Evidence from the Scandinavian Tree Line Since the Last Ice Age

1996 ◽  
Vol 7 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Wibjörn Karlén ◽  
Johan Kuylenstierna
Keyword(s):  
Solar Activity ◽  
Volcanic Eruptions ◽  
Cold Climate ◽  
Ice Age ◽  
Alpine Glacier ◽  
Glacial Sediments ◽  
Carbon 14 ◽  
Pine Tree ◽  
Summer Temperatures ◽  
Last Ice Age

The focus of this paper is to investigate the possible correlation between changes in the Scandinavian climate and solar activity. Information about climatic changes in Sweden and Norway has been obtained from three sources: the carbon-14 dating of pine wood retrieved from above the present pine tree limit, studies of glacial sediments and the carbon dating of alpine glacier moraines. Alpine tree limits reveal that summer temperatures in general were warmer during the millennia following the last ice age. Superimposed on this general trend are fluctuations of a few hundred years duration. A period probably as cold as the last several hundred years occurred around 8200 years ago. Other severe cooling took place around 4500,2200 and 1200 years ago. The timing of major climatic events has been compared with solar activity as measured by carbn-14 changes and shows a good correlation with cold periods in Scandinavia for most of the last 8000 years. Deviations between carbn-14 anomalies and the climatic record may be due to volcanic eruptions increasing the concentration of sulfate aerosols in the atmosphere. A similarity between the periods of cold climate and carbon-14 levels indicates that solar variability may be an important factor for climate change.

scholarly journals Hypersensitivity of glacial temperatures in Siberia

2019 ◽  
Author(s):  
Pepijn Bakker ◽  
Irina Rogozhina ◽  
Ute Merkel ◽  
Matthias Prange
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Stationary Wave ◽  
Wave Pattern ◽  
Cold Climate ◽  
Ice Age ◽  
Geological Evidence ◽  
Model Experiments ◽  
Summer Temperatures ◽  
Glacial Periods

Abstract. Climate change in Siberia is currently receiving a lot of attention as large permafrost-covered areas could provide a strong positive feedback to global warming through the release of carbon that has been sequestered there on glacial-interglacial time scales. Geological evidence and climate model experiments show that the Siberian region also played an exceptional role during glacial periods. The region that is currently known for its harsh cold climate did not experience major glaciations during the last ice age, including its severest stages around the Last Glacial Maximum (LGM). On the contrary, it is thought that glacial summer temperatures were comparable to present-day. We combine LGM experiments from the second and third phases of the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) with sensitivity experiments with the Community Earth System Model (CESM). Together these climate model experiments reveal that the intermodel spread in LGM summer temperatures in Siberia is much larger than in any other region of the globe and suggest that temperatures in Siberia are highly susceptible to changes in the imposed glacial boundary conditions, the included feedbacks and processes, and to the model physics of the different components of the climate model. We find that changes in the large-scale atmospheric stationary wave pattern and associated northward heat transport drive strong local snow and vegetation feedbacks and that this combination explains the susceptibility of LGM summer temperatures in Siberia. This suggests that a small difference between two glacial periods in terms of climate, ice buildup or their respective evolution towards maximum glacial conditions, can lead to strongly divergent summer temperatures in Siberia, that are sufficiently strong to allow for the buildup of an ice sheet during some glacial periods, while during others, above-freezing summer temperatures will preclude a multi-year snow-pack from forming.

scholarly journals Quantifying the potential causes of Neanderthal extinction: abrupt climate change versus competition and interbreeding

2020 ◽  
Author(s):  
Axel Timmermann
Keyword(s):  
Climate Change ◽  
Homo Sapiens ◽  
Volcanic Eruptions ◽  
Homo Erectus ◽  
Ice Age ◽  
Abrupt Climate Change ◽  
Modern Humans ◽  
Climatic Environment ◽  
Anatomically Modern Humans ◽  
Last Ice Age

Anatomically Modern Humans are the sole survivor of a group of hominins that inhabited our planet during the last ice age and that included, among others, Homo neanderthalensis, Homo denisova, and Homo erectus. Whether previous hominin extinctions were triggered by external factors, such as abrupt climate change, volcanic eruptions or whether competition and interbreeding played major roles in their demise still remains unresolved. Here I present a spatially resolved numerical hominin dispersal model (HDM) with empirically constrained key parameters that simulates the migration and interaction of Anatomically Modern Humans and Neanderthals in the rapidly varying climatic environment of the last ice age. The model simulations document that rapid temperature and vegetation changes associated with Dansgaard-Oeschger events were not major drivers of global Neanderthal extinction between 50-35 thousand years ago, but played important roles regionally, in particular over northern Europe. According to a series of parameter sensitivity experiments conducted with the HDM, a realistic extinction of the Neanderthal population can only be simulated when Homo sapiens is chosen to be considerably more effective in exploiting scarce glacial food resources as compared to Neanderthals.

