Interannual Variation in Stable Isotopes in Water Vapor Over the Northern Tibetan Plateau Linked to ENSO

The contrasting responses of ice core delta O-18 records (delta O-18(ice)) from the northern and southern Tibetan Plateau (TP) to the El Nino Southern Oscillation (ENSO) complicate delta O-18(ice)-based temperature reconstructions. These contrasting responses were explored using stable hydrogen isotopes in water vapor (delta D-v). We found that the interannual variation in delta D-v from the northern TP is influenced by midtropospheric moisture sources from the Indo-Pacific Warm Pool, with enriched (depleted) delta D-v values in La Nina (El Nino) years due to enhanced (weakened) deep convection. In comparison, the interannual delta D-v variation in the southern TP is mainly influenced by low-tropospheric moisture from the central Indian Continent, whose delta D-v is depleted (enriched) in La Nina (El Nino) years. These results demonstrate that moisture transported from different altitudes can lead to opposite isotopic signals of water vapor over the northern and southern TP and can be used to reconcile the contrasting responses of delta O-18(ice) to ENSO. Plain Language Summary The seasonal and interannual variations in stable hydrogen isotopes in water vapor (delta D-v) over the northern Tibetan Plateau (TP) are analyzed using satellite retrievals and model simulations. While seasonal variations in delta D-v from the northern TP are highly correlated with local temperature, the interannual variation in delta D-v is weakly related to local temperature but is significantly and positively correlated with the Southern Oscillation Index (SOI). Moreover, the positive correlation between the delta D-v and the SOI is in direct contrast with results from the southern TP. Our results indicate that reconstructed temperatures based on ice core delta O-18 records are biased higher (lower) in the northern (southern) TP when the tropical Pacific is in a La Nina phase, and vice versa when the tropical Pacific is in an El Nino phase. Hence, we suggest that the ENSO-related isotopic signals should be removed to constrain the uncertainty of temperature reconstruction in the TP.

Automated summary

Ice core records from the northern and southern Tibetan Plateau show contrasting responses to El Nino Southern Oscillation (ENSO), influenced by different moisture sources and isotopic signals. This study suggests that removing ENSO-related isotopic signals can help constrain the uncertainty of temperature reconstruction in the Tibetan Plateau.