| Research on Glaciers |
Research in Iceland
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Background to the Research in Iceland
I've been involved in glacier-related research in Iceland since 1988. I have had the opportunity to take part in some work on glacier-surface ablation, glacial impounding of drainage, and the release of ice-dammed lakes, but my primary interest has been in the origin of basal ice, especially as a geographical counterpoint to my work on that topic in Greenland. I have been fortunate to be able to make observations at most of the glaciers on the southern margins of Myrdalsjokull and Vatnajokull, from Solheimajokull in the west to Breidamerkurjokull in the east. Until about 2005 most of these observations were informal and unpublished, but around that time some interesting new material on Icelandic basal ice was appearing in the literature...
The interesting new work by other people
The interesting new work that I'd been hearing about from Iceland was all to do with a new idea that had been raised by a group of U.S. researchers including Dan Lawson, Ed Evenson, Richard Alley and others. They suggested, initially on the basis of their well-known work at the Matanuska Glacier in Alaska, that glaciohydraulic supercooling of subglacial water flowing upwards towards the margin through a subglacial basin can cause water to freeze onto the base of a glacier to create basal ice. Several UK researchers associated with an Earthwatch project headed up by Andy Russell at Keele subsequently observed ice at the margin of Skeidararjokull, in southern Iceland, that they believed might fit descriptions of basal ice formed by supercooling at Matanuska. One group of these UK researchers, including Russell, Matthew Roberts and others, started to work in co-operation with the U.S. group to elaborate the mechanisms of supercooling and basal ice formation at the Icelandic field site. However...
The Controversy
...as with all the most exciting bits of science, not everybody had the same idea about this issue! Supercooling and the origin of basal ice is a controversial topic. The controversy was not about whether it can happen. It was not even about whether it does happen. It was about how widespread it is and about the significance of its impact on both the basal ice layer and the regional hydrology. Some people argued that the supercooling mechanism contradicts previous theory and must be responsible for basal ice formation at all the other locations where basal ice of a certain type occurs . Other people argued that the supercooling mechanism complements existing theory, but that it only happens at specific types of location, and that similar types of basal ice can be derived from different subglacial processes. Some people argued that extensive layers of basal ice have been formed by this mechanism, while others argued that only localised patches of ice are formed this way, and that many of the extensive basal ice layers that are now being attributed to a supercooling origin are in fact created in other ways. Does supercooling only generate ice at tunnel outlets where rapidly rising subglacial water emerges from the glacier, or does it occur pervasively accross the bed, perhaps even in slow-flowing subglacial groundwater? No one yet knew how ice formed by supercooling, which has a very distinctive physical structure, changed diagenetically in response to glacier flow. If it forms subglacially and then loses its original structure in flowing towards the margin, can it still be differentiated, in ice-margin exposures, from basal ice formed in other ways? Is the chemistry distinctive? The isotope signature? The debris content? The chemical impact on waters in other parts of the system? There were lots of questions, and the answers would have lots of implications. So far, very little work had been published, and I had not had the opportunity to see any of the unpublished data, so from my point of view at that moment there seemed to be lots of questions and not yet many answers.
So then what?
I was very curious! I dug out my old notes
and photos, and planned togo back to the sites where people were seeing this
ice, just to have another look for myself!
2003: My New Project
In 2003 we were awarded a grant of ~ £19,000 to carry out
research involving new fieldwork in Iceland. This enabled us to follow
up some of the issues that have been mentioned on this page... see the
Leverhulme
Project page for details. I have also mentioned this issue briefly
in a "Classics Revisited" review for Progress in Physical Geography in
which I contrast the way in which the supercooling model has been
"tested" with the way Kamb and LaChapelle (1964) developed their theories
on basal processes. You can read
the paper here (.pdf file).
Update 2006: Having done some work on this...
Simon Cook has spent 3 years doing his PhD on this topic, and Debbie
and I have worked on the Leverhulme project grant, and done some independent
follow up work. Our overall conclusion so far is that SOME of the basal
ice may be formed by freezing of supercooled water, but a lot of the ice
evan at sites where supercooling occurs doesn't seem to be caused by the
supercooling. We are now working to identify diagnostic characteristics
of supercooling in basal ice facies, and working to clarify the significance
of supercooling both in modern glaciers and in the sedimentary record.
A list of some of our presentations and publications on this topic
are on the
Leverhulme Project page, here
.