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Cryospheric Sciences

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

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.

Seismic Spring, part 3: All systems go – at work on Storglaciären!

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 third post. If you haven’t already done so, be sure to check out his first and second posts.

This update comes half way through our stay in Tarfala and, coincidentally, half way through our scheduled work programme!  If the weather stopped us working for the first few days of our stay up here, we’ve well-and-truly made up for lost time since then.  The cold weather arrived (and still lingers: -12°C in Tarfala Valley today!), so the station’s snowmobiles had no problem making the 300m climb up the hardened snow at Storglaciären’s front to deliver the heaviest of our equipment to the survey site.  The result is that we’re on schedule, and getting some very promising data (I’ve also found time to celebrate my 31st birthday, and enjoy a specially-made raspberry cake…!).

My first view from Storglaciären came on Wednesday (28 March), while overseeing the transport of our kit.  After Tuesday’s difficulties, there was a real sense of satisfaction in finally getting up there.  Nonetheless, when you hear the snowmobile’s engine struggling against a sled of cargo and the frontal slope of Storglaciären, it’s easy to think that this isn’t your lucky day either!  But then the engine noise calms a little as the surface levels out, and you realise that the hardest part is over and the glacier has decided to cooperate after all!  So, I’m pleased to present the first views this spring across Storglaciären and Tarfala Valley.

Photos from Storglaciären: Left: a west-looking view into the accumulation area of the glacier. Right: looking east back into Tarfala valley, at the mountains on its opposite side, just beyond the steepest part of the climb.

Each morning, Roger, Charlotte, Tavi and I set off from Tarfala and head up to the glacier. The 2km journey takes a little over an hour, but this depends on how much equipment we’re carrying.  Although snowmobiles handle our heaviest items, the batteries for the seismic system require recharging so are ferried back and forth each day.  I therefore tow a sledge of gear behind me… it’s a difficult trudge, but a great way to keep warm – plus, I feel some small connection with the earliest polar explorers!  Walking around the glacier is generally pretty safe: there are crevasses in places but, at this time of year where we’re working, they are snow-covered so the chances of an accident are slim.  Nevertheless, we carry rope and harnesses just in case – and undertook last-minute rescue practice on a frozen snowdrift at the station!

Out and about on the ice. Left: Roger and me, ready for the walk back to Tarfala at the end of a day. Centre: Tavi and Charlotte lunching on the glacier. Right: Roger refreshes his crevasse rescue skills, before heading up to Storglaciären.

So, what does a seismic survey involve?  Basically, we deploy a line of sensors (geophones) and connect them through several hundred meters of cable to a control laptop.  The geophones are buried around 50cm in the snow, to reduce the noise caused by the wind.  We then generate seismic energy at some known location, and record the output from the geophones – and, a bit like using an echo-sounder, we expect to identify seismic reflections from Storglaciären’s bed.  In our survey, we have two seismic sources at our disposal.  The first simply involves whacking the surface of the glacier with a sledge hammer!  As inelegant as this method sounds, the data we’ve recorded actually look better than those produced with the second source – namely a ‘buffalo gun’.  This involves loading a small explosive charge (actually a blank shotgun cartridge) into a steel pole, and firing it at a depth of around 1m in the snow.  The photos below show various elements of the seismic survey, and some hot-off-the-press data.  Our specific equipment is a Geometrics GEODE system.

Underway with seismic surveying. Left: Roger’s seismic ‘office’ on the glacier, from where the survey is managed. Centre: A seismic shot with the sledge hammer; all the cables in the foreground connect up the geophones (inset, before being buried!). Right: A first-look at some seismic data. The red curve highlights what we’re here for – reflections from the glacier bed!

The best interpretations from our seismic data also need reliable information about Storglaciären’s surface topography and the thickness of its snow cover.  For these, we’ve brought along two other bits of kit: a differential GPS for obtaining a topographic profile, and a ground-penetrating radar (GPR) for measuring snow thickness.  Leaving Roger to finalise the seismic setup, Tavi surveyed the line with a GPS, while Charlotte and I made a snow profile with the GPR.  Radar is really effective for this job: it’s very fast, and provides high-resolution subsurface images.  In fact, the resolution is so high that in addition to imaging the base of the snow, we also get responses from our buried geophones, so these data are also great for accurately measuring their depth!

