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South China Sea hydrological changes and Pacific Walker Circulation variations over the last millennium.

Yan H, Sun L, Oppo DW, Wang Y, Liu Z, Xie Z, Liu X, Cheng W - Nat Commun (2011)

Bottom Line: Here we show that north-south ITCZ migration was not the only mechanism of tropical Pacific hydrologic variability during the last millennium, and that PWC variability profoundly influenced tropical Pacific hydrology.Our downcore grain size reconstructions indicate that this site received less precipitation during relatively warm periods, AD 1000-1400 and AD 1850-2000, compared with the cool period (AD 1400-1850).Including our new reconstructions in a synthesis of tropical Pacific records results in a spatial pattern of hydrologic variability that implicates the PWC.

View Article: PubMed Central - PubMed

Affiliation: Institute of Polar Environment, Department of Earth and Space Science, University of Science and Technology of China, Hefei, Anhui 230026, China.

ABSTRACT
The relative importance of north-south migrations of the intertropical convergence zone (ITCZ) versus El Niño-Southern Oscillation and its associated Pacific Walker Circulation (PWC) variability for past hydrological change in the western tropical Pacific is unclear. Here we show that north-south ITCZ migration was not the only mechanism of tropical Pacific hydrologic variability during the last millennium, and that PWC variability profoundly influenced tropical Pacific hydrology. We present hydrological reconstructions from Cattle Pond, Dongdao Island of the South China Sea, where multi-decadal rainfall and downcore grain size variations are correlated to the Southern Oscillation Index during the instrumental era. Our downcore grain size reconstructions indicate that this site received less precipitation during relatively warm periods, AD 1000-1400 and AD 1850-2000, compared with the cool period (AD 1400-1850). Including our new reconstructions in a synthesis of tropical Pacific records results in a spatial pattern of hydrologic variability that implicates the PWC.

No MeSH data available.


Related in: MedlinePlus

Grain size and isotopic records of lake sediment cores from the Dongdao Island.Downcore mean grain size variations (3 points sliding average) of DY2 (a), DY4 (b) and DY6 (c); δ13C (d) and δ18O (e) of ostracode shells from DY4 core18. The isotope values were based on the Vienna PeeDee Belemnite (VPDB). Grey bars represent the approximate period of the LIA (∼AD 1400–1850). The δ13C and δ18O data for the top 10 cm, indicated by diagonal shading, are questionable due to the absence of intact ostracode shells in this section.
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f3: Grain size and isotopic records of lake sediment cores from the Dongdao Island.Downcore mean grain size variations (3 points sliding average) of DY2 (a), DY4 (b) and DY6 (c); δ13C (d) and δ18O (e) of ostracode shells from DY4 core18. The isotope values were based on the Vienna PeeDee Belemnite (VPDB). Grey bars represent the approximate period of the LIA (∼AD 1400–1850). The δ13C and δ18O data for the top 10 cm, indicated by diagonal shading, are questionable due to the absence of intact ostracode shells in this section.

Mentions: Large fluctuations of mean grain size (Fig. 3) suggest substantial hydrological changes on Dongdao Island over the last millennium. Very consistently, all three records (DY2, DY4 and DY6) show similar changes: relatively small grain size before ∼AD 1400, increased grain size occurring during AD 1500–1700, and then reduced grain size over the last 150 years. Consistent with a runoff-transported mechanism, mean grain size gradually decreases from the water entrance to the deep centre of the pond (DY4>DY6>DY2, Supplementary Fig. S5 and Fig. 3). Based on the grain size records, we infer higher rainfall on the Dongdao Island approximately during the LIA (∼AD 1400–1850), compared with the periods before and after. This inference is further supported by the records of δ13C and δ18O of ostracode shells in DY4 core18, which are also related to hydrological conditions (Fig. 3). Both lower δ18O and δ13C values could be related to wetter conditions18. δ18O varied between −0.9‰ and −5.9‰ and δ13C ranged from −10.1‰ to −0.5‰ over the last millennium. Higher δ18O and δ13C values correspond to relatively small grain size, occurring during AD 1000–1400, whereas lower δ18O and δ13C values correspond to large grain size during AD 1500–1850. The δ18O and δ13C values for the last 150 years are probably unreliable as intact ostracode shells were not found in this section. Despite the common signal on centennial time scales, the mean grain size, δ18O, and δ13C proxy records do differ in some details. For instance, the mean grain size records show two distinct intervals of low values during the MCA, whereas δ18O does not (Fig. 3). In addition to the low resolution of the δ18O record, the discrepancy may reflect different controlling factors for mean grain size and δ18O: grain size is mainly linked with precipitation, but δ18O values of ostracode shells can be affected by precipitation amount, lake evaporation and δ18O of precipitation18. Overall, although individual proxies might be complicated by additional factors, the main common signal on centennial time scales in the records of grain size, δ18O and δ13C of ostracode shells from the Dongdao Island reflects hydrological changes.


