Wednesday, April 9, 2014

Taku Glacier

We just started a new project on the Taku Glacier. The goal is to take a closer look at glacier erosion. This glacier is amazing. In previous work we have found that it can excavate as much as 3 m of sediment per year. That is, the glacier is primarily growing at the bottom, by digging itself into soft sediments. Over the next three years we will take a detailed look at how this works. Last week we used radar and seismics to map the glacier bed. With a detailed seismic survey we hope to also find the depth of the sediments under the ice. Next year we will drill through the glacier to find out how it moves over its substrate.

Here are some pictures from this year's field work:

The Juneau Icefield

View from the camp site: Split Thumb

The tent camp

Alessio working on the seismic line on a windy day

The camp with the ocean in the background. If Taku kept advancing, it would eventually cut off the Taku River and create a huge lake. This has happened in the historic past, but the warming climate is unlikely to sustain the current advance for much longer.

The first days were quite windy with lots of blowing snow

The first wiggles show the return of seismic waves from the glacier bed

Orion on a clear night

At the moment, Taku Glacier is still advancing

Roman inspects the sediment bulges in front of the advancing ice

A tree is no match for advancing ice

Ice advancing over sediment

And the yellow bird that's taking us home again.

Flight to Juneau

I flew to Juneau for some field work on Taku Glacier last week. We experienced one of these days were all of Alaska had beautiful weather. On such a day, this must be one of the most amazing commercial jet flights there are. From Fairbanks to Anchorage we got a very close look of Denali, but the windows were too dirty for good pictures. Below are a few that I took on the way to Juneau from Anchorage.

College Fjord with Harvard and Yale Glacier, one is advancing, the other one retreating

Meares Glacier in Prince William Sound

Columbia Glacier: 20 years ago all of the water in this picture would have still been ice covered. Just a few years ago it separated into the two different branches.

A look over the upper Columbia Glacier into the Tazlina Glacier and into interior Alaska.

The Wrangell volcanoes (Drum, Sanford, Mt. Wrangell) in the background. These are the most inland volcanoes in Alaska. Mt. Wrangell (the big shield volcano on the right) is still thermally active with occasional steam plumes.

A look into the Copper River that cuts right through the Chugach Mountains. The Childs and Miles Glacier come into the river valley from either side. One can recognize the Million Dollar Bridge that was built as part of the railroad from Cordova to McCarthy to extract copper. It was abandoned in the late 1930s.

Parts of the Bering Glacier and the Bagley Ice Valley, the largest continuous ice mass in Alaska. In the background are the Wrangell volcanoes.

Icy Bay with Yahtse Glacier on the right

Tyndall Glacier descends from the 5400 m high Mt. St.Elias to sea level, probably one of the largest drops in elevation anywhere on the planet. In the background is Canada's highest mountain; the massive Mt. Logan.

A look from the large Malaspina Glacier through the 'Seward Throat' into the Bagley Ice Valley

Hubbard Glacier, one of the few advancing glaciers on Earth

Another look into the Hubbard Glacier. On the right is Russell Fiord, which might become a lake if the glacier keeps advancing.

Yakutat Glacier. We had a project there during the past few years and the glacier has lost more than 10 km2 of ice and separated into two branches in the past few years. The glacier front is difficult to recognize here, because of the frozen lake.

Alsek Lake and Alsek Glacier

Alsek Lake

And finally: landing in Juneau with Mendenhall Glacier.
What a flight!

Tuesday, January 14, 2014

More radar: Bisgletscher

Last week we took the radar to another spectacular spot: We flew up to Domhuette in Mattertal to look at Bisgletscher across the valley. Bisgletscher has been moving pretty rapidly and there is concern that pieces could fall off and threaten the road and railway near Randa.

Below is a view from Domhuette. The mountain across is Weisshorn, at 4,506 m. This picture shows 3000 m of vertical relief. The other side goes up by the same amount, making this the deepest valley in Europe. Just below the summit of Weisshorn is a hanging glacier that has lost major parts in the past. Further down is Bisgletscher, which we tried to survey this time. In the lower right corner are the leftovers from a massive rockfall that occurred in the early 90s.

Below is a radar interferogram calculated from two images taken 15 minutes apart. The colorscale extrapolates the motion that occurred in those 15 minutes (about 10 mm) to meters/day. So the glacier (circled in red) is moving at nearly 1 m/d towards us observers. The non-zero motion that shows up for bedrock is atmospheric noise that I have not yet removed.

Monday, January 6, 2014

Glacier speed with radar

We did a short day trip to Kleine Scheidegg (on the way to Jungfraujoch) to see how well we can measure the flow of hanging ice with a ground based radar interferometer. This is a nice instrument, built by Gamma Remote Sensing that can measure displacements as small as a few millimeters. In the case of Eigergletscher it took a few hours to get sufficient displacements.

The radar, ready to go.

And here is Eigergletscher as seen by the radar. The picture shows an interferogram taken from two images separated by several hours. The colored fringes near the center correspond to 8 mm of motion for one color cycle. Since we can count about three cycles, that corresponds to 24 mm of displacement.

Monday, August 26, 2013

Swiss glaciers

Last week I had the great opportunity to fly with a friend along the Swiss Alps and see some glaciers from the air. Ok, so this is not field work in the strict sense, but the pictures are nice anyway ...

The Claridenfirn is site of one of the longest mass balance series on Earth

Two groups of climbers crossing the Claridenfirn

The retreat of Rhonegletscher is exposing a new lake. In the shadow one can see an area of the glacier that is covered in white tarp to reduce melting of ice and protect an ice cave.

The upper Rhonegletscher still has a fair amount of snow on it, because of a very snow rich winter 2012/13. However, high temperatures in the summer have melted most of this snow.

Unteraargletscher has retreated dramatically, like so many other glaciers in the Alps. The lower glacier is now entirely dirt covered.

Aletschgletscher is the biggest glacier in the Alps and still a magnificent sight.

The tongue of Aletschgletscher

Riedgletscher with Mischabel mountains. My home town is located at the bottom of this glacier

Turtmanngletscher with the magnificent Weisshorn

A rockglacier in the Val d'Anniviers is flowing into a glacier.

Gornergletscher with Monte Rosa

Findelengletscher. This was the field site for my diploma thesis, but most of the study site has melted away in the past 20 years.

Tuesday, July 9, 2013

Black Rapids lake drainage

This was a quick trip for me to help set up some surveying instruments on Black Rapids Glacier. We were here to watch the effect of a draining lake. From past measurements we know that the glacier can start flowing 2-4 times faster when water reaches the base. We wanted to see whether such a speed-up can also draw in ice from a big tributary glacier.

Aurora Lake, full to the brim, and ready to drain. This is the biggest of the marginal lakes.
The upper Black Rapids Glacier has many of these potholes, old crevasses that often fill with water and then drain.

Looking up Black Rapids Glacier
Mt. McGinnis

Our surveying equipment: An automatic theodolite and a precise radar that allows us to measure deformation fields in the entire field of view.

While checking out various instruments, we had an opportunity to hike around the glacier. It's always nice to see the signs of life in the harsh conditions of the mountains.
A plugged up moulin; this hole leads right to the bottom of the glacier!

A ptarmigan nest ...

... and mama ptarmigan whom I inadvertently chased off her nest.

A panorama showing the Loket tributary as it enters the main valley of Black Rapids.
I recorded this video as I hiked out the glacier. Near the glacier front, water comes up from underneath the glacier and creates these big waves.