Climatic Reconstruction in Europe for 18,000 YR B.P. from Pollen Data

1998 ◽  
Vol 49 (2) ◽  
pp. 183-196 ◽  
Author(s):  
Odile Peyron ◽  
Joël Guiot ◽  
Rachid Cheddadi ◽  
Pavel Tarasov ◽  
Maurice Reille ◽  
...  
Keyword(s):  
Neural Network ◽  
Precipitation Anomaly ◽  
Present Climate ◽  
Pollen Data ◽  
Moisture Index ◽  
Pollen Types ◽  
Individual Taxon ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

An improved concept of the best analogs method is used to reconstruct the climate of the last glacial maximum from pollen data in Europe. In order to deal with the lack of perfect analogs of fossil assemblages and therefore to obtain a more accurate climate reconstruction, we used a combination of pollen types grouped according to plant phenology and present climate constraints rather than pollen percentages for each individual taxon. The distribution of pollen taxa into plant functional types (PFTs) is aimed to reflect the vegetation in terms of biomes which have a wider distribution than a species. The climatic variables are then calibrated on these PFTs using an artificial neural network technique. The use of PFTs allowed us to deal with situations where pollen assemblages have only partial modern analogs. The method is applied to the glacial steppic vegetation in Europe, using 15 pollen records. North of the Pyrenees–Alps line, the reconstructed temperatures were lower than today: −30 ± 10°C for the temperature of the coldest month ( Tc) and −12 ± 3°C for the annual mean ( Tann). South of that line, Tc and Tann anomalies were respectively, −15 ± 5°C and −10 ± 5°C. The available moisture index and annual precipitation were also lower than present: −60 ± 20% north of Mediterranean Sea, (−800 ± 100 mm for precipitation). In Italy and Greece, the available moisture was 20% lower, with a precipitation anomaly of ca. −600 ± 200 mm. Southward, the moisture index was close to that at present (±20%), and precipitation was lower (−300 ± 300 mm).

Absence of Last Glacial Maximum Records in Lowland Tropical Forests

1998 ◽  
Vol 49 (2) ◽  
pp. 233-237 ◽  
Author(s):  
Marie-Pierre Ledru ◽  
Jacques Bertaux ◽  
Abdelfettah Sifeddine ◽  
Kenitiro Suguio
Keyword(s):  
South America ◽  
Tropical Forests ◽  
Last Glacial Maximum ◽  
Sedimentation Rate ◽  
Glacial Maximum ◽  
Radiocarbon Dates ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

Environmental conditions of the lowland tropical forests during the last glacial maximum (LGM) between ca 20,000 and 18,000 14C yr B.P., are reevaluated in terms of dating control and lithology analyzed in seven pollen records from South America. The reevaluation shows that probably in none of the published records are LGM sediments present or abundant. This conclusion is based on the occurrence of abrupt lithologic changes coupled with changes in sedimentation rate interpolated from radiocarbon dates. These findings suggest that the LGM was represented probably by a hiatus of several thousand years, indicative of drier climates than before or after.

Grassland Vegetation in the Southern Great Plains during the Last Glacial Maximum

1995 ◽  
Vol 44 (2) ◽  
pp. 237-245 ◽  
Author(s):  
Stephen A. Hall ◽  
Salvatore Valastro
Keyword(s):  
Last Glacial Maximum ◽  
Great Plains ◽  
Glacial Maximum ◽  
High Plains ◽  
Edwards Plateau ◽  
Southern Great Plains ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
Pollen Records ◽  
The Last Glacial

AbstractNew pollen records from White Lake in the Southern High Plains and from Friesenhahn Cave on the southeastern Edwards Plateau of Texas indicate that the glacial-age vegetation of the southern Great Plains was a grassland. The High Plains was a treeless Artemisia grassland and the Edwards Plateau, at the south edge of the Great Plains, was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats. The glacial-age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog. The dominance of prairie vegetation during the last glacial maximum is compatible with late Pleistocene mammalian faunas and late-glacial grassland pollen records from the region. Earlier interpretations of a pine-spruce forest on the High Plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration, resulting in differential preservation of conifer pollen grains. Accordingly, the "Tahoka Pluvial" and other "climatic episodes" defined by High Plains pollen records are abandoned.

scholarly journals A simulation of the global distribution and radiative forcing of soil dust aerosols at the Last Glacial Maximum

