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.
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.
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!
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!
My friend, Bob McNabb, has written a summary of the paper Chris Larsen, Shad O’Neel, and I just published in Earth and Planetary Science Letters. You can read Bob’s review here.
In his summary, Bob describes some of the more significant results of our work and how these results affect our understanding of the behavior of ocean-ending glaciers. The full paper, in which we describe our observations and calculations of the ocean’s melting of the below-sea-level glacier terminus, is posted here. Bob is a post-doctoral researcher in glaciology at the University of Alaska Fairbanks, where he studies tidewater glaciers.
The Yahtse Glacier Project’s latest study will be published in the journal Earth and Planetary Science Letters.
In this study, Chris Larsen, Shad O’Neel and I show that melting below the sea surface can control the rate at which ice is lost from Yahtse Glacier’s toe. We estimate that warm ocean water melts back the submarine terminus at over 9 meters per day, and may reasonably equal 17 m/d. 17 m/d is the rate at which ice flows into the terminus region. Thus, during our observation period, any ice fracturing off the end of the glacier terminus (iceberg calving) may be the result of an iceberg having its foundation melted out from beneath it.
We also found that our late July measurements are fairly typical from an annual perspective. In September, when the ocean water is warmer and the amount of melt and rain water released at the glacier terminus is greater, we expect that submarine melt are even greater than the rates we report.
The accepted pre-print is available here.
We’re mid-way through 2.5 weeks of work at three adjacent ocean-terminating outlets of the Greenland Ice Sheet and our project is off to a great start.
I’m presently working with researchers from the Univ of Texas at Austin and the Univ of Kansas to try and understand why three adjacent glaciers on the northern west coast of Greenland have behaved so differently over the last decade. I’m leading the seismic component of our project- other team members are heading up the deployment of GPS receivers, weather stations, and the collection of a broad suite of oceanographic measurements. Our work is based out of Uummannak, a beautiful town with very friendly people at the foot of a jagged mountain. The water offshore is full of enormous icebergs and the far walls of the fjords consist of 4000′ cliffs. The town and its surroundings are an amazing place to work.
Our hard work and the early efforts by the lead scientists who got this work funded will really pay off next year when we recover the data that will be collected for us between now and then. In the mean time, my hard work will continue in Alaska when I return in mid-August to continue my research on Yahtse Glacier and complete my Ph.D.
While standing between streams of glacier meltwater, I lectured to our undergraduate students on the importance of liquid water on glacier motion, and how rapidly the link between hydrology and basal sliding can change. Afterwards, we hiked up into the alpine tundra for an overview of Kennicott Glacier, Hidden Creek Lake, and Mt. Blackburn, the 5th tallest mountain in the US. From that overlook, we discussed the 2008 Nature Geoscience paper that I published following fieldwork at this site.
I find this teaching to be great fun, and our students are consistently excited to learn about the spectacular landscape through which we’re traveling. The gorgeous weather we enjoyed certainly didn’t hurt anything! This was my 7th straight year of teaching in Alaska’s Wrangell Mountains.