A 7.5 ka chronology of stable carbon isotopes from tree rings with implications for their use in palaeo-cloud reconstruction

Samuli Helama, Laura Arppe, Mauri Timonen, Kari Mielikäinen, Markku Oinonen

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Tree-ring stable isotope chronologies provide very high-resolution palaeoclimatic data, and the number of records is increasing rapidly worldwide. To extend the chronologies back in time, before the period covered by the old living trees, the use of subfossil wood samples is required. Typically, the longest continuous subfossil chronologies consist of regionally collected tree-ring materials, rather than tree rings from a single site, and are likely more sensitive to data heterogeneity. Yet, the characteristics of such datasets remain hitherto unexplored. Here we produce a continuous, decadally resolved chronology of C-13/C-12 ratio (delta C-13) from Finnish Lapland over the past 7.5 ka (5500 BCE to 2010 CE) for which there is replication of at least five Pinus sylvestris trees. Less negative delta C-13 values were observed as trees age and for western sites (higher in elevation and further from the cold oceanic air flow). The age -related trends in living tree delta C-13 data were expressed mainly over the first fifty years mimicking the "juvenile effect" whereas the subfossil data showed trend over the trees' lifespan. These findings demonstrated the need to detrend the individual delta C-13 series before averaging them into the mean chronology. The corresponding biases were removed from the isotopic data using the methods frequently applied for tree-ring width and density proxies, the Regional Curve Standardization (RCS) combined with signal-free approach. While the RCS procedures commonly preserve the long-term variations in the resulting chronology, not all types of them did so as demonstrated for chronologies produced using separate RCS models for the delta C-13 series with relatively high and low isotopic level (offset from the grand mean). It was shown that these delta C-13 levels (i.e. the relative isotopic enrichment) result both from the low-frequency climate signal and biogeographical aspects (the site longitude/altitudes). The non-climatic biases were removed from the delta C-13 series by using separate RCS models for the subsets (western and eastern) of isotopic series. Similar to previous investigations using annually resolved delta C-13 data from Lapland, our chronology had strong negative correlations to variations in cloud cover. Here, a bootstrapping experiment was used to verify this dendroclimatic association. The resulting palaeo-cloud reconstruction portrayed decadal to multi-millennial variations with centennial anomalies coinciding with the mid and late Holocene events of climate transitions, highlighting the value of subfossil isotope chronologies from tree rings in synthesising climate dynamics from several proxy sources over the present interglacial.

Original languageEnglish
JournalGlobal and Planetary Change
Volume170
Pages (from-to)20-33
Number of pages14
ISSN0921-8181
DOIs
Publication statusPublished - Nov 2018
MoE publication typeA1 Journal article-refereed

Fields of Science

  • Isotope geochemistry
  • Palaeoclimate reconstruction
  • Geochronology
  • Dendrochronology
  • Regional curve standardization
  • Subarctic
  • SUMMER TEMPERATURE RECONSTRUCTION
  • REGIONAL CURVE STANDARDIZATION
  • SEGMENT LENGTH CURSE
  • FINNISH LAPLAND
  • CLIMATE-CHANGE
  • ATMOSPHERIC CIRCULATION
  • PINUS-SYLVESTRIS
  • KOLA-PENINSULA
  • SCOTS PINE
  • HOLOCENE
  • 1172 Environmental sciences