GPR system and data. Left: Our GPR (a Sensors and Software PulseEKKO PRO), deployed on the Storglaciären. Right: The image that the GPR produces! The main stripe is the snow-ice interface (at around 1.5m depth), and the responses above this come from our buried geophones. The disturbed region at the ice-snow interface is probably a snow-filled crevasse, and we can make out responses to deeper englacial features (e.g., channels, entrained rocks etc).

So, it’s all systems go!  We’re using Sunday to check the data we’ve recorded, and tomorrow we’ll again be heading up to Storglaciären to continue shooting.  I’ll update you mid-week – for now, thanks for checking up on us!

Links:
Geometrics
Sensors and Software
One of a number of polar explorers, in his centenary year

By Adam Booth, post-doc at Swansea University

Seismic Spring, part 2: Planes, trains and snowmobiles

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 is reporting on the expedition in a series of posts published here in GeoLog. This is his second post, and the first from the research station itself. Check out the first post here.

Hello, from Tarfala Research Station!  After 48 hours of travel, it’s really satisfying to be able to say these words! For those who like visualising journeys as a red line that links points on a map, Tavi, Charlotte, Roger and myself have traveled between:

• Swansea and London (by train – although Roger actually got a lift down from Leeds…),

• London and Stockholm (by plane),

• Stockholm and Kiruna (by overnight train),

• Kiruna and Nikkaluokta (by local bus), and finally

• Nikkaluokta to Tarfala Research Station (by snowmobile – see figure below for a close-up!).

Snowmobile route from Nikkaluokta to Tarfala, across Láddjujávri lake and up into Tarfala Valley; Storglaciären (SG) is highlighted, south-west of Tarfala (grid squares are 2km). Inset photos: Roger and I are all smiles, as we head out of Nikkaluokta (right). An Alltransport snowmobile under a darkening sky (centre). The Alltransport crew prepare to haul our kit up a steep slope in Tarfala Valley (left).

As lengthy as our journey was, it was only its last leg that posed any real problem – but this was most impressively overcome for us by Erik Sarri and his team of snowmobile aces at Nikkaluokta Alltransport.  We left Nikkaluokta on snowmobile sleds with just a few flakes of snow in the air, although the sky became heavier as we crossed the frozen Láddjujávri lake.  Twenty minutes later, we entered Tarfala Valley, where our drivers faced steep, deep snowdrifts and the occasional white-out, with a strong wind lashing the loose snow into their visors.  But with a combination of experience and sheer determination, Alltransport ensured that four scientists and 400kg of seismic kit were safely delivered to Tarfala Research Station.  Thanks a million to all the team!

I was last in Tarfala in summer 2009, again as part of a study of Storglaciären. Back then, every day for two weeks, Alessio Gusmeroli and I could look up to the glacier before setting off at a leisurely stroll.  Right now, Storglaciären cannot even be seen from Tarfala because the wind hasn’t eased up at all (gusting at up to 80kph!) so, beyond the dozen-or-so buildings that make up the research station, the world appears completely white!  To prove that Storglaciären is still there, Andreas Bergström (Tarfala’s station manager) and I tried to snowmobile a box of equipment onto the glacier this afternoon (see below).

Almost my first view of Storglaciären this spring...! I’m waiting with the equipment, while Andreas and the snowmobile (circled) attempt the climb. The view looks almost west, from the forefield of the glacier.

The complicating factor here is that the front of Storglaciären is quite steep.  Whilst Andreas could get the unladen snowmobile up the slope, it got bogged down when towing cargo.  It’s a problem of snow conditions: despite the wind, air temperatures are actually quite warm – it got slightly above 0°C today – and this partial melting makes the snow dense, sticky, and uncooperative when we’re struggling to tow geophysical equipment!  What we need is a big chill – a calm, cold night to refreeze the snow, and we’re expecting these conditions in a few days.

So, I’m forced to hand the initial victory to the weather!  But it’s not all bad news – we’ve had time today to unpack, check and organise all of our equipment, and Charlotte has been practicing walking on snowshoes.  As the photographer here, I tried to follow in her footsteps, but sank straight into the thigh-deep drift!  Clear proof – snowshoes really do work!

Charlotte test-driving the snowshoes around Tarfala. In my normal boots, I couldn’t stand on the same snowdrift (I’m sure it’s more about pressure than weight...!).

If the wind eases tomorrow, we’ll power up some of the equipment and test it around Tarfala, and hopefully we’ll get some kit up onto the ice.  Wish us luck, and I’ll keep you posted!

