Tim participates in international workshop to guide Greenland ice-ocean research

During the last several days, I have taken part in an international workshop to identify the major gaps in the scientific community’s understanding of interactions between the Greenland Ice Sheet and its surrounding ocean.

The workshop on Greenland Ice Sheet-Ocean Interactions, under the acronym GROCE, was hosted by the Alfred Wegener Institute, in Bremerhaven, Germany.  Over the two day meeting, ~28 scientists from Germany, Norway, the UK, Poland, Japan, Canada, the US and other countries framed the questions we considered most essential for understanding Greenland’s rapid changes, as well as the strategies and resources necessary to respond to those questions.  It was interesting and exciting to hear the commonalities and differences in research priorities from the broad cross section of glaciologists and oceanographers in attendance.

The report produced to summarize our workshop will be used to help guide funding agencies and the proposal efforts of the broader scientific community.

Next stop for me: San Francisco.  The annual meeting of the American Geophysical Union starts there on Monday.

Workshop attendees
Attendees at the 2014 GROCE workshop

New perspective on calving in press at Nature Geoscience

posted in: Publications, Research | 0

A new study, of which I am a co-author, examines globally-collected observations of iceberg calving and novel model results to present a new framework for understanding this important mass loss process.

Our study explains why calving rates vary so greatly over time, and how small changes in the environment can lead to tremendous changes in calving activity.  We show for the first time that calving belongs to a class of processes termed “self-organized critical.”  These processes occur in the same manner over many orders of magnitude such that there is no single, characteristic event size.  The calving terminus self-organizes to the point where it is always at the cusp of collapse. This property makes iceberg calving very challenging to predict.  However, in our manuscript, we demonstrate one potential solution for addressing this challenge and including self-organized critical calving in ice flow models.

Our paper will be published in a forthcoming issue of the journal Nature Geoscience.

Watch a presentation of my research

posted in: Outreach, Research | 0

I recently presented an overview of my research program to date at the weekly seminar of the Univ. of Texas Institute for Geophysics.  You can view it here.

In this talk, I describe my past and ongoing research into how ocean-terminating glaciers can rapidly lose mass through their termini.  This week, I’ll be traveling to Purdue University to make a similar presentation.  An abstract for this seminar is below:

The largest and most rapidly changing glaciers on Earth flow into the ocean. Ice loss from these glaciers will be the largest contributor to sea level rise in coming centuries and is also the least certain component of the sea level budget. These uncertainties are driven in large part by the poor understanding of two processes by which tidewater glaciers and ice sheets lose ice at their termini: submarine melting by warm ocean water and mechanical iceberg calving. 
The fronts of tidewater glaciers are among the most active and inaccessible geological environments.  These challenges have limited the long duration, high resolution calving and melt measurements that yield insight. Using seismology and oceanography, I identify the magnitudes and variability of submarine melt and iceberg calving at Yahtse Glacier, a major tidewater glacier in southern Alaska. I find that the submarine portion of the glacier terminus melts at over 10 m/d during much of the year. In addition, cavitation of icebergs beneath the sea surface can generate seismometer-recorded “icequakes,” revealing that calving varies seasonally and in response to ocean tides. Seismic tremor also offers the first ever view of subglacial discharge from a tidewater glacier.  Discharge increases during late summer, which promotes submarine melt.  Together, these multidiscipline observations improve our understanding of the geophysical processes responsible for rapid ice loss across the cryosphere.
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