scholarly journals Higher-than-present Medieval pine (Pinus sylvestris) treeline along the Swedish Scandes

2015 ◽  
Vol 42 ◽  
pp. 1-14 ◽  
Author(s):  
Leif Kullman
Keyword(s):  
Pinus Sylvestris ◽  
Ground Surface ◽  
Ice Age ◽  
Lapse Rate ◽  
Medieval Period ◽  
Climate Change And Variability ◽  
The Past ◽  
Northern Fennoscandia ◽  
Detection And Attribution ◽  
Summer Temperatures

The upper treeline of Scots pine (Pinus sylvestris L.) is renowned as a sensitive indicator of climate change and variability. By use of megafossil tree remains, preserved exposed on the ground surface, treeline shift over the past millennium was investigated at multiple sites along the Scandes in northern Sweden. Difference in thermal level between the present and the Medieval period, about AD 1000-1200, is a central, although controversial, aspect concerning the detection and attribution of anthropogenic climate warming. Radiocarbon-dated megafossil pines revealed that the treeline was consistently positioned as much as 115 m higher during the Medieval period than today (AD 2000-2010), after a century of warming and substantial treeline upshift. Drawing on the last-mentioned figure, and a lapse rate of 0.6oC/100 m, it may be inferred that Medieval summer temperatures were about 0.7 oC warmer than much of the past 100 years. Extensive pine mortality and treeline descent after the Medieval warming peak reflect substantially depressed temperatures during the Little Ice Age. Warmer-than-present conditions during the Medieval period concur with temperature reconstructions from different parts of northern Fennoscandia, northwestern Russia and Greenland. Modern warming has not been sufficient to restore Medieval treelines. Against this background, there is little reason to view further modest warming as unnatural.

scholarly journals Climatic changes in the Urals over the past millennium – an analysis of geothermal and meteorological data

2007 ◽  
Vol 3 (2) ◽  
pp. 237-242 ◽  
Author(s):  
D. Yu. Demezhko ◽  
I. V. Golovanova
Keyword(s):  
20Th Century ◽  
18Th Century ◽  
Meteorological Data ◽  
Ground Surface ◽  
Ice Age ◽  
Temperature History ◽  
Joint Analysis ◽  
The Urals ◽  
The Past ◽  
Mean Temperature

Abstract. This investigation is based on a study of two paleoclimatic curves obtained in the Urals (51–59° N, 58–61° E): i) a ground surface temperature history (GSTH) reconstruction since 800 A.D. and ii) meteorological data for the last 170 years. Temperature anomalies measured in 49 boreholes were used for the GSTH reconstruction. It is shown that a traditional averaging of the histories leads to the lowest estimates of amplitude of past temperature fluctuations. The interval estimates method, accounting separately for the rock's thermal diffusivity variations and the influence of a number of non-climatic causes, was used to obtain the average GSTH. Joint analysis of GSTH and meteorological data bring us to the following conclusions. First, ground surface temperatures in the Medieval maximum during 1100–1200 were 0.4 K higher than the 20th century mean temperature (1900–1960). The Little Ice Age cooling was culminated in 1720 when surface mean temperature was 1.6 K below the 20th century mean temperature. Secondly, contemporary warming began approximately one century prior to the first instrumental measurements in the Urals. The rate of warming was +0.25 K/100 years in the 18th century, +1.15 K/100 years in the 19th and +0.75 K/100 years in the first 80 years of the 20th century. Finally, the mean rate of warming increased in the final decades of 20th century. An analysis of linear regression coefficients in running intervals of 21 and 31 years, shows that there were periods of warming with almost the same rates in the past, including the 19th century.

A Quantitative Holocene Climatic Record from Diatoms in Northern Fennoscandia

2000 ◽  
Vol 54 (2) ◽  
pp. 284-294 ◽  
Author(s):  
Atte Korhola ◽  
Jan Weckström ◽  
Lasse Holmström ◽  
Panu Erästö
Keyword(s):  
Regional Climate ◽  
Ice Core ◽  
Ice Age ◽  
Calibration Model ◽  
Subarctic Lakes ◽  
Northern Fennoscandia ◽  
Summer Temperatures ◽  
Climatic Record ◽  
Climate Events

