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Fennoscandia revisited: a spatially improved tree-ring reconstruction of summer temperatures for the last 900 years

Linderholm, Hans; Björklund, Jesper; Seftigen, Kristina; Gunnarson, Björn and Fuentes, Mauricio (2014) In Climate Dynamics online first.
Abstract
Despite the spatially homogenous summer temperaturepattern in Fennoscandia, there are large spreadsamong the many existing reconstructions, resulting in anuncertainty in the timing and amplitude of past changes.Also, there has been a general bias towards northernmostFennoscandia. In an attempt to provide a more spatiallycoherent view of summer (June–August, JJA) temperaturevariability within the last millennium, we utilized sevendensity and three blue intensity Scots pine (Pinus sylvestrisL.) chronologies collected from the altitudinal (ScandinavianMountains) and latitudinal (northernmost part) treeline.To attain a JJA temperature signal as strong as possible,as well as preserving multicentury-scale variability,we used a new tree-ring... (More)
Despite the spatially homogenous summer temperaturepattern in Fennoscandia, there are large spreadsamong the many existing reconstructions, resulting in anuncertainty in the timing and amplitude of past changes.Also, there has been a general bias towards northernmostFennoscandia. In an attempt to provide a more spatiallycoherent view of summer (June–August, JJA) temperaturevariability within the last millennium, we utilized sevendensity and three blue intensity Scots pine (Pinus sylvestrisL.) chronologies collected from the altitudinal (ScandinavianMountains) and latitudinal (northernmost part) treeline.To attain a JJA temperature signal as strong as possible,as well as preserving multicentury-scale variability,we used a new tree-ring parameter, where the earlywoodinformation is removed from the maximum density andblue intensity, and a modified signal-free standardizationmethod. Two skilful reconstructions for the period 1100–2006 CE were made, one regional reconstruction basedon an average of the chronologies, and one field (gridded)reconstruction. The new reconstructions were shown tohave much improved spatial representations compared tothose based on data from only northern sites, thus makingit more valid for the whole region. An examination of some of the forcings of JJA mean temperatures in the regionshows an association with sea-surface temperature over theeastern North Atlantic, but also the subpolar and subtropicalgyres. Moreover, using Superposed Epoch Analysis, asignificant cooling in the year following a volcanic eruptionwas noted, and for the largest explosive eruptions, theeffect could remain for up to 4 years. This new improvedreconstruction provides a mean to reinforce our understandingof forcings on summer temperatures in the NorthEuropean sector. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Climate change, Tree rings, Density, Blue intensity, Forcings
in
Climate Dynamics
volume
online first
publisher
Springer
external identifiers
  • scopus:84935020163
ISSN
1432-0894
DOI
10.1007/s00382-014-2328-9
project
MERGE
language
English
LU publication?
no
id
5e3b8441-4ce1-4538-9529-11cadcc347bc (old id 7515372)
date added to LUP
2015-07-08 14:56:37
date last changed
2017-11-12 04:06:57
@article{5e3b8441-4ce1-4538-9529-11cadcc347bc,
  abstract     = {Despite the spatially homogenous summer temperaturepattern in Fennoscandia, there are large spreadsamong the many existing reconstructions, resulting in anuncertainty in the timing and amplitude of past changes.Also, there has been a general bias towards northernmostFennoscandia. In an attempt to provide a more spatiallycoherent view of summer (June–August, JJA) temperaturevariability within the last millennium, we utilized sevendensity and three blue intensity Scots pine (Pinus sylvestrisL.) chronologies collected from the altitudinal (ScandinavianMountains) and latitudinal (northernmost part) treeline.To attain a JJA temperature signal as strong as possible,as well as preserving multicentury-scale variability,we used a new tree-ring parameter, where the earlywoodinformation is removed from the maximum density andblue intensity, and a modified signal-free standardizationmethod. Two skilful reconstructions for the period 1100–2006 CE were made, one regional reconstruction basedon an average of the chronologies, and one field (gridded)reconstruction. The new reconstructions were shown tohave much improved spatial representations compared tothose based on data from only northern sites, thus makingit more valid for the whole region. An examination of some of the forcings of JJA mean temperatures in the regionshows an association with sea-surface temperature over theeastern North Atlantic, but also the subpolar and subtropicalgyres. Moreover, using Superposed Epoch Analysis, asignificant cooling in the year following a volcanic eruptionwas noted, and for the largest explosive eruptions, theeffect could remain for up to 4 years. This new improvedreconstruction provides a mean to reinforce our understandingof forcings on summer temperatures in the NorthEuropean sector.},
  author       = {Linderholm, Hans and Björklund, Jesper and Seftigen, Kristina and Gunnarson, Björn and Fuentes, Mauricio},
  issn         = {1432-0894},
  keyword      = {Climate change,Tree rings,Density,Blue intensity,Forcings},
  language     = {eng},
  publisher    = {Springer},
  series       = {Climate Dynamics},
  title        = {Fennoscandia revisited: a spatially improved tree-ring reconstruction of summer temperatures for the last 900 years},
  url          = {http://dx.doi.org/10.1007/s00382-014-2328-9},
  volume       = {online first},
  year         = {2014},
}