2009 ◽  
Vol 9 (9) ◽  
pp. 3061-3073 ◽  
Author(s):  
T. Takemura ◽  
M. Egashira ◽  
K. Matsuzawa ◽  
H. Ichijo ◽  
R. O'ishi ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Radiative Forcing ◽  
Global Distribution ◽  
Present Climate ◽  
Soil Dust ◽  
Radiative Forcings ◽  
Dust Aerosols ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. In this study an integrated simulation of the global distribution and the radiative forcing of soil dust aerosols at the Last Glacial Maximum (LGM) is performed with an aerosol climate model, SPRINTARS. It is compared with another simulation for the present climate condition. The global total emission flux of soil dust aerosols at the LGM is simulated to be about 2.4 times as large as that in the present climate, and the simulated deposition flux is in general agreement with estimations from ice core and marine sediment samplings though it appears to be underestimated over the Antarctic. The calculated direct radiative forcings of soil dust aerosols at the LGM is close to zero at the tropopause and −0.4 W m−2 at the surface. These radiative forcings are about twice as large as those in the present climate. SPRINTARS also includes the microphysical parameterizations of the cloud-aerosol interaction both for liquid water and ice crystals, which affect the radiation budget. The positive radiative forcing from the indirect effect of soil dust aerosols is mainly caused by their properties to act as ice nuclei. This effect is simulated to be smaller (−0.9 W m−2) at the LGM than in the present. It is suggested that atmospheric dust might contribute to the cold climate during the glacial periods both through the direct and indirect effects, relative to the interglacial periods.

scholarly journals A taxonomically harmonized and temporally standardized fossil pollen dataset from Siberia covering the last 40 kyr

2020 ◽  
Vol 12 (1) ◽  
pp. 119-135
Author(s):  
Xianyong Cao ◽  
Fang Tian ◽  
Andrei Andreev ◽  
Patricia M. Anderson ◽  
Anatoly V. Lozhkin ◽  
...  
Keyword(s):  
Original Data ◽  
Data Mapping ◽  
Pollen Data ◽  
Last Glacial Period ◽  
Pollen Counts ◽  
Data Source ◽  
Palynological Records ◽  
Percentage Data ◽  
Pollen Records ◽  
The Last Glacial

Abstract. Pollen records from Siberia are mostly absent in global or Northern Hemisphere synthesis works. Here we present a taxonomically harmonized and temporally standardized pollen dataset that was synthesized using 173 palynological records from Siberia and adjacent areas (northeastern Asia, 42–75∘ N, 50–180∘ E). Pollen data were taxonomically harmonized, i.e. the original 437 taxa were assigned to 106 combined pollen taxa. Age–depth models for all records were revised by applying a constant Bayesian age–depth modelling routine. The pollen dataset is available as count data and percentage data in a table format (taxa vs. samples), with age information for each sample. The dataset has relatively few sites covering the last glacial period between 40 and 11.5 ka (calibrated thousands of years before 1950 CE) particularly from the central and western part of the study area. In the Holocene period, the dataset has many sites from most of the area, with the exception of the central part of Siberia. Of the 173 pollen records, 81 % of pollen counts were downloaded from open databases (GPD, EPD, PANGAEA) and 10 % were contributions by the original data gatherers, while a few were digitized from publications. Most of the pollen records originate from peatlands (48 %) and lake sediments (33 %). Most of the records (83 %) have ≥3 dates, allowing the establishment of reliable chronologies. The dataset can be used for various purposes, including pollen data mapping (example maps for Larix at selected time slices are shown) as well as quantitative climate and vegetation reconstructions. The datasets for pollen counts and pollen percentages are available at https://doi.org/10.1594/PANGAEA.898616 (Cao et al., 2019a), also including the site information, data source, original publication, dating data, and the plant functional type for each pollen taxa.

scholarly journals Global distribution and radiative forcing of soil dust aerosols in the Last Glacial Maximum simulated by the aerosol climate model

2008 ◽  
Vol 8 (6) ◽  
pp. 20463-20500 ◽  
Author(s):  
T. Takemura ◽  
M. Egashira ◽  
K. Matsuzawa ◽  
H. Ichijo ◽  
R. O'ishi ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Radiative Forcing ◽  
Climate Model ◽  
Global Distribution ◽  
Present Climate ◽  
Soil Dust ◽  
Dust Aerosols ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. The integrated simulation for the global distribution and radiative forcing of soil dust aerosols in the Last Glacial Maximum (LGM) is done by an aerosol climate model, SPRINTARS, in this study. It is compared with another simulation in the present climate condition. The global total emission flux of soil dust aerosols in the LGM is simulated to be about 2.4 times as large as that in the present climate, and the simulated deposition flux is in general agreement with estimations from ice core and marine sediment samplings though it might be underestimated over the Antarctic. The calculated direct radiative forcing of soil dust aerosols in the LGM is close to zero at the tropopause and −0.4 W m−2 at the surface, which are about twice as large as those in the present climate. SPRINTARS also includes the microphysical parameterizations of the cloud-aerosol interaction both for liquid water and ice crystals, which affect the radiation budget. The positive radiative forcing of the indirect effect due to soil dust aerosols, that is mainly caused by a role of ice nuclei, is simulated to be smaller in the LGM than in the present. It is suggested that atmospheric dust might contribute to the cold climate during the glacial periods both through the direct and indirect effects, relative to the interglacial periods.

