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Climate change on the Tibetan Plateau in response to shifting atmospheric circulation since the LGM.

Zhu L, Lü X, Wang J, Peng P, Kasper T, Daut G, Haberzettl T, Frenzel P, Li Q, Yang R, Schwalb A, Mäusbacher R - Sci Rep (2015)

Bottom Line: The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood.Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM).From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Tibetan Environment Changes and Land Surface Processes (TEL), Institute of Tibetan Plateau Research (ITP), Chinese Academy of Sciences, Beijing, China.

ABSTRACT
The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

No MeSH data available.


Related in: MedlinePlus

The major airborne pollen taxa (relative abundances in %), the calculated PDI and the prevailing wind directions during the sampling period in the Nam Co catchment.The red line is the 5 point smoothed PDI, with negative values indicating enhanced ISM and positive values indicating enhanced Westerlies. The grey horizontal lines are the group centroids based on the respective discriminant scores. The main wind directions are expressed as the angle of circumference (0° = North, 90° = East, 270° = South and 360° = West.
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f2: The major airborne pollen taxa (relative abundances in %), the calculated PDI and the prevailing wind directions during the sampling period in the Nam Co catchment.The red line is the 5 point smoothed PDI, with negative values indicating enhanced ISM and positive values indicating enhanced Westerlies. The grey horizontal lines are the group centroids based on the respective discriminant scores. The main wind directions are expressed as the angle of circumference (0° = North, 90° = East, 270° = South and 360° = West.

Mentions: Records of the Nam Co weather station indicate that the prevailing wind direction is WWS (ca.255°) during the spring and winter, SSW (ca.195°) in the autumn, and south (ca.180°) in the summer18 (Supplementary, Fig. S2). The distribution of airborne pollen grains is generally influenced by the phenophase of the local plants15 and by these prevailing wind directions19. Hence, the pollen assemblages vary significantly with the season of deposition (Fig. 2). Because Pinus and Picea do not presently grow in the Nam Co catchment or its adjacent areas, these airborne pollen taxa are considered to be exotic (long distance). During the summer and fall, Pinus and Picea pollen may originate from the south or south-east, but these taxa occupy only a small proportion of the pollen assemblages because dominant local herbaceous taxa bloom during this period. However, in the winter, with the wind direction changing from south-southeast to west, and in the spring, with the prevailing western wind, the proportion of Pinus and Picea in the pollen assemblages is remarkably greater15. Therefore, the prevailing wind direction is assumed to be the primary reason for the presence of these exotic pollen taxa in the winter.


Climate change on the Tibetan Plateau in response to shifting atmospheric circulation since the LGM.

Zhu L, Lü X, Wang J, Peng P, Kasper T, Daut G, Haberzettl T, Frenzel P, Li Q, Yang R, Schwalb A, Mäusbacher R - Sci Rep (2015)

The major airborne pollen taxa (relative abundances in %), the calculated PDI and the prevailing wind directions during the sampling period in the Nam Co catchment.The red line is the 5 point smoothed PDI, with negative values indicating enhanced ISM and positive values indicating enhanced Westerlies. The grey horizontal lines are the group centroids based on the respective discriminant scores. The main wind directions are expressed as the angle of circumference (0° = North, 90° = East, 270° = South and 360° = West.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543934&req=5

f2: The major airborne pollen taxa (relative abundances in %), the calculated PDI and the prevailing wind directions during the sampling period in the Nam Co catchment.The red line is the 5 point smoothed PDI, with negative values indicating enhanced ISM and positive values indicating enhanced Westerlies. The grey horizontal lines are the group centroids based on the respective discriminant scores. The main wind directions are expressed as the angle of circumference (0° = North, 90° = East, 270° = South and 360° = West.
Mentions: Records of the Nam Co weather station indicate that the prevailing wind direction is WWS (ca.255°) during the spring and winter, SSW (ca.195°) in the autumn, and south (ca.180°) in the summer18 (Supplementary, Fig. S2). The distribution of airborne pollen grains is generally influenced by the phenophase of the local plants15 and by these prevailing wind directions19. Hence, the pollen assemblages vary significantly with the season of deposition (Fig. 2). Because Pinus and Picea do not presently grow in the Nam Co catchment or its adjacent areas, these airborne pollen taxa are considered to be exotic (long distance). During the summer and fall, Pinus and Picea pollen may originate from the south or south-east, but these taxa occupy only a small proportion of the pollen assemblages because dominant local herbaceous taxa bloom during this period. However, in the winter, with the wind direction changing from south-southeast to west, and in the spring, with the prevailing western wind, the proportion of Pinus and Picea in the pollen assemblages is remarkably greater15. Therefore, the prevailing wind direction is assumed to be the primary reason for the presence of these exotic pollen taxa in the winter.

Bottom Line: The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood.Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM).From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Tibetan Environment Changes and Land Surface Processes (TEL), Institute of Tibetan Plateau Research (ITP), Chinese Academy of Sciences, Beijing, China.

ABSTRACT
The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

No MeSH data available.


Related in: MedlinePlus