Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Thursday, August 12, 2010

Blowing Up the Arctic

Today marks the 25th anniversary of the end of my first real geological project, in which I got to detonate explosives in a pristine landscape--in Canada's High Arctic. And since another ice island is in the news, what better time than to take a trip down memory lane?

Map of part of the Canadian High Arctic. Plundered from here.

I spent several months living in a camp on an ice island--a chunk of ice that calved off the Ward Hunt Ice Shelf on Ellesmere Island (northernmost island on the map) drifted southwest and at the time I was on it, was roughly between Ellesmere Island and Axel Heiberg Island, and over the summer months moved southwest off the coast of Axel Heiberg Island. The hope was that the block of ice would circumnavigate the Arctic Ocean and we would get a "free" ride enabling us to survey and sample the seafloor there.

It didn't quite work out that way.

Instead the island (which was about 5 km long and over 40 m thick) drifted into the sound between Meighen Island and Axel Heiberg I., eventually grounding and breaking up.

A photo of the ice island in 1985, taken from a book about the Polar Continental Shelf Project, which administered it. The ice island is the relatively smooth area with the long "ripples". 

Although I flew a number of times to and from the thing, I never got a very good photo (those were the days when digital photography was just a dream).

The actual ice island in the photo above is surrounded by multi-year ice (the rougher looking stuff). The ice island itself is relatively smooth.

Landing a plane is no problem, once you've smoothed off the surface. Driving around on it on snowmobiles, hauling equipment equally so. Here we are, drilling and casing shotholes in the ice.

The multi-year ice is thinner and rougher. There is a definite (but smooth) drop as you run off the edge of the island onto the multi-year ice. The landscape is a lot more rugged as well.

The area is pretty bleak. Other than people I think I saw two arctic terns all summer. And once there was a long trail of footprints of some small animal checking out some of the cable we left lying around.

What were we up there for?

There was an idea that having a research crew on a piece of arctic ice would be a really fine idea. For our project, the idea was to carry out a seismic survey to understand the crustal structure beneath the Arctic Ocean, taking advantage of this large block of ice that was going to circumnavigate it. We wouldn't have any navigational control, but the thinking was that we would nevertheless get some valuable data.

And if it happened to enhance Canadian sovereignty, so much the better. It was, after all, the year of the Polar Sea incident.

From the article referenced above:

"The most direct challenge to Canada's sovereignty in Arctic waters came in 1985, when the U.S. sent its icebreaker Polar Sea through the Northwest Passage without informing Canada or asking permission. The political skirmish that followed led to the 1988 Arctic Co-operation Agreement between the two countries. Boiled down to its essence, the agreement said the U.S. would not send any more icebreakers through the passage without Canada's consent, and Canada would always give that consent. The wider issue of whether Canada's Arctic waters were internal or international was left unresolved."

Read more: http://www.cbc.ca/canada/story/2009/02/27/f-arctic-sovereignty.html#ixzz0wK7O4zhs

For us this meant that there were some job openings for recent graduates. Six of us were selected, three from UWO and three from U of S. We were asked to get firearms acquisition certificates (easy then, very difficult now) and blasting permits, although due to time constraints they dropped the latter--we were given some half-hour of on-the-job training in explosives handling and off we went.

Those really were the days!

The first thing we did when we were there was have a shooting contest. I won, was declared camp marksman, which didn't turn out to be nearly as much fun as I would have liked. Mostly it meant I was tasked with periodic oiling of all firearms on the island, in addition to my other duties, which were mostly preparing to blow up the Arctic and then actually blowing it up. 

Flying to the ice island from Resolute (home base of PCSP) via Twin Otter. Note skis.

The experiment required us to set up explosive charges in sequence underwater. The shockwaves would bounce around in the water column, but at least some of the energy would penetrate the seafloor and be reflected from rock layers within the Earth, allowing us to infer subsea structure. So we would need to install the means to set off the explosives and the instruments to detect the sonic returns (sensors called geophones).

The first part of our work was installing the sensors, which involved a great deal of digging. There were to be at least 120 stations, each of which required nine geophones, eight in a circle (as at left) and one in the middle. 

The stations were each about 30 m apart and had been surveyed and marked before our arrival. You might see the stake near the centre of the photo.

The lasting legacy of this job (for me personally) is that I was able to impress my future wife with my digging prowess when she installed a garden some fifteen years ago. I was like the Shoveler.

