Histoire holocène du climat et de la végétation à Lanoraie (Québec)

1982 ◽  
Vol 19 (10) ◽  
pp. 1938-1952 ◽  
Author(s):  
Paul Comtois
Keyword(s):  
Temperate Forest ◽  
Sugar Maple ◽  
Vegetation History ◽  
Isotopic Ratio ◽  
Isotopic Ratios ◽  
Climatic Variations ◽  
Pioneer Tree ◽  
History Of ◽  
Oxygen Isotopic ◽  
Climatic Cooling

Four different cores were recovered from the same peat complex at Lanoraie (Québec), and have been used to evaluate, by pollen analysis, possible differences in the representation of the vegetation history. The isotopic ratio of oxygen has been used to indicate climatic variations involved in these processes.This method was first tested and calibrated with modern moss samples. A transect of 15 samples, from the temperate forest to the tundra, indicates that annual mean temperatures and evapotranspiration rates have a predominant influence on oxygen isotopic ratios. A sequence of fossil sediments, interpreted in terms of these results, shows a climatic maximum at 3500 BP and a reduction of temperature since 1500 BP in the Lanoraie region.The history of the regional vegetation shows the following succession of stages: (1) establishment of pioneer tree vegetation of pine, oak, elm, and walnut; (2) buildup of a sugar maple forest, contemporaneous with the migration of beech and correlated with a maximum pollen influx and a climatic optimum at about 3500 BP; (3) increase of the representation of spruce and fir after 1500 BP, related to a climatic cooling. Paleobotanical data–the recurrence of ruderal spectra and the presence of Iva xanthifolia– suggest the occurrence of two prehistoric anthropic periods, one before 3500 BP and the other at ca. 1500 BP.

scholarly journals Temporal variations of the CO2 concentration and its carbon and oxygen isotopic ratios in a temperate forest in the central part of the main island of Japan

Tellus B ◽  
1997 ◽  
Vol 49 (4) ◽  
pp. 364-381 ◽  
Author(s):  
Takakiyo Nakazawa ◽  
Shohei Murayama ◽  
Mitsuko Toi ◽  
Misa Ishizawa ◽  
Kaori Otonashi ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Co2 Concentration ◽  
Temporal Variations ◽  
Isotopic Ratios ◽  
Main Island ◽  
Oxygen Isotopic

scholarly journals Recent ice-core climate records from the Cordillera Blanca, Peru

1995 ◽  
Vol 21 ◽  
pp. 225-230 ◽  
Author(s):  
M. E. Davis ◽  
L. G. Thompson ◽  
E. Mosley-Thompson ◽  
P. N. Lin ◽  
V. N. Mikhalenko ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Warming Trend ◽  
Isotopic Ratios ◽  
Weather Station ◽  
Climate Record ◽  
Climatic Variations ◽  
Recent Warming ◽  
Lower Elevation ◽  
Oxygen Isotopic

Ice cores recently drilled to bedrock on the col of Huascarán (9°06′ S, 77°36′ W, 6047 m a.s.l.) offer the potential for a long, annually resolved climate record from tropical South America. This paper presents the record from 1950 to 1993 preserved in microparticle and nitrate concentrations and oxygen-isotopic ratios. Average monthly temperatures from a satellite-linked automatic weather station installed on nearby Hualcán in 1991 are presented. Annual temperatures from local high-altitude meteorological stations, along with the annual Huascarán isotopic record, show a warming trend over the last two decades. The marked preservation of the climate record in oxygen-isotopic ratios on Huascarán is absent at lower-elevation sites, which have been affected by the recent warming. This paper demonstrates the establishment of a time-scale for the Huascarán core, the preservation of the climatic signal with depth and the linkage of the ice-core “proxy-climate” parameters with measured climatic variations.

scholarly journals Last Glacial Maximum and Deglacial Abyssal Seawater Oxygen Isotopic Ratios

