New papers on glacier thinning, form of MSGLs, and subglacial discharge plumes

posted in: Publications, Research | 0

Several new papers published this summer exemplify the diversity of our research group’s interests and methodologies.  Thanks to the outstanding scientists and co-authors who led these efforts: Denis Felikson, Rebecca Jackson, and Matteo Spagnolo.

The first of these, published in Nature Geoscience, uses analytical analysis of glacier flow to explain the extent of inland thinning in Greenland.  This work received a variety of media coverage in the scientific and popular press, including on Boise State Public Radio and a regional newspaper, the Inlander.

The second, in Geophysical Research Letters, draws on observations of buoyant freshwater plumes in glacierized fjords and assesses their relationship to the subglacial discharge that drives them.

The third, in the Journal of Geophysical Research, uses two dimensional spectral analysis to reveal the ice stream produced bedforms consist of multiple, distinct, wavelength peaks.  These peaks coarsen down flow and are consistent with self-organizing processes.  This paper was selected as an Editor’s Highlight:

This paper reports the first application of the 2-dimensional discrete Fourier transform method to describing and analyzing the orientation-specific roughness elements of mega-scale glacial lineations (MSGL). Applying the technique to several case study examples reveals characteristic, orientation-specific roughness scales that guide process-related inferences on MSGL formation and evolution.

 

 

A figure from Spagnolo et al., 2017 shows the dominant wavelengths of mega-scale glacial lineations and their downstream variation.

U Idaho group presents and participates in international workshops

posted in: Outreach, Research | 0

It’s been a busy summer for the Glacier Dynamics group, with a number of high-profile presentations focused around glacier seismology.

In June, Tim participated in back to back workshops on Environmental Seismology, then taught during a weeklong summer course on Glacier Seismology.  During the Environmental Seismology workshop, Tim gave one of the evening keynote lectures, during which he presented an overview of his and others efforts to use seismology to better understand glaciological processes.  The workshop took place in Bavaria, Germany, and was attended by approximately 60 international scientists, many of which took part in the excellent field trip to a rockfall monitoring site in the alps.

Following the meeting in Germany, Tim flew straight to Fort Collins, CO, for the Glacier Seismology course to present on glacier hydrology, iceberg calving, and the seismic signals produced through these mechanisms.  Margot, a member of our lab, participated as a sponsored student in the Glacier Seismology course, and presented her research to date on Taku Glacier during the course.

 

A slide from the wrap-up to the Environmental Seismology workshop playfully illustrates the mechanism by which falling icebergs produce calving icequakes [Bartholomaus et al., 2012]
Environmental seismologists return from their field trip in the alps.

New paper reveals the factors that allow glacier advance

posted in: Publications, Research | 0

While glacier advance is extremely rare, study of advancing glaciers offers a more complete picture of glacier dynamics and the factors that enable such advances.  In Alaska, Yahtse Glacier is the fastest advancing glacier.  After a 40-km 20th century retreat, it has advanced 2.5 km since 1990, and is thickening by several meters per year over its terminus.  During this advance, the terminal stresses have transitioned from tensile to compressive, and the driving stresses have dropped by a factor of 3.  All of these changes at the Yahtse terminus have occurred despite net mass loss over the entire Yahtse Glacier basin, reflected by thinning in the upper reaches of the glacier.

Along flow and seasonal variations in ice speed, over the course of Yahtse Glacier’s advance.

 

We suggest that continued growth and progradation of a submarine morainal bank, and a steep icefall which dynamically isolates the terminus region from the upper basin, are critical for the sustained advance of Yahtse Glacier.

This work was led by Joey Durkin, a Ph.D. student at Cornell University, and published in Frontiers in Earth Science.

Setting up my scientific computing environment

posted in: Research | 0

I use macs at work due to their fluid interface with the unix environment, and their ability to run unix/linux programs.  I’ve recently bought a new mac, which has required that I get it set up for my scientific computing.  Below are the pieces of software I’ve needed, which help streamline your own computational workflows.

 

I start with most of Alejandro Soto’s instructions here (http://alejandrosoto.net/blog/2016/08/16/setting-up-my-mac-for-climate-research/), including iTerm, the XCode developer tools, XQuartz, Homebrew, and Anaconda (for Python).

Obspy for working with seismic data (https://github.com/obspy/obspy/wiki/Installation-via-Anaconda)

ffmpeg for working with video files and making timelapse movies – I used

brew install ffmpeg --with-fdk-aac --with-ffplay --with-freetype --with-libass --with-libquvi --with-libvorbis --with-libvpx --with-opus --with-x265

(https://trac.ffmpeg.org/wiki/CompilationGuide/MacOSX)

Octave, for my legacy Matlab code.  Octave is a free substitute for Matlab, with most of the same functionality.  I’m pleased to learn that it has a new GUI that also reproduces the Matlab GUI.  At the terminal:

brew install octave

BasicTex from Mactex-2016 for latex typesetting (because I think the full MacTex download of 2.8 Gb is obscene) (https://tug.org/mactex/morepackages.html) and then also TeXShop and LaTeXIt, from the same page

Cyberduck to have an easy to use GUI for transferring files between different computers/servers  (https://cyberduck.io/?l=en)

The Microsoft Office Suite, available through the University of Idaho

Google Earth Pro, available as a free download, for quickly learning about field sites (https://www.google.com/earth/download/gep/agree.html)

Dropbox, Google Drive, and OneDrive, for my online file storage.

