Billy Armstrong
@app-glaciers.bsky.social
App State associate professor interested in glacier processes, glacier change, and downstream impacts
@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!
July 29, 2025 at 3:49 PM
@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!
This work is funded by NSF and in collaboration with @terrawonderer.bsky.social and Dave Sutherland. I couldn’t ask for a better team!
July 29, 2025 at 3:20 PM
This work is funded by NSF and in collaboration with @terrawonderer.bsky.social and Dave Sutherland. I couldn’t ask for a better team!
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.
July 29, 2025 at 3:17 PM
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.
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.
July 29, 2025 at 3:12 PM
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.
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
July 29, 2025 at 3:07 PM
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
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!
May 23, 2025 at 2:40 PM
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!
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
May 23, 2025 at 2:34 PM
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
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
May 23, 2025 at 2:31 PM
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
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
May 23, 2025 at 2:25 PM
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
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...
authors.elsevier.com
February 18, 2025 at 12:51 PM
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.
February 18, 2025 at 12:48 PM
Declining suspended sediment was the predominant trend for glacier-fed rivers with upstream lakes, while trends were more mixed for rivers without 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.
February 18, 2025 at 11:16 AM
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.
We use handheld ones for doing point sampling in class that are more on the order of $250 made by hanna instruments
January 26, 2025 at 1:24 AM
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..
January 26, 2025 at 1:21 AM
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..
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?
January 24, 2025 at 1:09 AM
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..)
January 24, 2025 at 1:07 AM
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
January 23, 2025 at 8:46 PM
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..
January 23, 2025 at 7:23 PM
I definitely shed many tears over GPS strangeness in grad school..
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.
January 23, 2025 at 7:22 PM
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.