Cave streams in Iceland?

The massive snowpack up at Hengill has left many of our streams buried in 8-10 feet of the miserable white stuff. There was only one thing to do on our trip this month: DIG! Here are some shots of various folks down the resulting holes:

The warmer streams in particular have carved tunnels through the snow with up to 2 or 3 feet of crawl-space, making at least Alex and I feel like we were back in an Alabama cave stream. A weird convergence. Here's a shot of Stream 9 flowing through its "cave." There is some light filtering through the snow - we'll find out if any primary production is occurring.

The little heat exchanger that could

Things are looking a little precarious for the heat exchanger. Iceland's heaviest snowpack in almost thirty years has left 10-12 feet of snow towering all around the pool in Stream 8 where the exchanger sits. We're hoping it all melts in a laid-back fashion, but we're prepared in case it doesn't. Here's a shot of Alex Huryn standing at the edge of the pool. You can see the pipes and manifolds of the heat exchanger at the bottom of the photo.

Despite all the snow, the heat exchanger has been working like a champ. Here's a plot of the differences in temperature upstream and downstream of the heat exchanger outlet in Stream 7. The pre-manipulation anomaly has been normalized to zero. Based on winter differences between upstream and downstream, we have a warming of 2.7 degrees C. If it hadn't been for the hiccup last December (see earlier posts), we would have been close to a 3 degree increase.

A welcome back and winter sampling

It has been a busy month of February up at Hengill. I arrived back in Reykjavik after an unplanned 3+ month hiatus to a warm welcome from friends at the

Veiðimálostofnun, my very own Veiði coffee mug! Now I am officially part of the family.

Properly caffeinated, I was quickly brought up to speed on winter sampling in Iceland after digging multiple snow pits in an unsuccessful search of pressure loggers from the
2+ meters of snow covering some of our streams.

Luckily for us Jims we shortly would have a crew from the US to aid us in our search. After lots of sweat and PI "encouragement" from Alex, Jon, and Wyatt we liberated all the logger data, completed a good chunk of the winter quarterly sampling, and spent good times around a wood fire in the scout cabin we rented for the week.

Check out a few photo highlights in the album to the right, and keep posted for more highlights and pictures.

The Hengill region became blanketed in snow much earlier this year than last. The snow has greatly limited our access to our sites. We've tried walking (3 hours one way), skiing (2 hours one way), and earlier we described what happened the last time we used a truck. On Friday, the University of Iceland's Geology department allowed us to rent a couple of snowmobiles and borrow Sveinbjörn, a technician who helped out with the equipment and our reconstruction of our heat exchanger. We were able to get to our sites in 20 minutes on the snow mobiles (pics 1, 2, & 3).













The dam feeding water from stream 7 into the heat exchanger was breached in late November. Before we could return and fix the system the water left in the pipes froze. The heat exchanger was fine.


Friday, we traveled in by snow mobile, rebuilt the dam, and excavated three different sections of iced up pipe. One section of pipe was covered in a meter of snow in places (pic 6). After excavating the pipes we let them thaw in stream 8 (20˚C) and then reattached all the piping (pics 4 & 5). Everything was running smoothly when we left Friday evening.













After we finished up with the heat exchanger we went over to our reference stream to retrieve some dissolved oxygen probes before the holiday break. Normally this is a 45 minute drive in the summer, but it only takes 20 minutes on snow mobiles. I know what I was for Christmas. About 70% of OH2 was covered in a layer of hard packed, wind blown snow (1 to 3 meters worth). Here is Jim trying to pull a probe out of the lower section of OH2. There's really a stream down there. I swear.

Snow

Hengill has gotten a lot of snow recently. So, for our December sampling we got help accessing our streams from the Hveragerði Rescue Squad. Most Icelandic towns have Rescue Squads. These are all volunteer organizations which help people lost, hurt, or stranded at sea, on land, and on top of glaciers. In their off time, they generously help us get to our field sites. The Hveragerði Rescue Squad has a truck with very wide tires. When the tires are slightly deflated the truck "floats" on the snow like its wearing snowshoes.

