Typhoon Control of Precipitation Dual Isotopes in Southern China and Its Palaeoenvironmental Implications

Abstract

AbstractHigh‐resolution stalagmite oxygen isotope (δ18O) records are widely employed in palaeoclimate studies as indicators of East Asian Monsoon intensity in southern China. A key issue is whether the East Asian Monsoon or other factors control δ18O in precipitation in southern China, which requires modern observations to confirm. To understand which factors control the dual isotopes (δD and δ18O) of precipitation in southern China, δD and δ18O were measured from 412 precipitation events (including 144 rainwater samples from a total of 43 typhoon events) from May 2015 to April 2020 in Zhanjiang, a tropical city frequently affected by typhoon events in southern China. The overall relationship between δD and δ18O can be expressed as δD = 8.961 δ18O + 6.235; significantly lower intercept and larger slope of this relationship compared to these of the global meteoric water line (GMWL) and the China meteoric water line (CMWL). Remarkably, significantly low D‐excess and the lowest δD and δ18O occurred in the typhoon periods, suggesting that typhoon events could bring large amounts of remote moisture to this tropical city from the Western Pacific and South China Sea. The moisture from remote oceans would affect precipitation with the lowest δ18O and D‐excess, which could be responsible for the deviation of the slope and intercept from those of the CMWL and GMWL. Therefore, variations of the δ18O in precipitation are intensively influenced by typhoons, not by the East Asian Monsoon, providing new understanding for the interpretation of palaeo‐isotope data in southern China.