Samuli Helama
Biographic Data
| ID | 3646644 |
|---|---|
| NAME | Samuli Helama |
| GIVEN NAMES | Samuli |
| FAMILY NAME | Helama |
| SIGNATURE | HELAMA S |
| AFFILIATIONS | Natural Resources Institute Finland |
| ORCID | 0000-0002-9777-3354 |
| VERIFIED | Yes |
| TOTAL WORKS | 26 |
| TOTAL CITATIONS | 36 |
| AUTHOR COUNT | 26 |
| EDITOR COUNT | 0 |
| FIRST PUBLICATION YEAR | 2002 |
| LATEST PUBLICATION YEAR | 2026 |
| H-INDEX | 4 |
Extreme events and the spread of Uralic languages
In this paper we present novel aspects concerning the possible connection between the 4.2 ka climatic event and the early spread of Uralic languages from western Siberia to North-East Europe. We discuss different reasons for the divergence of Proto-Uralic and the spread of the Uralic languages, and propose a scenario where the 4.2 ka climatic event and the early spread of Uralic languages is connected via three themes: 1) habitat changes, 2) anim…
The Fimbulwinter myth in the context of Nordic tree-ring climate proxy data
High-magnitude Late-Holocene volcanic eruptions contributed to the climate-related hardships of past societies. It has been theorised that memories of one of the volcanic events and its terrible consequences are recorded in the Old Norse traditions of the Fimbulwinter and Ragnarök (possibly also in the Old Kalevala). This Fimbulwinter theory suggests that the eruption (or double-eruption) responsible for the calamity was the one that caused the A…
Early 14 C increase in high-latitude trees at 665–664 BC
The discovery of radiocarbon ( 14 C) peaks in AD 774–775 and AD 993–994 sparked the search for other anomalous events, leading to the identification of one around 660 BC. However, the ∼660 BC event appears to show a more prolonged increase, raising the question whether the event is qualitatively different. To investigate this, we measured high-latitude tree rings from Finnish Lapland, expected to be highly sensitive to energetic particle events. …
Low-frequency patterns in Late-Holocene tree-ring records from northern Fennoscandia
Northern Fennoscandia is a cradle of tree-ring based climate reconstructions. These Late-Holocene data come from several types of tree-ring proxies and are typically used for discussing the extent of past climate excursions such as the Medieval Climate Anomaly and Little Ice Age, relative to the modern temperatures. This article compares tree-ring records published from the region over the past two decades with those produced here by recalculatio…
Nonoverlapping Magisteria Versus Science-Religion Integration
The principle of nonoverlapping magisteria (NOMA), by Stephen Jay Gould, is commonly cited in the science-religion literature as an archetype of a model separating the domains of science and religion. As such, NOMA represents the independence category in Ian Barbour’s science-religion typology. However, it is commonly neglected that NOMA also permits dialogue and even integration of scientific and religious inputs at the personal level, i.e. beyo…
The 4.2 ka event
In recent years, much evidence has been presented on the 4.2 ka event. A review of 317 palaeoclimate papers shows that dry conditions were common during the event, especially from Eastern Mediterranean to India. The 4.2 ka event was not, however, a global drought event. Wet conditions were reported especially for central/northern Europe and sub-Saharan Africa. The 4.2 ka event is typically characterized either as short (4.2–4.0 ka) or long (4.4–3…
Solar-type periodicities in the climate variability of Northern Fennoscandia during the last three centuries
Fifteen proxy records of summer temperature in Fennoscandia, Northern Europe and in Yamal and Taymir Peninsulas (Western Siberia) were analyzed for the AD 1700–2000 period. Century-long (70–100 year) and quasi bi-decadal periodicities were found from proxy records representing different parts of Fennoscandia. Decadal variation was revealed in a smaller number of records. Statistically significant correlations were revealed between the timescale-d…
Historical trends in spring ice breakup for the Aura River in Southwest Finland, AD 1749–2018
Ice breakup (IBU) observations have been recorded for Aura River in Turku, southwest Finland, since the mid-18th century. The latest long-term investigation covered the period 1749–1906, but the series contains several biases. In this article, we present a fully revised and extended IBU series (1749–2018) of Aura River for climate research purposes. Instead of typical univariate IBU data (a single time series with one data point per year), this s…
Dark Ages Cold Period