The holes were dug through the snow cover down to the ice surface. In most places this was no more than a couple of feet down, but at one end of the array we ran into an old drainage channel, and there had to dig holes more than eight feet deep.

Once on the ice, the auger came into play, as we had to auger a hole down some six to eight feet or so, suspend the geophone in the hole, then fill it with water so it would freeze into place. The cables were suspended above the snow so we could hook them up later.

The cables were about 3 km long, so untangling them as they came out of the box was, shall we say, a chore. At 30 m intervals, there were nine takeouts, and these would be connected to the geophones that we had already buried. The other end led into the bank of computers in a special hut a couple of pictures up.

Next came the shotholes. We used a heat exchanger to melt a narrow tunnel from the top of the ice to the bottom, dropping out into the ocean. Now, since the ice island is about -40C in the middle, how do we keep the holes from refreezing?

The holes were lined with plastic tubing--about six inch diameter IIRC. The sections were screwed together until we had a continuous lined tube right through from the surface to the sea.

Then we filled the tubing with the Government of Canada's own secret blend of diesel fuel and trichloroethane (TCE). The stuff was a horror show. It soaked through your clothes, and was almost instantly absorbed through the skin and for a week everybody had a TCE hangover.

The mix was designed to be the same density as ice, so that as we filled the pipe, when the level of fluid within the pipe had risen to the level of the ice, all the seawater would have been displaced from the pipe. This blend had a freezing point well below the temperature of the ice, so the holes would stay open. 

Next the detonating cables were laid in. One end went to the data collection hut, and the other end of each went to one of the twelve shotholes. There was a lot of loose cable at the end, because the ends of it would be connected to the detonators, which were electrical. They would be fired from the hut. There was a circuit at the top of each shothole which allowed you to short the system so that you didn't accidentally fire off the detonator before the explosive was lowered down the hole.

Additionally, the detonators were of a special type that needed a fairly substantial voltage to fire, because static charges on snow could be large enough to accidentally fire off the standard issue detonators.

We were all a little tentative handling the explosive when we started off, but after a few days without anybody blowing up we really began throwing the stuff around. One of the guys even managed to crash a skidoo into a wall of dynamite boxes without mishap. Well, the engine cowling of the skidoo was crushed. I swear it wasn't me. But I did manage to sink a skidoo into one of the meltwater ponds.

Detonation control. Plug in the cable, charge the capacitator from the battery, select the station, and kaboom.

Things went swimmingly. As the summer progressed, the snow melted and the camp was surrounded by a lake of meltwater which we had to drain by drilling holes in the middle of camp. The original runway disappeared, and we spent some days making a new one. There were amusing and occasionally difficult issues with sewage and sanitation.

Meltwater was an ongoing problem as the temperature rose. Eventually we had to drain the camp.

The island shook itself free of the surrounding pack ice and began drifting. Every kilometre or so we travelled, we were to set off a series of explosions (ideally all twelve in sequence--though I don't remember how much time between shots).

There were several hitches that plagued the program. One of the most important ones was the reaction between the explosives and the TCE/diesel fuel blend. Since you had to punch a hole in the stick of explosive and insert the detonator, as the explosive was lowered through the special blend, there was an opportunity for some sort of chemical reaction to occur (which I infer from all the hissing and spluttering of the explosive when unexploded sticks were retrieved), and as a result occasionally when the detonator exploded, the explosive did not follow suit.

The work was hard on the cables, especially the ones that were constantly being connected to detonator cables. They would fray, or break, and I would have to strip insulation and occasionally solder the ends of the cables together. It was so cold that the solder would melt, or the flux, but never both at the same time.

Lastly, as the island was moving around, it was sometimes difficult for supply aircraft to find.

I had a two-week break in early June and when we flew back from Resolute (now Qausuittuq) we couldn't find the place. Fog had completely socked in the island during the flight. We flew in circles for awhile looking for it, but didn't have enough fuel to return to Resolute so we were forced to land at Eureka, which in comparison to the ice island, was paradise.

Eureka - paradise on Earth. Really. In mid-June, you have 24 hour sunlight, the weather is good, temperature mid-20s (C).

By July we were locked in fog and rain. The bright sun we had in the early days was due to the dryness and the cold (-30). It was warmer in the summer, but unpleasant. It was actually better when it was colder. You could even sunbathe--on top of the seismics hut where you were out of the wind in full sun you felt warm in a matter of minutes.

Ultimately papers were published. I remember looking a little bit at the raw data. One of the other students did an MSc thesis on the data. I later did my Master's in marine geology at MUN.

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