Reflectivity of snow decreases after deposition of particles

Various measurements and experiments in different parts of the world show that various particles are affecting the reflectivity of snow, according to a research report.

As snow is the most reflective natural surface on Earth, covering vast areas in the Northern Hemisphere during parts of the year, it plays a crucial role in the climate system, said a press release of Finnish Meteorological Institute quoting the research report.

Changes to the reflectivity will absorb more sunlight, and consequently snow melt, said the thesis work.

A team of researchers spread different types of particles onto snow surfaces in outdoor experiments in different parts of Finland with a focus on studying soot particles and how the deposition of the particles in different amounts decreased the snow reflectivity and increased snow melt.

"These sorts of experiments have never been done before on a natural snowpack outdoors, and we were able to obtain some interesting results that support theoretical snow reflectivity work. The results provide helpful information to the modelling community that simulate the wider climatic implications of particles in snow for larger scale-areas", said researcher Jonas Svensson.

Aside from measurements in Finland and the Arctic, Jonas was also part of a project that studied air pollution in India and how that influences Indian glaciers.

He participated in a few expeditions to the Indian Himalayas and made observations in glacier snow. In addition to the pollution originating from soot particles emitted in very large amounts in India, the glaciers snow reflectivity are also affected by another light-absorbing particle: mineral dust. Usually originating from deserts and semi-dry areas, he measured such high dust concentrations at certain times that it may be decreasing the snow reflectivity at the glacier to a larger extent than the more light-absorbing soot particles.

Meltwater from glaciers in the Himalaya provide a crucial fresh water source for many nations, and so understanding mechanisms and processes that affect glacier melt is of great importance. Jonas adds, "In the end, I have focused on investigating some small-scale processes, which are important to understand and quantify in order to accurately estimate the bigger picture of how light-absorbing particles are affecting the cryosphere.”

The Swedish researcher studied at Stockholm University before joining FMI in 2011. Jonas's thesis "Climatic effect of light-absorbing impurities on snow: experimental and field observations" will be publicly examined on 8 December, 2017 at the Auditorium Brainstorm of the Finnish Meteorological Institute.

The opponent is Dr. Hans-Werner Jacobi, Research Director, Institute for Geosciences and Environmental Research, University Grenoble Alpes/CNRS/Grenoble INP/IRD France. The Custos is Professor Pekka Kauppi from the University of Helsinki.