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Stable carbon and oxygen isotopes in Sphagnum fuscum peat from subarctic Canada: implications for palaeoclimate studies
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
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2010 (English)In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 270, no 1-4, 216-226 p.Article in journal (Refereed) Published
Abstract [en]

Stable carbon and oxygen isotope ratios in single plant components in Sphagnum peat have a good potential to reveal environmental changes in peat archives. Two peat profiles, covering the past ~6000 years, and a Sphagnum hummock from a discontinuous permafrost area in west central Canada were studied in order to evaluate the effect of decomposition rate on isotope records and to assess which plant components are most suitable for climate reconstructions. The stable isotope values from the most recently forming Sphagnum tissues were compared with observational climate data to study the impact of variations in temperature and precipitation on the peat isotopes. Our results show that there is high correlation between δ13C values in α-cellulose isolated from Sphagnum fuscum stems and summer temperatures, whereas δ18O in the plant tissues is controlled by several factors, such as summer precipitation, summer temperature and evaporation. According to our results, decomposition as derived from C/N values and colorimetry does not seem to affect the oxygen and carbon isotope values of α-cellulose from Sphagnum fuscum peat significantly. There is, however, a (quasi-) constant offset between the isotope values of branches and stems and between whole plant material and  α-cellulose, which makes it crucial to select single moss-fractions when past climate and environmental changes are to be derived from the isotope record.

Place, publisher, year, edition, pages
2010. Vol. 270, no 1-4, 216-226 p.
Keyword [en]
Sphagnum peat, stable isotopes, Canadian subarctic, climate change, peat decomposition
National Category
Geology
Research subject
Quarternary Geology
Identifiers
URN: urn:nbn:se:su:diva-43378DOI: 10.1016/j.chemgeo.2009.12.001ISI: 000274989800019OAI: oai:DiVA.org:su-43378DiVA: diva2:356107
Projects
Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Available from: 2010-10-11 Created: 2010-10-11 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Holocene climate change in high latitudes recorded by stable isotopes in peat
Open this publication in new window or tab >>Holocene climate change in high latitudes recorded by stable isotopes in peat
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

A key to the understanding of natural and human induced climate variations is to reconstruct past changes from different environments. No outstanding method for general use has been pinpointed, instead, a need of multi-proxy studies is often stressed and the reconstructions are under constant improvement by new techniques. The aim of my PhD project is to test a relatively new method, stable carbon and oxygen isotopes isolated from single moss species, and develop climate reconstructions based on them. The main interest is to implement the method in records from northern peatlands where permafrost conditions prevail, and contribute to the discussion about the warming Arctic.

The first part of the Licentiate thesis is a method study about the variation of stable carbon and oxygen isotope ratios in different moss plant components. Modern isotopic values were calibrated against instrumental climate records from the study region in west-central Canada. The impact of peat decay on proxies was investigated by colorimetric and chemical (C/N) methods. The results indicate that the isotope signal is well preserved in peat that started to accumulate c. 6000 years ago. Furthermore, statistical analyses imply that the variation of stable carbon isotope ratios in Sphagnum fuscum is significantly correlated to the variation of summer temperatures.

A temperature reconstruction was developed in the second part of the thesis, based on stable carbon isotope ratios. Wet/dry periods were derived from the stable oxygen isotope record, macrofossil analysis, and the peat humification record. The results were compared with other proxy records from the vicinity of the study area. The main climate periods, such as The Mediaeval Warm Period and The Little Ice Age were registered in the temperature record. The amplitude of the temperature change was similar to especially those in chironomid based reconstructions, showing c. 6.5±1°C variation in July temperatures during the past 6.2 ka.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2010
Keyword
-
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-43380 (URN)
Presentation
2010-04-23, Institutionen för naturgeografi och kvartärgeologi, Svante Arrhenius väg 8, Stockholm, 11:23 (English)
Opponent
Supervisors
Projects
Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Available from: 2010-10-19 Created: 2010-10-11 Last updated: 2012-04-10Bibliographically approved
2. Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Open this publication in new window or tab >>Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, stable carbon and oxygen isotopes in α-cellulose isolated from Sphagnum fuscum moss remains were used as climate proxies. The main focus was to implement the methods in records from high latitude peatlands in the Northern Hemisphere (west-central Canada and north-eastern European Russia), reconstruct palaeoclimate of the studied regions during the Holocene, and evaluate the compatibility of results with other proxy records, especially tree-ring isotope time-series. The variation of stable carbon and oxygen isotope ratios (δ13C, δ18O) in different moss plant components was investigated and differences between untreated plants and α-cellulose extracts were evaluated. The impact of peat decay on the stable isotope proxies was studied by colorimetric and chemical (C/N) methods. Temperature reconstructions were developed based on the statistically significant relationship between δ13C and modern summer temperature records. Wet/dry periods were derived from a combination of δ18O records, macrofossil analysis, and a peat humification record in west-central Canada. A tentative reconstruction of snow depth in north-eastern European Russian tundra and northern taiga was based on δ18O records. The most promising result of the thesis is that stable carbon isotope variability in α-cellulose isolated from Sphagnum fuscum stems can be used to reconstruct and quantify palaeotemperatures several millennia back in time and to reveal both long-term and rapid climate shifts from peat archives.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2012. 36 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 32
Keyword
stable isotopes, Holocene, subarctic, climate, Sphagnum fuscum
National Category
Earth and Related Environmental Sciences
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-75026 (URN)978-91-7447-472-5 (ISBN)
Public defence
2012-05-11, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.

Available from: 2012-04-19 Created: 2012-04-03 Last updated: 2013-09-20Bibliographically approved

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