A diatom-based calibration model for predicting summer temperatures was developed using climatically sensitive subarctic lakes in northern Fennoscandia. The model was applied to a sediment core from a treeline lake to infer trends in Holocene climate. The record exhibits long-term variations, as well as a series of shorter-term fluctuations on a time scale of centuries. Summers were warmest in the area about 6200 cal yr B.P. and featured distinct cooling episodes around 8300, 7200, 4200, 3000, and 400 cal yr B.P., most of these coinciding with some known climate events (e.g., the 8200 cal yr B.P. event and the Little Ice Age). The similarity of the observed shifts with the pacings of climate events from marine and ice-core records represents evidence for coupled ocean–atmosphere forcing of the regional climate.

scholarly journals Millennial-to-centennial patterns and trends in the hydroclimate of North America over the past 2000 years

2017 ◽  
Author(s):  
Bryan N. Shuman ◽  
Cody Routson ◽  
Nicholas McKay ◽  
Sherilyn Fritz ◽  
Darrell Kaufman ◽  
...  
Keyword(s):  
Pacific Northwest ◽  
Ice Age ◽  
The Arctic ◽  
Medieval Period ◽  
The Past ◽  
Past 2000 Years ◽  
Annual Range ◽  
The Common ◽  
Common Era ◽  
Millennial Scale

Abstract. A synthesis of 93 hydrologic records from across North and Central America, and adjacent tropical and Arctic islands, reveals centennial to millennial trends in the regional hydroclimates of the Common Era (CE; past 2000 years). The hydrological records derive from materials stored in lakes, bogs, caves, and ice from extant glaciers, which have the continuity through time to preserve low-frequency (> 100 year) climate signals that may not be well represented by other shorter-lived archives, such as tree-ring chronologies. The most common pattern, represented in 46 (49 %) of the records, indicates that the centuries before 1000 CE were drier than the centuries since that time. Principal components analysis indicates that millennial-scale trends represent the dominant pattern of variance in the southwest and northeast U.S., the mid-continent, Pacific Northwest, the Arctic, and the tropics, although not all records within a region show the same direction of change. The Pacific Northwest, Greenland, and the southernmost tier of the tropical sites tended to dry toward present, as many other areas became wetter than before. Twenty-two records (24 %) indicate that the Medieval period (800–1300 CE) was drier than the Little Ice Age (1400–1900 CE), but in many cases the difference was part of the longer millennial-scale trend, and, in 25 records (27 %), the Medieval period represented a pluvial (wet) phase. Where quantitative records permitted a comparison, we found that centennial-scale fluctuations over the Common Era represented changes of 3–7 % of the modern inter-annual range of variability in precipitation, but the accumulation of these long-term trends over the entirety of the Holocene caused recent centuries to be significantly wetter, on average, than most of the past 11 000 years.

scholarly journals Climate trends in northern Ontario and Québec from borehole temperature profiles

2016 ◽  
Vol 12 (12) ◽  
pp. 2215-2227 ◽  
Author(s):  
Carolyne Pickler ◽  
Hugo Beltrami ◽  
Jean-Claude Mareschal
Keyword(s):  
Surface Temperature ◽  
Ground Surface ◽  
Ice Age ◽  
Climate Trends ◽  
James Bay ◽  
Northern Ontario ◽  
Ground Surface Temperature ◽  
Cooling Period ◽  
The Past ◽  
Discontinuous Permafrost

Abstract. The ground surface temperature histories of the past 500 years were reconstructed at 10 sites containing 18 boreholes in northeastern Canada. The boreholes, between 400 and 800 m deep, are located north of 51° N and west and east of James Bay in northern Ontario and Québec. We find that both sides of James Bay have experienced similar ground surface temperature histories with a warming of 1.51 ± 0.76 K during the period of 1850 to 2000, similar to borehole reconstructions for the southern portion of the Superior Province and in agreement with available proxy data. A cooling period corresponding to the Little Ice Age was found at only one site. Despite permafrost maps locating the sites in a region of discontinuous permafrost, the ground surface temperature histories suggest that the potential for permafrost was minimal to absent over the past 500 years. This could be the result of air surface temperature interpolation used in permafrost models being unsuitable to account for the spatial variability of ground temperatures along with an offset between ground and air surface temperatures due to the snow cover.

scholarly journals Climatic changes in the Urals over the past millennium. An analysis of geothermal and meteorological data

2007 ◽  
Vol 3 (1) ◽  
pp. 1-17
Author(s):  
D. Yu. Demezhko ◽  
I. V. Golovanova
Keyword(s):  
20Th Century ◽  
18Th Century ◽  
Meteorological Data ◽  
Ground Surface ◽  
Ice Age ◽  
Temperature History ◽  
Joint Analysis ◽  
The Urals ◽  
The Past ◽  
Mean Temperature

