Rockfall at Franz Josef glacier

27 10 2011

Glaciers transport material down-valley in a variety of different ways.  It can be carried in meltwater (glaciofluvial), entrained and dragged along the base of a glacier (subglacial), buried within the ice (englacial), or carried on the glacier surface (supraglacial).

Of course these processes vary both spatially and temporally, a single rock or grain of sand may experience all of these transport mechanisms during its journey from the top of a mountain to a glacier foreland.  For example, a rock may fall onto the surface of the ice and be carried supraglacially, before being buried and becoming englacial, brought to the base of a glacier and transported subglacially, and finally melting out and transported down valley glaciofluvially.

Supraglacial material is derived from mass movement events on free face valley walls or nunataks adjacent to the glacier. The video at the top of this post shows one such event on the Franz Josef glacier, South Island, New Zealand. This was captured on video by a lucky (no one was hurt) tour party that visited the glacier that day.

Debris covered glaciers have a lower albedo than clean-ice glaciers.  This insulating debris layer means ablation is lower; therefore debris-covered glaciers are less sensitive to climatic change.  It has been hypothesised a rockfall event at the Franz Josef glacier ~13,000 years ago caused a non-climatic glacial advance, responsible for depositing a large terminal moraine, named the Waiho Loop, 14km downvalley of the current glacier terminus.

This theory originated when it was found that a lot of the Waiho Loop moraine was made of supraglacial debris.  Supraglacial debris is typically very angular (see the rock the tour guide is holding at 1 min 40 seconds), as it has undergone very little active transport, compared to debris that is rounded at the base of a glacier .

This is a controversial theory, as it proposes that the moraine represents a non-climatic glacier signal.  However, many glaciologists still believe that the Waiho Loop was deposited during glacier response to cooling events in the aftermath of deglaciation from the last glacial maximum.  However, current efforts to date the precise age of this advance, using radiocarbon and cosmogenic nuclides, suggest that the dynamics of the Franz Josef glacier were out of sync with other South Island glaciers and local climate at this time. There are many potential sources of error involved with these techniques, so the debate continues.  This is just one of many examples of equifinality we find in the natural world; where an end result can potentially be reached in many ways.  As Quaternary scientists, it’s our job to pick apart the causative mechanisms, and come to conclusions.Who knows, maybe this event will cause another glacial advance…

In the mean time, enjoy the video.

This video was found on The Landslides Blog. A story from the local paper can also be found here.

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Any Questions? – with Tim Lane

6 10 2011

This is the first of what we hope will become a regular feature, in which we interview someone working in the Quaternary Science field to find out what they do and what they like about doing it (and more importantly what they don’t). First up is the co-author of this blog Mr Timothy Lane, a PhD student at Durham University in the UK.

IQSB: Can you explain for our readers what you are researching?

TL:  Essentially I am trying to reconstruct the thickness, extent and behaviour of a large ice stream in central west Greenland, from about 20,000 years ago to the present day.  An ice stream is a fast flowing glacier, and about 20,000 years ago, during the last glaciation, the ice in Greenland was far more extensive.  We’re using a variety of methods to reconstruct this ice stream.  We look at the sediment and landscape it leaves behind so we can tell where the ice was, and in which direction it flowed, and we can use material from both lakes and rocks to try and constrain a date on when the ice retreated.

Hopefully this will help other scientists who are trying to look at the entire Greenland Ice Sheet, and reconstruct its behaviour.  It will also help to feed information into models of sea level change.

IQSB: Cool, got any good photos?

TL: Yeh!

There are more here from 2010:

Greenland

And here from 2011:

Greenland 2011

IQSB: What made you want to undertake a PhD?

TL: While I was doing my Masters at Royal Holloway and UCL, I realised that I loved research, and it was the only thing I really wanted to do in the future.  Funding is always an issue, and I was lucky enough to get a fair amount of funding.  I’ve had to scrape together money for the fieldtrips, but I count myself as lucky!  It took me a bit of time to decide I definitely wanted to go ahead with one, but I knew it was right, and loved the project.

IQSB: What have you found hardest about the process thus far?

TL: Hmm.  I’d say that the complete independence can be a curse as well as a blessing.  If you’re having a bad week, or get knocked back by negative feedback/results not working etc it can be hard to drag yourself back to get on with your work.  The trouble is that there’s no one else to tell you to do it, other than your supervisor.  Similarly, it can be a lonely experience.  I’m lucky in Durham as they have a strong postgraduate community, both through the department and Ustinov College (a sort of halls of residence with a bar and social/sports community attached).

IQSB: Can you describe a typical day?

TL: I guess it depends really.  I am normally in the office by about 8.45-9.00am, and if I have nothing else on will work at my computer all day (Split up by coffee breaks of course!)!  If I have lab work to do I will spend the day in the Geography department labs, or in the GIS room.  We also tutor undergraduates, and demonstrate on modules, so my day is often broken up with helping them.  Obviously when I’m on fieldwork it’s quite a different daily routine…..

IQSB: What are your plans for when you graduate?

TL:  I’m not entirely sure yet.  I’d love to stay in academia or research, but it’s a competitive field so we’ll see how it goes.  Ideally I’d like to work as a postdoctoral researcher overseas somewhere.  At the moment I’m thinking of Norway, Canada, America or New Zealand.  I like the idea of moving country to change scene, meet new people, and experience the ways research works in other institutions and countries.

IQSB: And finally, what is the coolest thing about being a glaciology PhD student at Durham University?

TL: Well Durham itself is a great town, small and beautiful.  The flexibility the PhD offers is another massive positive, and as long as you’re prepared to put the hard work in then the rewards are massive.  The best part of the PhD has got to be the fieldwork though.  Getting the chance to go to remote areas of Greenland as part of my “job” is incredible.  Spending a month camping in complete isolation with just two other people is a great experience, and the fact that we’re researching areas which have really never been studied before is very rewarding.  You see some incredible places that 99.9% of the world will never see, and have numerous experiences which you will remember for the rest of your life.