Energetic and thermodynamic controls on the meridional distribution of meteoric isotopes
Abstract
Meteoric 𝛿18 O is often used as a proxy for temperature (T) or precipitation amount (P), but these empirical relationships differ greatly by location, for reasons that are not well understood. Here we propose a simple framework for representing the zonal-mean distribution of meteoric 𝛿18 O in terms of three variables: 1) evaporation, 2) condensation temperature, and 3) the length scale of moisture transport. Energetic and thermodynamic constraints dictate how each of these variables responds to climate change, providing insight into the mechanisms controlling 𝛿18 O variability globally. At high latitudes, we find that the positive 𝛿18 O-T regression slope in the ice core record mostly reflects temperature-driven variability in the spatial pattern of ocean evaporation, challenging the conventional interpretation that is based on a simple understanding of Rayleigh distillation. In the tropics, the spatial pattern of evaporation is bound to be more uniform, and variability in 𝛿18 O is thus controlled by predictable changes in the length scale of moisture transport, resulting in negative 𝛿18 O-T and 𝛿18 O-P regression slopes in the intertropical convergence zone. Our framework thus provides a simple, unified explanation for much of the observed meridional variability in temporal correlations between temperature, precipitation, and 𝛿18 O in the paleo record.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP21A..01R
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1041 Stable isotope geochemistry;
- GEOCHEMISTRY;
- 1655 Water cycles;
- GLOBAL CHANGE;
- 1833 Hydroclimatology;
- HYDROLOGY