Several late Quaternary studies have recorded cold and disturbed climates centred during the mid-first millennium AD and discussed these conditions under the term ‘Dark Ages Cold Period’ (DACP). A review of 114 palaeoclimate papers indicated that cold climates were common in the Northern Hemisphere between AD 400 and 765. There are also suggestions that some regions may have been relatively wet during the DACP, while those around the Mediterranea…
Something old, something new, something borrowed
Distant impact
Reconstructing crop yield variability in Finland
Lack of documentation on past harvest fluctuations limits the exploration of long-term trends in crop production and agricultural adaptation strategies. A long-term perspective is needed, however, to understand the wide spectrum of potential human responses to environment and climate change. Therefore, we used tree-ring density series as proxy data to reconstruct climate-mediated yield ratio (harvested grain in relation to sown) in central and no…
Regional curve standardization
Tree rings are commonly used proxy data for past climate variability. Probably the simplest practical solution for transforming raw tree-ring data into proxy estimates and retaining information on low-frequency tree-growth forcing is the regional curve standardization (RCS). This paper reviews the RCS concept and the development of this standardization method over the past 25 years. Tree-ring based estimation of low-frequency climate variability …
Dendrochronological dating of wooden artifacts by measuring the tree rings using magnifying glass and photography-assisted method
Old World megadroughts and pluvials during the Common Era
An atlas of megadroughts in Europe and in the Mediterranean Basin during the Common Era provides insights into climate variability.
Direct transformation of tree-ring measurements into palaeoclimate reconstructions in three-dimensional space
Here we propose a new method for dendroclimatic reconstructions. This DIrect REConstruction Technique (DIRECT) performs modelling of the age-dependent association between climate and growth in three-dimensional space and directly transforms the raw tree-ring values (on the scale of original growth units) into climate variability while considering the effect of age in this relationship. DIRECT was applied to maximum latewood density (MXD) data fro…
Significant changes of subseries-means in the Finnish tree-ring index of 7638 years, with comparisons to glaciological evidence from Greenland and Alps
Climatic signatures in crops and grain prices in 19th-century Sweden
Climate and weather variation affect agricultural productivity, with consequences for both overall food availability and the wider economy. Knowledge of these processes has implications for understanding historical demography and predicting effects of climate change on societies. We studied the relationships between ambient temperature and the yields and prices of principle grains (wheat, rye, barley oats) in Sweden from 1803 to 1914. We found th…
Stone Age midden deposition assessed by bivalve sclerochronology and radiocarbon wiggle-matching of Arctica islandica shell increments
Evaluating Contemporaneity and Post‐mortem Age of Malacological Remains Using Sclerochronology and Dendrochronology
Sclerochronology and dendrochronology are based on series of incremental skeletal and cambial growths that have been correctly aligned in time via cross‐dating (i.e., incremental dating through synchronization of the growth variability on a visual and statistical basis). Here we report a study of the shell increments of two anthropogenic death assemblages of freshwater pearl mussel ( Margaritifera margaritifera ) originating from Finnish Lapland.…
Little Ice Age Farming in Finland
X-ray microdensitometry applied to subfossil tree-rings
Climatic variability and the population dynamics of historical hunter–gatherers
Our current knowledge on climate-mediated effects on human population dynamics is based on preindustrial agrarian societies where climate-induced crop failures had a major impact on fertility and mortality rates. However, because most of the human evolutionary history has been shaped by hunter-gatherer lifestyle relying on diverse plant and animal food sources, it is also important to understand how climate affected the population dynamics of hun…
Multicentennial Ring-Width Chronologies of Scots Pine Along a North–South Gradient Across Finland
