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Prof. Martyn Tranter
Dept of Geographical Sciences, University of Bristol
22 October 2004
Professor Tranter is the director of the Bristol Glaciology Centre in the University of Bristol. He is a chemist interested in the movement of water through glaciers, and has done field work in the Alps, Norway, Svalbard, Greenland and the Antarctic.
Glaciers are important to the people who live near them for a number of reasons. The Tien-Shan range of mountains contains the glaciers that feed the semi-arid areas nearby and it is important to understand their behaviour in order to best manage the water in the district. Similarly, the Swiss are interested as they derive hydroelectric schemes from the melt water from glaciers; and it is important to know how much water will flow and when.
The normal methods of research would entail making several boreholes through the ice to the bedrock to investigate depths and motions. and to insert kilograms of dyes into crevasses to see where and when the water emerges. However, this sort of work is expensive in manpower and time. Early investigations were carried out in small ‘valley’ glaciers at Haut Glacier d'Arolla in Switzerland, and it was expected that water with very few contaminants would derive from within the ice itself, but if there was a high level of dissolved chemicals it would have made it to the bed of the glacier and dissolved some of the crushed rock that always lies there.
However, the resulting analysis was unexpected. Some of the water was anoxic, a lot had too much solute, and the isotopic distribution for carbon, oxygen and sulphur did not match what was expected of a-biological processes. The conclusion was that life existed in the water flows in and under glaciers.
A simple model to explain these results was that there was a population of bacteria growing and dying, with some other organic matter and sulphate reducing bacteria. It seemed to imply that there were bacteria that ate rock. Yet, every glacier showed evidence of biological activity,even in Antarctica.
Near Mount Erebus, there are some dry valleys where the precipitation is less than 10cm per year, but the evaporation rate is over one meter per year. These valleys are fed by glaciers, at the ends of which is a US research station at Lake Hoare. The surface of these glaciers contain what are known as ‘goldfish bowls’, which are typically clear ice balls about 30-50cm deep and 30cm across, and are completely frozen solid in winter. But in the summer, the sunlight is absorbed by dust in the bowls which then warms just enough to melt the ice at the bottom of the bowl, but leaves the surface frozen. The water in these bowls has a pH of 11, comparable to the East African soda lakes, and is among the most alkaline on the planet. Because the water is separated from the atmosphere there is almost no CO2 to increase the acidity. However, photosynthesis can take place, and some small blue-green algae survive there, along with some diatoms. Once every ten years, the weather allows the surface of the bowls to unfreeze, and then the chemical composition is drastically changed when it comes into contact with the atmosphere, which in turn flushes out the living population which is recolonised before freezing over again.
There are other strategies for survival and distribution in a climate with an average air temperature of 20C and strong katabatic winds. In the spring, the surface of a lake becomes covered in tufts of brown organisms. These had warmed under the ice when the sun struck the lake, and slowly melted their way up to the surface. The wind would then carry them away to some other ice lake where they would sink through the ice again. When divers went through the 5m ice cover on the lake, they found red algal mats on the bottom, and floating phytoplankton. Some small predators in the water also could photosynthesise in the summer, thus preserving valuable energy and materials. Curiously, there are also a lot of viruses in this environment, and it is thought that this would ensure a rapid turnover of organic matter, thus providing food for all occupants of the lake.
Other microbes make use of the so-called ‘blood falls’ in Taylor Glacier. There is just sufficient geothermal heat to melt the base of the glacier, where there is about 3-4 atmospheres pressure of dissolved CO2, which then fizzes up taking with it iron and other salts. The iron oxidises giving colour to the phenomenon, and the gas provides carbon for microbial activity to take place.
We can see then that the base of a glacier is wet, has a stable environment, and usually has sulphides in the rock which can first be oxidised to sulphate, and then in later anoxic conditions, can be reduced again, giving bacteria a chance to grab the energy released.
Some microbes contain proteins which act as anti-freeze, and others contain fats to withstand high pressures. This diversity makes us confident that there will be life in all lakes; even Lake Vostok deep in Antarctica under 3,500m of ice. It makes glaciers refugia for life, even in very early times when it is thought the Earth could have been completely covered by ice.
NASA are interested in this work because photographs of Europa, one of Jupiter's moons, show that it is covered in ice with some red lines across the surface. These may show biological activity, or at least biogenic material.
A Russian research team is trying to drill through to Lake Vostok, but want to reduce the possibility of contamination from the environment. However, they are not as concerned as once they were, because it is realised that any bacteria found would be highly specialised, having been separated from the rest of the world for so long. Even the slow movement of ice across its surface brings material that is at least one million years already.
It is worth noting that in Scandinavia, the glaciers are advancing due to an increase in winter snowfall, whereas in other parts of the world, they are retreating as the temperature rises globally.