Sea ice holds deep secrets

Biologists and climatologists are among the beneficiaries of this basic research. Industry players with activities in ice-covered waters, such as petroleum and shipping companies, will also need the best possible information about the properties of ice.

3D observations of ice structures

"Nearly five per cent of the world's oceans are covered with sea ice," explains Dr Maus. "It plays an important role in the Arctic and global climate and ecosystems, yet we know very little about what it looks like at the microscopic level. The physical structure of sea ice is affected by elements such as how sunlight penetrates the ice, how it cracks and melts, how it presses against boats and platforms, and how it hosts microorganisms."

There were no previous three-dimensional observations of ice structures at the microscopic level, but Dr Maus has achieved them using ultra-high-energy X-rays known as synchrotron beamlines.

Stresses on ice

In the coming years, sea ice in the Arctic Basin may melt due to climate change. Nations with territorial claims there as well as petroleum companies will want to take advantage of this by exploring for and recovering potential petroleum resources. Meanwhile, new shipping lanes will be opened, shortening routes between Asia and Europe via the Northeast Passage (along Russia's northern coast) and the Northwest Passage (through the waters of northern Canada).

Young sea ice and icing problems will nevertheless remain, causing wear and tear on ships and installations. It will be crucial for companies involved to know as much as possible about the tensile strength of ice and its other mechanical properties. "Now we can compile data to combine with previous experience to give us much more fundamental knowledge of ice physics," says Dr Maus.

Climate and biology

His project also advances knowledge about microchannels in ice structures. Plankton live in these channels and pores, so the ice serves as a major biotope for vast numbers of living organisms -- a critical function in the Arctic Ocean ecosystem. The research project is generating new knowledge about the salinity of ice, another vital parameter. Besides revealing how old the ice is, salinity affects the vertical ocean currents so fundamental to our climate patterns.

Dr Maus believes that this X-raying method also holds major potential for the food industry in assessing how the freezing process affects food quality. "So synchrotron-based cryotomography and chemical analysis have an important general application," he asserts.

Demanding method development

Dr Maus reveals that developing the physical method was one of the greatest challenges in the project.

"Taking samples of Arctic ice is simple, but shipping the ice to the synchrotron facility (the Swiss Light Source at the Paul Scherrer Institute) in Switzerland without disturbing its microstructure demands real care. In the end, we solved it by centrifuging the water out of the ice, keeping the temperature constant during transport, and building a specialised instrument at the synchrotron facility for extracting samples."

Using synchrotron beamlines, Dr Maus was able to take high-resolution photographs with high brilliance over a very short time span. "We were also able to focus large, individual salt crystals on a scale of microns in order to find out how the structures form."