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Merging chironomid training sets: Implications for palaeoclimate reconstructions

Record type: Article

Icelandic and Norwegian chironomid calibration or training sets were merged to investigate whether a larger combined training set would be useful to apply to subfossil chironomid data from Iceland for periods such as the early Holocene, the Holocene Thermal Maximum and the Little Ice Age, when temperatures can be expected to be outside the current temperature range of the Icelandic training set. Following taxonomic harmonisation, the Icelandic and Norwegian data sets were compared before being merged to form a combined Norwegian-Icelandic training set. Analyses showed that it was biologically and statistically valid to merge the two data sets. The resulting combined inference model for mean July air temperature had improved performance statistics (r2jack = 0.87; RMSEPjack = 1.13) when compared to the best performing Icelandic model (r2jack = 0.61; RMSEPjack = 0.83), due to the longer environmental gradient covered (Icelandic 6–11 °C; combined 3.5–16 °C), and to the increased number of samples (Icelandic = 53 lakes; combined = 207 lakes) and taxa (Icelandic = 47 taxa; combined = 133 taxa) present within the combined training set. The inference models were applied to an early Holocene chironomid sequence from Vatnamýri, north Iceland, and a 450-year recent record from Myfluguvatn, north-west Iceland, to compare the reconstructions produced. The various inference models produced similar trends and patterns of temperature reconstruction, but the inference model based on the combined training set produced a larger range of reconstructed temperatures than the Icelandic model. It was found that different inference models produced more variation in the reconstruction than when different training sets were used. A comparison of the Myfluguvatn reconstructions with meteorological observations showed that the combined Norwegian–Icelandic inference model produced more reliable results than the Icelandic or Norwegian inference models alone.

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Citation

Holmes, Naomi, Langdon, Peter G., Caseldine, Chris, Brooks, Stephen J. and Birks, H. John B. (2011) Merging chironomid training sets: Implications for palaeoclimate reconstructions Quaternary Science Reviews, 30, (19-20), pp. 2793-2804. (doi:10.1016/j.quascirev.2011.06.013).

More information

Published date: 14 July 2011
Keywords: chironomid, holocene, iceland, palaeoclimate, training set
Organisations: Environmental Processes & Change

Identifiers

Local EPrints ID: 194501
URI: http://eprints.soton.ac.uk/id/eprint/194501
ISSN: 0277-3791
PURE UUID: b405bca1-97e5-4bbc-8e3e-a20557121a3f
ORCID for Peter G. Langdon: ORCID iD orcid.org/0000-0003-2724-2643

Catalogue record

Date deposited: 29 Jul 2011 08:12
Last modified: 18 Jul 2017 11:27

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Contributors

Author: Naomi Holmes
Author: Chris Caseldine
Author: Stephen J. Brooks
Author: H. John B. Birks

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