Storm-Scale Variations of Water Isotopes in the Tropical High Andes
Abstract
Comprehensive understanding of the climatic controls on stable water isotopes (HD, δ18O)in precipitation over the tropical high Andes is fundamental to developing paleoclimatic reconstructions developed from regional ice cores. To establish how meteorological events transmit isotopic signals to snowpacks we utilize a mesoscale network of precipitation collection sites and process data with the Quelccaya Isotope Profile Utility (QUIPU), an analytical tool that utilizes climatological data to simulate depth profiles of δ18O variations in mountaintop annual layer snowpacks.
In this presentation, we demonstrate how QUIPU and in situ data collections improve climatological inference that can be derived from sub-seasonal to annual isotope signals preserved in low-latitude ice cores. In 2017 and 2018, our joint US-Peru-Bolivia team obtained snow pit annual layer isotope profiles from high Andean mountains at elevations between 5,250-6,265 m ASL along a 600 km transect, extending from Nevado Salkantay, Peru to Nevado Illimani, Bolivia. Daily precipitation amount and isotopic content measurements, collected at 12 sites in Peru and Bolivia by citizen-scientist observers, provide date-specific age model estimates for each snowpit profile and validation for QUIPU simulations. We identify a regionally coherent subseasonal signal in precipitation δ18O featuring alternating periods of enriched and depleted isotopic content of 6-30 day duration. This signal reflects variability in precipitation delivery driven by synoptic conditions, and closely relates to variations in the strength of the South American Low Level Jet and tropospheric moisture content. The annual layer snowpack retains this subseasonal signal into the subsequent dry season, demonstrating that synoptic variability is transmitted from the atmosphere to mountaintop snow packs synchronously across a broad region. As such, precipitation sample collections when paired with QUIPU enable determination of the controls on δ18O annual layer profiles by meteorological phenomena under modern climatic conditions; this in turn can inform interpretation of the climatic conditions associated with older δ18O registered prior to the instrumental era and retrievable in ice core records.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP14B..03S
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSESDE: 1041 Stable isotope geochemistry;
- GEOCHEMISTRYDE: 1655 Water cycles;
- GLOBAL CHANGEDE: 1833 Hydroclimatology;
- HYDROLOGY