Holocene ecosystem ontogeny and element cycling in the subarctic catchment of lake Torneträsk, NW Sweden: Large lake sensitivity to climate change
(English)Manuscript (preprint) (Other academic)
Understanding the response of sensitive Arctic and subarctic landscapes to climate changes is essential to determine the risks of ongoing and projected climate warming. Responses to climate change are not likely to be uniform because of site-specific differences in ecosystem susceptibility to climate forcing. Here we present a multi-proxy study of the development of the 330 km2 lake Torneträsk in northern Fennoscandia over the past 10000 years. By comparing responses of this large-lake system to past climatic and environmental change with those in small lakes in its catchment, we assessed when the magnitude of change was sufficient to affect an entire region rather than only specific areas of a watershed that may be more sensitive to environmental changes. Our results show three major periods of regional landscape alteration during the Holocene with distinct changes in the sediment composition: i) early landscape development (from c. 10000 until c. 5300 cal yr BP) following deglaciation, ii) increased soil erosion from c. 1300 until c. 100 cal yr BP, and iii) a rapid change during the past century to conditions similar to those before 1300 cal yr BP related to ongoing climate change. However, the timing and type of response to the different forcings differed fundamentally. The gradual early landscape development led to a successive change of the sediment composition, whereas the gradual climate cooling during the late Holocene, which altered terrestrial inputs to the lake, caused a rather abrupt shift in the sediment composition. However, this composition change occurred ~2000 years later than the first indications for climate cooling recorded in small lakes in the Torneträsk catchment; this suggests that a critical threshold was crossed around 1300 cal yr BP. In contrast to the gradual changes in the early/mid-Holocene and abrupt but delayed response at 1300 cal yr BP, the ongoing response to recent climate changes was immediate and of equal magnitude, emphasizing the unprecedented scale of the ongoing climate changes in subarctic Fennoscandia.
Geochemistry, soil erosion, climate change, oxygen isotopes, silicon isotopes, paleoecology, Holocene
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:umu:diva-111628OAI: oai:DiVA.org:umu-111628DiVA: diva2:872248