Precipitation stable isotopic signatures of tropical cyclones in Metropolitan Manila, Philippines, show significant negative isotopic excursions

Tropical cyclones have devastating impacts on the environment, economies, and societies and may intensify in the coming decades due to climate change. Stable water isotopes serve as tracers of the hydrological cycle, as isotope fractionation processes leave distinct precipitation isotopic signatures. Here we present a record of daily precipitation isotope measurements from March 2014 to October 2015 for Metropolitan Manila, a first-of-a-kind dataset for the Philippines and Southeast Asia. We show that precipitation isotopic variation at our study site is closely related to tropical cyclones. The most negative shift in delta O-18 values (-13.84 parts per thousand) leading to a clear isotopic signal was caused by Typhoon Rammasun, which directly hit Metropolitan Manila. The average delta O-18 value of precipitation associated with tropical cyclones is -10.24 parts per thousand, whereas the mean isotopic value for rainfall associated with non-cyclone events is -5.29 parts per thousand. Further, the closer the storm track is to the sampling site, the more negative the isotopic values are, indicating that in situ isotope measurements can provide a direct linkage between isotopes and typhoon activities in the Philippines.

Automated summary

This study shows that precipitation isotopic variation in Metropolitan Manila is closely related to tropical cyclones, with Typhoon Rammasun causing the most significant shift in isotopic values. The average isotopic value of precipitation associated with cyclones is lower than that associated with non-cyclone events. Additionally, the proximity of the storm track to the sampling site is directly linked to more negative isotopic values, indicating the potential for in situ isotope measurements to provide insight into typhoon activities in the Philippines.