Global warming alone is not enough to account for the increasingly rapid melting of the ice sheet. Other factors are darkening the ice sheet surface, which results in greater rates of melting. The main focus of this collaborative research project is based on the hypothesis that microbes thrive and bloom on melting snow and ice surfaces, and darken the ice sheet surface as a consequence.

Life exists wherever there is liquid water on the Earth’s surface, and ice sheet surfaces are no exception. Just one drop of ice melt contains up to 10,000 microbes. Many of these are tiny organisms have green chlorophyll, similar to plants, to capture sunlight and grow via photosynthesis. They also develop their own dark-coloured sun block, often coloured red, purple or brown, which protects them from damage by the fierce sunlight that shines for 24 hours a day in the height of the Arctic summer. The microbes can turn the surface of the ice sheet purple to black when they multiply rapidly and bloom, which means that the ice sheet surface warms and melts much faster than if the surface were white and lifeless.

It is only recently that microbiologists have shown that dark-coloured microorganisms grow in melting ice. Over the next five years, the scientists will study these microbes and evaluate how their distribution and growth combine with the other factors to darken the ice surface and enhance the melting of the Greenland Ice Sheet.

Professor Martyn Tranter, Principal Investigator for the Bristol team and Professor of Polar Biogeochemistry in the University of Bristol's School of Geographical Sciences, said: ‘We aim to understand what controls the growth and blooming of the microorganisms. We want to know how they stick to the small amounts of dark particles present in the snow and ice, including dust and black soot, and if they retain those particles at the surface for long periods.’

The researchers will be joined by a team of international partner scientists from Denmark, the Netherlands, the US, France, Belgium, Canada, Czech Republic and Japan.

The work will support findings from fieldwork already undertaken on the Greenland Ice Sheet by partners at the Geological Survey of Denmark and Greenland (GEUS) as part of the Dark Snow Project. 

Data from the project on surface darkening will eventually be fed into a melt model of the whole ice sheet that will be used to predict how much sea level rise will occur in the future.