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Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids

Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids
Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids
Much of Greenland experienced summers warmer than present during parts of the early to middle Holocene, during a precession-driven positive anomaly in summer insolation. However, the magnitude of that warmth remains poorly known, and its timing and spatial pattern are uncertain. Here we describe the first quantitative Holocene palaeotemperature reconstruction from central East Greenland based upon insect (chironomid) assemblages preserved in lake sediments. We postulate that landscapes like our study site, characterized by minimal soil and vegetation development through the Holocene and thus less influenced by some important secondary gradients, are especially well-suited to the use of chironomids to reconstruct Holocene temperatures. The inferred timing of warmth at our study site near Scoresby Sund agrees well with other nearby evidence, including glacial geological reconstructions and temperatures inferred from precipitation isotopes at Renland ice cap, supporting the use of chironomids to reconstruct temperatures at this site. We infer highest temperatures from ~10 to 5.5 ka, followed by gradual cooling after 5.5 ka and progressively colder and less productive conditions after 3.5 ka. Models based upon two independent training sets yield similar inferred temperature trends, and suggest an average summer temperature anomaly from ~10 to 5.5 ka of 3 to 4 °C relative to the preindustrial last millennium. The estimated overall rate of Neoglacial cooling averaged over the period from 5.5 to 0.5 ka was 0.6 to 0.8 °C per thousand years, more than twice the rate previously estimated for the Arctic as a whole. Given strong apparent spatial variability in Holocene climate around the Arctic, and the utility of palaeoclimate data for improving climate and ice sheet models, it should be a priority to further quantify past temperature changes around the margins of the Greenland Ice Sheet, where few quantitative reconstructions exist and future warming will affect global sea level.
0300-9483
Axford, Yarrow
57d964d8-424f-40ef-a5f8-77fbf5bfe916
Levy, Laura
cdd50c3c-2b8d-4595-8f25-ee8c657acd11
Kelly, Meredith
8f38db5c-47f0-4363-a8db-e0966dd78926
Francis, Donna
87e63536-1c94-4cf2-ba97-cc935403078b
Hall, Brenda
54433963-ae04-49b8-8f24-e02bcd65fb0b
Langdon, Peter
95b97671-f9fe-4884-aca6-9aa3cd1a6d7f
Lowell, Thomas
dd4df9f9-52ab-4ff7-b4e4-1c7d362558d6
Axford, Yarrow
57d964d8-424f-40ef-a5f8-77fbf5bfe916
Levy, Laura
cdd50c3c-2b8d-4595-8f25-ee8c657acd11
Kelly, Meredith
8f38db5c-47f0-4363-a8db-e0966dd78926
Francis, Donna
87e63536-1c94-4cf2-ba97-cc935403078b
Hall, Brenda
54433963-ae04-49b8-8f24-e02bcd65fb0b
Langdon, Peter
95b97671-f9fe-4884-aca6-9aa3cd1a6d7f
Lowell, Thomas
dd4df9f9-52ab-4ff7-b4e4-1c7d362558d6

Axford, Yarrow, Levy, Laura, Kelly, Meredith, Francis, Donna, Hall, Brenda, Langdon, Peter and Lowell, Thomas (2017) Timing and magnitude of early to middle Holocene warming in East Greenland inferred from chironomids. Boreas. (In Press)

Record type: Article

Abstract

Much of Greenland experienced summers warmer than present during parts of the early to middle Holocene, during a precession-driven positive anomaly in summer insolation. However, the magnitude of that warmth remains poorly known, and its timing and spatial pattern are uncertain. Here we describe the first quantitative Holocene palaeotemperature reconstruction from central East Greenland based upon insect (chironomid) assemblages preserved in lake sediments. We postulate that landscapes like our study site, characterized by minimal soil and vegetation development through the Holocene and thus less influenced by some important secondary gradients, are especially well-suited to the use of chironomids to reconstruct Holocene temperatures. The inferred timing of warmth at our study site near Scoresby Sund agrees well with other nearby evidence, including glacial geological reconstructions and temperatures inferred from precipitation isotopes at Renland ice cap, supporting the use of chironomids to reconstruct temperatures at this site. We infer highest temperatures from ~10 to 5.5 ka, followed by gradual cooling after 5.5 ka and progressively colder and less productive conditions after 3.5 ka. Models based upon two independent training sets yield similar inferred temperature trends, and suggest an average summer temperature anomaly from ~10 to 5.5 ka of 3 to 4 °C relative to the preindustrial last millennium. The estimated overall rate of Neoglacial cooling averaged over the period from 5.5 to 0.5 ka was 0.6 to 0.8 °C per thousand years, more than twice the rate previously estimated for the Arctic as a whole. Given strong apparent spatial variability in Holocene climate around the Arctic, and the utility of palaeoclimate data for improving climate and ice sheet models, it should be a priority to further quantify past temperature changes around the margins of the Greenland Ice Sheet, where few quantitative reconstructions exist and future warming will affect global sea level.

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Axford et al Boreas accepted Feb 2017 - Accepted Manuscript
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More information

Accepted/In Press date: 24 February 2017
Organisations: Palaeoenvironment Laboratory (PLUS)

Identifiers

Local EPrints ID: 407641
URI: http://eprints.soton.ac.uk/id/eprint/407641
ISSN: 0300-9483
PURE UUID: f6c088e8-3e71-45c1-a1a7-1473c42c50e6
ORCID for Peter Langdon: ORCID iD orcid.org/0000-0003-2724-2643

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Date deposited: 16 Apr 2017 17:08
Last modified: 14 Mar 2019 06:08

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