Useful links: Nikkaluokta AlltransportAlessio Gusmeroli

By Adam Booth, post-doc at Swansea University

Seismic Spring: A geophysical field campaign on Storglaciären, Sweden

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.

Hi, and thanks for your interest in our field trip! For the next two weeks, my colleagues and I will be sending back reports from our campaign on Storglaciären – today’s post introduces the project and, of course, the team.

I’m writing this from my office at Swansea University, ahead of our trip to northern Sweden. My name is Adam Booth, I’m a post-doc in Swansea’s Glaciology Group, funded by the Climate Change Consortium of Wales, C3W, project, and I specialise in the application of geophysical methods (specifically seismic and radar) to glaciological problems. I use geophysics both to measure the thickness of a glacier, but also to quantify various physical properties of the ice and the material it sits on. For example, the speed of seismic energy can tell me how much liquid water a glacier contains [1], whereas the strength of a seismic reflection tells me a great deal about the material beneath the glacier bed [2]. It is this latter method that we will apply at Storglaciären, and we hope to introduce a new dimension to glaciological interpretation of seismic datasets.

Me! Dr Adam Booth

Storglaciären is 3.2 km long, has a maximum thickness of 230 m, and sits some 150 km north of the Arctic Circle in the shadow of Kebnekaise, Sweden’s highest mountain at 2104 m. Such ‘mountain glaciers’ are important to understand for climate change purposes, since their melt currently contributes more to global sea-level rise than the larger Greenland and Antarctic ice sheets [3]. For our group, however, Storglaciären also represents an ideal ‘natural laboratory’ where we can test new geophysical ideas. Although we’d certainly aim to apply our methods on Antarctica, it is far easier and cheaper to develop new techniques at Storglaciären – particularly because of the logistical support offered by the Tarfala Research Station, which is within snowshoed walking distance of the glacier front.

Four of us are making this journey north. Joining me from Swansea University are Prof. Tavi Murray and PhD student Charlotte Axtell, and we also bring along Dr. Roger Clark from the Institute of Geophysics and Tectonics at the University of Leeds.

Tavi is Swansea’s Chair of Glaciology and, as such, has enormous glaciological expertise and is an accomplished geophysicist in her own right; she has completed field campaigns on too many glaciers to list, and has close links with the British Antarctic Survey. Charlotte, by the end of her PhD, will know Storglaciären inside-out, as her project focuses on seismic and radar methods to investigate the glacier’s liquid-water content. At the moment, she is attending a glaciology training course on Svalbard, from where she informs me that, “it is amazing, and if I could, I’d just stay here!” Finally, Roger has near-encyclopedic knowledge of the cutting-edge seismic methods that are developed and used in the hydrocarbons industry. In recent years, he has been instrumental in helping us open that toolbox for glaciological applications.

I should also acknowledge support from the INTERACT scheme, who funds this fieldwork. This is a truly fantastic initiative, which provides logistical support and access to Arctic research stations. And it’s not only for glaciologists! INTERACT’s website currently highlights diverse research themes, including for studying biodiversity, palaeo-climatology and geochemistry.

Aerial view of Storglaciären (from Google Earth). The Kebnekaise mountain is immediately west of the glacier, and Tarfala Research Station is the small collection of huts in the red circle. Inset: our location in Sweden

Joining me in the field… Left: Prof. Tavi Murray. Centre: Charlotte Axtell. Right: Dr. Roger Clark

We leave for Sweden on 23 March, and we hope to be in Tarfala two days later. I’m hoping for a smooth journey – but also that the recent high-activity Northern Lights are still active by the time we arrive. Watch this space for updates, and the latest on our project’s progress!

Further reading:
[1] Endres AL, Murray T, Booth AD and West LJ (2009): A new framework for estimating englacial water content and pore geometry using combined radar and seismic wave velocities. Geophysical Research Letters, 36, L04501.
[2] Booth AD, Clark RA, Kulessa B, Murray T and Hubbard A (2012): Thin-layer effects in glaciological seismic AVA analysis: implications for characterising a subglacial till unit, Russell Glacier, West Greenland. The Cryosphere Discuss, 6, 759-792
[3] Intergovernmental Panel on Climate Change (IPCC) (2007): IPCC 4th Assessment Report: Climate Change 2007 (AR4).

By Adam Booth, post-doc at Swansea University

Check out the second post in the series here!