The “Be Focused” app, from the App Store, which has a timer I use to keep targeted during my days.  It’s based on the pomodoro technique.

 

Understanding subglacial hydrology through seismology

Last week, I visited the Boise State Geosciences department to give a seminar on the use of seismology to understand subglacial water flow and sediment transport.  I reviewed two of my recent papers, published in GRL (this in 2015, and this in 2016), and also presented some of the initial results from my work with graduate student, Margot Vore, from Taku Glacier.  I enjoyed getting to know some other Idaho geophysicists and identifying new opportunities for collaboration.

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Seismic data collected from Taku Glacier

posted in: Field work, Research | 0

I’m just back from Taku Glacier, Alaska, where UI grad student Margot Vore, UT-Austin grad student Taylor Borgfeldt, and I retrieved new seismic data from a network set up on and around the glacier.  We had a great trip, and were treated to unexpectedly phenomenal weather, with warm air, and clear, calm skies.  The seismic data we collected will form the foundation for Margot’s MS thesis, and a paper examining the temporal and spatial evolution of subglacial discharge through the melt season.  We’re looking forward to digging into the data.

This project was initiated with Jake Walter, at the UT Institute for Geophysics, and is part of a much broader collaboration on the dynamics of the Taku Glacier terminus, with glaciologists and seismologists from University of Alaska Southeast, University of Alaska Fairbanks, and Central Washington University.

 

 

Welcoming Margot Vore

posted in: Research, Teaching | 0

I’m excited to welcome Margot Vore to my glacier dynamics group at UI.  Margot will be working to better understand the flow of water through and under glaciers, through the analysis of seismic data.  She’ll be analyzing seismic data recorded in 2016 near the terminus of Taku Glacier, outside of Juneau, in Southeast Alaska.  Margot comes to UI from CU-Denver, where she completed her Bachelor of Science degree majoring in math, and minoring in environmental science.  We’re happy to have her here in Moscow!

Glacier Dynamics at the University of Idaho

This fall, I’ve moved to the University of Idaho to begin work as an Assistant Professor and expand my lab group.  I’ve begun working with a graduate student who will work with glaciohydraulic tremor data to better understand changes in subglacial hydrologic processes.  Moscow, ID, home to the university, is a great town and I’m looking forward to getting to know the community and landscape while I establish my research here.

Please get in touch if you’re interested in joining my glacier dynamics group as a grad student or postdoc, or otherwise collaborating.

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Seismology for glaciology

posted in: Outreach, Research | 0

I’ll be giving a talk in the plenary session on Renaissance Seismology: Seismology for Non-Traditional Targets at the upcoming IRIS National Workshop, in Vancouver, WA.  I’m looking forward to sharing my perspectives on the tremendous utility of seismology for glacier problems, and learning about the latest seismological research and techniques.  I’m also happy about this being a short trip.  It’s my first meeting out of my new home in Moscow, ID, where I’ll start as an Assistant Professor at the University of Idaho in the fall.

IRIS is the national coordinating body for seismological research in the US – it stands for Incorporated Research Institutions for Seismology.

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New papers on ice-ocean interactions, glacier seismicity and subglacial hydrology accepted

posted in: Publications, Research | 0

Three new papers are now in press in Geophysical Research Letters, Journal of Glaciology and the Annals of Glaciology.  These papers are:

 

Bartholomaus, T. C., L. A. Stearns, D. A. Sutherland, E. L. Shroyer, J. D. Nash, R. Walker, G. Catania, D. Felikson, D. Carroll, M. J. Fried, B. Noël, M. van den Broeke (in press), Contrasts in the response of adjacent fjords and glaciers to surface melt in western Greenland, Annals of Glaciology.

In which we integrate glaciological and oceanographic observations from the west coast of Greenland to demonstrate how subglacial hydrology has contrasting effects on the glacier and fjord dynamics within neighboring systems.

Gimbert, F., V. C. Tsai, J. M. Amundson, T. C. Bartholomaus, and J. I. Walter (in press), Sub-seasonal pressure, geometry and sediment transport changes observed in subglacial channels, Geophysical Research Letters.

In which we demonstrate how seismic and discharge measurements can be combined to identify how subglacial pressure gradients within Rothlisberger channels and channel size vary over the course of the melt season at a glacier in Alaska.  Additionally, we discuss variations in sediment transport and the impact of flowing water on glacier motion.

Brinkerhoff, D., C. R. Meyer, E. Bueler, M. Truffer, and T. C. Bartholomaus (in press), Inversion of a glacier hydrology model, Annals of Glaciology, 57(72).

In which we constrain the evolution of the subglacial hydrologic system through measurements of glacier water discharge, glacier motion, and estimates of water inputs.

 

 

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