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A long-term, high-latitude record of Eocene hydrological change in the Greenland region

A long-term, high-latitude record of Eocene hydrological change in the Greenland region
A long-term, high-latitude record of Eocene hydrological change in the Greenland region
A range of proxy approaches have been used to reconstruct short-term changes to Earth's hydrological cycle during the early Eocene hyperthermals. However, little is known about the response of Earth's hydrological and biogeochemical systems to long-term Cenozoic cooling, which began following the Early Eocene Climatic Optimum (53.3 – 49.4 million years ago; Ma). Here, we use the molecular distribution and isotopic composition of terrestrial biomarkers preserved in marine sediments of ODP Site 913, East Greenland, to develop a long-term record of high-latitude hydrological change between 50 and 34 Ma. There is a marked decline in the concentration of conifer-derived diterpenoids and angiosperm-derived triterpenoids during the Eocene. As the input of wind-blown conifer pollen remains stable during this interval, this implies that decreasing di- and triterpenoid concentrations reflect declining influence of fluvial inputs – and perhaps terrestrial runoff – throughout the Eocene. Branched GDGTs and bacterial-derived hopanes indicate an increased input of soil- and kerogen-derived organic matter, respectively, after 38 Ma. This coincides with evidence for ice rafted debris and suggests input of organic matter via glacial processes. This also implies some continental glaciation occurred on East Greenland in the middle-to-late Eocene. Leaf wax hydrogen isotopes extending throughout this section – the first such long-term record from the Paleogene - indicate that precipitation δ2H was persistently higher than that of modern coastal Greenland, consistent with warmer ocean source waters and enhanced poleward moisture transport. Non-intuitively, however, this effect appears to have been smallest during the warmest part of the record, and higher δ2H values occur in the middle Eocene. Although interpretation of these hydrogen isotope trends is unclear, they clearly indicate – alongside the changes in biomarker abundances – a perturbed hydrological cycle through the Eocene in coastal Greenland. More long-term records are required to ascertain if this represents regional or global hydrological reorganisation.
Biomarkers Alkanes Vegetation Cenozoic Palaeogene
0031-0182
1-13
Inglis, Gordon N.
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Carmichael, Matthew J.
943dcc2c-5c5b-4693-a9eb-9f8905b7293d
Farnsworth, Alexander
42c07817-9776-49d0-af90-e562d8b85482
Lunt, Daniel J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1
Inglis, Gordon N.
1651196d-916c-43cb-b5a0-9b3ecaf5d664
Carmichael, Matthew J.
943dcc2c-5c5b-4693-a9eb-9f8905b7293d
Farnsworth, Alexander
42c07817-9776-49d0-af90-e562d8b85482
Lunt, Daniel J.
931ecfb5-1f50-412c-8f01-a46d69b1f82f
Pancost, Richard D.
5914e19e-7777-4304-9fd8-86e2e9cfe8a1

Inglis, Gordon N., Carmichael, Matthew J., Farnsworth, Alexander, Lunt, Daniel J. and Pancost, Richard D. (2020) A long-term, high-latitude record of Eocene hydrological change in the Greenland region. Palaeogeography, Palaeoclimatology, Palaeoecology, 537, 1-13, [109378]. (doi:10.1016/j.palaeo.2019.109378).

Record type: Article

Abstract

A range of proxy approaches have been used to reconstruct short-term changes to Earth's hydrological cycle during the early Eocene hyperthermals. However, little is known about the response of Earth's hydrological and biogeochemical systems to long-term Cenozoic cooling, which began following the Early Eocene Climatic Optimum (53.3 – 49.4 million years ago; Ma). Here, we use the molecular distribution and isotopic composition of terrestrial biomarkers preserved in marine sediments of ODP Site 913, East Greenland, to develop a long-term record of high-latitude hydrological change between 50 and 34 Ma. There is a marked decline in the concentration of conifer-derived diterpenoids and angiosperm-derived triterpenoids during the Eocene. As the input of wind-blown conifer pollen remains stable during this interval, this implies that decreasing di- and triterpenoid concentrations reflect declining influence of fluvial inputs – and perhaps terrestrial runoff – throughout the Eocene. Branched GDGTs and bacterial-derived hopanes indicate an increased input of soil- and kerogen-derived organic matter, respectively, after 38 Ma. This coincides with evidence for ice rafted debris and suggests input of organic matter via glacial processes. This also implies some continental glaciation occurred on East Greenland in the middle-to-late Eocene. Leaf wax hydrogen isotopes extending throughout this section – the first such long-term record from the Paleogene - indicate that precipitation δ2H was persistently higher than that of modern coastal Greenland, consistent with warmer ocean source waters and enhanced poleward moisture transport. Non-intuitively, however, this effect appears to have been smallest during the warmest part of the record, and higher δ2H values occur in the middle Eocene. Although interpretation of these hydrogen isotope trends is unclear, they clearly indicate – alongside the changes in biomarker abundances – a perturbed hydrological cycle through the Eocene in coastal Greenland. More long-term records are required to ascertain if this represents regional or global hydrological reorganisation.

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More information

Accepted/In Press date: 15 September 2019
e-pub ahead of print date: 3 October 2019
Published date: 1 January 2020
Additional Information: Funding Information: Geochemical data can be accessed via the online supporting information or from the corresponding author (email: gordon.inglis@bristol.ac.uk ). Model data can be accessed via https://www.paleo.bristol.ac.uk/ummodel/scripts/papers/ . We thank the NERC Life Sciences Mass Spectrometry Facility (Bristol) for analytical support. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme ( FP/2007–2013 ; ERC Grant Agreement number 340923 (TGRES, awarded to RDP) and NERC Descent into the Icehouse grant ( NE/I005714/1 ). R.D.P. acknowledges the Royal Society Wolfson Research Merit Award . RDP, DL, AF and GNI also thank NERC grant for additional funding ( NE/K014757/1 ; NE/P01903X/1 ). Publisher Copyright: © 2019 Elsevier B.V.
Keywords: Biomarkers Alkanes Vegetation Cenozoic Palaeogene

Identifiers

Local EPrints ID: 437523
URI: http://eprints.soton.ac.uk/id/eprint/437523
ISSN: 0031-0182
PURE UUID: 9b2b0f6e-7943-430a-b759-d31f3c5085fa
ORCID for Gordon N. Inglis: ORCID iD orcid.org/0000-0002-0032-4668

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Date deposited: 04 Feb 2020 17:30
Last modified: 17 Mar 2024 04:00

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Contributors

Author: Matthew J. Carmichael
Author: Alexander Farnsworth
Author: Daniel J. Lunt
Author: Richard D. Pancost

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