Walters for these images.

Figure 5:  Juneau Icefield Research Program students and scientists wade along the flooded ‘trail’ between Llewellyn Glacier and Llewellyn Inlet.  “As we hiked out there were plenty of trees which were flattened in the direction of water flow and also uprooted trees floating around in Llewellyn Inlet with roots completely in tact.”  Photo and quote courtesy of Kent Walters.

Figure 6:  Looking towards “Lake 2” and Llewellyn Glacier from the trail leading to Llewellyn Inlet.  The flooded area in the foreground was previously dry.  The primary “Llewellyn Inlet River” channel is on the left of this image.  Photo courtesy of Kent Walters.

The rerouting of water away from “Sloko Inlet River” to “Llewellyn Inlet River” was the result of the recession of Llewellyn Glacier away from a bedrock ridge.  The glacier previously served as a dam between “Lake 1” and “Lake 2”.  Further recession may uncover lower-elevation bedrock, possibly resulting in a similar failing of the ice ‘dam’ and a sudden pulse of water into “Lake 2” and “Llewellyn River Inlet”.  However, this will be determined by sub-glacial bedrock topography, behavior of Llewellyn Glacier, and the difference in elevation between the two lakes – if a difference remains after the flooding event of 2011.  A reemergence of “Sloko Inlet River” is unlikely without an advance of Llewellyn Glacier, and a damming of the channel between “Lake 1” and “Lake 2”.

Links to additional information:

Atlin Lake Provincial Park

CBC Article:  ‘Disappearance of glacial river stuns B.C. hikers’

Freely-available Satellite Imagery

Extent change of BC glaciers from the 1980s to 2005

References:

Beedle, M. J. and Raup, B., 2008, A GLIMS inventory of the Juneau Icefield, Alaska, IGS International Workshop on World Glacier Inventory, Lanzhou, China, Sept. 20-24, 2008.

For further inquiries about this post please be in touch via email:  connect@glacierchange.org

Leave a comment:




Comments:

Mauri Pelto

October 23, 2011

That makes for a much more unpleasant hike off the icefield. This change is not unexpected but is quite a step in the evolution of this deglaciating lowland.

Brad Thayer

October 27, 2011

[NOTE: The following is a post by Brad Thayer, who has spent a great deal of time in the Llewellyn Glacier area, and was one of the first to discover the ‘disappearance’ of the river.]

A large river dries up while miles away another rages wildly.

Near the south end of Atlin Lake it’s about a three km hike to a spectacular river gorge. We have visited this gorge many times over the past years to stand in awe of the thunderous roar of a large glacier melt river.The roar of water through this gorge could be heard as much as five km away when the glacier melting was heaviest. This August we were leading some friends to this gorge,the gorge that we promised would be rushing with melt water,when we noticed an eerie silence. As we approached the gorge while still in dense forest the silence became almost unbearable. When we finally came out to where we could see a dry river bed down stream from the gorge our imaginations went wild.At the local coffee shop in Atlin there had been no mention of a major river drying up.Nothing had prepared us for what we were seeing. Our first thoughts were that this big river could come thundering back with a mountainous amount of water at any moment.After calmly analyzing the situation we mustered the courage to walk up the mostly dry river bed to the glacier lake source that we had seen by air and on maps but had never been able to get to by foot.At the lake outlet to the now dry river, we were stunned even more to find huge ice bergs resting on the exposed portions of the lake bed. At first we timidly tried to walk down into the muddy lake bed towards the grounded bergs, being ever so carefull to test each step for quick sand. After a while we learned that most of the exposed lake bottom was very walkable and that we were not the first visitors on the lake bottom.There were wolf and bear tracks where no mammal had walked for perhaps thousands of years. The excitement of walking amongst the bergs out weighed our caution about being in the mud next to huge and possibly unstable melting bergs.

Sometime this summer, in our far northwest corner of British Columbia, mother nature made some big geographical changes but aparently no human wittnessed these changes as they happened. We are left with plenty of evidence but no eye wittness accounts of what happened except for maybe the wolves and mountain goats that can’t tell us their stories. This part of B.C. is sparsely populated and with all of the grandeur of the area it’s not surprising that these events went un noticed. We don’t know when, but our best guess is, that sometime in August much of the water from a glacier lake drained into another lower glacier lake in what appears to have caused a catastrophic surge of flood water down an existing river that empties into Atlin Lake at Llewellyn Inlet. The upper lake dropped approximately 15 meters below it’s outlet,which caused Atlin Lake’s largest tributary to stop flowing abruptly. Huge ice bergs were left stranded on the muddy exposed lake bed of the partialy drained upper lake.At the same time, several kilometers away and separated by a mountain, another equally awesome event was taking place.Spruce and pine trees, some more than 100 years old, were being uprooted. The combined melt water of two rivers and the water draining from a two km by seven km lake was forced to find it’s way, down an existing smaller river channel, to 85 mile long Atlin Lake.It now seems that B.C.’s largest natural lake has been altered in regards to rock flour concentrations.The once beautiful turquois water of Llewelleyn Inlet is now a muddy gray and the muddy gray of Sloko Inlet, miles away in Atlin lake, is now changing to a beautiful blue color. Since Llewellyn Glacier has been receding for years, it’s very unlikely that melt water will soon flow again through the channel that was Atlin Lake’s largest tributary for perhaps thousands of years.

