Extracting long‐period climate fluctuations from tree‐ring chronologies over timescales of centuries to millennia

Helama, Samuli; Timonen, Mauri; Lindholm, Markus; Meriläinen, Jouko; Eronen, Matti

doi:10.1002/joc.1215

Cited by 57 publications

(57 citation statements)

References 43 publications

(78 reference statements)

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“…Moreover, NAOindex, which describes the oscillation of atmospheric mass between the Arctic (Iceland) and the subtropical Atlantic (Azores), was used because it markedly dictates winter climate in northwest Europe (Hurrell et al 2001). The reconstructed NAO-index of Luterbacher et al (2002) since 1659 and two types of tree-ring chronologies of Scots pine (Pinus sylvestris L.) from northern Fennoscandia were used: tree-ring width chronology of Helama et al (2005) and maximum density chronology of Briffa et al (1990). These three datasets were integrated into one palaeoclimatic model using a linear regression to reconstruct annual mean temperature (in Celsius) in the study region (Helle & Helama 2007).…”

Section: Methodsmentioning

confidence: 99%

Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons

2007

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The birth sex ratio of vertebrates with chromosomal sex determination has been shown to respond to environmental variability, such as temperature. However, in humans the few previous studies on environmental temperature and birth sex ratios have produced mixed results. We examined whether reconstructed annual mean temperatures were associated with annual offspring sex ratio at birth in the eighteenth to nineteenth century Sami from northern Finland. We found that warm years correlated with a malebiased sex ratio, whereas a warm previous year skewed sex ratio towards females. The net effect of one degree Celsius increase in mean temperature during these 2 years corresponded to approximately 1% more sons born annually. Although the physiological and ecological mechanisms mediating these effects and their evolutionary consequences on parental fitness remain unknown, our results show that environmental temperature may affect human birth sex ratio.

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Section: Methodsmentioning

confidence: 99%

Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons

2007

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“…This effect is confirmed by the RC's of the pines analyzed in this study, where also the wet micro-site shows less wood production compared to the dry site. The flat wet_RC mimics characteristics of suppressed growth in closed canopy stands (Helama et al 2005). …”

Section: Growth Rate Differencesmentioning

confidence: 99%

On the hidden significance of differing micro-sites on tree-ring based climate reconstructions

Düthorn¹,

Schneider²,

Konter³

et al. 2015

Silva Fenn.

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2015). On the hidden significance of differing micro-sites on tree-ring based climate reconstructions. Silva Fennica vol. 49 no. 1 article id 1220. 12 p. Highlights• Pines and spruces show growth level differences in wet and dry micro-sites with higher growth rates in the dry sites.• Spruces show a robust climate-growth relationship with June-July temperatures.• Application of collective detrending methods can bias long-term trends in climate reconstructions, if relict and recent samples originate from different micro-sites. AbstractTree-ring chronologies are commonly extended back in time by combining samples from living trees with relict material preserved in man-made structures or natural archives (e.g. lakes). Although spatially close, these natural archives and living-tree-sites often comprise different micro-climates. Inhomogeneous growth conditions among these habitats, which may yield offsets in growth-rates, require caution in data processing. Here we assess species-specific growth dynamics in two micro-habitats and their potential effects on long chronologies by combining tree-ring data from different living-tree-sites with an "artificial" subfossil dataset. Well replicated (n > 80) Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) chronologies from northern Fennoscandia, sampled directly at the lakeshore (wet) and several meters beyond the lakeshore (dry) reveal high coherence of the variance between micro-sites (r spruce = 0.59, r pine = 0.68). Significant differences of the Regional Curves (RC) indicate faster growth of both species at the drier site though. Growth differences are more pronounced between the spruce micro-sites. The combination of recent dry and wet spruce data with artificial relict data results in two long chronologies covering the last 800 years with substantially different trends, although they consist of the same relict material and the micro-site chronologies correlate significantly over the past two centuries. The combination of spruce samples from dry inland micro-sites with subfossil samples originating from the wet lake shore can result in an underestimation of past temperatures prior to the 19th century. Such effects, hidden in the composition of long chronologies (living trees + subfossil samples) can bias long-term trends in climate reconstructions.

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“…Contrasting the new palaeoclimate information with existing tree-ring based summer temperature reconstructions from northern Finland and Fennoscandia (Helama et al, 2009a(Helama et al, , 2009b(Helama et al, , 2010aEsper et al, 2012) enables the north-south comparison of temperature variations on annual resolution. It outlines the spatial palaeoclimate variations in the region where previous palaeoclimate research have highlighted notable climatic shifts through the Medieval Climate Anomaly to Little Ice Age (Grudd et al, 2002;Helama et al, 2005bHelama et al, , 2009aHelama et al, , 2009bHelama et al, , 2010aGunnarson et al, 2011;Esper et al, 2012) during the past thirteen centuries.…”

Section: Introductionmentioning

confidence: 99%

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

Helama¹,

Vartiainen²,

Holopainen

et al. 2014

Geochronometria

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X-ray based tree-ring data of maximum latewood densities (MXD) was combined for south-eastern Finland. This data originated from subfossil and modern pine (Pinus sylvestris L.) materials comprising a continuous dendroclimatic record over the past millennium. Calibrating and verifying the MXD chronologies against the instrumental temperature data showed a promising opportunity to reconstruct warm-season (May through September) temperature variability. A new palaeotemperature record correlated statistically significantly with the long instrumental temperature records in the region and adjacent areas since the 1740s. Comparisons with tree-ring based (MXD and tree-ring width) reconstructions from northern Fennoscandia and northern Finland exhibited consistent summer temperature variations through the Medieval Climate Anomaly, Little Ice Age, and the 20 th century warmth. A culmination of the LIA cooling during the early 18 th century appeared consistently with the Maunder Minimum, when the solar activity was drastically reduced. A number of coolest reconstructed events between AD 1407 and 1902 were coeval to years of crop failure and famine as documented in the agro-historical chronicles. Results indicate an encouraging possibility of warm-season temperature reconstructions using middle/south boreal tree-ring archives to detail and enhance the understanding of past interactions between humans, ecosystems and the earth.

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Extracting long‐period climate fluctuations from tree‐ring chronologies over timescales of centuries to millennia

Cited by 57 publications

References 43 publications

Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons

Temperature-related birth sex ratio bias in historical Sami: warm years bring more sons

On the hidden significance of differing micro-sites on tree-ring based climate reconstructions

A palaeotemperature record for the Finnish Lakeland based on microdensitometric variations in tree rings

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