Stable isotopes in global precipitation: A unified interpretation based on atmospheric moisture residence time

Abstract

[1] We present a new approach based on atmospheric moisture residence time (RT) to interpret precipitation stable isotope ratio variations in all climate regimes, including tropical and polar, on monthly or inter-annual time scales. d 18 O and ln RT are positively correlated and a single regression line describes variations in d 18 O and RT anomalies, overcoming limitations of existing Rayleigh distillationbased approaches for tracing moisture dynamics and precipitation processes. We use this approach to characterize changes in tropical precipitation during El Nino events and suggest that increased precipitation in a warmer climate may occur with higher d 18 O values, contrary to assumptions made in interpreting proxy climate records in speleothems and other archives. Our results will allow the use of isotopes to monitor climate change impacts on the character and intensity of precipitation and to improve the performance of climate models by providing a direct means to calibrate model results.

Proportions of convective and stratiform precipitation revealed in water isotope ratios

“…1a) is also consistent with the previously observed positive correlation between δ 18 O and moisture residence time 17 because residence time would be lower, and stratiform fractions higher, in well-organized, mesoscale convective systems and extratropical cyclones 19,21 .…”

“…14), and most or all of this variability may be observed in single or consecutive storm events 1,6,8,15,16 . Recently, precipitation δ 18 O has been correlated globally with a single climate parameter 17 (atmospheric moisture residence time), which reflects the degree of hydrological organization or structures of precipitating clouds. Tropical and midlatitude precipitation sampled on the Earth's surface almost always consists of varying proportions of two fundamental rain types 18-23 -stratiform and convective-with significantly different characteristics of temporal and spatial variability 20-25 arising from differences in cloud vertical air motions and microphysical processes during hydrometeor formation, growth, and descent to the surface.…”

Isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa Rica

“…17 O-excess) [27]. Particularly, collection and analyses techniques of these naturally occurring tracers have been shown to be useful in elucidating atmospheric moisture sources and their implications for the hydrological cycle [28][29][30][31][32]. Light stable isotopic compositions of tropical meteoric waters have proven to be an important indicator of modern climate variability [33][34][35][36][37][38][39].…”

Comparing proxy and model estimates of hydroclimate variability and change over the Common Era

“…Lastly, some studies show that speleothem δ 18 O can reflect changes in the source of precipitation, which alters the δ 18 O of rainfall (Aggarwal et al, 2004;Breitenbach et al, 2010). Unified frameworks and theories are now being tested to determine the underlying mechanisms controlling rainfall δ 18 O in order to more directly compare rainfall output from climate models with speleothem δ 18 O records (e.g., Lewis et al, 2010;Aggarwal et al, 2012;Jones et al, 2016;Tharammal et al, 2017). These efforts are also relevant for other proxy records of precipitation δ 18 O and δD, for example sediments (Sect.…”