Journal of Paleolimnology

, Volume 23, Issue 1, pp 77–89

Chironomid-inferred late-glacial and early-Holocene mean July air temperatures for Kråkenes Lake, western Norway

  • Stepehn J. Brooks
  • H.J.B. Birks
Article

DOI: 10.1023/A:1008044211484

Cite this article as:
Brooks, S.J. & Birks, H. Journal of Paleolimnology (2000) 23: 77. doi:10.1023/A:1008044211484

Abstract

A chironomid data-set calibrated to July air temperatures, based on 44 lakes in western Norway, is used to reconstruct mean July air temperatures from late-glacial and early-Holocene fossil chironomid assemblages at Kråkenes Lake. The calibration function is based on Weighted Averaging Partial Least Squares regression and has a root mean square error of prediction (RMSEP) of 1.13 °C, a r2 of 0.69, and a maximum bias of 2.66 °C. All these statistics are based on leave-one-out cross-validation. A calibration function based on summer surface-water temperatures has a poorer performance (RMSEP = 2.22 °C, r2 = 0.30, maximum bias = 5.29 °C). The reconstructed July air temperatures at Kråkenes rise to 10.5 °C soon after deglaciation, are about 11.5 °C in the Allerød, decrease to 9.5-10 °C in the Younger Dryas, and rise rapidly within 15 yrs to 11.5 °C at the onset of the Holocene. There is a two-step rise to 13 °C or more in the early-Holocene. The likely over-estimation of Younger Dryas temperatures and under-estimation of early-Holocene temperatures probably result from the limited temperature range represented by the existing calibration set. The data set is currently being expanded to include lakes with warmer air temperatures (> 14 °C) and with colder air temperatures (< 8 °C).

chironomidsclimate reconstructioncalibrationWeighted Averaging Partial Least Squareslate-glacialKråenesYounger DryasAllerød

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Stepehn J. Brooks
    • 1
  • H.J.B. Birks
    • 2
    • 3
  1. 1.Department of EntomologyNatural History MuseumLondonUK
  2. 2.Botanical InstituteUniversity of BergenBergenNorway
  3. 3.University College LondonLondonUK