Emerging Holocene paleoclimate datasets point to a non-linear response of Icelandic climate against a background of steady orbital cooling. The Vestfirðir peninsula (NW Iceland) is an ideal target for continued climate reconstructions due to the presence of a small ice cap (Drangajökull) and numerous lakes, which provide two independent means to evaluate existing Icelandic climate records and to constrain the forcing mechanisms behind centennial-scale cold anomalies. Here, we present new evidence for Holocene expansions of Drangajökull based on 14C dates from entombed dead vegetation as well as two continuous Holocene lake sediment records. Lake sediments were analyzed for both bulk physical (MS) and biological (%TOC, δ13C, C/N, and BSi) parameters. Composite BSi and C/N records from the two lakes yield a sub-centennial qualitative perspective on algal (diatom) productivity and terrestrial landscape stability, respectively. The Vestfirðir lake proxies suggest initiation of the Holocene Thermal Maximum by ∼8.8 ka with subsequent and pronounced cooling not apparent until ∼3 ka. Synchronous periods of reduced algal productivity and accelerated landscape instability point to cold anomalies centered at ∼8.2, 6.6, 4.2, 3.3, 2.3, 1.8, 1, and 0.25 ka. Triggers for cold anomalies are linked to variable combinations of freshwater pulses, low total solar irradiance, explosive and effusive volcanism, and internal modes of climate variability, with cooling likely sustained by ocean/sea-ice feedbacks. The climate evolution reflected by our glacial and organic proxy records corresponds closely to marine records from the North Iceland Shelf.
Bibliographical noteFunding Information:
This work was supported by the Icelandic Center for Research through grants awarded to DJH (# 163431051 ) and to ÁG and GHM (# 130775051 , Grant-of-Excellence # 141573052 ) as well as the University of Iceland Research Fund . A CU Geological Sciences Department Mentor Grant supported Eric Gunderson, who assisted in developing both FTIR-BSi records. We thank Siggi and others from West Tours, Ísafjörður, for facilitating boat transportation to Hrafnsfjörður in August 2016. þorsteinn Jónsson, Sveinbjörn Steinþórsson and Sydney Gunnarson are kindly thanked for exceptional assistance and company in the field. We appreciate the constructive comments provided by two anonymous reviewers, which contributed to the overall improvement of this manuscript.
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- 8.2 ka event
- Dead vegetation
- Lake sediment
- Little Ice Age
- North Atlantic
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