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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.


Hydrological records from tropical Pacific.Hydrologic records from the PA of tropical western Pacific (W1—mean grain size of Cattle Pond sediments, W2—inferred seawater δ18O of Indonesia7 and W3—δDwax data from Indonesia marine sediment for the C30 n-acids8) and NA of eastern mid-tropical Pacific (M1—inferred lake salinity of Washington Island17, E1—sand percentages of El Junco lake sediment13 and E2—red colour intensity of Laguna Pallcacocha sediment12). Site locations are given in Figure 1. All time series are three-points smoothed (except E2, 30-points smoothed) and normalized to standard Z-scores. Standard Z-scores are calculated according to Z=(X−V)/SD; here X is original value, V is the averaged value of the time series, and SD is the standard deviation of the time series. In all records, blue indicates relatively wet periods, and red relatively dry periods.
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f4: Hydrological records from tropical Pacific.Hydrologic records from the PA of tropical western Pacific (W1—mean grain size of Cattle Pond sediments, W2—inferred seawater δ18O of Indonesia7 and W3—δDwax data from Indonesia marine sediment for the C30 n-acids8) and NA of eastern mid-tropical Pacific (M1—inferred lake salinity of Washington Island17, E1—sand percentages of El Junco lake sediment13 and E2—red colour intensity of Laguna Pallcacocha sediment12). Site locations are given in Figure 1. All time series are three-points smoothed (except E2, 30-points smoothed) and normalized to standard Z-scores. Standard Z-scores are calculated according to Z=(X−V)/SD; here X is original value, V is the averaged value of the time series, and SD is the standard deviation of the time series. In all records, blue indicates relatively wet periods, and red relatively dry periods.

Mentions: To assess this hypothesis further, we compared our South China Sea records with hydrological records from other areas that are strongly influenced by ENSO/Walker circulation in modern climatology. The SOI is positively correlated with the precipitation over the Indo-Pacific warm pool and negatively correlated with the precipitation over the eastern and mid-tropical Pacific3. For convenience of discussion, we define the areas with correlation coefficient above 0.6 as PA or positive areas and below −0.6 as NA or negative areas3; both PA and NA are deeply influenced by ENSO/walker circulation (Fig. 1). As seen in Figure 4, the records from PA67818 and NA121317 contained substantial multi-decadal variability characterized by an anti-phase oscillatory behaviour over the last millennium. During the LIA (AD 1400–1850), proxy records indicate wetness in the western Pacific and aridity in the eastern-central tropical Pacific, suggesting an enhanced and westward PWC, with the opposite conditions prevailing during the MCA. We note, however, that according to the age models of the various records, hydrological changes were not synchronous throughout the tropical Pacific, and that in the South China Sea, the transition between dry and wet conditions might occur early in the LIA.


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)

Hydrological records from tropical Pacific.Hydrologic records from the PA of tropical western Pacific (W1—mean grain size of Cattle Pond sediments, W2—inferred seawater δ18O of Indonesia7 and W3—δDwax data from Indonesia marine sediment for the C30 n-acids8) and NA of eastern mid-tropical Pacific (M1—inferred lake salinity of Washington Island17, E1—sand percentages of El Junco lake sediment13 and E2—red colour intensity of Laguna Pallcacocha sediment12). Site locations are given in Figure 1. All time series are three-points smoothed (except E2, 30-points smoothed) and normalized to standard Z-scores. Standard Z-scores are calculated according to Z=(X−V)/SD; here X is original value, V is the averaged value of the time series, and SD is the standard deviation of the time series. In all records, blue indicates relatively wet periods, and red relatively dry periods.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Hydrological records from tropical Pacific.Hydrologic records from the PA of tropical western Pacific (W1—mean grain size of Cattle Pond sediments, W2—inferred seawater δ18O of Indonesia7 and W3—δDwax data from Indonesia marine sediment for the C30 n-acids8) and NA of eastern mid-tropical Pacific (M1—inferred lake salinity of Washington Island17, E1—sand percentages of El Junco lake sediment13 and E2—red colour intensity of Laguna Pallcacocha sediment12). Site locations are given in Figure 1. All time series are three-points smoothed (except E2, 30-points smoothed) and normalized to standard Z-scores. Standard Z-scores are calculated according to Z=(X−V)/SD; here X is original value, V is the averaged value of the time series, and SD is the standard deviation of the time series. In all records, blue indicates relatively wet periods, and red relatively dry periods.
Mentions: To assess this hypothesis further, we compared our South China Sea records with hydrological records from other areas that are strongly influenced by ENSO/Walker circulation in modern climatology. The SOI is positively correlated with the precipitation over the Indo-Pacific warm pool and negatively correlated with the precipitation over the eastern and mid-tropical Pacific3. For convenience of discussion, we define the areas with correlation coefficient above 0.6 as PA or positive areas and below −0.6 as NA or negative areas3; both PA and NA are deeply influenced by ENSO/walker circulation (Fig. 1). As seen in Figure 4, the records from PA67818 and NA121317 contained substantial multi-decadal variability characterized by an anti-phase oscillatory behaviour over the last millennium. During the LIA (AD 1400–1850), proxy records indicate wetness in the western Pacific and aridity in the eastern-central tropical Pacific, suggesting an enhanced and westward PWC, with the opposite conditions prevailing during the MCA. We note, however, that according to the age models of the various records, hydrological changes were not synchronous throughout the tropical Pacific, and that in the South China Sea, the transition between dry and wet conditions might occur early in the LIA.

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.