South China Sea hydrological changes and Pacific Walker Circulation variations over the last millennium.

Yan H, Sun L, Oppo DW, Wang Y, Liu Z, Xie Z, Liu X, Cheng W - Nat Commun (2011)

Grain size and isotopic records of lake sediment cores from the Dongdao Island.Downcore mean grain size variations (3 points sliding average) of DY2 (a), DY4 (b) and DY6 (c); δ13C (d) and δ18O (e) of ostracode shells from DY4 core18. The isotope values were based on the Vienna PeeDee Belemnite (VPDB). Grey bars represent the approximate period of the LIA (∼AD 1400–1850). The δ13C and δ18O data for the top 10 cm, indicated by diagonal shading, are questionable due to the absence of intact ostracode shells in this section.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3104522&req=5

f3: Grain size and isotopic records of lake sediment cores from the Dongdao Island.Downcore mean grain size variations (3 points sliding average) of DY2 (a), DY4 (b) and DY6 (c); δ13C (d) and δ18O (e) of ostracode shells from DY4 core18. The isotope values were based on the Vienna PeeDee Belemnite (VPDB). Grey bars represent the approximate period of the LIA (∼AD 1400–1850). The δ13C and δ18O data for the top 10 cm, indicated by diagonal shading, are questionable due to the absence of intact ostracode shells in this section.
Mentions: Large fluctuations of mean grain size (Fig. 3) suggest substantial hydrological changes on Dongdao Island over the last millennium. Very consistently, all three records (DY2, DY4 and DY6) show similar changes: relatively small grain size before ∼AD 1400, increased grain size occurring during AD 1500–1700, and then reduced grain size over the last 150 years. Consistent with a runoff-transported mechanism, mean grain size gradually decreases from the water entrance to the deep centre of the pond (DY4>DY6>DY2, Supplementary Fig. S5 and Fig. 3). Based on the grain size records, we infer higher rainfall on the Dongdao Island approximately during the LIA (∼AD 1400–1850), compared with the periods before and after. This inference is further supported by the records of δ13C and δ18O of ostracode shells in DY4 core18, which are also related to hydrological conditions (Fig. 3). Both lower δ18O and δ13C values could be related to wetter conditions18. δ18O varied between −0.9‰ and −5.9‰ and δ13C ranged from −10.1‰ to −0.5‰ over the last millennium. Higher δ18O and δ13C values correspond to relatively small grain size, occurring during AD 1000–1400, whereas lower δ18O and δ13C values correspond to large grain size during AD 1500–1850. The δ18O and δ13C values for the last 150 years are probably unreliable as intact ostracode shells were not found in this section. Despite the common signal on centennial time scales, the mean grain size, δ18O, and δ13C proxy records do differ in some details. For instance, the mean grain size records show two distinct intervals of low values during the MCA, whereas δ18O does not (Fig. 3). In addition to the low resolution of the δ18O record, the discrepancy may reflect different controlling factors for mean grain size and δ18O: grain size is mainly linked with precipitation, but δ18O values of ostracode shells can be affected by precipitation amount, lake evaporation and δ18O of precipitation18. Overall, although individual proxies might be complicated by additional factors, the main common signal on centennial time scales in the records of grain size, δ18O and δ13C of ostracode shells from the Dongdao Island reflects hydrological changes.

Bottom Line: Here we show that north-south ITCZ migration was not the only mechanism of tropical Pacific hydrologic variability during the last millennium, and that PWC variability profoundly influenced tropical Pacific hydrology.Our downcore grain size reconstructions indicate that this site received less precipitation during relatively warm periods, AD 1000-1400 and AD 1850-2000, compared with the cool period (AD 1400-1850).Including our new reconstructions in a synthesis of tropical Pacific records results in a spatial pattern of hydrologic variability that implicates the PWC.

View Article: PubMed Central - PubMed

Affiliation: Institute of Polar Environment, Department of Earth and Space Science, University of Science and Technology of China, Hefei, Anhui 230026, China.

ABSTRACT
The relative importance of north-south migrations of the intertropical convergence zone (ITCZ) versus El Niño-Southern Oscillation and its associated Pacific Walker Circulation (PWC) variability for past hydrological change in the western tropical Pacific is unclear. Here we show that north-south ITCZ migration was not the only mechanism of tropical Pacific hydrologic variability during the last millennium, and that PWC variability profoundly influenced tropical Pacific hydrology. We present hydrological reconstructions from Cattle Pond, Dongdao Island of the South China Sea, where multi-decadal rainfall and downcore grain size variations are correlated to the Southern Oscillation Index during the instrumental era. Our downcore grain size reconstructions indicate that this site received less precipitation during relatively warm periods, AD 1000-1400 and AD 1850-2000, compared with the cool period (AD 1400-1850). Including our new reconstructions in a synthesis of tropical Pacific records results in a spatial pattern of hydrologic variability that implicates the PWC.

No MeSH data available.


Related in: MedlinePlus