HR: 1340h
AN: PP33B-1563    [Abstracts]
TI: Assessing the Timing and Magnitude of the Holocene Thermal Maximum (HTM) Using Temperature Reconstructions from Chironomids
AU: * Langdon, P G
EM: p.g.langdon@ex.ac.uk
AF: University of Exeter, Department of Geography, Amory Building, Rennes Drive, Exeter, EX4 4RJ United Kingdom
AU: Brooks, S J
EM: s.brooks@nhm.ac.uk
AF: Natural History Museum, Department of Entomology, Cromwell Road, London, SW7 5BD United Kingdom
AU: Massaferro, J
EM: julimassaferro@crub.uncoma.edu.ar
AF: University of Comahue, CRUB, Bariloche, 8400 Argentina
AU: Gilchrist, S
EM: sjlg@geos.ed.ac.uk
AF: University of Edinburgh, School of Geosciences, Drummond Street, Edinburgh, EH8 9XP United Kingdom
AB: The magnitude and timing of Holocene maximum warmth has been the subject of considerable recent interest, particularly in the context of future climate change. Recent data syntheses from the Western Hemisphere of the Arctic (0-180 deg W; north of c.60 deg N) indicate that the HTM was time-transgressive over this region, with warming being particularly delayed in the vicinity of residual Laurentide ice, although the primary forcing was governed by orbital variations that scaled with latitude (Kaufman et al. 2004). Over 140 sites were used for this study, mainly relying on pollen and plant macrofossil reconstructions, with only 16 terrestrial sites providing quantitative reconstructions. Here, we present syntheses of HTM temperature reconstructions from chironomid stratigraphies using transfer functions based on modern calibration. Chironomids have been shown to be particularly sensitive indicators of summer temperatures especially during the early Holocene, where as well as indicating the timing and magnitude of peak warmth, they are also able to pick out minor climatic oscillations across a broad European transect (e.g. Caseldine et al., submitted; Brooks et al., in prep). The northern European chironomid reconstructions indicate HTM conditions from relatively high latitudes occurred around 10k cal. BP. Reconstructions from relatively lower latitudes, however, clearly demonstrate a relatively cool, unstable early Holocene that eventually leads to an HTM of conditions warmer than today after about 8k cal. yr BP that lasted for about 1.5-2.0k years, at least 2k years later than HTM conditions at higher Arctic latitudes. Some Holocene chironomid reconstructions have been undertaken from the southern hemisphere (e.g. Massaferro and Brooks, 2002), notably around central and southern Chile, although as yet no temperature-inference transfer functions exist for these regions. Preliminary comparisons will, however, be made between the different hemispheric chironomid records, relating in particular to the timing and magnitude of changes in chironomid fauna throughout the early Holocene. References Brooks, S.J., Heiri, O., Lang, B., Langdon, P.G., Velle, G. and Holmes, N. The response of Chironomidae to early Holocene summer temperature variability in northern and central Europe. In prep Quaternary Science Reviews. Caseldine, C.J., Langdon, P.G. and Holmes, N. Early Holocene climate variability and the timing and extent of the Holocene Thermal Maximum (HTM) in Northern Iceland. Submitted to Quaternary Science Reviews. Kaufmann, D.S. and 27 others. 2004. Holocene thermal maximum in the western Arctic (0-180W). Quaternary Science Reviews 23, 529-560. Massaferro, J. and Brooks, S.J. 2002. The response of chironomids to Late Quaternary climate change in the Taitao Peninsula, southern Chile. Journal of Quaternary Science 17: 101-111.
DE: 4901 Abrupt/rapid climate change (1605)
DE: 4938 Interhemispheric phasing
DE: 4942 Limnology (0458, 1845, 4239)
DE: 4950 Paleoecology
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005