Abstract. This investigation is based on a study of two paleoclimatic curves obtained in the Urals (51–59° N, 58–61° E): i) a ground surface temperature history (GSTH) reconstruction since 800 AD and ii) meteorological data for the last 170 years. Temperature anomalies measured in 49 boreholes were used for the GSTH reconstruction. It is shown that a traditional averaging of the histories leads to the lowest estimates of amplitude of past temperature fluctuations. The interval estimates method, accounting separately for the rock's thermal diffusivity variations and the influence of a number of non-climatic causes, was used for obtaining the average GSTH. Joint analysis of GSTH and meteorological data bring us to the following conclusions. First, ground surface temperatures in the Medieval maximum during 1100–1200 was 0.38 K higher than the 20th century mean temperature (1900–1960). The Little Ice Age cooling was culminated in 1720 when surface mean temperature was 1.58 K below than the 20th century mean temperature. Secondly, contemporary warming began approximately one century prior to the first instrumental measurements in the Urals. The rate of warming was +0.25K/100years in the 18th century, +1.15 K/100years in the 19th and +0.75 K/100years in the first 80 years of the 20th. Finally, the mean rate of temperature warming increased in final decades of 20th century. An analysis of linear regression coefficients in running intervals of 11, 21 and 31 years, shows that there were periods of warming with almost the same rates in the past, including the 19th century.

scholarly journals Climate trends in northern Ontario and Quebec from borehole temperature profiles

2016 ◽  
Author(s):  
C. Pickler ◽  
H. Beltrami ◽  
J.-C. Mareschal
Keyword(s):  
Surface Temperature ◽  
Ground Surface ◽  
Ice Age ◽  
Climate Trends ◽  
James Bay ◽  
Northern Ontario ◽  
Ground Surface Temperature ◽  
Cooling Period ◽  
The Past ◽  
Discontinuous Permafrost

Abstract. The ground surface temperature histories of the past 500 years were reconstructed at 10 sites containing 18 boreholes in northeastern Canada. The boreholes, between 400 and 800 m deep, are located north of 51° N, and west and east of James Bay in northern Ontario and Quebec. We find that both sides of James Bay have experienced similar ground surface temperature histories with a warming of ~ 1–2 K for the last 150 years, similar to borehole reconstructions for the southern portion of the Superior Province and in agreement with available proxy data. A cooling period corresponding to the little ice age was found at only one site. Despite permafrost maps locating the sites in a region of discontinuous permafrost, the ground surface temperature histories suggest that the entire region is and was free of permafrost for the past 500 years. This could be the result of air surface temperature interpolation used in permafrost models being unsuitable to represent the spatial variability of ground temperatures along with an offset between ground and air surface temperatures due to the snow cover.

Temperature patterns over the past eight centuries in Northern Fennoscandia inferred from sedimentary diatoms

2006 ◽  
Vol 66 (1) ◽  
pp. 78-86 ◽  
Author(s):  
Jan Weckström ◽  
Atte Korhola ◽  
Panu Erästö ◽  
Lasse Holmström
Keyword(s):  
Temperature Variability ◽  
Ice Age ◽  
Terminal Phase ◽  
Polar Regions ◽  
The Past ◽  
Northern Fennoscandia ◽  
Finnish Lapland ◽  
Sedimentary Diatoms ◽  
Natural Climate

AbstractEstablishing natural climate variability becomes particularly important in remote polar regions, especially when considering questions regarding higher than average warming. We present a high-resolution record of temperature variability for the past 800 yr based on sedimentary diatoms from a treeline lake in Finnish Lapland. The BSiZer multiscale smoothing technique is applied to the data to identify significant features in the record at different temporal levels. The overall reconstruction shows relatively large multi-centennial temperature variability with a total range of about 0.6–0.8°C. At millennial scales, the temperatures exhibit a statistically significant long-term cooling trend prior to industrialization (ΔT = −0.03°C/century). At the centennial timescale, three warm time intervals were identified around AD 1200–1300 (terminal phase of the Medieval Warm Period, MWP), 1380–1550 and from 1920 until the present. Pronounced coolness occurred between AD 1600 and 1920, indicative of the Little Ice Age (LIA). At the decadal level, certain shorter-term climate excursions were revealed. The warmest ∼10–30 yr, non-overlapping periods occurred in AD 1220–1250, 1470–1500 and 1970–2000, respectively. The classic events of MWP and LIA are evident in our record, as is also the 20th century warming.