Four regional Scots pine ring-width chronologies at the northern forest-limit, and in the northern, middle and southern boreal forest belts in Finland cover the last fourteen centuries. Tree-ring statistics and response functions were examined, and tree-ring width variation was also compared to North Atlantic Oscillation (NAO) and volcanic forcing. The tree-ring statistics show evidence of an ecogeographical gradient along a north–south transect.…
Centennial-to-millennial fluctuations in July temperatures in North Finland as recorded by timberline tree rings of Scots pine
A tree-ring proxy of summer temperature anomalies for northern Finland for the past 7500 yr was analyzed using Fourier spectrum and wavelet approaches. Multicentennial (250–450 yr) variability is present in the proxy record during most of the time range. This variability is suggested to reflect low-frequency variability in the North Atlantic Oscillation. Century-scale (90–130 yr) variation is another important feature of the tree-ring proxy data …
The supra-long Scots pine tree-ring record for Finnish Lapland
Midsummer (July) temperatures are reconstructed for the last 7500 years using the long ring-width chronology of Scots pine (Pinus sylvestris L.) from northern Finland. The chronology was built using regional curve standardization (RCS), which allows for long-term (low-frequency) variability to be extracted from this annually resolved record of 1087 samples from living trees and subfossil timber. Short-and long-term changes in reconstructed July t…
Distant impact
Regional curve standardization
Tree rings are commonly used proxy data for past climate variability. Probably the simplest practical solution for transforming raw tree-ring data into proxy estimates and retaining information on low-frequency tree-growth forcing is the regional curve standardization (RCS). This paper reviews the RCS concept and the development of this standardization method over the past 25 years. Tree-ring based estimation of low-frequency climate variability …
Stone Age midden deposition assessed by bivalve sclerochronology and radiocarbon wiggle-matching of Arctica islandica shell increments
Reconstructing crop yield variability in Finland
Lack of documentation on past harvest fluctuations limits the exploration of long-term trends in crop production and agricultural adaptation strategies. A long-term perspective is needed, however, to understand the wide spectrum of potential human responses to environment and climate change. Therefore, we used tree-ring density series as proxy data to reconstruct climate-mediated yield ratio (harvested grain in relation to sown) in central and no…
Climatic signatures in crops and grain prices in 19th-century Sweden
Climate and weather variation affect agricultural productivity, with consequences for both overall food availability and the wider economy. Knowledge of these processes has implications for understanding historical demography and predicting effects of climate change on societies. We studied the relationships between ambient temperature and the yields and prices of principle grains (wheat, rye, barley oats) in Sweden from 1803 to 1914. We found th…
Little Ice Age Farming in Finland
X-ray microdensitometry applied to subfossil tree-rings
Dendrochronological dating of wooden artifacts by measuring the tree rings using magnifying glass and photography-assisted method
Direct transformation of tree-ring measurements into palaeoclimate reconstructions in three-dimensional space
Here we propose a new method for dendroclimatic reconstructions. This DIrect REConstruction Technique (DIRECT) performs modelling of the age-dependent association between climate and growth in three-dimensional space and directly transforms the raw tree-ring values (on the scale of original growth units) into climate variability while considering the effect of age in this relationship. DIRECT was applied to maximum latewood density (MXD) data fro…
The supra-long Scots pine tree-ring record for Finnish Lapland
Midsummer (July) temperatures are reconstructed for the last 7500 years using the long ring-width chronology of Scots pine (Pinus sylvestris L.) from northern Finland. The chronology was built using regional curve standardization (RCS), which allows for long-term (low-frequency) variability to be extracted from this annually resolved record of 1087 samples from living trees and subfossil timber. Short-and long-term changes in reconstructed July t…
Multicentennial Ring-Width Chronologies of Scots Pine Along a North–South Gradient Across Finland
