Mild Little Ice Age and unprecedented recent warmth in an 1800 year lake sediment record from Svalbard

Publication Title

Geology

Document Type

Article

Department or Program

Geology

Publication Date

2012

Keywords

19th century, alkenones, anthropogenic global warning, Arctic climate, Arctic regions, climate anomalies, climate variation, cold temperatures, heat transport, high arctic lakes, Holocenes, lake sediments, lake-sediment records, little ice age, paleoclimate records, spitsbergen, summer temperature, Svalbard, tephrochronology, West Spitsbergen currents

Abstract

The Arctic region is subject to a great amplitude of climate vari- ability and is currently undergoing large-scale changes due in part to anthropogenic global warming. Accurate projections of future change depend on anticipating the response of the Arctic climate system to forcing, and understanding how the response to human forcing will interact with natural climate variations. The Svalbard Archipelago occupies an important location for studying patterns and causes of Arctic climate variability; however, available paleoclimate records from Svalbard are of restricted use due to limitations of existing cli- mate proxies. Here we present a sub-decadal- to multidecadal-scale record of summer temperature for the past 1800 yr from lake sedi- ments of Kongressvatnet on West Spitsbergen, Svalbard, based on the fi rst instrumental calibration of the alkenone paleothermometer. The age model for the High Arctic lake sediments is based on 210Pb, plutonium activity, and the fi rst application of tephrochronology to lake sediments in this region. We fi nd that the summer warmth of the past 50 yr recorded in both the instrumental and alkenone records was unmatched in West Spitsbergen in the course of the past 1800 yr, including during the Medieval Climate Anomaly, and that summers during the Little Ice Age (LIA) of the 18th and 19th centuries on Sval- bard were not particularly cold, even though glaciers occupied their maximum Holocene extent. Our results suggest that increased winter- time precipitation, rather than cold temperatures, was responsible for LIA glaciations on Svalbard and that increased heat transport into the Arctic via the West Spitsbergen Current began ca. A.D. 1600.

Comments

Original version is available from the publisher at: https://doi.org/10.1130/G33365.1

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