The climate in Svalbard changes rapidly. The temperature increase the last three decades is the highest in Europe. Changes are particularly pronounced during winter – precipitation comes more often as rain, mild spells are more frequent, and the sea ice is absent. Is this the future Svalbard winter? What are the consequences for the environment and societies? These are questions that project “Vinterregn” (Winter rain) aims at answering.
Climate change is expected to result in more extreme weather events. In parts of the Arctic, mild spells and heavy rain during winter are already becoming more frequent. With a 4-5 degrees increase in average mid-winter temperatures since the nineties, Svalbard represents a hotspot for studying Arctic climate change effects. Another characteristic feature of the archipelago is the unique network of weather stations with long and continuous measurements. The available research infrastructure also enables scientists to collect important data on, for instance, permafrost temperatures, snow and ice conditions, and fluctuations in plant and animal populations.
Project «Vinterregn» got a kick-off start due to the extreme weather in January-February 2012, when it was raining buckets and Longyearbyen at some point (30 January) was mildest in Norway. The maximum temperature reached 7.8 °C (8 February) at Akseløya, the highest ever recorded in Svalbard in February. The warm spell, which dominated the weather across the archipelago for two weeks, brought large amounts of precipitation. 272 mm precipitation (mostly rain) fell in Ny-Ålesund, and as much as 98 mm of this in one single day (30 January). This corresponds to one quarter of the mean annual precipitation and is a weather event with a return period of 500 years (based on historical records) but with much higher probability of occurring in the future, given IPCC’s expectations of global warming. Simulations of climate scenarios show that the mid-winter (December-February) mean temperature in Longyearbyen most likely will exceed the freezing point in some winters during this century. To put this in perspective: the average mid-winter temperature has been -13.6 °C since the measurements started in 1898, with winter 2011-12 (-5.2 °C) and last winter (-4.6 °C) as the warmest ever. There was close to no precipitation falling during the warm spell last winter, but a rise in winter temperatures will indeed lead to increased probability of precipitation falling as rain rather than snow.
The extreme weather in 2012 altered the snow conditions dramatically and resulted in record-high temperatures in the permafrost. During the second half of January and the first half of February, the average temperature in the upper three meters of the permafrost and the two meter active layer on top (which thaws in summer) on Janssonhaugen was as high as -6 °C. Compared with the period 2000-11, the temperature was ca. 4 °C and 7 °C higher in the upper permafrost layer and the active layer, respectively. This example of how the permafrost changes during and after such extreme weather events provides valuable insight into how rapidly the frozen ground can heat up in a future climate. A further substantial rise in the permafrost temperature can destabilize soils and mountain sides, which in turn may have implications for buildings, roads and other infrastructure in Svalbard.
The permafrost and the upper active layer still represent a considerable “cold storage”. This means that mild weather and rain in mid-winter often leads to ice-layer formation on the ground. The thickness and extent of this ice-layer depend on the amount and duration of the rainfall, as well as the air temperature, topography and amount of snow. As soon as the temperatures dropped following the extreme warm spell in February 2012, it became clear (especially for snow mobile drivers) that large parts of the tundra in Svalbard were covered by a thick, slippery ice-coat. Snow and ice thicknesses are measured every winter in Adventdalen, Reindalen, Colesdalen and the Ny-Ålesund area, and in February 2012 the ground-ice was record thick and averaged more than 15 cm in some areas.
The changes in snow conditions had a huge effect on the society and infrastructure. The FM-antennas were out of function for a period due to icing. Roads were closed because of slush avalanches, one of which destroyed the pedestrians’ bridge crossing Vannledningsdalen. Many flights were cancelled or postponed due to slippery runways, and it was nearly impossible to move around on the tundra. Many put spikes on their snow mobile belt, but numbers from Visit Svalbard AS and Statistics of Norway show a considerable reduction in the number of guided snow mobile trips (28 % reduction), ice caving trips (62 %) and glacier hiking trips (57 %) compared with the previous year. The number of hotel overnight stays also went down for the months February-May compared with the previous year, while the months prior to the extreme weather event had shown an increase.
Winter rain and icing may have dramatic effects on wildlife species in Svalbard, and especially herbivores such as reindeer and ptarmigan, for which the forage plants may be inaccessible due to the thick ice-coat. This was confirmed following the winter 2011-12 as the reindeer mortality rates (based on the number of carcasses and the number of live animals the previous year) were high in all monitored populations. In Sassendalen the mortality was the highest ever recorded – this in spite of the fact that the icing occurred rather late in the season and that the winter feeding conditions were good up to the event. From previous studies we know that icy winters also affect other species like the Arctic fox, which pup production partly depends on the availability of reindeer carcasses in spring. This means that annual fluctuations in winter weather cause more or less synchronous population dynamics across all the overwintering species on the Svalbard tundra.
Behavioural studies from Reindalen, Colesdalen and the Ny-Ålesund area show that the reindeer may change their space use following icing events, for instance by seeking high altitudes (where there is less ice) or alternative food sources such as seaweed and kelp along the beach. These changes in diet and habitat use include some drawbacks in terms of avalanche risk, falling, and problems with diarrhea (from the salty marine food), and most likely represent a last option to avoid starvation.
Our analyses show that the Svalbard winter has become warmer and more rainy, and that this trend is likely to continue in the future. The “extreme weather” in 2012 and the exceptionally mild winter last year may represent the normal winter already in a few decades, and the examples of the effects on the society, environment and wildlife may provide a hint of what to expect.
Project “Vinterregn” has received support from the Svalbard Environmental Protection Fund. We will hold a public lecture about the results at the University Centre in Svalbard (UNIS) on Monday 24 November 19:00.
Brage Bremset Hansen (Researcher at Norwegian University of Science and Technology)
Øystein Varpe (Ass. Prof. at University Centre in Svalbard and Researcher at Akvaplan-niva)
Ketil Isaksen (Climate researcher at Norwegian Meteorological Institute)