Cite this

@article{09ab9287509445a29aec05c4a14f05de,
title = "A 7.5 ka chronology of stable carbon isotopes from tree rings with implications for their use in palaeo-cloud reconstruction",
abstract = "Tree-ring stable isotope chronologies provide very high-resolution palaeoclimatic data, and the number of records is increasing rapidly worldwide. To extend the chronologies back in time, before the period covered by the old living trees, the use of subfossil wood samples is required. Typically, the longest continuous subfossil chronologies consist of regionally collected tree-ring materials, rather than tree rings from a single site, and are likely more sensitive to data heterogeneity. Yet, the characteristics of such datasets remain hitherto unexplored. Here we produce a continuous, decadally resolved chronology of C-13/C-12 ratio (delta C-13) from Finnish Lapland over the past 7.5 ka (5500 BCE to 2010 CE) for which there is replication of at least five Pinus sylvestris trees. Less negative delta C-13 values were observed as trees age and for western sites (higher in elevation and further from the cold oceanic air flow). The age -related trends in living tree delta C-13 data were expressed mainly over the first fifty years mimicking the {"}juvenile effect{"} whereas the subfossil data showed trend over the trees' lifespan. These findings demonstrated the need to detrend the individual delta C-13 series before averaging them into the mean chronology. The corresponding biases were removed from the isotopic data using the methods frequently applied for tree-ring width and density proxies, the Regional Curve Standardization (RCS) combined with signal-free approach. While the RCS procedures commonly preserve the long-term variations in the resulting chronology, not all types of them did so as demonstrated for chronologies produced using separate RCS models for the delta C-13 series with relatively high and low isotopic level (offset from the grand mean). It was shown that these delta C-13 levels (i.e. the relative isotopic enrichment) result both from the low-frequency climate signal and biogeographical aspects (the site longitude/altitudes). The non-climatic biases were removed from the delta C-13 series by using separate RCS models for the subsets (western and eastern) of isotopic series. Similar to previous investigations using annually resolved delta C-13 data from Lapland, our chronology had strong negative correlations to variations in cloud cover. Here, a bootstrapping experiment was used to verify this dendroclimatic association. The resulting palaeo-cloud reconstruction portrayed decadal to multi-millennial variations with centennial anomalies coinciding with the mid and late Holocene events of climate transitions, highlighting the value of subfossil isotope chronologies from tree rings in synthesising climate dynamics from several proxy sources over the present interglacial.",
keywords = "Isotope geochemistry, Palaeoclimate reconstruction, Geochronology, Dendrochronology, Regional curve standardization, Subarctic, SUMMER TEMPERATURE RECONSTRUCTION, REGIONAL CURVE STANDARDIZATION, SEGMENT LENGTH CURSE, FINNISH LAPLAND, CLIMATE-CHANGE, ATMOSPHERIC CIRCULATION, PINUS-SYLVESTRIS, KOLA-PENINSULA, SCOTS PINE, HOLOCENE, 1172 Environmental sciences",
author = "Samuli Helama and Laura Arppe and Mauri Timonen and Kari Mielik{\"a}inen and Markku Oinonen",
year = "2018",
month = "11",
doi = "10.1016/j.gloplacha.2018.08.002",
language = "English",
volume = "170",
pages = "20--33",
journal = "Global and Planetary Change",
issn = "0921-8181",
publisher = "Elsevier Scientific Publ. Co",

}

A 7.5 ka chronology of stable carbon isotopes from tree rings with implications for their use in palaeo-cloud reconstruction. / Helama, Samuli; Arppe, Laura; Timonen, Mauri; Mielikäinen, Kari; Oinonen, Markku.

In: Global and Planetary Change, Vol. 170, 11.2018, p. 20-33.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - A 7.5 ka chronology of stable carbon isotopes from tree rings with implications for their use in palaeo-cloud reconstruction

AU - Helama, Samuli

AU - Arppe, Laura

AU - Timonen, Mauri

AU - Mielikäinen, Kari

AU - Oinonen, Markku

PY - 2018/11

Y1 - 2018/11

N2 - Tree-ring stable isotope chronologies provide very high-resolution palaeoclimatic data, and the number of records is increasing rapidly worldwide. To extend the chronologies back in time, before the period covered by the old living trees, the use of subfossil wood samples is required. Typically, the longest continuous subfossil chronologies consist of regionally collected tree-ring materials, rather than tree rings from a single site, and are likely more sensitive to data heterogeneity. Yet, the characteristics of such datasets remain hitherto unexplored. Here we produce a continuous, decadally resolved chronology of C-13/C-12 ratio (delta C-13) from Finnish Lapland over the past 7.5 ka (5500 BCE to 2010 CE) for which there is replication of at least five Pinus sylvestris trees. Less negative delta C-13 values were observed as trees age and for western sites (higher in elevation and further from the cold oceanic air flow). The age -related trends in living tree delta C-13 data were expressed mainly over the first fifty years mimicking the "juvenile effect" whereas the subfossil data showed trend over the trees' lifespan. These findings demonstrated the need to detrend the individual delta C-13 series before averaging them into the mean chronology. The corresponding biases were removed from the isotopic data using the methods frequently applied for tree-ring width and density proxies, the Regional Curve Standardization (RCS) combined with signal-free approach. While the RCS procedures commonly preserve the long-term variations in the resulting chronology, not all types of them did so as demonstrated for chronologies produced using separate RCS models for the delta C-13 series with relatively high and low isotopic level (offset from the grand mean). It was shown that these delta C-13 levels (i.e. the relative isotopic enrichment) result both from the low-frequency climate signal and biogeographical aspects (the site longitude/altitudes). The non-climatic biases were removed from the delta C-13 series by using separate RCS models for the subsets (western and eastern) of isotopic series. Similar to previous investigations using annually resolved delta C-13 data from Lapland, our chronology had strong negative correlations to variations in cloud cover. Here, a bootstrapping experiment was used to verify this dendroclimatic association. The resulting palaeo-cloud reconstruction portrayed decadal to multi-millennial variations with centennial anomalies coinciding with the mid and late Holocene events of climate transitions, highlighting the value of subfossil isotope chronologies from tree rings in synthesising climate dynamics from several proxy sources over the present interglacial.