Volcanic dust in the atmosphere; with a chronology and assessment of its meteorological significance

1970 ◽  
Vol 266 (1178) ◽  
pp. 425-533 ◽  
Keyword(s):  
Atmospheric Circulation ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Polar Regions ◽  
Particle Sizes ◽  
Direct Effects ◽  
Northwest Europe ◽  
Circulation Parameters ◽  
Last Ice Age ◽  
Main Influence

After defining the terms commonly used in reporting volcanic eruptions and noting previous approaches to assessment of their magnitudes, this study proceeds to examine aspects of importance, or possible importance, to meteorology―principally the dust veils created in the atmosphere, particle sizes and distribution, heights, fall speeds and atmospheric residence times. Later sections deal with spread of the dust by the atmospheric circulation and the direct effects apparent upon radiation, surface temperature and extent of ice in the polar regions. These effects, as well as various crude measures of the total quantity of solid matter thrown up, are used to arrive at numerical assessments of volcanic eruptions in terms of a dust veil index (d. v. i.). The latitude of origin of the dust (latitude of the volcano) receives some attention, and apparently affects the course of development of the atmospheric circulation over the three or four years following, at least in the case of great eruptions (d. v. i. > 100 over one hemisphere). Effects upon the extent of ice on the polar seas may be of somewhat longer duration, and thereby influence the atmospheric circulation over a longer period of years, since there seems to be some association with the cumulative d.v.i. values when successive great eruptions occur with only few years between. The time distribution of volcanic dust since the last Ice Age, and since a. d. 1500, are indicated in as much detail as the evidence permits. Some associations with changes of climate are suggested, but it is clear that volcanic dust is not the only, and probably not the main, influence in this. The appendices give a chronology of eruptions (including those which it seems possible to dismiss as regards any effect on world weather or climate) and a chronology of d. v. i. values. A third appendix displays by means of graphs the variation of some circulation parameters in January and July in the region of northwest Europe over the years immediately following forty of the greatest eruptions since 1680.

scholarly journals Hypersensitivity of glacial summer temperatures in Siberia

2020 ◽  
Vol 16 (1) ◽  
pp. 371-386
Author(s):  
Pepijn Bakker ◽  
Irina Rogozhina ◽  
Ute Merkel ◽  
Matthias Prange
Keyword(s):  
Climate Model ◽  
Stationary Wave ◽  
Wave Pattern ◽  
Cold Climate ◽  
Ice Age ◽  
Geological Evidence ◽  
Model Experiments ◽  
Community Earth System Model ◽  
Summer Temperatures ◽  
Glacial Periods

Abstract. Climate change in Siberia is currently receiving a lot of attention because large permafrost-covered areas could provide a strong positive feedback to global warming through the release of carbon that has been sequestered there on glacial–interglacial timescales. Geological evidence and climate model experiments show that the Siberian region also played an exceptional role during glacial periods. The region that is currently known for its harsh cold climate did not experience major glaciations during the last ice age, including its severest stages around the Last Glacial Maximum (LGM). On the contrary, it is thought that glacial summer temperatures were comparable to the present day. However, evidence of glaciation has been found for several older glacial periods. We combine LGM experiments from the second and third phases of the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) with sensitivity experiments using the Community Earth System Model (CESM). Together, these climate model experiments reveal that the intermodel spread in LGM summer temperatures in Siberia is much larger than in any other region of the globe and suggest that temperatures in Siberia are highly susceptible to changes in the imposed glacial boundary conditions, the included feedbacks and processes, and to the model physics of the different components of the climate model. We find that changes in the circumpolar atmospheric stationary wave pattern and associated northward heat transport drive strong local snow and vegetation feedbacks and that this combination explains the susceptibility of LGM summer temperatures in Siberia. This suggests that a small difference between two glacial periods in terms of climate, ice buildup or their respective evolution towards maximum glacial conditions can lead to strongly divergent summer temperatures in Siberia, allowing for the buildup of an ice sheet during some glacial periods, while during others, above-freezing summer temperatures preclude a multi-year snowpack from forming.

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.

scholarly journals Arctic Ocean stratification set by sea level and freshwater inputs since the last ice age

2021 ◽  
Author(s):  
Jesse R. Farmer ◽  
Daniel M. Sigman ◽  
Julie Granger ◽  
Ona M. Underwood ◽  
François Fripiat ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Surface Waters ◽  
Ice Age ◽  
The Arctic ◽  
Bering Strait ◽  
Central Arctic Ocean ◽  
Phytoplankton Productivity ◽  
Nitrate Consumption ◽  
Western Arctic ◽  
Last Ice Age

AbstractSalinity-driven density stratification of the upper Arctic Ocean isolates sea-ice cover and cold, nutrient-poor surface waters from underlying warmer, nutrient-rich waters. Recently, stratification has strengthened in the western Arctic but has weakened in the eastern Arctic; it is unknown if these trends will continue. Here we present foraminifera-bound nitrogen isotopes from Arctic Ocean sediments since 35,000 years ago to reconstruct past changes in nutrient sources and the degree of nutrient consumption in surface waters, the latter reflecting stratification. During the last ice age and early deglaciation, the Arctic was dominated by Atlantic-sourced nitrate and incomplete nitrate consumption, indicating weaker stratification. Starting at 11,000 years ago in the western Arctic, there is a clear isotopic signal of Pacific-sourced nitrate and complete nitrate consumption associated with the flooding of the Bering Strait. These changes reveal that the strong stratification of the western Arctic relies on low-salinity inflow through the Bering Strait. In the central Arctic, nitrate consumption was complete during the early Holocene, then declined after 5,000 years ago as summer insolation decreased. This sequence suggests that precipitation and riverine freshwater fluxes control the stratification of the central Arctic Ocean. Based on these findings, ongoing warming will cause strong stratification to expand into the central Arctic, slowing the nutrient supply to surface waters and thus limiting future phytoplankton productivity.

