Holocene and Lateglacial summer temperature reconstruction in the Swiss Alps based on fossil assemblages of aquatic organisms: a review

Abstract

2005 (November): Holocene and Lateglacial summer temperature reconstruction in the Swiss Alps based on fossil assemblages of aquatic organisms: a review. Boreas, Vol. 34, pp. 506-516. Oslo. ISSN 0300-9483.The taxonomic composition of chironomid, cladoceran and diatom assemblages in small lakes in the Alpine region shows a strong relationship with summer temperature. Since fossils of all three organism groups preserve well and remain identifiable in lake sediments, summer temperature transfer-functions can be developed based on the modern distribution of these organisms and applied to fossil records to reconstruct past summer temperature variability. We provide a summary of the chironomid-, cladoceran-and diatom-based transfer functions available from the Swiss Alps and discuss the potential problem of co-variation between summer temperature and lake nutrient conditions for transfer-function development. Whereas the diatom-based summer temperature transfer function remains to be evaluated in down-core reconstructions, the cladoceran-and chironomid-based transfer functions have been used successfully to produce summer temperature records on Lateglacial and Holocene time scales that are in good agreement with other temperature reconstructions in the Alps. Major problems that can be encountered when using fossil assemblages of aquatic organisms for temperature reconstruction in the Alpine region are biases in the inferred temperatures associated with human impact on lakes and parameters other than temperature affecting the fossil assemblages. A multi-proxy approach to palaeoenvironmental reconstruction is recommended to keep a close control on past catchment and within-lake processes during the time interval of interest.

How does taxonomic resolution affect chironomid-based temperature reconstruction?

“…Subfossil chironomid assemblages in the surface sediments of 114 lakes in and around the Swiss Alps and July air temperature estimates for these sites were available for calculating chironomid-based transfer functions for temperature Heiri and Lotter 2005;Bigler et al 2006). Assemblage data were based on subfossil chironomid remains isolated from the top 1-2 cm of sediment obtained from the deepest part of the lake basins.…”

Climate warming and vegetation response after Heinrich event 1 (16 700–16 000 cal yr BP) in Europe south of the Alps

“…Many chironomidbased palaeoclimate reconstructions from the alpine region (e.g. Heiri et al, 2003;Heiri and Lotter, 2005;Ilyashuk et al, 2009) and elsewhere in the North Atlantic realm (e.g. Brooks, 1997;Brooks and Birks, 2000;Heiri et al, 2007a) have documented marked climatic shifts during the Late Glacial and Early Holocene period.…”

“…The strong relationship between the distribution of chironomids and summer air temperature (Lotter et al, 1997;Brooks and Birks, 2001;Heiri and Lotter, 2005) has led to the development of chironomid-based inference models for reconstructing past summer temperatures (so-called transfer functions) and allowed chironomid-based palaeotemperature records to be produced (Brooks, 2006). Many chironomidbased palaeoclimate reconstructions from the alpine region (e.g.…”

Chironomid-based palaeotemperature estimates for northeast Finland during Oxygen Isotope Stage 3

“…Larocque and Hall (2003) elegantly show that in their study there was a close similarity between measured and chironomid-inferred summer temperatures, but they also state that on longer temporal timescales, this relationship might not remain constant. Therefore, each record showing midge-palaeotemperature reconstructions must be interpreted cautiously, and in the context of all palaeoenvironmental data available (Heiri and Lotter 2005;Walker and Cwynar 2006).…”