Abstract
The exact extent, by which the hydrologic cycle in the Neotropics was affected by external forcing during the last deglaciation, remains poorly understood. Here we present a new paleo-rainfall reconstruction based on high-resolution speleothem δ18O records from the core region of the South American Monsoon System (SAMS), documenting the changing hydrological conditions over tropical South America (SA), in particular during abrupt millennial-scale events. This new record provides the best-resolved and most accurately constrained geochronology of any proxy from South America for this time period, spanning from the Last Glacial Maximum (LGM) to the mid-Holocene.
Highlights
The influence of Antarctic temperature on tropical South America (SA) precipitation on the other hand is not nearly as clear[6]
We establish that the isotopic composition of rainfall (δ18O) at our site is anti-correlated with precipitation amount on seasonal timescales
Novello et al.[18] recently documented, based on 30 years of measurements performed at a nearby station (Cuiabá) by the International Atomic Energy Agency (IAEA) that this anti-correlation between δ18O and precipitation amount holds on interannual timescales, confirming earlier results from the same location by Vuille et al.[17]
Summary
The influence of Antarctic temperature on tropical SA precipitation on the other hand is not nearly as clear[6]. Southern Hemisphere (SH) millennial-scale events documented in the isotopic record from Antarctica, such as the Antarctic Isotope Maxima events (AIMs), or the Antarctic Cold Reversal (ACR) may potentially have affected precipitation in tropical SA, as these events have been documented in glacial records from the Andes as well as in some other proxies from southern SA6,10,11. We present a new paleo-rainfall record based on oxygen isotopes in speleothems This record contains the most highly-resolved data and the most accurately constrained geochronology of any proxy from SA for the time period spanning from the Last Glacial Maximum (LGM) to the Holocene. Fornace et al.[15] recently published a stable isotopic record derived from leaf waxes in lake sediments from a shallow lake located at the Brazil-Bolivia border, a few hundred kilometers to the northwest from our site Their record covers the past 40,000 years, but at a very low resolution (~1000 years), insufficient to resolve millennial-scale variability
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