scholarly journals Latin America in Global History: An Historiographic Overview

2017 ◽  
Vol 30 (60) ◽  
pp. 253-272 ◽  
Author(s):  
Diego Olstein
Keyword(s):  
Latin America ◽  
Sixteenth Century ◽  
New World ◽  
World History ◽  
The Other ◽  
Ice Age ◽  
Global History ◽  
The World ◽  
Last Ice Age ◽  
Great Divergence

Abstract World history can be arranged into three major regional divergences: the 'Greatest Divergence' starting at the end of the last Ice Age (ca. 15,000 years ago) and isolating the Old and the New Worlds from one another till 1500; the 'Great Divergence' bifurcating the paths of Europe and Afro-Asia since 1500; and the 'American Divergence' which divided the fortunes of New World societies from 1500 onwards. Accordingly, all world regions have confronted two divergences: one disassociating the fates of the Old and New Worlds, and the other within either the Old or the New World. Latin America is in the uneasy position that in both divergences it ended up on the 'losing side.' As a result, a contentious historiography of Latin America evolved from the very moment that it was incorporated into the wider world. Three basic attitudes toward the place of Latin America in global history have since emerged and developed: admiration for the major impact that the emergence on Latin America on the world scene imprinted on global history; hostility and disdain over Latin America since it entered the world scene; direct rejection of and head on confrontation in reaction the former. This paper examines each of these three attitudes in five periods: the 'long sixteenth century' (1492-1650); the 'age of crisis' (1650-1780); 'the long nineteenth century' (1780-1914); 'the short twentieth century' (1914-1991); and 'contemporary globalization' (1991 onwards).

Evidence for a large surface ablation zone in central East Antarctica during the last Ice Age

2003 ◽  
Vol 59 (1) ◽  
pp. 114-121 ◽  
Author(s):  
Martin J. Siegert ◽  
Richard C. A. Hindmarsh ◽  
Gordon S. Hamilton
Keyword(s):  
Ice Core ◽  
Remote Sensing Data ◽  
Ice Age ◽  
Internal Layers ◽  
Ice Flow ◽  
Glacial Ice ◽  
Ice Surface ◽  
Ice Flows ◽  
Last Ice Age ◽  
The Hill

AbstractInternal isochronous ice sheet layers, recorded by airborne ice-penetrating radar, were measured along an ice flowline across a large (>1 km high) subglacial hill in the foreground of the Transantarctic Mountains. The layers, dated through an existing stratigraphic link with the Vostok ice core, converge with the ice surface as ice flows over the hill without noticeable change to their separation with each other or the ice base. A two-dimensional ice flow model that calculates isochrons and particle flowpaths and accounts for ice flow over the hill under steady-state conditions requires net ablation (via sublimation) over the stoss face for the predicted isochrons to match the measured internal layers. Satellite remote sensing data show no sign of exposed ancient ice at this site, however. Given the lack of exposed glacial ice, surface balance conditions must have changed recently from the net ablation that is predicted at this site for the last 85,000 years to accumulation.

scholarly journals Atmospheric Lead in Antarctic Ice during the Last Climatic Cycle

1988 ◽  
Vol 10 ◽  
pp. 5-9 ◽  
Author(s):  
Claude F. Boutron ◽  
Clair C. Patterson ◽  
Claude Lorius ◽  
V.N. Petrov ◽  
N.I. Barkov
Keyword(s):  
Isotope Dilution Mass Spectrometry ◽  
Ice Cores ◽  
Ice Age ◽  
Crustal Rock ◽  
Last Interglacial ◽  
Toxic Heavy Metal ◽  
Mass Spectrometry Technique ◽  
Spectrometry Technique ◽  
Last Ice Age ◽  
The Antarctic

Concentrations of lead (Pb) have been measured by the ultra-clean isotope dilution mass spectrometry technique in various sections of the Antarctic Dome C and Vostok deep ice cores, whose ages range from 3.85 to 155 ka B.P., in order to assess the natural, pre-human, sources of this toxic heavy metal in the global troposphere. Pb concentrations were very low, as low as about 0.3 pg Pb/g during the Holocene and probably during the last interglacial and part of the last ice age. On the other hand, they were quite high, up to about 40 pg Pb/g, during the Last Glacial Maximum and at the end of the penultimate ice age. Wind-blown dust from crustal rock and soil appears to be the main natural source of Pb in the global troposphere. Pb contribution from volcanoes is significant during periods of low Pb only. Contribution from the oceans is insignificant.

Sign in / Sign up

Export Citation Format

Share Document