Orbital modulation of subtropical versus subantarctic moisture sources in the southeast Pacific mid-latitudes.

Reconstructing rainfall variability and moisture sources is a critical aspect to understand past and future hydroclimate dynamics. Here, we use changes in the deuterium content of land-plant leaf waxes from two marine sediment cores located off Chile to reconstruct changes in rainfall amount and variation in moisture sources over the last ~50 ka. The records indicate increased moisture in central Chile during precession maxima, but an obliquity modulation is evident in southern Chile.

A novel post-1950 CE atmospheric C record for the tropics using absolutely dated tree rings in the equatorial Amazon.

In this study, we present a comprehensive atmospheric radiocarbon (C) record spanning from 1940 to 2016, derived from 77 single tree rings of Cedrela odorata located in the Eastern Amazon Basin (EAB). This record, comprising 175 high-precision C measurements obtained through accelerator mass spectrometry (AMS), offers a detailed chronology of post-1950 CE (Common Era) C fluctuations in the Tropical Low-Pressure Belt (TLPB). To ensure accuracy and reliability, we included C-AMS results from intra-annual successive cuts of the tree rings associated to the calendar years 1962 and 1963 and conducted interlaboratory comparisons.

High-precision C measurements of parenchyma-rich Hymenolobium petraeum tree species confirm bomb-peak atmospheric levels and reveal local fossil-fuel CO emissions in the Central Amazon.

Atmospheric radiocarbon (C) recorded in tree rings has been widely used for atmospheric C calibration purposes and climate studies. But atmospheric C records have been limited along tropical latitudes. Here we report a sequence from 1938 to 2007 of precisely measured C dates in tree rings of the parenchyma-rich Hymenolobium petraeum tree species (Porto Trombetas, 1°S, 56°W) from the Central Brazilian Amazon.

A source of isotopically light organic carbon in a low-pH anoxic marine zone.

Geochemical and stable isotope measurements in the anoxic marine zone (AMZ) off northern Chile during periods of contrasting oceanographic conditions indicate that microbial processes mediating sulfur and nitrogen cycling exert a significant control on the carbonate chemistry (pH, A, DIC and pCO) of this region. Here we show that in 2015, a large isotopic fractionation between DIC and POC, a DIC and N deficit in AMZ waters indicate the predominance of in situ dark carbon fixation by sulfur-driven autotrophic denitrification in addition to anammox. In 2018, however, the fractionation between DIC and POC was significantly lower, while the total alkalinity increased in the low-pH AMZ core, suggesting a predominance of heterotrophic processes.