Going to sea to study glaciers

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I recently joined the UT Marine Geology and Geophysics field course on the Gulf of Mexico to learn about methods to study the seafloor.  When deployed at the fronts of glaciers, these techniques can help us identify the stability of glaciers that end in the ocean.

My research frequently draws on a wide variety of disciplines to answer questions about glacier behavior.  Seafloor sediments not only reveal when a glacier last occupied a specific location, but rapid submarine sediment accumulation can help to stabilize a tidewater glacier terminus.  When a terminus is in contact with a barrier of thick sediment, ice loss is decreased because the sediment can shield the glacier terminus from warm ocean water and reduce the rate of stretching at the glacier front.  These topics are pertinent to the past, present, and future dynamics of ocean-terminating glaciers.

While based out of Galveston, TX, I joined the UT MG&G field course for two days on a Gulf of Mexico research vessel.  We acquired CHIRP and reflection seismic data to investigate the properties of the seafloor subsurface at two different scales/resolutions (~cm resolution for ~10 m, and ~m resolution for ~100 m).  We also took vibracore samples of the top meter or so of the seafloor.  Not only did I learn a great deal about the capabilities of these techniques, I had a lot of fun.  Thanks to Dr. Sean Gulick, Dr. John Goff, Marcy Davis, and Dan Duncan for welcoming me to their program.

I look forward to including these techniques in future research to better understand the dynamics of tidewater glaciers in Greenland, Alaska, and elsewhere.

 Deploying the CHIRP instrument to toe behind the vessel while underway.

Securing a core barrel to the vibrating head that will sample the shallow seafloor sediments.

 Lowering the CHIRP off the back of the vessel.

New technology for understanding glacier motion

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This week, I’ve been in Fairbanks learning how to use radar to gain an unprecedentedly sharp view of glacier motion.  We’ll be deploying this technology in Greenland this summer.

While camping at the terminus of Rink Isbrae (71.5 degrees N) for 8 days, we’ll be scanning the toe of the glacier every 3 minutes and recording motion between consecutive scans.  Variations in glacier flow speed at these high frequencies can tell us about the forces that drive and resist glacier motion, as well as connections between motion and iceberg production.  These data will support the broader project goal of understanding the factors controlling the retreat and acceleration of glaciers that flow into the ocean.

Thanks go to Mark Fahnestock, a professor at the Geophysical Institute at the University of Alaska Fairbanks, for lending our Univ. of Texas and Univ. of Kansas team one of his new radar instruments for our fieldwork.

Anticipating new data

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Since arriving at UTIG in January, I’ve been continuing to explore how seismology can inform us about glacier behavior.  Now, with the summer field season approaching, colleagues and I are preparing to return to Greenland and recover a year’s worth of data on tidewater glacier and fjord interactions.

Planning is now in full swing with colleagues here at the University of Texas Institute for Geophysics, as well as the Univ. of Kansas, Univ. of Oregon, Oregon State Univ., and NASA, to return to the coast of western Greenland.  Our teams of glaciologists and oceanographers will be in the field from mid-July through mid-August to collect data recorded since July 2013, and reset instruments for another year of remote operation.  We all are excited to see how our equipment managed through the harsh winter at 71 degrees N, at the edge of the Greenland Ice Sheet.

The data we collect will help us better understand some of the intricacies of glacier response to changing climate, and project how Greenland’s glaciers may continue to change in the face of ongoing climate change.

100+ citations

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My co-authors’ and my 2008 paper on subglacial hydrology and basal motion, published in Nature Geoscience, has now received over 100 citations.

In Bartholomaus et al. (2008), we showed how the Kennicott Glacier flows fastest when water storage within and beneath the glacier is increasing.  I carried out this work with Bob Anderson and Suzanne Anderson, as part of my Master’s research at the University of Colorado.  The citations are listed by Google Scholar.

Presentation at AGU awarded

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My final AGU talk as a graduate student has been awarded an Outstanding Student Presentation Award.  Thanks to all of the judges and administrators for the time volunteered to run this program.

In my talk, I described how seismic waves produced by iceberg calving, known as calving “icequakes,” can be used to produce time series of iceberg calving flux.  The calving icequakes reveal both seasonal and tidal variations in the rate of calving.  I received previous Outstanding Student Presentation Awards at the 2006 and 2012 Fall Meetings of the American Geophysical Union.

Profiles by the UAF Center for Global Change

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The UAF Center for Global Change (CGC) has recently published a short profile about my work, while the Cooperative Institute for Alaska Research (CIFAR) reported on a new publication they supported.

In 2010, I received a research grant from the CGC, with funds from CIFAR, to make oceanographic measurements within Icy Bay, Alaska.  The purpose of this work was to investigate the importance of submarine melt at the terminus of Yahtse Glacier.  With co-authors, I published the results of this work in EPSL, earlier this year.

Many thanks!

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I successfully passed my defense on Oct. 17th, and had a wonderful celebration with many friends and family.  I expect to receive my Ph.D. in several weeks, after completing revisions to my dissertation.  Many thanks to all those who supported me from near and far during this exciting time!

Dissertation defense on Oct. 17th!

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I’ll be defending my Ph.D. dissertation in just two weeks–on Thursday, October 17th, at 8:30 am, in the Elvey Auditorium of the Geophysical Institute at UAF.  My title is “Seismicity, seawater and seasonality: new insights into iceberg calving from Yahtse Glacier, Alaska.”

During my talk, I’ll describe some of the new things my advisers, collaborators and I have learned about iceberg calving by studying glacier seismicity and the fjord water properties at Yahtse Glacier in southern Alaska.  Some highlights: The implosion of huge air bubbles in the fjord after iceberg calving produces icequakes detected hundreds of miles from the glacier terminus!  Seawater in front of Yahtse reaches over 50 degrees F and can melt the glacier front at over 30 feet per day!  Glacier termini are delicate– variations in the tides trigger variations in the rate of iceberg calving.  But when the seawater is coldest in winter, very few icebergs fall into the fjord!

All of this helps us better understand one of the really major ways in which huge glaciers lose ice, and track iceberg calving remotely and automatically.  So many thanks to my family, friends and coworkers who have helped to make this work happen.

I hope to see you there if you can make it!

An iceberg calves off of Yahtse Glacier into Icy Bay.  Timothy Bartholomaus