2016 ◽  
Author(s):  
Carl Wunsch
Keyword(s):  
Deep Sea ◽  
Sea Water ◽  
Initial Conditions ◽  
Isotopic Ratio ◽  
Isotopic Ratios ◽  
Pore Waters ◽  
Ice Volume ◽  
Oxygen Isotopic ◽  
Pore Water Salinity ◽  
Methods Of Control

Abstract. An earlier analysis of pore water salinity/chlorinity in two deep-sea cores, using terminal constraint methods of control theory, concluded that although a salinity amplification in the abyss was possible during the LGM, it was not required by the data. Here the same methodology is applied to δ18Ow in the upper 100 m of four deep-sea cores. An ice volume amplification to the isotopic ratio is, again, consistent with the data but not required by it. In particular, results are very sensitive, with conventional diffusion values, to the assumed initial conditions at −100 ky. If the calcite values of δ18O are fully reliable, then inferred enriched values of the ratio in sea water are necessary to preclude sub-freezing temperatures, but the sea water δ18O in pore waters does not independently support the conclusion.

scholarly journals The role of light as vital effect on coral skeleton oxygen isotopic ratio

2018 ◽  
Author(s):  
Anne Juillet-Leclerc
Keyword(s):  
Isotopic Ratio ◽  
Environmental Parameter ◽  
Data Series ◽  
Isotopic Ratios ◽  
Relative Distribution ◽  
Light Levels ◽  
Vital Effect ◽  
Oxygen Isotopic ◽  
Role Of Light

Abstract. Light, an environmental parameter playing a crucial role in coral aragonite growth and δ18O formulation, is always neglected in the geochemical literature. However, by revisiting already published studies, we demonstrated that light might be considered as a vital effect affecting coral aragonite oxygen isotopic ratios. Re-examining data series included in a publication by Weber and Woodhead (1972), we stressed that annual δ18O–annual temperature calibrations of all considered coral genera may be compared because their assessment assumes homogenous light levels. Temperature prevails on δ18O because it influences δ18O in two ways: firstly it acts as is thermodynamically predicted implying a δ18O decrease; and secondly it induces an enhancement of photosynthesis causing δ18O increase. When the highest annual temperature occurs simultaneously with the highest annual irradiation, the annual δ18O amplitude is shortened. The annual δ18O–annual temperature calibration is also explained by the relative distribution of microstructures, centres of calcification or COC and fibers, according to morphology, and in turn taxonomy. We also investigated monthly δ18O–monthly temperature calibrations of Porites grown at the same sites as by Stephans and Quinn (2002), Linsley et al. (1999, 2000) and Maier et al. (2004). Multiple evidence showed that temperature is the prevailing environment forcing on δ18O and that the mixture of temperature and light also determines the relative distribution of microstructures, explaining the relationships between Porites calibration constants. By examining monthly and annual δ18O–monthly and annual temperature calibrations, we revealed that monthly calibration results from the superimposition of seasonal and annual variability over time. Seasonal δ18O strongly impacted by seasonal light fluctuations, may be obtained by removing interannual δ18O only weakly affected by light. Such features necessitate the reconstitution of tools frequently utilised, such as the coupled δ18O–Sr / Ca or pseudo-coral concepts.

Temporal variations of the CO2 concentration and its carbon and oxygen isotopic ratios in a temperate forest in the central part of the main island of Japan

Tellus B ◽  
1997 ◽  
Vol 49 (4) ◽  
pp. 364-381 ◽  
Author(s):  
TAKAKIYO NAKAZAWA ◽  
SHOHEI MURAYAMA ◽  
MITSUKO TOI ◽  
MISA ISHIZAWA ◽  
KAORI OTONASHI ◽  
...  
Keyword(s):  
Temperate Forest ◽  
Co2 Concentration ◽  
Temporal Variations ◽  
Isotopic Ratios ◽  
Main Island ◽  
Oxygen Isotopic

scholarly journals Last Glacial Maximum and deglacial abyssal seawater oxygen isotopic ratios

