August 2011

Here is a short video interview with Glaciologist Dorthe Dahl-Jensen by APECS (Association of Polar Early Career Scientists).  Professor Dahl-Jensen heads up the Greenland ice-core drilling project at Summit camp this is the highest point on the Greenland Ice Sheet (~3200 metres above sea level).  She describes how she got into Glaciology and Climate research and why we collect ice-cores in Greenland.

Katharine Hayhoe, is a climate scientist and associate professor at Texas Tech University.  She also happens to be Canadian as well as a Christian who is married to a pastor of an evangelical bible church in west Texas.  She is known for her efforts in increasing the public understanding of climate science, especially within conservative communities.  (Note: Conservatives and Evangelicals in the US seem to have developed a default position of climate change denial).

She has been featured on Biologos as part of their video blog series:

There is also an interview with her in Yale 360 on how to find common ground in the bitter climate debate.

Here is how she would response to Rick Perry’s (the current Texas governor and Republican US presidential candidate) head-in-the-sand opinions on climate science.

She has also written a book with her husband entitled “A Climate for Change: Global Warming Facts for Faith-Based Decisions” which maybe I’ll get around to reading at some point.

Here is an amazing animation revealing a complete picture of ice flow across Antarctica:


Follow this link for a BBC article on this map which is built from a composite of billions of radar data points collected between 1996 and 2009 by three different satellites (Europe’s Envisat, Japan’s Alos, and Canada’s Radarsat-2).

The research work which produced this fascinating insight into ice flow across the whole ice sheet has been published in the journal Science.

“We present a reference, comprehensive, high-resolution, digital mosaic of ice motion in Antarctica assembled from multiple satellite interferometric synthetic-aperture radar data acquired during the International Polar Year 2007-2009. The data reveal widespread, patterned, enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland, over the entire continent. This view of ice-sheet motion emphasizes the importance of basal-slip–dominated tributary flow over deformation-dominated ice-sheet flow, redefines our understanding of ice-sheet dynamics, and has far-reaching implications for the reconstruction and prediction of ice-sheet evolution.”
Rignot, Mouginot, and Scheuchi. Ice Flow of the Antarctic Ice Sheet, Science, 2011.

doi: 10.1126/science.1208336 [subscription required for full article access]

Here is my submitted abstract for the American Geophysical Union (AGU) Fall Meeting, San Francisco, 5-9 December, 2011.

Modeling seasonal velocity variability and assessing the influence of glacial hydrology and sea-ice buttressing at the Belcher Glacier, Arctic Canada

“Seasonal ice dynamics on marine outlet glaciers can be influenced by the effects of both glacial hydrology and sea-ice buttressing.  In summer surface meltwater finds its way through crevasses and moulins into the subglacial drainage system thereby modulating the extent of glacier sliding.  Whereas in winter sea-ice build-up in front of the glacier terminus provides a buttressing effect exerting a back stress on the glacier ice.  In this study we seek to distinguish between contributions from these two processes at a large fast-flowing tidewater-terminating Arctic glacier.  The Belcher Glacier is the largest outlet glacier of the Devon Island Ice Cap in the Canadian high-Arctic.  We employ the use of a hydrologically coupled higher-order ice-flow model together with field data collected in 2008 and 2009.  Model output is compared against surface GPS observations as well as remotely sensed velocities derived using speckle tracking methods on Radarsat-2 imagery.  Five major drainage sub-catchments have been identified on the Belcher and a melt model is used to generate daily surface runoff for each sub-catchment.  The observed timing of lake drainage and moulin openings in each sub-catchment allow a seasonal timeseries of meltwater inputs to the subglacial drainage system to be constructed.  Model simulations for 2008 and 2009 forced with this meltwater input timeseries are presented.  Model responses to tidal forcing and changes in sea-ice back stress at the terminus are examined and compared alongside hydrologically driven accelerations.”

by Pimentel*, Flowers, Boon, Clavano, Copland, Danielson, Duncan, Kavanaugh, Sharp, and Van Wychen.

Update: The above abstract has been cancelled as I will no longer be able to attend the meeting.

I’m also an author on another abstract:

Subglacial hydrological modelling of a rapid lake drainage event on the Russell Glacier catchment, SW Greenland

“We use local-scale subglacial hydrological models to assess the development of the basal drainage system in response to a rapid lake tapping event on the Russell Glacier catchment, SW Greenland. Water inputs to the model are constrained by in-situ records of the lake drainage rate. Subglacial conditions are estimated from active seismic line analysis including basal topography and substrate characteristics.

A borehole slug test model is used to determine the radial flux of water from the drainage input point. Water flowing in the downstream direction is used to drive a 1-D flowband model, which allows development of interacting channelised and distributed drainage systems. The simulated basal water pressures are applied to an elastic beam model to assess vertical uplift at the lake drainage site. Modelled uplift outputs are compared with results from GPS stations located next to the lake.  Initial modelling results suggest that channels are necessary for evacuation of water from rapid lake drainage events, even with the presence of a sediment-based bed, the latter of which is usually associated with distributed drainage.”

by Dow*, Pimentel, Doyle, Booth, Fitzpatrick, Jones, Kulessa and Hubbard.

Want to know how a glacier works!?  Check out this great online glacier simulator.  You can select a mountain glacier or a tidewater terminating glacier.  Experiment by changing the air temperature to see how this effects the glacier.  Click here to try it yourself.

Apparently by trauma-induced coagulopathy! according to a new study published in the Journal of Forensic and Legal Medicine:

Joseph W. Bergeron, The crucifixion of Jesus: Review of hypothesized mechanisms of death and implications of shock and trauma-induced coagulopathy, doi:10.1016/j.jflm.2011.06.001 (subscription required).

My understanding was that crucifixion victims would likely have died of suffocation, so exhausted that they could no longer pull themselves up to breathe – yes a brutal way to die!!!  (For further reading on crucifixion in the ancient world check out Larry Hurtado’s blog entry.)

However, according to this article this is only one of six leading theories on the exact mechanism of Jesus’ death:

1) Pulmonary embolism

2) Cardiac rupture

3) Suspension trauma

4) Asphyxiation

5) Fatal stab wound

6) Shock

A reconstruction (left) showing how the skeletal foot of the crucified man from the Giv'at ha-Mivtar tomb (1st C Jewish remains) would have been fixed to the cross, with the original nail and heel bone (Calcaneus) on the right.

This new article has already been trashed by Piers Mitchell, a biological anthropologist at the University of Cambridge (see this link), who himself wrote a paper on the subject in the Journal of the Royal Society of Medicine in early 2006:

Matthew W Maslen and Piers D Mitchell, Medical theories on the cause of death in crucifixion, J. R. Soc. Med., 2006; 99: 185 – 188. 

Here is a quote from their conclusions on the matter:

“Our conclusion is that, at present, there is insufficient evidence to safely state exactly how people did die from crucifixion in Roman times. It is quite likely that different individuals died from different physiological causes, and we would expect that the orientation in which they were crucified would be crucial in this respect. Until new archaeological or textual evidence comes to light then it is only through more realistic humane re-enactment research that we may move closer to an answer.”