CaltechAUTHORS
  A Caltech Library Service

Modern constraints on the sources and climate signals recorded by sedimentary plant waxes in west Greenland

Dion-Kirschner, Hannah and McFarlin, Jamie M. and Masterson, Andrew L. and Axford, Yarrow and Osburn, Magdalena R. (2020) Modern constraints on the sources and climate signals recorded by sedimentary plant waxes in west Greenland. Geochimica et Cosmochimica Acta, 286 . pp. 336-354. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20200911-133139424

[img] MS Word (Supplementary data 1) - Supplemental Material
See Usage Policy.

575Kb
[img] MS Excel (Supplementary data 2) - Supplemental Material
See Usage Policy.

84Kb

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20200911-133139424

Abstract

The hydrogen isotopic composition (δ²H values) of plant waxes preserved in the sedimentary record is a useful proxy for past hydroclimate, but a number of known biological and environmental factors can confound the climate signal this proxy records. High-latitude ecology and environmental conditions differ from those of the better-studied low latitudes, and the influence of arctic conditions on factors that affect δ²H records of climate is poorly constrained. Direct observations of arctic plant waxes and their δ²H values, particularly from aquatic plants, are very limited. Here we present a study of n-alkane and n-alkanoic acid homologue distributions, δ²H values, and δ¹³C values from west Greenland, including measurements of terrestrial and aquatic plants, algae, and Nostoc (colonial cyanobacteria). By examining samples collected from the same region and season, we focus on climate-independent factors that may affect the δ²H values of sedimentary plant waxes. We observe that the average abundance of leaf n-alkyl lipids (C₂₀-C₃₁) in common terrestrial plants from this region exceeds that in aquatic sources by up to 30×. We also note weaker source specificity in n-alkanoic acids than in n-alkanes. A comparison of these data with surface sedimentary plant waxes from a lake within the study area, previously reported by McFarlin et al. (2019), indicates that at this site both mid-chain and long-chain sedimentary waxes are likely to derive from dominantly terrestrial sources, particularly biased towards the genus Salix. Abundance-weighted isotope data reveal that while terrestrial plants show taxonomic trends in δ²H values, the amplitude of these trends is unlikely to exceed the error of the proxy (the standard deviation on calculated ε_(app)). n-Alkane ε_(app) values are more variable in aquatic than in terrestrial sources, with median values ranging from −115‰ in n-C₃₁ to −143‰ in n-C₂₁. However, because sedimentary waxes at our study site are most similar to terrestrial plants for all homologues (in isotopic composition and proportional abundance), the large variability in aquatic ε_(app) is unlikely to strongly impact sedimentary wax δ²H values here and in comparable environments. Our findings do not support using comparisons of mid- and long-chain homologues to infer differences between lake water and precipitation without independent validation of the source of mid-chain waxes. Nevertheless, we show that homologue abundance, δ²H values, and δ¹³C values of sedimentary n-alkanes can inform wax-based reconstructions of paleoclimate at high latitudes. This work provides new insights into the wax contributions from west Greenland plant communities and highlights important areas for future studies of arctic plants and plant wax proxies.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.gca.2020.07.027DOIArticle
ORCID:
AuthorORCID
Osburn, Magdalena R.0000-0001-9180-559X
Additional Information:© 2020 Elsevier. Received 22 October 2019, Accepted 16 July 2020, Available online 24 July 2020. This project was supported by the National Science Foundation (NSF) Office of Polar Programs Award #1454734 (to YA), the NSF Geography and Spatial Sciences Program Doctoral Dissertation Research Improvement Award #1634118 (to YA, MRO, JMM), the NSF Graduate Research Fellowship Program (to JMM), the Institute for Sustainability and Energy at Northwestern (to MRO, YA), and the Northwestern University Undergraduate Research Grant program (to HDK). We express our gratitude to Andrew Jacobson, the Kangerlussuaq International Science Station, Polar Field Services, Inc. (Kathy Young, Kyli Cosper), and the US Air National Guard for field logistical support; to Grace Andrews, Johnny Ryan, and Aaron Hartz for assistance in sample collection during fieldwork; to Lauren Culler and Simone Whitecloud for help with plant identification; and to Grace Schellinger, Sohyun Lee, and Jordan Todes for assistance in the laboratory. We also thank Bernhard Aichner, Aaron Diefendorf, Sarah Feakins, Nemiah Ladd, Jess Tierney, and three anonymous reviewers for their thorough and insightful comments on versions of this manuscript. Research data. All lipid abundance and isotopic data produced for and described in this work are included within the electronic annex file. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funders:
Funding AgencyGrant Number
NSFOPP-1454734
NSFBCS-1634118
NSF Graduate Research FellowshipUNSPECIFIED
Northwestern UniversityUNSPECIFIED
Subject Keywords:Compound-specific hydrogen isotopes; Compound-specific carbon isotopes; Leaf waxes; Paleohydrology; Paleoclimate; Arctic lakes; Greenland; Kangerlussuaq
Record Number:CaltechAUTHORS:20200911-133139424
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200911-133139424
Official Citation:Hannah Dion-Kirschner, Jamie M. McFarlin, Andrew L. Masterson, Yarrow Axford, Magdalena R. Osburn, Modern constraints on the sources and climate signals recorded by sedimentary plant waxes in west Greenland, Geochimica et Cosmochimica Acta, Volume 286, 2020, Pages 336-354, ISSN 0016-7037, https://doi.org/10.1016/j.gca.2020.07.027.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105358
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:14 Sep 2020 22:42
Last Modified:14 Sep 2020 22:42

Repository Staff Only: item control page