AB - Tree-ring stable isotope chronologies provide very high-resolution palaeoclimatic data, and the number of records is increasing rapidly worldwide. To extend the chronologies back in time, before the period covered by the old living trees, the use of subfossil wood samples is required. Typically, the longest continuous subfossil chronologies consist of regionally collected tree-ring materials, rather than tree rings from a single site, and are likely more sensitive to data heterogeneity. Yet, the characteristics of such datasets remain hitherto unexplored. Here we produce a continuous, decadally resolved chronology of C-13/C-12 ratio (delta C-13) from Finnish Lapland over the past 7.5 ka (5500 BCE to 2010 CE) for which there is replication of at least five Pinus sylvestris trees. Less negative delta C-13 values were observed as trees age and for western sites (higher in elevation and further from the cold oceanic air flow). The age -related trends in living tree delta C-13 data were expressed mainly over the first fifty years mimicking the "juvenile effect" whereas the subfossil data showed trend over the trees' lifespan. These findings demonstrated the need to detrend the individual delta C-13 series before averaging them into the mean chronology. The corresponding biases were removed from the isotopic data using the methods frequently applied for tree-ring width and density proxies, the Regional Curve Standardization (RCS) combined with signal-free approach. While the RCS procedures commonly preserve the long-term variations in the resulting chronology, not all types of them did so as demonstrated for chronologies produced using separate RCS models for the delta C-13 series with relatively high and low isotopic level (offset from the grand mean). It was shown that these delta C-13 levels (i.e. the relative isotopic enrichment) result both from the low-frequency climate signal and biogeographical aspects (the site longitude/altitudes). The non-climatic biases were removed from the delta C-13 series by using separate RCS models for the subsets (western and eastern) of isotopic series. Similar to previous investigations using annually resolved delta C-13 data from Lapland, our chronology had strong negative correlations to variations in cloud cover. Here, a bootstrapping experiment was used to verify this dendroclimatic association. The resulting palaeo-cloud reconstruction portrayed decadal to multi-millennial variations with centennial anomalies coinciding with the mid and late Holocene events of climate transitions, highlighting the value of subfossil isotope chronologies from tree rings in synthesising climate dynamics from several proxy sources over the present interglacial.

KW - Isotope geochemistry

KW - Palaeoclimate reconstruction

KW - Geochronology

KW - Dendrochronology

KW - Regional curve standardization

KW - Subarctic

KW - SUMMER TEMPERATURE RECONSTRUCTION

KW - REGIONAL CURVE STANDARDIZATION

KW - SEGMENT LENGTH CURSE

KW - FINNISH LAPLAND

KW - CLIMATE-CHANGE

KW - ATMOSPHERIC CIRCULATION

KW - PINUS-SYLVESTRIS

KW - KOLA-PENINSULA

KW - SCOTS PINE

KW - HOLOCENE

KW - 1172 Environmental sciences

U2 - 10.1016/j.gloplacha.2018.08.002

DO - 10.1016/j.gloplacha.2018.08.002

M3 - Article

VL - 170

SP - 20

EP - 33

JO - Global and Planetary Change

JF - Global and Planetary Change

SN - 0921-8181

ER -