Seismic Spring, part 4: The fieldwork finale – starting the journey home!

10 Apr

As the Arctic wakes up from its polar night, Dr Adam Booth is leading a team of UK geophysicists on a two-week campaign of seismic investigations on Storglaciären, a mountain glacier in northern Sweden. He will be reporting on the expedition in a series of posts published here in GeoLog. This is his fourth and final post. If you haven’t already done so, be sure to check out his firstsecond, and third posts.

Hello!  I’ve got a change of scenery for this final blog post, writing not from Tarfala Research Station, but from the restaurant of Nikkaluokta Fjällstation.  Yes, our planned survey of Storglaciären is complete, and we have started our return journey to the UK.  Tavi travelled home ahead of us, a few days ago, and I’m taking the opportunity to write while Charlotte and Roger check out the souvenirs of Swedish Lapland in the Nikkaluokta gift-shop.  After sending our equipment to Nikkaluokta yesterday, we were ourselves snowmobiled back to the station early this morning (April 7).

Another two days of seismic and ground-penetrating radar (GPR) acquisitions followed the previous blog post.  On Monday morning (April 2), after the stroll onto the glacier, our first job was to dig into the snow to extract our carefully-buried geophones – and promptly re-bury them!  Although this might seem like a pretty pointless exercise, the second phase of our survey involved changing the orientation of our geophones to allow them to record a different component of seismic energy.  Digging through compacted snow is another great way to keep warm, particularly in temperatures approaching -20°C!  Recording these two components of the seismic wavefield is one of the novel aspects of our survey, and it should provide us with a more comprehensive interpretation of the internal structure of Storglaciären.

A kilometre of cable – Roger, Charlotte and me, repositioning geophones along the seismic line. The mountain in the background is Kebnekaise, Sweden’s highest peak.

A mention of cold temperatures can’t really pass without also commending Roger’s impressive tolerance of them!  While Tavi, Charlotte and I triggered seismic measurements along the line, Roger’s role was to operate the seismic computer.  With his movements restricted to occasional mouse-clicks and keyboard-taps, and with air temperatures dropping and a breeze blowing in, Roger really does start to freeze!  Of course, his frozen fingers weren’t helped by my (entirely accidental!) survey design, which placed his ‘recording office’ in the first part of the glacier to fall into shade, around 2 pm each afternoon.  I’ve therefore promised him that I will at least pack him a tent for the next Arctic survey we do…!

An air-conditioned office! Roger braves the cold to record our seismic data.

The next day (Tuesday, April 3), we were joined on the ice by Allen Pope, a PhD student at the Scott Polar Research Institute, and currently a volunteer at Tarfala.  His first experience of geophysical fieldwork involved  a couple of small seismic refraction and GPR surveys, just to make sure we have a good handle on the properties of the glacier’s snow cover.  As it happens, we think we’ve got this pretty well understood: our predicted snow thickness differed by less than 10cm when compared to that measured in a snow-pit at the same location – reassurance for us that geophysics really can work!  This then left nothing but to pack up the equipment, and wait for Tarfala’s snowmobiles to bring it back down to base.

A job well done – Tavi, Roger and Charlotte after completing the main phase of the seismic survey.

While it’s always a little sad to leave the wilderness and return to the office – especially when there’s such a friendly atmosphere at Tarfala – we’re headed home fully satisfied with the progress of the survey and the geophysical data that we’ve collected.  Really, we couldn’t have asked for more: perfect conditions for surveying, smooth field logistics and a really interesting set of seismic observations.

This might sound strange, but the thing that always strikes me on returning from the mountains is coming back to a land of trees!  On the outbound journey, heading up to a glacier, I never notice how suddenly the landscape changes from woodland into open snowfields.  On coming back, however, the sharpness of the tree-line always amazes me and descending back into a forested landscape – despite the lack of leaves – feels like the first ‘welcome home’.

The way back home. Left: heading back down Tarfala Valley, on the route to Nikkaluokta. Right: trees and a warm sun just outside Nikkaluokta Station.

But what a difference two weeks make – spring has really sprung around Nikkaluokta!  We crossed streams that actually contained flowing water, whereas on the way up to Tarfala they were frozen solid.  The sun even feels warm on my face, and here and there are shoots of grass sticking up through the snow.  I can definitely feel more southerly latitudes calling me back, on the other side of a sixteen hour train journey!

So, just time for some final words…!  I’d like to thank the whole of the field team – Charlotte, Tavi and Roger – for their efforts in making this trip such a successful one.  The same goes for the crew at Tarfala Research Station – a really excellent place to do science (you’d barely notice the wind and snow outside!).  Funding this science is the INTERACT scheme: a really valuable initiative, essentially providing free field opportunities for Arctic scientists.  Finally, I’d like to thank you for your interest in our project, and I hope you’ve enjoyed finding about the work that we do!  Be sure to check up on Swansea University glaciologists (Charlotte returns to Tarfala in July, for a Storglaciären summer!) and Leeds geophysicists, and the other research teams featured by the European Geosciences Union.

My last photo from Tarfala – thanks everyone!!

By Adam Booth, post-doc at Swansea University

And thank you, Adam, for reporting back on your work adventures in Tarfala! It was a pleasure to publish your guest posts in your blog, and I’m sure GeoLog readers enjoyed the insider’s perspective on a glaciology field trip as much as we did.

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