Bjerknessenteret for klimaforskning er et samarbeid mellom Universitetet i Bergen, NORCE, Nansensenteret og Havforskningsinstituttet. 

Snow cover in a part of southern Norway in November 2018 - not as good as the in snow-rich spring. Oslo is located in the lower right of the image. Image credit: MODIS Land Rapid Response Team, NASA GSFC

Still caring about last winter's snow?

Last Easter, Harald Sodemann asked Bjerknes Centre scientists to bring snow home from the mountains. Read his account from this pilot skiing citizen science project here.

Written by Harald Sodemann, professor at the Bjerknes Centre for Climate Research and the Geophysical Institute at the University of Bergen

With all the rain pouring down this autumn, some may already look forward to an equally snow-rich winter as last year's in Western Norway. While the seasonal forecasts have not yet reached a consensus, at least by now some Bjerknes scientists know more about last year's snow.

In April of 2018, just before the Easter vacation, I, as leader of the SNOWPACE project invited Bjerknes scientists for a pilot citizen science project. How useful are samples of fresh snow taken by average skiers enjoying peak snow with sunshine at their hytte* for a top-notch research project?

Sodemann and his team got 6 participants that picked up their snow sampling kit: a spoon, several bags, three glass tubes with a unique sample ID on it, and a sampling sheet. Out of the 6 participants, 5 finally did take a sample, and delivered up to three glass tubes with melted snow from the Norwegian påskefjellet. With such a citizen science project, not everything goes as expected. Some sample tubes dropped and broke on the way home. Some tubes leaked, and some took several weeks to finally return to the lab. The overall success rate was still impressive, with 16 returned samples out of 23 that were handed out to participants - a success rate of 70%.

And the coverage was overall quite impressive as well. Samples were taken over a period from 23 March to 01 April 2018, between the region of Finse and northern Sweden, and with an elevation range of between 150 m to 1270 m above sea level (Fig. 1). While the scientists had hoped for fresh snow, the Easter vacation week was mostly windstill and sunny. In any case, there was surely enough snow around this year to at least take samples of the older snow pack.

Snow sample locations
Figure 1: Isotope composition at snow sampling locations in Norway during Easter 2018. Colour indicates stable isotope composition regarding oxygen-18. Most negative samples were found at high elevation.

Back in Bergen, SNOWPACE scientists analysed the samples at FARLAB by  injecting one millionth of a litre of the sample water into a heated tube, where the water first evaporated, and was then guided further through into an analyser where a laser tuned to the absorption wavelength of different isotopes of water waited for the making its measurement.

Given the wide spatial coverage of the samples, also measurements showed a substantial variation. The general pattern is that these heavy isotopes become more rare the further air moves inland (Fig. 1). This is was scientists expected, since due to their lower vapour pressure heavy isotopes condense and rain out first. Compared to ocean water, the samples contained between 0.73 to 2.15 percent less of the heavy isotope 18O. Another parameter, the Deuterium excess, indicated that evaporation conditions were dominated by a situation with a cold atmosphere over a relatively warm ocean (Fig. 2). One sample showed a large outlier that could be traced to a leaky sample tube.

Snow sample locations
Figure 2: Variation of the isotope parameter deuterium excess (d) in southern Norway. A value of d below 10 points to evaporation affecting the snow samples.

Overall, it is impressive what can be achieved with a targeted citizen science project. Based on minimal preparations and organisation, and at minimal cost, a wide spatial coverage could be achieved, with 70% success rate, good documentation, and timely return of samples. Next Easter, the citizen science project will be expanded to include a larger audience, adding more UiB employees and the University of Oslo. The project scientists are already now curious what next year's snow will have to tell.

* hytte - Norwegian word for cabin or hut used for recreation purposes. Many families have a hytte in the mountains or near the sea. It is common to spend Easter in a hytte in the mountains and go skiing.