July 25, 2012 Digging to Permafrost
They look friendly don't they?…until they say you can't have lunch until we hit permafrost. Today, I was a true field assistant with all the achy bones that go along with it. I left my limnological team as they had some data workup to do back at the station and joined Elin and Hanna of the AG212 course to work on their Karst lake and geomorphic mapping of the surrounding area.
My role here at Isfjord Radio/Linnevatnet has vacillated between logistics (rifles & radios), quaternary consultant, boat captain (I'll be back Helena and Dion!), and full on grunt. I pick things up, I put things down. Today, we dug holes, we filled them in.
The field day started with our typical hike in and ferry across Lake Linne, this time to the northeast shore which is the daily drop-off for students heading out to the karst lake territory. With 5 in the red boat, our 'taxi,' the going was slow but gave us all a little time to take in the morning sunshine and patchwork fog. On shore we split into groups with Lauren and Lukas headed to their lakes to complete bathymetric work, Sara to complete some solo MA-thesis research, and Elin, Hanna, and I to make a go at the earth's core.
Being one of my first days solely with the AG212 course I was psyched to have a bit of scenery change. The major goals of those in the course are as follows: 1. Students are grouped in pairs to accomplish field projects that examine the thermal regimes of the periglacial landscape and the interactions between lake reservoirs, the karst system, the continuous permafrost, and features/processes within the active layer on top of the permafrost. 2. Students are out here to gain skills in completing various geomorphic and limnological field techniques but also learn how to design an independent field research project. Such techniques include bathymetric mapping of the lakes (depth profiles & maps), geomorphic mapping, installing temperature and lake level probes, taking water column chemistry/sedimentological profiles, and working up the statistically and graphically at the base station. Back to our day…
So I've mentioned a hundred times that this area is underlain by continuous permafrost i.e. the ground is frozen all of the time at a certain depth. How do you know? Well, the active thawed layer does all kinds of fun solufluction stuff on top (see patterned ground photos) and students have used a ground probe to infer they are running into permafrost at depth but there is only one way to really know what is down there/verify the probe data and that is to dig to it. Upon reaching Elin and Hanna's karst lake we set to finding suitable places to excavate. Being a sensitive landscape we brought not only our implements of destruction but also a large plastic tarp to place any materials we dug out of the landscape. These sediments would then be filled back in leaving the environment as untouched as possible (leave no trace!…ok, only a little trace!).
Our first site was located in marine sand and gravel deposits rather close (~20m) to the lake and after reaching about a meter in depth we ran into groundwater. The hole started to fill with water and thus we got a quick temperature profile and filled it back in. Anyone who's done landscaping before knows the feeling of digging into coarse gravels and the skeletal vibrations caused by an enthusiastic spade plunge into large rocks…there were a few of those. Taking a short break from digging, we decided to do a bit of geomorphic mapping just below the outlet of the karst lake. Interestingly, we think we may have found another karst-like earth eating area and a large solufluction lobe being drawn through a bedrock saddle toward the lowlands of the Linneelva lake outlet.
Following mapping it was time to get serious about digging We chose another location nearer the high grounds of a marine terrace east of the lake and set to work. This time we managed to dig into the gravels to a depth of 1.2 meters but again had to abandon our efforts because of the temperature profile in the hole we encountered. In a permafrost environment one would expect that temperatures should decrease with depth on the way to the frozen ground. In this hole they certainly did but only to about 6 degrees C at 1.2 meters depth compared to around 8.7 at the surface. This meant we were not close to permafrost. Also, if anyone thinks that 1.2 meters is nothing, go out back behind your house and get back to us when you've got there : ). Excavator operators need not apply.
With the afternoon now getting on to about 2 pm we made one last effort at reaching the permafrost by changing our location to dig into the marine muds on the northwestern shore of the lake, a good distance and elevation from the shore to stay away from groundwater. The first shovel in the mud yielded the digging characteristics we knew we'd encounter the whole way down: stiff, heavy clay. On the bright side we hit very few rocks and the sediment consolidated itself into manageable scoop fuels making the excavation slow but productive. After about 1.5 hours and some shovel techniques that could be a cover story in Geology (our favorite scientific publication) we hit permafrost!
The permafrost layer was like running into an overly-frozen rocky road ice cream that differed in color as a brighter gray unit (as compared to the more mottled dark gray of the upper muds). We were psyched, dirtier than 'pig-pen,' and immediately took a temperature profile. The temperature profile was taken using a small scientific hand thermometer that basically looked like an overgrown meat thermometer. Such profiles can be affected by proximity to water reservoirs, the sediment type, permafrost depth, and any number of other environmental parameters. Sure enough, the temps. in our hole made their way down nice and neatly from around 9 C to 0 C at the bottom of the hole. They were so nice and neat that upon return to the station I had to hit the spreadsheets and make up a graph. Data in the notebook is a good thing but a graph is worth twice when it comes to grandiose hypotheses and arm-wavings. This sparked others to join in the graphing fun and we were able to make some fun comparisons between our data and the temperature gradients others found in the surrounding areas.
With permafrost found, we waited for Sara and our other karst friends, filled in the hole, and set about gathering our things to call it a day. When we were almost back to the station Lauren spotted some huge mist sprays in the fjord and sure enough there was a large whale breaching the surface to give us a show in the evening sun. Of this I know, it was not a beluga, it was dark blue-ish, about the size of the house we're staying in, and I did not get a picture. However, it is a memory I'll never forget, watching the whale spray mist high into the sky and seeing its back and tail disappear in the waves under the never-ending sun of Spitsbergen. A very good day…