Monday, August 17, 2015

Taku Glacier drilling

We just got back from Taku Glacier, one of the few remaining advancing glaciers in the world, where we study the motion of the glacier, both ice deformation and how it moves over the bottom; and how this changes seasonally. We also look at how the glacier deforms proglacial sediments and erodes its base. To do this, we use a whole range of glaciological measurements, including surveys with GPS, radar, active and passive seismics, borehole invetigations, timelapse cameras, stream measurements and dye tracing tests. All of this activity sure made for an interesting field camp with up to 13 people there at times.

Below some pictures from the field work in no particular order.

Chris and Dale and I are installing a new instrument we developed: an instrumented subglacial dragspool that measures ice and till deformation, water pressures and sliding of ice over till.

The drill camp on a nice day.

A moulin that conducts water from the surface to the bottom of the glacier.

The daily commute from the drill site to the camp at the front of the glacier.

A nice evening at camp.
Near the glacier front.

Looking out over the Taku River and Taku Inlet. Everything in this image was at least 100 m deep ocean about 100 years ago.

The glacier terminus.

The main glacier outflow on the eastern glacier side.

The glacier terminus.

The glacier advances in winter and spring and then retreats in the summer because of the very high melt rates, leaving push moraines behind.

Here the glacier advanced across the Norris River last winter and has now retreated again.

Taku Glacier used to calve into tidewater. Now the only calving happens into a small section of the Norris River.

Two ice marginal lakes on the Norris River drained while we were in the field. We noticed the very high stage of the river and got to see the cause on the flight back to Juneau.

Thursday, June 4, 2015

Walsh Glacier surge

With Operation IceBridge we get to see a large number of glaciers, and every once in a while, some that show unusual behavior. This time around it was the Walsh Glacier: it is currently surging. During a glacier surge, the glacier can start moving faster by a factor of 10 or more. A normally smooth ice surface becomes severely crevassed, the glacier builds up impressive bulges. If the surge reaches the front it can sometimes advance several kilometers in just a few months. The Walsh Glacier has not yet reached the front, but this is only the first year of it. Many surges seem to come in two stages, so there is some hope.

The Walsh Glacier last surged in the 1960s in a really spectacular surge.

Thursday, May 28, 2015

Yakutat Glacier keeps on falling apart

I've written about Yakutat Glacier before, since we had a NSF funded project there a few years ago. This is a big glacier and one of the most rapidly changing in Alaska. In fact, in a recent paper we showed that the glacier is very likely to disappear within this century, even without further warming. In the past few years the glacier has lost well over 10 km2 of area, and this rapid retreat is continuing. Now, it is the east branch that is rapidly falling apart.

Monday, May 25, 2015

Mapping the Malaspina Glacier

The Malaspina Glacier is a large so-called piedmont glacier. It is fed by the vast icefields of the Coastal Mountains and extends out to the coastal plain. Much of its ice is at very low elevation (near sea level). A large part of it has become stagnant and has been thinning for decades now. We mapped the glacier with radar to see how much of the base is located below sea level. That makes it particularly vulnerable to rapid change.

Much of the ice has become so stagnant that trees are growing on top of the glacier!

The vast expense of the Malaspina Glacier

Collapsing ice is the only indication that this tree-covered landscape is actually a glacier

Looking out from near St.Elias towards the Pacific Ocean

Ocean water is reaching the glacier front in this lagoon. If the glacier started to calve ice into lakes like this, the demise of the ice could be accelerated greatly.

Moraine patterns

An example of a radar profile. Radar waves can penetrate several 100 m's into glacier ice and measure its thickness.

Impressions from Operation IceBridge Alaska

Each year we fly over many of Alaska's glaciers with lasers and radar to measure how much the ice surface is changing (laser) and how thick the ice is (radar). Here are some impressions from the May campaign that was just concluded.
The first few pictures are from Icy Bay, one of the most spectacular places I've ever seen.

The mighty Mt. St. Elias (5,489 m)

The top of Mt. Wrangell, a massive ice-covered shield volcano

Hubbard Glacier is one of the very few advancing glaciers in Alaska and indeed the whole world. If the advance continues, it threatens to close of an entire fjord and turn it into a lake. We expect that to happen (at least temporarily) in the next few years. But not this year, apparently. The gap at Gilbert Point is much wider than it usually is this time of the year. It's possible that this is attributable to much warmer than usual ocean water in the Gulf of Alaska.

The gap at Gilbert Point

Dirt-covered glacier ice advancing onto a glacial outwash plain

Snow runnels, higher up on the glacier

The Burrough's Glacier in Glacier Bay is a left-over from the collapse of a large ice field that has occurred during the past 250 years. It is a remnant glacier the last of which will quickly disappear.

Beautiful blue supraglacial lake. Melt is earlier than usual this year with record May temperatures.

The Bagley Icevalley

This lake has filled, clearing the ice, and then drained, leaving clean ice exposed

The Kennicott Glacier by McCarthy with the beautiful Stairway Icefall, which must be one of the highest ice falls in the world.

A rockfall on the West Fork Glacier in the Alaska Range. It happened during the 2002 Denali Fault Earthquake.

Mt. Blackburn and the Kennicott Glacier