Limits...
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.


Comparisons of environmental proxies from Lake Nam Co during the past 24 cal kyr BP.The PDI exhibits a clear shift at 16.5 cal kyr BP, revealing a change in domination from the Westerlies to the ISM. TOC is a proxy for biological productivity, and C/N indicates the origin of the organic matter (higher values = terrestrial, lower values = aquatic), Ca is a proxy for lake level variations (high values = low lake level, low values = high lake level), and Fe/Mn is an indicator of redox conditions, which are coupled to the lake level stage.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4543934&req=5

f3: Comparisons of environmental proxies from Lake Nam Co during the past 24 cal kyr BP.The PDI exhibits a clear shift at 16.5 cal kyr BP, revealing a change in domination from the Westerlies to the ISM. TOC is a proxy for biological productivity, and C/N indicates the origin of the organic matter (higher values = terrestrial, lower values = aquatic), Ca is a proxy for lake level variations (high values = low lake level, low values = high lake level), and Fe/Mn is an indicator of redox conditions, which are coupled to the lake level stage.

Mentions: Environmental, climatic and circulation proxies derived from the sedimentary record of Lake Nam Co reveal high variability throughout the examined period (Fig. 3). However, the most prominent shift in the palynological proxies, likely indicating a shift in the atmospheric circulation system, occurs at ca. 16.5 cal kyr BP (Fig. 3). Between 24 and 16.5 cal kyr BP (I-1 and I-2, Fig. 3), a decrease in humidity-preferring Cyperaceae and an increase in arid-preferring Artemisia24 indicate shrinkage in the wetland areas around the lake. A continuous decrease in Pediastrum indicates fewer nutrients in the lake water25, possibly caused by the inflow of nutrient-poor glacial melt water26 into Lake Nam Co. The volume and thus the surface area of Lake Nam Co are assumed to have increased, as suggested by the previously observed decreases in sediment accumulation rates after 19.5 cal kyr BP17 (Fig. S1). Although the total pollen concentration (TPC) is lower, Pinus and Picea account for greater than 30% of the pollen. Because the pollen of these species is regarded as exotic and is highly correlated with a positive PDI, this high abundance indicates that the lake catchment has been dominantly influenced by the Westerlies (Fig. 4a). The Westerlies even appear to increase in strength approximately 20.5 cal kyr BP, likely resulting from an advance of the polar ice sheet during the LGM5.


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)

Comparisons of environmental proxies from Lake Nam Co during the past 24 cal kyr BP.The PDI exhibits a clear shift at 16.5 cal kyr BP, revealing a change in domination from the Westerlies to the ISM. TOC is a proxy for biological productivity, and C/N indicates the origin of the organic matter (higher values = terrestrial, lower values = aquatic), Ca is a proxy for lake level variations (high values = low lake level, low values = high lake level), and Fe/Mn is an indicator of redox conditions, which are coupled to the lake level stage.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: Comparisons of environmental proxies from Lake Nam Co during the past 24 cal kyr BP.The PDI exhibits a clear shift at 16.5 cal kyr BP, revealing a change in domination from the Westerlies to the ISM. TOC is a proxy for biological productivity, and C/N indicates the origin of the organic matter (higher values = terrestrial, lower values = aquatic), Ca is a proxy for lake level variations (high values = low lake level, low values = high lake level), and Fe/Mn is an indicator of redox conditions, which are coupled to the lake level stage.
Mentions: Environmental, climatic and circulation proxies derived from the sedimentary record of Lake Nam Co reveal high variability throughout the examined period (Fig. 3). However, the most prominent shift in the palynological proxies, likely indicating a shift in the atmospheric circulation system, occurs at ca. 16.5 cal kyr BP (Fig. 3). Between 24 and 16.5 cal kyr BP (I-1 and I-2, Fig. 3), a decrease in humidity-preferring Cyperaceae and an increase in arid-preferring Artemisia24 indicate shrinkage in the wetland areas around the lake. A continuous decrease in Pediastrum indicates fewer nutrients in the lake water25, possibly caused by the inflow of nutrient-poor glacial melt water26 into Lake Nam Co. The volume and thus the surface area of Lake Nam Co are assumed to have increased, as suggested by the previously observed decreases in sediment accumulation rates after 19.5 cal kyr BP17 (Fig. S1). Although the total pollen concentration (TPC) is lower, Pinus and Picea account for greater than 30% of the pollen. Because the pollen of these species is regarded as exotic and is highly correlated with a positive PDI, this high abundance indicates that the lake catchment has been dominantly influenced by the Westerlies (Fig. 4a). The Westerlies even appear to increase in strength approximately 20.5 cal kyr BP, likely resulting from an advance of the polar ice sheet during the LGM5.

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.