scholarly journals Climate simulations and pollen data reveal the distribution and connectivity of temperate tree populations in eastern Asia during the Last Glacial Maximum

2020 ◽  
Vol 16 (6) ◽  
pp. 2039-2054
Author(s):  
Suzanne Alice Ghislaine Leroy ◽  
Klaus Arpe ◽  
Uwe Mikolajewicz ◽  
Jing Wu
Keyword(s):  
Climate Model ◽  
Deciduous Tree ◽  
Eastern Asia ◽  
Pollen Data ◽  
Model Simulations ◽  
Climate Simulations ◽  
Temperate Deciduous ◽  
Climate Model Simulations ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Publications on temperate deciduous tree refugia in Europe are abundant, but little is known about the patterns of temperate tree refugia in eastern Asia, an area where biodiversity survived Quaternary glaciations and which has the world's most diverse temperate flora. Our goal is to compare climate model simulations with pollen data in order to establish the location of glacial refugia during the Last Glacial Maximum (LGM). Limits in which temperate deciduous trees can survive are taken from the literature. The model outputs are first tested for the present by comparing climate models with published modern pollen data. As this method turned out to be satisfactory for the present, the same approach was used for the LGM. Climate model simulations (ECHAM5 T106), statistically further downscaled, are used to infer the temperate deciduous tree distribution during the LGM. These were compared with available fossil temperate tree pollen occurrences. The impact of the LGM on the eastern Asian climate was much weaker than on the European climate. The area of possible tree growth shifts only by about 2∘ to the south between the present and the LGM. This contributes to explaining the greater biodiversity of forests in eastern Asia compared to Europe. Climate simulations and the available, although fractional, fossil pollen data agree. Therefore, climate estimations can safely be used to fill areas without pollen data by mapping potential refugia distributions. The results show two important areas with population connectivity: the Yellow Sea emerged shelf and the southern Himalayas. These two areas were suitable for temperate deciduous tree growth, providing corridors for population migration and connectivity (i.e. less population fragmentation) in glacial periods. Many tree populations live in interglacial refugia, not glacial ones. The fact that the model simulation for the LGM fits so well with observed pollen distribution is another indication that the model used is good enough to also simulate the LGM period.

scholarly journals A taxonomically harmonized and temporally standardized fossil pollen dataset from Siberia covering the last 40 ka

2019 ◽  
Author(s):  
Xianyong Cao ◽  
Fang Tian ◽  
Andrei Andreev ◽  
Patricia M. Anderson ◽  
Anatoly V. Lozhkin ◽  
...  
Keyword(s):  
Northeast Asia ◽  
Original Data ◽  
Data Mapping ◽  
Pollen Data ◽  
Last Glacial Period ◽  
Pollen Counts ◽  
Palynological Records ◽  
Percentage Data ◽  
Pollen Records ◽  
The Last Glacial

Abstract. Pollen records from Siberia are mostly absent in global or Northern Hemisphere synthesis works. Here we present a taxonomically harmonized and temporally standardized pollen dataset that was synthesized using 173 palynological records from Siberia and adjacent areas (northeast Asia, 50°–180° E and 42°–75° N). Pollen data were taxonomically harmonized, that is the original 437 taxa were transformed to 106 combined pollen taxa. Age-depth models for all records were revised by applying a constant Bayesian age-depth modelling routine. The pollen dataset is available as count data and percentage data in a table format (taxa vs. samples) with age information for each sample. The dataset has relatively few sites covering the last glacial period between 40 and 11.5 cal ka BP (calibrated thousand years before present 1950 CE) particularly from the central and western part of the study area. In the Holocene period, the dataset has many sites from most of the area except the central part of Siberia. Of the 173 pollen records, 81 % of pollen counts were downloaded from open databases (GPD, EPD, Pangaea) and 10 % were contributions of the original data gatherers, while a few were digitized from publications. Most of the pollen records originate from peatlands (48 %) and lake sediments (33 %). Most of the records (83 %) have ≥ 3 dates allowing the establishment of reliable chronologies. The dataset can be used for various purposes including pollen data mapping (example maps for Larix at selected time-slices are shown) as well as quantitative climate and vegetation reconstructions. The datasets for pollen counts and pollen percentages are available at https://doi.pangaea.de/10.1594/PANGAEA.898616 (Cao et al., 2019).

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