11.5 Abisko NS

NEWS FEATURE NATURE|Vol 441|11 May 2006

P. ROSEN P. The mountain Lapporten looms over the village and research station of Abisko, Sweden.

ON THIN ICE The Arctic is the bellwether of climate change, which shows up there first and fastest. Quirin Schiermeier visits ecologists struggling to keep up.

n a splendid, freezing spring morn- Russia and Canada to move further north. ing in Sweden’s far north, global The Abisko station has become a prime A r warming seems far away. The pris- c t i c C i r c l e Abisko location for studying the effect of climate Otine landscape around the Abisko change on terrestrial Arctic ecosystems. Scientific Research Station, 200 kilometres Norwegian Streams of very warm air masses have been inside the Arctic Circle, is glistening white. Sea observed here at least once every winter over Thick ice covers nearby Lake Torneträsk. the past seven years, causing temperatures The spring equinox has passed, and the days SWEDEN near the surface to rise by 25 °C or more are quickly getting longer. But it is –15 °C as FINLAND within a day. The warm air melts the snow Gareth Phoenix, a plant ecologist from the cover, exposing and sometimes killing the University of Sheffield, UK, who has wintered plants beneath. If the melted snow then at the station, wades outside to check a ‘snow refreezes, the shrubs and lichens become melt’ experiment installed between mountain NORWAY encrusted with ice and are no longer accessible birches. as food for lemmings and reindeer. Recent Thin heating cables and four 1,500-watt population crashes of wild reindeer on the lamps hanging half a metre above the ground Arctic island of Svalbard are thought to be have melted the snow in small patches, expos- linked with such ‘icing’ events, although a con- ing shrubs and lichens. Phoenix looks pleased. nection is not proven. “Warming the Arctic outdoors in winter isn’t terribly easy,” he notes. With Massachusetts- Unknown unknowns based engineer Frank Bowles, Phoenix has Change comes faster in the Arctic than else- Experiments such as the snow-melt study, spent weeks tinkering with the array so that it where. As the snow-free season lengthens and which will run for at least three years, are melts snow without toasting the plants. He sea ice becomes less abundant, albedo — the meant to clarify the short- and long-term thinks he’s got it right now: the heat has melted proportion of sunlight reflected by the ocean effects of the melting episodes. Mimicking 45 centimetres of snow in three-and-a-half and the ground — decreases. The sunlight nature is not nature itself, however: Phoenix days, exactly what can happen during extreme that’s not being reflected by snow and ice is says that much more study is needed before warming events in the Arctic winter. absorbed instead, and this amplifies climate scientists can hope to understand the com- Such warming events occur much more fre- warming at high northern latitudes. Computer plexity of the changes going on. “The problem quently at Abisko now than at any time since models and on-the-ground observations both is to find out what the most interesting thing is climate records began there in 1913, says the suggest that the most pronounced warming of what you are measuring,” he says. “You often centre’s scientific director, Terry Callaghan. will occur in winter1. don’t know what you don’t know.” Ecologists are worried that the short-lived At the Abisko station, mean temperatures Each year, around 700 scientists and stu- melting episodes, and the sudden return to between December and February have risen dents come to Abisko to study Arctic climate cold weather afterwards, could harm plants by around 5.5 °C over the past century — eight and environment, carbon cycles, lake ecosys- and soils. Such disturbances could resonate times more than the average rise in the North- tems and geomorphology. The station has through the whole ecosystem in such areas, ern Hemisphere2. Similar warming has been plenty of rooms and lab space, as well as a new they suspect, with potentially devastating observed throughout the Arctic, causing glac- scenic lecture theatre and conference facility. knock-on effects for nutrient supply, plant iers in Greenland to flow faster, permafrost And unlike remote Arctic research bases, growth and animal populations. soils in Siberia to thaw, and boreal forests in Abisko is wired with electrical power. This

146 © 2006 Nature Publishing Group NATURE|Vol 441|11 May 2006 NEWS FEATURE luxury not only makes a stay at the station a comfortable experience; it is also a prerequisite for running long-term outdoor experiments

that require a constant energy supply. “It SCHIERMEIER Q. would hardly be possible to run a winter snow- melt experiment at a place like Toolik Lake station in Alaska, where you have only diesel generators,” says Jerry Melillo, co-director of the Ecosystems Centre at the Marine Biologi- cal Laboratory in Woods Hole, Massachusetts. For his part, Callaghan argues that many more long-term stations, like Abisko, are needed for the monitoring efforts (see pages 127 and 133).

