What are the Dominant Drivers of Precipitation Change in NE Mexico? A 75,000 Year Precipitation Record Reconstructed through Speleothem Proxies
Abstract
Northeast Mexico is threatened by projections of enhanced aridity, which would drastically impact the region's fragile ecosystems, rare microclimates, and prosperous agriculture-based economy. It is also uniquely situated, as it is affected by ocean-atmosphere variability known to facilitate droughts across the Americas. Unfortunately, significant inter-model discrepancies and limited records of past rainfall in the region have left many unknowns, namely regarding the spatial distribution, magnitude, timing, and drivers of hydroclimate variability in the region. This uncertainty inhibits predictions of future precipitation change. Here, we present the region's first multi-proxy (d18O, d13C and Mg/Ca) U-Th-dated speleothem record from Tamaulipas, Mexico, which recorded precipitation variability between 7,900 and 75,000 years BP. As one of the longest continuous and high-resolution hydroclimate records from North America, the new archive will help us explore the Mexico-North Atlantic teleconnection, as well as the role of changing atmospheric pCO2, ice volume, and insolation on precipitation.
Over 2400 stable isotope and trace element measurements (20-50 year resolution) record millennial-scale drying in response to North Atlantic freshening and weakened Atlantic Meridional Overturning Circulation during the Younger Dryas and Heinrich Stadials 1-6. Orbital forcing plays a weaker role in modulating precipitation in comparison to these millennial-scale events, except in the transition from the late-Pleistocene towards more pluvial conditions in the early-Holocene. Given the consistent proxy responses, as well as results from our cave monitoring program, precipitation isotope analyses, and a suite of Hysplit model back trajectory analyses, we interpret our data as evidence for drying at both the local and regional scale. We hypothesize that these shifts are a consequence of a southward shift in the Intertropical Convergence Zone driving a weakening of the Caribbean Low-Level Jet, but we will further explore the underlying dynamics using paleoclimate model analyses. This work will help understand the dominant drivers of hydrological change in northern Mexico, ultimately providing a pathway to improve the predictability of precipitation under future climate scenarios.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP51A..07W
- Keywords:
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- 1620 Climate dynamics;
- GLOBAL CHANGE;
- 1627 Coupled models of the climate system;
- GLOBAL CHANGE;
- 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY;
- 4910 Astronomical forcing;
- PALEOCEANOGRAPHY