Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Oxygen isotopes from Chinese caves
T2 - records not of monsoon rainfall but circulation regime
AU - Maher, Barbara
AU - Thompson, Roy
PY - 2012/8
Y1 - 2012/8
N2 - Oxygen isotope variations in Chinese stalagmites have been widely interpreted as a record of the amount of East Asian summer monsoonal rainfall. This interpretation infers decreasing monsoonal rainfall from the mid-Holocene and large, dipolar rainfall oscillations within glaciations. However, the speleothem δ18O variations conflict with independent palaeoclimate proxies (cave δ13C, loess/palaeosol magnetic properties, n-alkanes), which indicate no systematic decline in rainfall from the mid-Holocene, and no glacial rainfall maxima. Using mass balance calculations, we demonstrate that the cave δ18O variations cannot be accounted for by summer rainfall changes, nor rainfall seasonality nor winter cooling, but instead reflect changes in moisture source. A possible driver of the δ18O variations in Chinese stalagmites is precessional forcing of inter-hemispheric temperature gradients, and resultant shifts in the position and intensity of the subtropical pressure cells. Through such forcing, Indian monsoon-sourced δ18O may have dominated at times of high boreal summer insolation, local Pacific-sourced moisture at low insolation. Suppression of summer monsoonal rainfall during glacial stages may reflect diminished sea and land surface temperatures and the radiative impacts of increased regional dust fluxes.
AB - Oxygen isotope variations in Chinese stalagmites have been widely interpreted as a record of the amount of East Asian summer monsoonal rainfall. This interpretation infers decreasing monsoonal rainfall from the mid-Holocene and large, dipolar rainfall oscillations within glaciations. However, the speleothem δ18O variations conflict with independent palaeoclimate proxies (cave δ13C, loess/palaeosol magnetic properties, n-alkanes), which indicate no systematic decline in rainfall from the mid-Holocene, and no glacial rainfall maxima. Using mass balance calculations, we demonstrate that the cave δ18O variations cannot be accounted for by summer rainfall changes, nor rainfall seasonality nor winter cooling, but instead reflect changes in moisture source. A possible driver of the δ18O variations in Chinese stalagmites is precessional forcing of inter-hemispheric temperature gradients, and resultant shifts in the position and intensity of the subtropical pressure cells. Through such forcing, Indian monsoon-sourced δ18O may have dominated at times of high boreal summer insolation, local Pacific-sourced moisture at low insolation. Suppression of summer monsoonal rainfall during glacial stages may reflect diminished sea and land surface temperatures and the radiative impacts of increased regional dust fluxes.
KW - Chinese caves
KW - loess
KW - magnetic susceptibility
KW - mass balance calculations
KW - monsoon rainfall
KW - oxygen isotopes
U2 - 10.1002/jqs.2553
DO - 10.1002/jqs.2553
M3 - Journal article
VL - 27
SP - 615
EP - 624
JO - Journal of Quaternary Science
JF - Journal of Quaternary Science
SN - 0267-8179
IS - 6
ER -