University of Helsinki

Tales from an Arctic crater lake

When the Professor of Environmental Geology returns from Canada to Kumpula Campus, his research group will have half a million years of environmental history preserved in a 30-metre tube. Unless they are surprised by an Arctic storm, that is.

Flat permafrost-hardened tundra as far as the eye can see, and in the middle of the plain a perfectly round meteor impact hole over

one million years old, half-covered in ice. It is as if one were looking at the set of a science fiction film or a photograph of a strange moon taken by a space researcher. In actual fact, the photograph was taken on the Ungava Peninsula,” says Veli-Pekka Salonen, Professor of Environmental Geology.

In addition to the photo of Pingualuit Crater Lake, Salonen goes through his recent purchases: several pairs of non-slip devices attachable to the shoe soles, a few robust ice picks, augers and ice saws with handles – the best that money can buy in Finland. He has borrowed a sleeping bag capable of dealing with temperatures of -30 degrees Celsius from the FINNARP, which concentrates on Antarctic research but he has yet to acquire Arctic rubber boots.

“This photo was taken in July,” says Salonen turning back to the crater lake. “When we reach Pingualuit, the ice cover will be almost two metres thick. I’m a bit nervous because I’m in charge of making the hole in the ice and it must be done by hand. You can only guess the force of the water that will gush out of the hole.”

By “us” Salonen means himself and four other geologists and palaeolimnologists with an ambitious plan. The expedition aims to bore a sediment sample from the bottom of the 267-metre deep lake, which stores a half a million years’ worth of North American environmental history.

Igloo as storm shelter

Pingualuit is the Inuit word for a place where the land rises. The treeless plain in the photograph does not provide the viewer with scale, so there is no clue to the fact that the rim of the crater lake is a veritable precipice, dozens of metres high. The diameter of the lake is approximately three kilometres.

The researchers, who will travel in the nature conservation area by sledges, have a great deal of physical work to do before the research equipment is safely by the hole in the ice, and the sediment sample packed in warm boxes and transferred to a heliport by Lake Laflamme a few kilometres away. “The chopper will take the samples to Québec, to Laval University, the home university of the head of our project Reinhard Pienitz,” Salonen explains.

The expedition may, however, face even harder obstacles than mere physical work, adds the Professor. The conditions are like in Svalbard. The treeline is hundreds of kilometres south. “I would assume that the temperature will be bearable, close to zero degrees, but the winds can be terrible. Hopefully, we won’t encounter a two-week Arctic storm.”

Eight days are scheduled for working on the lake, at least on two of which it is imperative that the conditions allow proper work. “We have with us two Inuit guides and an employee of the nature reserve, who have promised to build an igloo for us on the edge of the crater, but we are prepared to sleep in tents or even outside if need be. In emergencies, we also have access to a well-equipped barrack hut with a stove but it is impossible to work in a severe storm.”

Salonen says that they did not dare move the expedition closer to the summer since water gathering on the ice might prevent the work. “A stable ice foundation is necessary for our coring devide.”

The lightweight compressor corer – a new gadget that has only been tested on Swiss lakes – is, in addition to the chopper visiting the area, the only noisy piece of equipment the researchers use in Pingualuit. The reserve is a closely guarded natural park, where, for example, snow mobiles are banned.

“Initially, acquiring permission for the research was quite difficult but now the employees of the nature reserve are quite excited about the project. They believe that the status of the place will rise when unique information about the climate history is dug up from there. They want to develop high-quality wilderness tourism in Pingualuit ,” says Salonen giving praise to the co-operation.

Deep, clear and odourless

The lake has been studied before, for example, by means of seismic sounding from a boat. Thanks to the experienced geologist Michel A. Bouchard, in particular, Salonen and his colleagues have a good understanding of where to position their corer. “Hopefully, we won’t run into large boulders or other impenetrable obstacles. We have only so many tries to get it right.”

On the basis of echo sounding, it appears that the most fruitful and safest spot for sampling is found in the deepest depression, which is also the deepest lake depression in Canada. There are no visible landslide strata there, instead the sediment has settled on the bottom peacefully and slowly as if in the depths of an ocean. A one-centimetre slice tells stories of a thousand years.

All in all, there are over one hundred metres of sediment resting on the bottom of Pingualuit. The researchers are aiming to get samples from the first thirty metres. Organic residue, such as diatoms and chironomid larvae, has been compacted between the sand, silt and sludge. The intention is to recover five of these organic layers which were laid down mostly between glacial periods.

The scarcity of organic material means that the water in Pingualuit is clear, colourless and odourless. Transparency is better than in any other lake in the world with the exception of Masyuko in Japan.

Secrets under the ice sheet?

In addition to the difficulty of cutting a hole in the ice, Veli-Pekka Salonen’s mind wanders to July when the samples will be extracted from the tubes. At that time, Tomi Luoto, who is working on a doctoral dissertation on Pingualuit under Salonen’s supervision and is specialising in the determination of oxygen isotopes, will travel to Laval.

However, time is not wasted thinking about July. Before the sand and sludge are allowed into contact with oxygen, the sample will be thoroughly analysed in its tube. “We’ll be making, for example, magnetometric and X-ray fluorescens measurements, which will reveal the composition of the sediment, grain size and water content.” The first scientific results will be presented at a limnology conference in Montreal in August.

One of the most exciting questions is whether Pingualuit’s history will reveal a stage when it was liquid water under the ice sheet. If this were to be the case, Pienitz and his team will soon be able to admire with their microscopes the world’s first samples of sediment from a lake under the ice sheet. “We could then deduce all kinds of things from processes going on, for example, under the ice sheet of the Antarctic,” says Salonen dreamily.

The Canadian foundation funding the project is cautiously optimistic. The researchers will receive the funds reserved for analysing the samples only if they attain 30 per cent of their goals – that is, they succeed in boring a ten-metre length from the bottom of the lake. “Upon our return to Montreal, we’ll know how full the sample tubes we have loaded on the helicopter are.”

Virve Pohjanpalo

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