In early September we spent six days kayaking amongst the ice bergs on the partially drained lake while returning each night to our camping spot which was very close to the new channel that now connects the two glacier lakes. Loud cracks and sounds like rolling thunder mixing with the sound of waterfalls within the glacier were our constant companions throughout this time. Our tent was positioned so that we could see five of the six calving spots (hot spots) right from our sleeping bags.The new channel opening between the two glacier terminus lakes allowed us to stand safely just one hundred meters or less from an active blue ice glacier terminus.There are few places in the world where a person can be so close to a calving glacier without having to be in a boat which can be very dangerous at these close distances.Each day I would assure my more cautious and sensible wife that kayaking near grounded ice bergs was perfectly safe.The old adage or saying that “Ignorance is bliss”was certainly holding true in my case.After returning home and reading about how dangerous it is to kayak near grounded or floating bergs, I felt like hanging my head in shame.The previous summer we had back packed and then lined our loaded kayak up the river to the lower glacier terminus lake and learned to be wary of tsunamai like waves from calving at the blue ice terminus wall.Since the lower lake had very few floating bergs we learned nothing about the dangers of kayaking near them.Our first day of kayaking on the partially drained lake was truly glorious with a cloudless sky,no wind and a pack of wolves howling across the lake from our camp. With the adage that “Ignorance is bliss” and a lot of good luck we kayaked under overhanging bergs and through narrow channels barely wide enough to squeeze through.During our first night at the lake there was a hard frost which formed a quarter inch thick sheet of ice for us to break through the next day.After paddling about a km through this new ice sheet, I started to worry that maybe the sharp edges of the new ice sheet were cutting into our inflatable double Seeker II kayak, so we decided to go ashore and explore on foot more of the bergs that had been left high and dry on the lake bed.Day three dawned and there was still no wind to prevent a new skim of ice from forming but by afternoon we were able to kayak with ease again.Later that same afternoon we forced our kayak into heavy brash ice mixed with large bergs that had just recently broken from the glacier terminus. I told my wife that these large bergs were surly grounded now because of the lowered lake level and that it would be safe to kayak amongst them. That night a wind came up and by morning all but one enormous berg had blown to the north end of this lowered lake. After seeing that all of these so called grounded bergs had just floated away during one night of mild wind she decided to use her veto power of the kayak rudder which she controlled from the stern. Had a wind come up while we were deep into brash ice and large bergs, things could have turned very ugly for us.The next few days we stayed away from shallow water to avoid the ever present tsunamai threat from the glacial calving and drilled ourselves mentaly at turning the bow of our kayak into the sound of thunder from the ice wall.Riding a calving wave in deep water is like riding a sea swell. Staying a safe distance from large bergs was also part of our new agenda but since the visibility in glaciel rock flour water is nil we couldn’t tell how far the under water ice extended from the above water ice.Many times we ran up on to or hit our paddles on hidden ice that was part of a berg fifty meters or more from it’s visible part.After we got home we started thinking about what would have happened if one of these large bergs had decided to roll when we were over it’s hidden part.I now know that any time that a berg looses a chunk of it’s mass from breakage it will try to reposition itself to maintain the same proportion of exposed ice mass to underwater ice mass which is roughly one to eight. On day five of this trip we were astonished to see a berg near our camp roll over in calm water for no apparent reason.
A week after our kayak trip we spent another five days exploring the aftermath of the huge water surge down the river that empties into Llewelleyn Inlet.The most interesting section of this newly devastated channel began to look almost impossible to get to without crossing the now much larger river flow.A steep mountain was on our left going down stream. Our only chance to photograph this area was to walk down stream along the west edge of the river with chest waders, being very carefull to not step into any deep holes in the rock flour water.Walking this way was like walking with a blind fold on.After fighting our way through thick alder and stepping into quicksand we finally decided to abandon this method of trying to reach the interesting area which was mostly on the opposite side of the river anyway.Since it was getting late in the day we decided to change back into our hiking boots and bushwhack our way over the mountain to our west where we intersected the trail leading to our boat on Atlin Lake.Not being people to give up easily we devised a new plan to reach our goal.We would move our comfortable boat several km to a parallel inlet on the east side of the river.There would still be a mountain separating us from the river,but this new base camp gave us a chance to carry our inflatable kayak up a short distance through a steep pass to another lake.Kayaking to the far west end of this other lake would then position us to within an easy 45 min. hike to our goal.What we saw was well worth the effort. Hundreds of large trees were laid over and huge sand dunes had formed on and around these partially uprooted trees.Most of the trees that were still upright held logs and other flood debris entangled in them. Looking up four meters at sticks and debris caught in trees made us suspect that the upper glacier lake had drained much faster than we had previously thought.The new river channels,uprooted trees,river channels left dry and new sand dunes in this drainage are truly amazing.The combined flow of the two rivers will continue to erode and change the landscape on the path to Llewellyn inlet but on the other side of the mountain there will be a silent gorge that few people will want to visit.

Michael Ledurinta

December 13, 2011

But travel to Shakes Lake and Shakes Glacier is not possible this year, due to the large amount of glacial ice blocking the route probably due to global warming .