Climate change and ice cover in one Arctic lake. December 16, 2012.
Average air temperatures have risen across much of the globe in recent decades, nowhere more quickly than in the Arctic. However, the consequences of rapid warming for the environmental conditions that shape life in the Arctic remain poorly understood. A new article published in the journal Climatic Change by an international team of scholars under lead author Ruibo Lei uses 44 years of ice data from Lake Kilpisjärvi, in the Northwestern fringe of Finland, as a case study to improve our understanding of recent shifts in Arctic ice cover. Because the workings of lake ice can be easily related to large-scale atmospheric changes, past ice records can shed new light on local and regional climate change. Extensive regional ice monitoring dates back to 1964, and the remoteness of the lake ensures that human influences other than anthropogenic change likely had little to no impact on the ice data. Fluctuations in atmospheric pressure at sea level that constitute the North Atlantic Oscillation also have a regionally minimal effect on ice cover.
Ice records from Lake Kilpisjärvi are unusually extensive and include, for example, the length of the ice season, freeze-up and breakup dates, snow depth on the ice, and total ice thickness. Together, they reveal a trend that is even more significant than what has been uncovered for other Northern Hemisphere lakes. Lake Kilpisjärvi, usually covered by ice from November until June, has frozen an average of 2.3 days per decade later since 1964. This coincides with a 3.4 day/decade reduction in total ice cover, and a thinning in annual average ice thickness from the mid-1980s until 2008, the last year of ice data included within the study. Ultimately, the article concludes that an increase in regional surface air temperature of 1°C is associated with a 3.4 day average delay in complete lake freezing, and a sooner ice breakup by 3.6 days.
The decline in ice duration at Lake Kilpisjärvi is similar to what has been recorded for the Baltic Sea, and reflects profound changes in Arctic ice cover that, in turn, will ripple through the region's ecosystem. In future decades changes in regional precipitation will prove nearly as important for northern Scandinavian ice cover as accelerating warming. Still, the new analysis of past records reflects the scale of the changes that have already taken place, while suggesting that even more significant transformations are not far off.
Lei, Ruibo et. al., "Changes in ice-season characteristics of a European Arctic
lake from 1964 to 2008." Climatic Change 115 (2012): 725–739.