New evidence of warm early-Holocene summers in subarctic Finland based on an enhanced regional chironomid-based temperature calibration model

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Paleoclimate reconstructions based on biological proxies present methodological challenges, especially during
non-analog conditions, such as the early Holocene. Here, two chironomid-based training sets from Finland were
amalgamated to create a more accurate transfer function of summer air temperature. The aim was to reconstruct
Holocene paleoclimate in northernmost Lapland, in an area that has been either too warm or too cold for reliable
reconstructions using the original calibration models. The results showed that the combined calibration model had
improvedperformance statistics.The temperaturetrends inferredfromthedowncore chironomid recordusingthe
original and combinedmodelswere very similar. However, thereweremajor changes in their absolute values with
the combined model showing greatly improved accuracy. The chironomid-based temperature reconstruction
showed significant correlation with the previous pollen-based reconstructions fromnorthwestern Finnish Lapland.
However, differences were observed in the temperature trends of the early Holocene, when the chironomidinferred
temperatures rapidly increased, but the pollen-based reconstructions lagged behind suggesting that a
cool climate continued for much longer. However, similar to the chironomid record, new plant macrofossil
evidence from northwestern Finland also showed warmer-than-present early Holocene temperatures. Therefore,
we conclude that the early Holocene was probably warm in northern Lapland.
TidskriftQuaternary Research
Sidor (från-till)50-62
Antal sidor13
StatusPublicerad - jan 2014
MoE-publikationstypA1 Tidskriftsartikel-refererad


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