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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

Map of the position of Lake Nam Co (including sites of the airborne pollen trap, surface sediment samples and the investigated core, NC 08/01).The inset shows the main atmospheric circulation systems influencing the TP. The terrain map of the catchment was generated using ArcGIS 10.0 based on the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) from the U.S. Geological Survey. (https://lta.cr.usgs.gov/citation). The isobath lines of the lake were generated based on 305720 in situ survey points of the water depth (performed by the authors).
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f1: Map of the position of Lake Nam Co (including sites of the airborne pollen trap, surface sediment samples and the investigated core, NC 08/01).The inset shows the main atmospheric circulation systems influencing the TP. The terrain map of the catchment was generated using ArcGIS 10.0 based on the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) from the U.S. Geological Survey. (https://lta.cr.usgs.gov/citation). The isobath lines of the lake were generated based on 305720 in situ survey points of the water depth (performed by the authors).

Mentions: The lacustrine core (NC 08/01, 10.41 m length) was recovered from the centre of Lake Nam Co at a water depth of 93 m (Fig. 1). Chronological control is based upon 24 AMS radiocarbon ages in combination with radio isotopic (210Pb, 137Cs) measurements and magnetostratigraphy for the upper portion. Modern airborne pollen was collected over the period from September 1st, 2005 to August 31st, 2006. Pollen concentrations and pollen types within each sample were identified15, and their relationships plus local wind direction and frequency, near surface wind field and backward air mass trajectories were used to establish the PDI. To confirm the consistency between the airborne pollen assemblages from the traps and those deposited in the lake sediments, the annual airborne samples were compared with simultaneously obtained lake surface sediment samples. Applying identical palynological methods to the 24 cal kyr BP sedimentary record from Lake Nam Co resulted in a Westerly-ISM discrimination index. Total organic carbon (TOC), total nitrogen (TN) and their molar ratio (C/N) were used to interpret the source of the organic matter and its environmental significance. The elemental concentrations of Ca and the ratio of Fe and Mn are used to indicate hydrological (lake level) changes to support the pollen-derived proxies.


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)

Map of the position of Lake Nam Co (including sites of the airborne pollen trap, surface sediment samples and the investigated core, NC 08/01).The inset shows the main atmospheric circulation systems influencing the TP. The terrain map of the catchment was generated using ArcGIS 10.0 based on the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) from the U.S. Geological Survey. (https://lta.cr.usgs.gov/citation). The isobath lines of the lake were generated based on 305720 in situ survey points of the water depth (performed by the authors).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Map of the position of Lake Nam Co (including sites of the airborne pollen trap, surface sediment samples and the investigated core, NC 08/01).The inset shows the main atmospheric circulation systems influencing the TP. The terrain map of the catchment was generated using ArcGIS 10.0 based on the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) from the U.S. Geological Survey. (https://lta.cr.usgs.gov/citation). The isobath lines of the lake were generated based on 305720 in situ survey points of the water depth (performed by the authors).
Mentions: The lacustrine core (NC 08/01, 10.41 m length) was recovered from the centre of Lake Nam Co at a water depth of 93 m (Fig. 1). Chronological control is based upon 24 AMS radiocarbon ages in combination with radio isotopic (210Pb, 137Cs) measurements and magnetostratigraphy for the upper portion. Modern airborne pollen was collected over the period from September 1st, 2005 to August 31st, 2006. Pollen concentrations and pollen types within each sample were identified15, and their relationships plus local wind direction and frequency, near surface wind field and backward air mass trajectories were used to establish the PDI. To confirm the consistency between the airborne pollen assemblages from the traps and those deposited in the lake sediments, the annual airborne samples were compared with simultaneously obtained lake surface sediment samples. Applying identical palynological methods to the 24 cal kyr BP sedimentary record from Lake Nam Co resulted in a Westerly-ISM discrimination index. Total organic carbon (TOC), total nitrogen (TN) and their molar ratio (C/N) were used to interpret the source of the organic matter and its environmental significance. The elemental concentrations of Ca and the ratio of Fe and Mn are used to indicate hydrological (lake level) changes to support the pollen-derived proxies.

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