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Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
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 [en]
stable isotopes, Holocene, subarctic, climate, Sphagnum fuscum
National Category
Earth and Related Environmental Sciences
Research subject
Quarternary Geology
Identifiers
URN: urn:nbn:se:su:diva-75026ISBN: 978-91-7447-472-5 (print)OAI: oai:DiVA.org:su-75026DiVA: diva2:513725
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
List of papers
1. Stable carbon and oxygen isotopes in Sphagnum fuscum peat from subarctic Canada: implications for palaeoclimate studies
Open this publication in new window or tab >>Stable carbon and oxygen isotopes in Sphagnum fuscum peat from subarctic Canada: implications for palaeoclimate studies
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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.

Keyword
Sphagnum peat, stable isotopes, Canadian subarctic, climate change, peat decomposition
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-43378 (URN)10.1016/j.chemgeo.2009.12.001 (DOI)000274989800019 ()
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
2. Long-term climate variability in continental subarctic Canada: A 6200-year record derived from stable isotopes in peat
Open this publication in new window or tab >>Long-term climate variability in continental subarctic Canada: A 6200-year record derived from stable isotopes in peat
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2010 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 298, no 3, 235-246 p.Article in journal (Refereed) Published
Abstract [en]

The rapid warming of arctic regions during recent decades has been recorded by instrumental monitoring, but the natural climate variability in the past is still sparsely reconstructed across many areas. We have reconstructed past climate changes in subarctic west-central Canada. Stable carbon and oxygen isotope ratios (δ13C, δ18O) were derived from a single Sphagnum fuscum plant component; α-cellulose isolated from stems. Periods of warmer and cooler conditions identified in this region, described in terms of a “Mediaeval Climatic Anomaly” and “Little Ice Age” were registered in the temperature reconstruction based on the δ13C record. Some conclusions could be drawn about wet/dry shifts during the same time interval from the δ18O record, humification indices and the macrofossil analysis. The results were compared with other proxy data from the vicinity of the study area. The amplitude of the temperature change was similar to that in chironomid based reconstructions, showing c. 6.5±2.3°C variability in July temperatures during the past 6.2 ka.

Keyword
stable isotopes, subarctic, Sphagnum, climate reconstruction
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-48254 (URN)10.1016/j.palaeo.2010.09.029 (DOI)
Projects
Holocene climate and environmental change in high latitudes as recorded by stable isotopes in peat deposits
Available from: 2010-12-06 Created: 2010-12-06 Last updated: 2017-12-12Bibliographically approved
3. Comparison of stable carbon and oxygen isotopes in Picea glauca tree rings and Sphagnum fuscum moss remains from subarctic Canada
Open this publication in new window or tab >>Comparison of stable carbon and oxygen isotopes in Picea glauca tree rings and Sphagnum fuscum moss remains from subarctic Canada
2012 (English)In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 78, no 2, 295-302 p.Article in journal (Refereed) Published
Abstract [en]

Stable isotope ratios from tree rings and peatland mosses have become important proxies of past climate variations. We here compare recent stable carbon and oxygen isotope ratios in cellulose of tree rings from white spruce (Picea glauca), growing near the arctic tree line; and cellulose of Sphagnum fuscum stems, growing in a hummock of a subarctic peatland, in west-central Canada. Results show that carbon isotopes in S. fuscum correlate significantly with July temperatures over the past similar to 20 yr. The oxygen isotopes correlate with both summer temperature and precipitation. Analyses of the tree-ring isotopes revealed summer temperatures to be the main controlling factor for carbon isotope variations, whereas tree-ring oxygen isotope ratios are controlled by a combination of spring temperatures and precipitation totals. We also explore the potential of combining high-frequency (annual) climate signals derived from long tree-ring series with low-frequency (decadal to centennial) climate signals derived from the moss remains in peat deposits. This cross-archive comparison revealed no association between the oxygen isotopes, which likely results from the varying sensitivity of the archives to different seasons. For the carbon isotopes, common variance could be achieved through adjustments of the Sphagnum age model within dating error.

Keyword
Stable isotopes, Canadian sub-Arctic, Tree rings, Peat moss
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-81254 (URN)10.1016/j.yqres.2012.05.014 (DOI)000308516000015 ()
Note

AuthorCount:4;

Available from: 2012-10-15 Created: 2012-10-15 Last updated: 2017-12-07Bibliographically approved
4. Stable isotope records of Sphagnum fuscum peat as late Holocene climate proxies in north-eastern European Russia
Open this publication in new window or tab >>Stable isotope records of Sphagnum fuscum peat as late Holocene climate proxies in north-eastern European Russia
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(English)Manuscript (preprint) (Other academic)
Keyword
stable isotopes, climate, tundra, northern taiga, peat, Sphagnum
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-74696 (URN)
Projects
Holocene climate and environmental change as recorded by stable isotopes in peat deposits
Available from: 2012-03-20 Created: 2012-03-20 Last updated: 2012-04-10Bibliographically approved

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