Four regional Scots pine ring-width chronologies at the northern forest-limit, and in the northern, middle and southern boreal forest belts in Finland cover the last fourteen centuries. Tree-ring statistics and response functions were examined, and tree-ring width variation was also compared to North Atlantic Oscillation (NAO) and volcanic forcing. The tree-ring statistics show evidence of an ecogeographical gradient along a north–south transect.…
Centennial-to-millennial fluctuations in July temperatures in North Finland as recorded by timberline tree rings of Scots pine
A tree-ring proxy of summer temperature anomalies for northern Finland for the past 7500 yr was analyzed using Fourier spectrum and wavelet approaches. Multicentennial (250–450 yr) variability is present in the proxy record during most of the time range. This variability is suggested to reflect low-frequency variability in the North Atlantic Oscillation. Century-scale (90–130 yr) variation is another important feature of the tree-ring proxy data …
Climatic variability and the population dynamics of historical hunter–gatherers
Our current knowledge on climate-mediated effects on human population dynamics is based on preindustrial agrarian societies where climate-induced crop failures had a major impact on fertility and mortality rates. However, because most of the human evolutionary history has been shaped by hunter-gatherer lifestyle relying on diverse plant and animal food sources, it is also important to understand how climate affected the population dynamics of hun…
X-ray microdensitometry applied to subfossil tree-rings
Evaluating Contemporaneity and Post‐mortem Age of Malacological Remains Using Sclerochronology and Dendrochronology
Sclerochronology and dendrochronology are based on series of incremental skeletal and cambial growths that have been correctly aligned in time via cross‐dating (i.e., incremental dating through synchronization of the growth variability on a visual and statistical basis). Here we report a study of the shell increments of two anthropogenic death assemblages of freshwater pearl mussel ( Margaritifera margaritifera ) originating from Finnish Lapland.…
Little Ice Age Farming in Finland
Stone Age midden deposition assessed by bivalve sclerochronology and radiocarbon wiggle-matching of Arctica islandica shell increments
Climatic signatures in crops and grain prices in 19th-century Sweden
Climate and weather variation affect agricultural productivity, with consequences for both overall food availability and the wider economy. Knowledge of these processes has implications for understanding historical demography and predicting effects of climate change on societies. We studied the relationships between ambient temperature and the yields and prices of principle grains (wheat, rye, barley oats) in Sweden from 1803 to 1914. We found th…
Significant changes of subseries-means in the Finnish tree-ring index of 7638 years, with comparisons to glaciological evidence from Greenland and Alps
Old World megadroughts and pluvials during the Common Era
An atlas of megadroughts in Europe and in the Mediterranean Basin during the Common Era provides insights into climate variability.
Direct transformation of tree-ring measurements into palaeoclimate reconstructions in three-dimensional space
Here we propose a new method for dendroclimatic reconstructions. This DIrect REConstruction Technique (DIRECT) performs modelling of the age-dependent association between climate and growth in three-dimensional space and directly transforms the raw tree-ring values (on the scale of original growth units) into climate variability while considering the effect of age in this relationship. DIRECT was applied to maximum latewood density (MXD) data fro…
Reconstructing crop yield variability in Finland
Lack of documentation on past harvest fluctuations limits the exploration of long-term trends in crop production and agricultural adaptation strategies. A long-term perspective is needed, however, to understand the wide spectrum of potential human responses to environment and climate change. Therefore, we used tree-ring density series as proxy data to reconstruct climate-mediated yield ratio (harvested grain in relation to sown) in central and no…
Regional curve standardization
Tree rings are commonly used proxy data for past climate variability. Probably the simplest practical solution for transforming raw tree-ring data into proxy estimates and retaining information on low-frequency tree-growth forcing is the regional curve standardization (RCS). This paper reviews the RCS concept and the development of this standardization method over the past 25 years. Tree-ring based estimation of low-frequency climate variability …
