Billy Armstrong

App State students surveying a wetland in Environmental Science Field Methods

We’re hiring a NTT lecturer in the Department of Geological and Environmental Sciences at Appalachian State University! We are a big (>300 majors) collegial undergraduate-only department in the Blue Ridge Mountains (southeastern US). See the full job post:

appstate.peopleadmin.com/postings/53077

ChatGPT's response about it's own weaknesses for writing research papers

I'm teaching a scientific writing course and figuring out how to talk about effective use of AI writing tools. I was interested to see ChatGPT's response about its weaknesses. Do other people have effective activities for talking about ethical LLM use with undergraduates?
chatgpt.com/share/68a620...

Feet plunging into murky water

@watershedlab.bsky.social Super turbid! Jocelyn Reahl at @instaar.bsky.social collected water samples at various depths and is going to be working the sediments angle. It will be cool to see if/how sediments significantly alter glacier behavior here!

Field team at mendenhall lake

This work is funded by NSF and in collaboration with @terrawonderer.bsky.social and Dave Sutherland. I couldn’t ask for a better team!

Using a 4 m long ice auger to anchor a GPS antenna

We will combine these datasets with stationary moorings, on glacier GPS, and sediment traps to assess how much ice is being lost through subaqueous melt and iceberg calving at Gilkey Glacier. We will also assess how much this matters for the glacier’s past and future evolution.

Running a radar transect on Gilkey Glacier. Photo by Lynn Kaluzienski

We used radio echo sounding to measure ice thickness. These data, in combination with terminus multibeam scans, show that the glacier tongue is not floating at present, though remote sensing data suggest this has varied in the past.

Multibeam sonar measuring water depth near an iceberg. Photo by Victoria Benson

We used a multibeam sonar to measure lake bathymetry and conduct repeat terminus scans. We found maximum lake depth of 200 m with a relatively flat floor, suggesting significant sediment infilling post retreat

Evening light on the terminus of Gilkey Glacier

Just got back from a week of work on the lake-terminating Gilkey Glacier near Juneau #Alaska. A quick summary of data collected and some initial results:

Many thanks to collaborators @iamdonovan.bsky.social @glacierdoc.bsky.social and others, data/method developers like #NASA and @jamesmlea.bsky.social, and #NSF funding - this work wouldn't have been possible without your support!

Comparison of Alaska & Patagonia lake-terminating glaciers

We find that #Alaska lake-terminating glaciers lose ~5x less mass through the terminus than an Alaska marine-terminating glacier and ~3x less than a #Patagonia lake-terminating glacier. Warming or deepening of proglacial lakes could push the region's glaciers toward higher rates of mass loss

Distributions of lake length (left) and lake-terminating retreat duration (right) under different ice thickness scenarios (line colors)

We estimate the average Alaska lake-terminating glacier has 9 km of lake expansion potential and will remain in contact with its proglacial lake for the next 74 years. This makes process understanding of glacier-lake interactions important for projecting glacier response to #climatechange

Maps showing retreat rates and frontal ablation rates for Alaska lake-terminating glaciers

On average, the region's lake-terminating #glaciers retreated by 60 m/yr over 1984-2021. The glaciers lost 0.04 Gt/yr of ice through iceberg calving and subaqueous melt over 2009-2018, equivalent to 25 cm w.e./yr surface lowering if spread evenly across the glacier surface

Schematic illustrating estimation of frontal ablation on lake-terminating glaciers

Excited that Noah Caldwell's work is officially out in @igsoc.bsky.social Journal of Glaciology! Noah used satellite remote sensing to estimate how much ice is being lost to iceberg calving and subaqueous melt on 55 Alaska lake-terminating glaciers. Read more: doi.org/10.1017/jog....

Hundreds of weather forecasters fired in latest wave of DOGE cuts Federal workers who were not let go said the afternoon layoffs included meteorologists who do crucial local forecasts in National Weather Service offices across the U.S.

I’m thinking we should spread this news about the firings at NOAA as far and wide as possible. Like cancer research, weather forecasting seems likely to be broadly popular across the political spectrum. apnews.com/article/nati...

N.S.F. Cuts Raise Fears of a Reduced U.S. Presence in Polar Regions The National Science Foundation has fired workers at the office that manages polar research, raising fears about a reduced U.S. presence in two strategic regions.

Why does science need government funding?

What are the impacts to the US of cutting polar science?

@zhonggg.bsky.social paints the picture here
www.nytimes.com/2025/02/25/c...

Changing suspended sediment concentration impacts aquatic habitat, geomorphology, and infrastructure. Our work provides some clues into how sediment dynamics are changing on glacier-fed streams in a warming climate. You can read the full article (for free) here: authors.elsevier.com/c/1kd8J,3sl4...

Declining suspended sediment was the predominant trend for glacier-fed rivers with upstream lakes, while trends were more mixed for rivers without upstream lakes.

box plot showing SSC difference by presence or absence of upstream lakes

Glacier-fed rivers without an upstream lake had the highest suspended sediment concentration (SSC). Rivers with well-developed upstream lakes had the lowest SSC, showing these lakes are acting as efficient sediment traps. Rivers with newly-formed lakes upstream had widely varying SSC.

Schematic of proglacial lake development.

Very proud to see Lily Vowels' senior thesis work published in #Geomorphology! Lily used #Landsat imagery to investigate how suspended sediment in #Alaska glacier-fed rivers has changed over the last ~40 years as #glaciers have retreated and terminal #lakes have formed and grown 🧪

We use handheld ones for doing point sampling in class that are more on the order of $250 made by hanna instruments

The solinst EC probes are very easy to use (integrated data logger, long battery life, intuitive download & programming) but they’re fairly expensive (~$500-1000 per), which I could imagine being prohibitive..

GPS position jumping

The jumps are several times the L1/L2 wavelength, which is 19-25 cm. I would have expected this length scale to pop up if it were integer ambiguity, but maybe it’s not so simple?

Great questions - I have wondered these kind of things but don’t know enough about what’s going on under the hood (Kristine Larson will be sad to see me say this b/c I sat in on her GPS class..)

Thanks for all these ideas, Julie! We are going to try to process some with TRACK (we do have a base station at the site) and see if the same issue persists

I definitely shed many tears over GPS strangeness in grad school..

Gps position jumping

This is a great idea - I’ll look into it. It seems like NRCan is finding 3 possible solutions for antenna positions that differ by an identical amount at all sites (separated by several km). I could see this being something where it’s jumping to a previous guess.

Gps position jumping

Thanks for this idea - I will check into it, but don’t think it’s likely as we’ve used the same receivers/antennas at almost the exact same place, and there is no time-of-day pattern to the position jumping - it’s constant. See my reply to Julie for more context here

GPS position jumping

I dug into this and feel even more lost - the position jumping is happening ~constantly. There is no pattern to time of day, but 5 stations are jumping by the ~exact same amount in all 3 coordinates - it’s like there’s 3 possible solutions for their positions?

Hi everyone! CryoCommunity is now on BlueSky! Please share us around so everyone who has switched over to this app can find us! Thank you! ❄️

#glaciology #cryosphere

Hi Julie! I’ll check tomorrow - you mean like are the jumps always happening at 1:45 pm every day or something like that?It happens at multiple sites separated by a few km over a month-long period. I haven’t checked timing in detail yet but will follow up