2016 ◽  
Vol 12 (6) ◽  
pp. 1281-1296 ◽  
Author(s):  
Carl Wunsch
Keyword(s):  
Control Theory ◽  
Pore Water ◽  
Deep Sea ◽  
Initial Conditions ◽  
Isotopic Ratio ◽  
Isotopic Ratios ◽  
Ice Volume ◽  
Oxygen Isotopic ◽  
Pore Water Salinity ◽  
Methods Of Control

Abstract. An earlier analysis of pore-water salinity (chlorinity) in two deep-sea cores, using terminal constraint methods of control theory, concluded that although a salinity amplification in the abyss was possible during the LGM, it was not required by the data. Here the same methodology is applied to δ18Ow in the upper 100 m of four deep-sea cores. An ice volume amplification to the isotopic ratio is, again, consistent with the data but not required by it. In particular, results are very sensitive, with conventional diffusion values, to the assumed initial conditions at −100 ky and a long list of noise (uncertainty) assumptions. If the calcite values of δ18O are fully reliable, then published enriched values of the ratio in seawater are necessary to preclude sub-freezing temperatures, but the seawater δ18O in pore fluids does not independently require the conclusion.

scholarly journals Recent ice-core climate records from the Cordillera Blanca, Peru

1995 ◽  
Vol 21 ◽  
pp. 225-230 ◽  
Author(s):  
M. E. Davis ◽  
L. G. Thompson ◽  
E. Mosley-Thompson ◽  
P. N. Lin ◽  
V. N. Mikhalenko ◽  
...  
Keyword(s):  
Ice Core ◽  
Ice Cores ◽  
Warming Trend ◽  
Isotopic Ratios ◽  
Weather Station ◽  
Climate Record ◽  
Climatic Variations ◽  
Recent Warming ◽  
Lower Elevation ◽  
Oxygen Isotopic

Ice cores recently drilled to bedrock on the col of Huascarán (9°06′ S, 77°36′ W, 6047 m a.s.l.) offer the potential for a long, annually resolved climate record from tropical South America. This paper presents the record from 1950 to 1993 preserved in microparticle and nitrate concentrations and oxygen-isotopic ratios. Average monthly temperatures from a satellite-linked automatic weather station installed on nearby Hualcán in 1991 are presented. Annual temperatures from local high-altitude meteorological stations, along with the annual Huascarán isotopic record, show a warming trend over the last two decades. The marked preservation of the climate record in oxygen-isotopic ratios on Huascarán is absent at lower-elevation sites, which have been affected by the recent warming. This paper demonstrates the establishment of a time-scale for the Huascarán core, the preservation of the climatic signal with depth and the linkage of the ice-core “proxy-climate” parameters with measured climatic variations.

Changes of Ionic and Oxygen Isotopic Composition of the Snowpack at the Glacier Austre Okstindbreen, Norway, 1995

1998 ◽  
Vol 29 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Peter Raben ◽  
Wilfred H. Theakstone
Keyword(s):  
Isotopic Composition ◽  
Sea Level ◽  
Oxygen Isotopes ◽  
Oxygen Isotopic Composition ◽  
Isotopic Ratios ◽  
Vertical Variations ◽  
Oxygen Isotopic ◽  
The Difference ◽  
Liquid Precipitation ◽  
Different Altitudes

Marked vertical variations of ions and oxygen isotopes were present in the snowpack at the glacier Austre Okstindbreen during the pre-melting phase in 1995 at sites between 825 m and 1,470 m above sea level. As the first meltwater percolated from the top of the pack, ions were moved to a greater depth, but the isotopic composition remained relatively unchanged. Ions continued to move downwards through the pack during the melting phase, even when there was little surface melting and no addition of liquid precipitation. The at-a-depth correlation between ionic concentrations and isotopic ratios, strong in the pre-melting phase, weakened during melting. In August, concentrations of Na+ and Mg2+ ions in the residual pack were low and vertical variations were slight; 18O enrichment had occurred. The difference of the time at which melting of the snowpack starts at different altitudes influences the input of ions and isotopes to the underlying glacier.

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