Dendrochronological dating of wooden artifacts by measuring the tree rings using magnifying glass and photography-assisted method
Dark Ages Cold Period
Several late Quaternary studies have recorded cold and disturbed climates centred during the mid-first millennium AD and discussed these conditions under the term ‘Dark Ages Cold Period’ (DACP). A review of 114 palaeoclimate papers indicated that cold climates were common in the Northern Hemisphere between AD 400 and 765. There are also suggestions that some regions may have been relatively wet during the DACP, while those around the Mediterranea…
Something old, something new, something borrowed
Distant impact
Historical trends in spring ice breakup for the Aura River in Southwest Finland, AD 1749–2018
Ice breakup (IBU) observations have been recorded for Aura River in Turku, southwest Finland, since the mid-18th century. The latest long-term investigation covered the period 1749–1906, but the series contains several biases. In this article, we present a fully revised and extended IBU series (1749–2018) of Aura River for climate research purposes. Instead of typical univariate IBU data (a single time series with one data point per year), this s…
Solar-type periodicities in the climate variability of Northern Fennoscandia during the last three centuries
Fifteen proxy records of summer temperature in Fennoscandia, Northern Europe and in Yamal and Taymir Peninsulas (Western Siberia) were analyzed for the AD 1700–2000 period. Century-long (70–100 year) and quasi bi-decadal periodicities were found from proxy records representing different parts of Fennoscandia. Decadal variation was revealed in a smaller number of records. Statistically significant correlations were revealed between the timescale-d…
Nonoverlapping Magisteria Versus Science-Religion Integration
The principle of nonoverlapping magisteria (NOMA), by Stephen Jay Gould, is commonly cited in the science-religion literature as an archetype of a model separating the domains of science and religion. As such, NOMA represents the independence category in Ian Barbour’s science-religion typology. However, it is commonly neglected that NOMA also permits dialogue and even integration of scientific and religious inputs at the personal level, i.e. beyo…
The 4.2 ka event
In recent years, much evidence has been presented on the 4.2 ka event. A review of 317 palaeoclimate papers shows that dry conditions were common during the event, especially from Eastern Mediterranean to India. The 4.2 ka event was not, however, a global drought event. Wet conditions were reported especially for central/northern Europe and sub-Saharan Africa. The 4.2 ka event is typically characterized either as short (4.2–4.0 ka) or long (4.4–3…
Low-frequency patterns in Late-Holocene tree-ring records from northern Fennoscandia
Northern Fennoscandia is a cradle of tree-ring based climate reconstructions. These Late-Holocene data come from several types of tree-ring proxies and are typically used for discussing the extent of past climate excursions such as the Medieval Climate Anomaly and Little Ice Age, relative to the modern temperatures. This article compares tree-ring records published from the region over the past two decades with those produced here by recalculatio…
Extreme events and the spread of Uralic languages
In this paper we present novel aspects concerning the possible connection between the 4.2 ka climatic event and the early spread of Uralic languages from western Siberia to North-East Europe. We discuss different reasons for the divergence of Proto-Uralic and the spread of the Uralic languages, and propose a scenario where the 4.2 ka climatic event and the early spread of Uralic languages is connected via three themes: 1) habitat changes, 2) anim…
The Fimbulwinter myth in the context of Nordic tree-ring climate proxy data
High-magnitude Late-Holocene volcanic eruptions contributed to the climate-related hardships of past societies. It has been theorised that memories of one of the volcanic events and its terrible consequences are recorded in the Old Norse traditions of the Fimbulwinter and Ragnarök (possibly also in the Old Kalevala). This Fimbulwinter theory suggests that the eruption (or double-eruption) responsible for the calamity was the one that caused the A…
Geography (21 works) · Tree-ring climate responses (20 works) · Geology and Paleoclimatology Research (18 works) · Physical geography (14 works) · Geology (13 works) · Archaeology (12 works) · Climate change (12 works) · Climatology (11 works) · Dendrochronology (11 works) · Plant Water Relations and Carbon Dynamics (11 works)