Classifying the Past: Discriminant Analysis and its Application to Medieval Farming Systems

1996 ◽  
Vol 8 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Ken Bartley
Keyword(s):  
Cluster Analysis ◽  
Discriminant Analysis ◽  
Processing Time ◽  
Farming Systems ◽  
Frame Of Reference ◽  
Analytical Models ◽  
Successful Implementation ◽  
Medieval Period ◽  
The Past ◽  
Livestock Management

This paper discusses the need for nationally based analytical models of the medieval period. The use of cluster analysis as a method for classifying demesne farms, by the crops they grew and their livestock management, is explained. Successful implementation of cluster analysis requires both the existence of a large base sample, to permit isolation of specific groupings within the data, and access to considerable processing time. The paper concludes by demonstrating how discriminant analysis can provide an efficient and systematic way of classifying even a single manor within a national frame of reference.

An integrated approach for tracking climate-driven changes in treeline environments on different time scales in the Valle d’Aosta, Italian Alps

The Holocene ◽  
2021 ◽  
pp. 095968362110259
Author(s):  
Anna Masseroli ◽  
Giovanni Leonelli ◽  
Umberto Morra di Cella ◽  
Eric P Verrecchia ◽  
David Sebag ◽  
...  
Keyword(s):  
Integrated Approach ◽  
Early Summer ◽  
Ice Age ◽  
Limiting Factor ◽  
Alpine Treeline ◽  
Growing Seasons ◽  
Direct Measurements ◽  
Soil Temperatures ◽  
Summer Temperatures ◽  
Local Station

Both biotic and abiotic components, characterizing the mountain treeline ecotone, respond differently to climate variations. This study aims at reconstructing climate-driven changes by analyzing soil evolution in the late Holocene and by assessing the climatic trends for the last centuries and years in a key high-altitude climatic treeline (2515 m a.s.l.) on the SW slope of the Becca di Viou mountain (Aosta Valley Region, Italy). This approach is based on soil science and dendrochronological techniques, together with daily air/soil temperature monitoring of four recent growing seasons. Direct measurements show that the ongoing soil temperatures during the growing season, at the treeline and above, are higher than the predicted reference values for the Alpine treeline. Thus, they do not represent a limiting factor for tree establishment and growth, including at the highest altitudes of the potential treeline (2625 m a.s.l.). Dendrochronological evidences show a marked sensitivity of tree-ring growth to early-summer temperatures. During the recent 10-year period 2006–2015, trees at around 2300 m a.s.l. have grown at a rate that is approximately 1.9 times higher than during the 10-year period 1810–1819, one of the coolest periods of the Little Ice Age. On the other hand, soils show only an incipient response to the ongoing climate warming, likely because of its resilience regarding the changeable environmental conditions and the different factors influencing the soil development. The rising air temperature, and the consequent treeline upward shift, could be the cause of a shift from Regosol to soil with more marked Umbric characteristics, but only for soil profiles located on the N facing slopes. Overall, the results of this integrated approach permitted a quantification of the different responses in abiotic and biotic components through time, emphasizing the influence of local station conditions in responding to the past and ongoing climate change.

Modulation of the relationship between summer temperatures in the Qinghai–Tibetan Plateau and Arctic over the past millennium by external forcings

2021 ◽  
pp. 1-9
Author(s):  
Feng Shi ◽  
Anmin Duan ◽  
Qiuzhen Yin ◽  
John T Bruun ◽  
Cunde Xiao ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Global Climate ◽  
Volcanic Eruptions ◽  
Warm Period ◽  
Temperature Correlation ◽  
The Past ◽  
External Forcings ◽  
Centennial Variation ◽  
Summer Temperatures ◽  
Past Millennium

Abstract The Qinghai–Tibetan Plateau and Arctic both have an important influence on global climate, but the correlation between climate variations in these two regions remains unclear. Here we reconstructed and compared the summer temperature anomalies over the past 1,120 yr (900–2019 CE) in the Qinghai–Tibetan Plateau and Arctic. The temperature correlation during the past millennium in these two regions has a distinct centennial variation caused by volcanic eruptions. Furthermore, the abrupt weak-to-strong transition in the temperature correlation during the sixteenth century could be analogous to this type of transition during the Modern Warm Period. The former was forced by volcanic eruptions, while the latter was controlled by changes in greenhouse gases. This implies that anthropogenic, as opposed to natural, forcing has acted to amplify the teleconnection between the Qinghai–Tibetan Plateau and Arctic during the Modern Warm Period.

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