Sunday, August 23, 2020

Frozen debris lobes

 Recently I had an opportunity to look at something else in the frozen world: Frozen Debris Lobes. These are masses of debris on mountain sides that contain ice and become mobilized. As was made clear to me, they are not rock glaciers. If you don't believe me, watch this. My favorites are Infiltration Ice and Not a Rock Glacier.

I brought a Terrestrial Radar Interferometer up the Dalton Highway to try to measure the motion of these debris lobes. We have used this instrument on glaciers quite a bit, but it turns out to work really well on slower moving things as well. After a few hours of measurements we could confirm that one of the lobes moves at about 15 cm/day. 

Here is a look at FDL 7. It is a feature just left of the center of the image across the valley.




 Here is how the radar sees it (the units are in meters/day)




This picture was taken on top of a debris lobes. Opening cracks split this tree into five sections.

Margaret Darrow, the frozen debris lobe lady

Frozen Debris Lobe A is just about to take over an old road bed of the Dalton Highway. The highway was moved downslope a few years ago.


Tuesday, June 9, 2020

Every glacier seems to want a lake

We just returned from a successful Operation IceBridge mission. This is a NASA sponsored program to measure many of Alaska's glaciers annually. The main goal are repeat measurements of the surface with a Lidar to document the loss of ice in Alaska. But we also operate a radar to measure ice thickness, which is really challenging in the wet ice that doesn't lend itself to radar wave penetration and because of the very mountainous terrain that reflects a lot of radar waves and obscures the signal from the bottom of the glacier.

One particular treat of these survey flights is that we get to see parts of Alaska's mountains that are generally very difficult to reach and that are quite remote. I'll post some pictures in the next several posts. This first one here is about lakes.

Glaciers have the odd tendency to dig themselves into holes, so when they retreat they often leave depressions that are then filled with water to create glacial lakes. Because so many glaciers are retreating, proglacial lakes are very common in Alaska, and they are rapidly expanding. Here are some examples. I'll try to add some links to Google Maps, and for many areas you can easily see the growing lakes by looking through satellite imagery in Google Earth, for example.








This glacier near Seward has been retreating really rapidly (see also AGU's From A Glacier's Perspective blog) and forming a large lake in the process. The iceberg in the picture is quite impressive in size.



The Allen Glacier is located in the Copper River Valley. The Miles Glacier is just visible in the distance (on the left). It also has a large lake. The Copper River Railroad went down this valley to bring the copper ore from Kennecott to the port of Cordova. It was abandoned in the late 1930s. The spur is still visible in the picture. At the time the Allen Glacier was much more advanced and the railroad tracks were actually laid across the debris covered ice of this glacier and had to be frequently maintained.



According to Wikipedia, Nabesna Glacier is the 'longest interior valley glacier on the planet'. I haven't tried to fact-check this, but it is a long glacier... As many of its friends, it is rapidly losing mass and building a big lake. There are large portions of floating ice that are ready to break off soon.



These glaciers are located in a phenomenal setting, where Mt. Fairweather rises 15,000 ft (4,500 m) straight from sea level. Both have been retreating rapidly forming big lakes.

This view is from Alsek Lake onto the Grand Plateau Glacier:

Alsek Glacier

A side branch of the Grand Plateau, creating its own lake

Terminus of Grand Plateau into Alsek Lake


I  have written about Yakutat Glacier before, since we had an NSF funded project there. This glacier is essentially doomed, since it really doesn't have any accumulation area left and it is subject to a positive feedback as the average elevation gets lower over time. The lake area in this picture was almost entirely ice covered just a few years ago.





Saturday, May 9, 2020

Black Rapids in the time of Corona

Each year we make a visit to Black Rapids Glacier to keep track of its mass loss or gains (mostly the former). The time series goes back to the early 1970s, but for the past decades it has not been funded anymore. We've been able to keep it going thanks to friendly helpers with airplanes. This year we were delayed for quite a while by weather, Covid-19 restrictions, and airplane maintenance issues. But then finally things aligned and the last two weekends we had perfect weather conditions. I enlisted my daughters as helpers, that way we didn't have to break any social distancing rules. I have not yet finished looking at the data, but it is already clear that 2019 was one of the biggest melt years in the entire, almost fifty year, record.









Wednesday, February 19, 2020

Big skies at Thwaites

I loved the cloud formations that we saw at Thwaites, especially when the weather was changing and new fronts moving through. Here's a selection:











Monday, February 17, 2020

Drilling through the Thwaites Glacier

The last time I wrote here we were desperately trying to get out of McMurdo and onto the Thwaites Glacier. It's a long journey to a very remote location, so nothing comes easy. But, by now, I am comfortably back in Alaska (although it is colder here than it has been in Antarctica ...).

But all in due order. On 13 December, after one month in McMurdo things all of a sudden started moving quickly. After two false starts with lots of waiting, I was part of an advance team to WAIS Divide, where a big camp was set up to receive major amounts of cargo. Once at WAIS Divide we immediately transferred from the big LC-130 aircraft to a Basler (a converted DC-3) and arrived that same day on our field site; the home for the next five weeks. During that time we were doing lots of surveying with radar and seismic methods. I was in charge of hot water drilling. We completed two holes through the Thwaites Glacier Iceshelf, did some profiling of the underlying ocean, took sediment cores and installed ocean moorings and a fibre that allows us to monitor temperatures throughout the ice and water column. The work went very well, and we are now excited to see the data come in via satellite from one of the most rapidly changing places on this planet. More on the project and the whole collaboration is at thwaitesglacier.org

The Thwaites work is getting a huge amount of attention, for example from the BBC (although this report mostly covers a companion project with very similar goals).

Here are some of my pictures to give an impression of the work.

The Basler is a converted DC-3. This airplane was built in 1942, but was refurbished with new engines. It is now one of the power houses of Antarctic field work.
Here is the Basler and the other Antarctic workhorse, the Twin Otter. They have just landed at our field site.

Day 1: Still looking fairly well groomed

After a month on the ice my iphone face recognition didn't work all that well anymore...
Dale is taking stock of all our equipment that now has to be assembled

A radar survey team is slowly disappearing into a whiteout. We had to careful mark all routes, so we wouldn't get disoriented and end up in heavily crevassed area.


Our kitchen tent

Erin and Ted are cooking a yummy dinner

The hot water drill is set up: In the foreground are several diesel heaters that bring water to almost 80 deg C. In the background are two holding tanks. We pump water back out of the borehole into the holding tank, heat it up and then use it to drill through the cold ice.

The big wheel is a capstan winch over which the drill hose is guided into the hole. The smaller crescent guides another hose and an electric cable into the upper part of the hole. This is used to pump water back.

James is happy about the first sediment core from underneath the Thwaites Glacier iceshelf. Hopefully it will give us information about the history of ice cover in this area.


Drifting snow

One of our field guides, Blair, is ready for a cup of tea after some time shoveling tents out of the drifting snow.
After the storm

All our equipment is moveable by snow machine



Bruce pulling hose

James and Dale look a bit like two retired guys in Italy thinking about their next game of Boccia
Bruce is finishing up the AMIGOS installation.

And here it is after our camp was removed. This will be sending data for the next 2-3 years, we hope.
 
And here are Dale and I on the way out after 5 weeks on the ice

Back to WAIS Divide, the hub for all the activities on the Thwaites Glacier

Kenn Borek Twin Otter




Loading the drill equipment into a LC-130 Hercules