From sink to source A key problem, he says, will be to determine whether the Arctic, which currently accounts for one-third of soil carbon storage on Earth, is likely to remain a carbon sink, or whether it will turn into a source of carbon. As soils grow Thaw point: an experiment to study what happens to plants when snow cover melts and refreezes. warmer, many worry that greater microbial activity could increase the rate of decomposi- which has not recovered since. Insect out- what governments may say, forest growth may tion and lead to increased releases of methane breaks such as this can convert a whole area do more harm than good to the climate,” says and carbon dioxide3. from a carbon sink into a source. Callaghan. For the moment, computer models suggest Climate warming sometimes brings what The Abisko station has taken a lead role in that the Arctic is still a small carbon sink. But may look like good news. In Lapland, for the European Union-funded BALANCE pro- the trends are highly inconsistent, says example, the tree line has risen 60 metres since ject, which investigates present and future Callaghan. Most Arctic lakes, for example, 1900, and satellite images confirm that forests climate-change vulnerabilities in the region. seem to be saturated with carbon dioxide and and shrublands have also In so doing, the researchers at have turned into carbon sources. increased in the northern parts “Mean temperatures Abisko have turned to some At Abisko, tall measurement towers and of Siberia, Canada and Alaska. in winter have risen valuable allies: the local Sami small chambers around individual plants The extra biomass, some population of reindeer herders, monitor the carbon flowing from soils and believe, could suck up more by 5.5 degrees over whose indigenous knowledge vegetation to the atmosphere and back again. carbon dioxide. the past century.” of the area could help scientists Such data are then fed into complex carbon But once again, the picture assess changes in terrestrial balance and vegetation models. But adding isn’t simple. Because trees decrease albedo in Arctic ecosystems. carbon-flux data from just one additional site comparison with the tundra vegetation they “The Sami are all around the landscape and can have a huge impact on the overall picture. replace, their spread might actually accelerate they see many things we don’t,” says Callaghan. At Abisko, Callaghan has seen how small warming in Arctic regions. A recent study in “They are really the missing link between our perturbations can affect the carbon balance of Alaska suggested that terrestrial changes in individual observations and satellite imagery. a whole region. From his office window, he summer albedo plus lengthening of the snow- And including indigenous knowledge just points at a bare slope on the distant shore of free season already has an effect similar in makes our own experiments more relevant.” Lake Torneträsk. During the exceptionally magnitude to the warming expected from a For instance, this spring saw the launch of a warm winters of 1950 and 2004, eggs of the doubling of carbon dioxide. And as shrubs and joint research project, including linguists, autumn moth (Epirrita autumnata), a cater- trees continue to proliferate, as some models anthropologists and Sami academics at the pillar feeding on mountain birch, survived predict they will in a carbon dioxide-rich Nordic Sami Institute in Kautokeino, Norway. there in vast numbers. Later in the year the world, they could further amplify Arctic ‘Snow and Ice’ will assess the impact of envi- insects destroyed large swaths of the forest, warming by two to seven times4. “Despite ronmental changes and extreme events on reindeer herding and the movement of reindeer and people through the region. Lessons from the winter snow-melt experiment are just one thing scientists at Abisko

hope to share with the Sami. As night falls over SCHIERMEIER Q. Lake Torneträsk, the eerie green veils of the aurora borealis drift across the starry sky. Relaxing in the improvised ‘tundra bar’ in the station’s cellar, Callaghan is scheming about supplying the Sami with small, portable weather stations. Then they too could become part of Abisko’s science network. ■ Quirin Schiermeier is Nature’s German correspondent.

1. Arctic Climate Impact Assessment Impacts of a Warming Arctic (Cambridge Univ. Press, 2004). Herding reindeer has given Norway’s Sami 2. Callaghan, T. et al. Polar Research (in the press). population an intimate knowledge of their environment. 3. Mack, M. et al. Nature 431, 440–443 (2004). 4. Chapin, F. et al. Science 310, 657–660 (2005).