Holocene climatic change reconstructed from diatoms, chironomids, pollen and near-infrared spectroscopy at an alpine lake (Sjuodjijaure) in northern Sweden

Abstract

spectroscopy at an alpine lake (Sjuodjijaure) in northern SwedenHolocene climatic change reconstructed from diatoms, chironomids, pollen and near-infrared http://hol.sagepub.com/cgi/content/abstract/11/5/551The online version of this article can be found at: Abstract:The results of a multiproxy study reconstructing the climate history of the last 9300 years in northern Sweden are presented. It is based on diatom, chironomid and pollen analyses, as well as near-infrared spectroscopy (NIRS), of a radiocarbon dated sediment core from Sjuodjijaure (67°22ЈN, 18°04ЈE), situated 100 m above tree-line in the Scandes mountains. Mean July air temperature was reconstructed using transfer functions established for the region. The biological proxies show significant changes in composition during the Holocene and the inferred temperatures all follow the same general trend. For the period between about 9300 to 7300 cal. BP the reconstructions should be interpreted with caution due to the lack of convincing modern analogues in the training set. However the reconstruction suggest that July temperature was on average about the same as today, with several rapid short-term cold and warm periods. Cold periods were dated to about 8500, 8200 and 7600 cal. years BP and a warm period to about 7700 cal. BP. About 7300 cal. BP, a major shift to a warmer climate occurred. Pine migrated into the area, which was previously covered with birch forest. From the mid-Holocene until today the sediment record suggests a descending tree-limit and a gradual lowering of July temperature.

Holocene fire in Fennoscandia and Denmark

“…The mid-Holocene thermal maximum (HTM) is well documented throughout Scandinavia (Rosén et al 2001;Seppä and Birks 2001;Davis et al 2003) and is characterised by warm, dry climatic conditions. The timing of the HTM varies, usually between 6000 and 7000 cal years BP (Davis et al 2003) and coincides with an increase in continentality recorded in areas east of the Scandes Mountains .…”

Climate Change During the Holocene (Past 12,000 Years)

“…By using inference models that link present distribution and abundance of chironomids to contemporary climate, the past climate can be quantified from fossil assemblages. Chironomid populations respond rapidly to climate change and occur in a wide variety of modern environmental conditions Birks 2000, 2001; Kalniņa et al (2012Kalniņa et al ( , 2003Kalniņa et al ( , 2012 (Rosén et al 2001). Dendroclimatological data are more successfully used to reconstruct climate in those sites where climate is a limiting factor (such as at the latitudinal or altitudinal boundary of the forest).…”

“…Davis et al (2003) reconstructed quantitative characteristics of the climate for the past 12,000 years in western Europe based on analyses of pollen data from more than 500 sections. In northern Scandinavia, summer air temperatures close to the modern levels have been inferred from pollen data (Seppä and Birks 2001) and independent estimates based on chironomid and diatom assemblages (Rosén et al 2001).…”

Multi-proxy studies in palaeolimnology

“…Developing proxies include near-infrared spectroscopy (Rosén et al 2000(Rosén et al , 2001) and bio-markers in sediment organic geochemistry. The last is particularly useful as it is a record of organic compounds produced by organisms that leave no visible remains, such as algal groups, bacteria and cyanobacteria (e.g.…”