Last week we ran into some problems trying to drive into Hengill. While driving across a field we ran into a snow covered trench. The truck's front tires were hopelessly stuck. We had to call some people from the Selfoss Rescue Squad to pull the truck out.

The snow is just to deep for trucks. We'll have to ski or hike into our sites until the snow melts. Hopefully that will happen before May.

November Showers

After a fairly sunny summer, there has been a lot of rain this fall. In November, discharge in many of our streams was approximately 10 times higher than during the summer, although the discharge in some streams has hardly changed. These differences in flow arise because some of our streams drain large watersheds (like stream 14, shown above in Nov and below in July) while others have tiny watersheds and appear to derive almost all of their water from springs (e.g., stream 8). These differences in discharge variability among streams likely translates into large differences in disturbance. Disturbance is known to play an important role in shaping stream food webs and ecosystems.

Below, Wyatt dances while he measures nutrient uptake in stream 14 sometime in July.

Since the summer, we’ve been measuring the magnitude of disturbance in each of our landscape streams. We use super glue to attach tiny pieces of flagging tape to 50 randomly selected rocks in each stream. The photo below shows a transect of flagged rocks in stream 7. The flagged rock at the bottom of the photo has been moved downstream away from the transect.

After three months, we return to each streams and determine whether each rock has moved. In sum, these rock movement measurements give us a metric of the degree of disturbance in each stream.

Heat exchanger goes online!

What began as a pipe-dream (pardon the pun) more than two years ago has finally come to fruition. Five members of the University of Alabama team (Alex Huryn, Jon Benstead, Dan Nelson, Vija Pelekis and Philip Johnson) left on 19 October to install the heat exchanger at Hengill. Here we are unloading 750 lbs of gear at Birmingham airport. Those 14 bags came to $950 in excess baggage charges. Not bad for overnighting all that stuff to Iceland.

We were joined in Iceland by our stalwart postdoc Jim Hood and Ryan McClure, an undergraduate from Wyatt Cross's lab at Montana State University. With limited time, we had to hit the ground running. So the red-eye flight was followed only by a change of clothes, lots of coffee and obligatory hot-dogs. Then the rather groggy team headed out to Hengill for a long day's work, starting with some punishing sand-bag detail (Dr. Wyatt Cross's absence was more than conspicuous at this point :-) :). With the sandbags filled and carried to the site, we could begin constructing the heat exchanger. Here's a couple of shots of Alex Huryn and our intrepid engineer Philip Johnson joining the stainless steel pipes and starting to attach them to the PVC manifolds.

By mid-morning the next day, the heat exchanger was complete and the flexible 2" tubing for moving water through it was in place on the hillside. Here's a shot of the completed exchanger, with Alex, Philip and Gisli Gislason in the background.

It was soon lifted into place in the pool at the head of the warm stream and hooked up to the flexible tubing.

All that was left was to submerge the heat exchanger by damming the warm stream. Here's a shot of the completed set-up.

We could finally begin the warming manipulation, with immediate and impressive results! Here's a plot from four temperature loggers spaced along the experimental warming reach. All showed an increase of 3 degrees C (the upper logger [A] showed some variability as we adjusted the position of the diffuser at the outlet). This is good news, given that discharge in the cold stream is high at the moment, with only 40% of its flow going through the heat exchanger. Our potential warming will increase as discharge declines.

Here's a final shot from the opposite hillside, showing the position of all the components of the heat exchanger (including the vital engineer!). The whole set-up creates a ~30-m reach of the right-hand (cold) stream that will be warmed at 3 to 5 degrees C above ambient, hopefully for the next three years. We've already been studying this reach (and a reference cold stream) for a year. Every month we collect microbial, algal and invertebrate samples, as well as measuring nutrient uptake and whole-stream metabolism.

All in all, a fantastically successful trip and the result of many months of preparation by a large group of people. Special mention should go to our engineer, Dr. Philip Johnson, and Chau Tran, who helped Jon Benstead test the heat exchanger over the summer and then packed all of its components for shipping from Alabama.

Watch this space!