A novel post-1950Â CE atmospheric 14C record for the tropics using absolutely dated tree rings in the equatorial Amazon

In this study, we present a comprehensive atmospheric radiocarbon (14C) 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 14C measurements obtained through accelerator mass spectrometry (AMS), offers a detailed chronology of post-1950 CE (Common Era) 14C fluctuations in the Tropical Low-Pressure Belt (TLPB). To ensure accuracy and reliability, we included 14C-AMS results from intra-annual successive cuts of the tree rings associated to the calendar years 1962 and 1963 and conducted interlaboratory comparisons. In addition, 14C concentrations in 1962 and 1963 single-year cuts also allowed to verify tissue growth seasonality. The strategic location of the tree, just above the Amazon River and estuary areas, prevented the influence of local fossil-CO2 emissions from mining and trade activities in the Central Amazon Basin on the 14C record. Our findings reveal a notabl..., Sample selection: For this atmospheric tree-ring based 14C dataset, a Cedrela odorata specimen was sourced from an established 231-year tree-ring chronology (Granato-Souza et al., 2019, 2020; https://www.ncei.noaa.gov/access/paleo-search/study/24110). A wood segment (P45) with clear tree ring boundaries was then used, and 77 tree rings spanning the period 1940 to 2016 were individually sampled from it for high-precision 14C accelerator mass spectrometry (AMS) and stable isotope (δ13C) analysis.
Cellulose extraction:  Tree-ring cellulose extraction to alpha-cellulose was performed at three laboratories, i.e., the Keck Carbon Cycle AMS facility at the University of California, Irvine (KCCAMS/UCI), the Lamont-Doherty Earth Observatory (LDEO), and the Australian Nuclear Science and Technology Organization (ANSTO). Once KCCAMS/UCI completed the microscope inspection of all tree rings singled out, samples and/or subsamples were accordingly redistributed to other labs for alpha-cellulose extra..., , # Data from: A novel post-1950 CE atmospheric 14C record for the tropics using absolutely dated tree rings in the equatorial Amazon

## Data S1 and S2

S1. EAB_14C_record_weighted mean
S2. EAB_14C_dataset complete

## Brief description of dataset contents

\***Data file S1** (EAB 14C record - averaged data) contains the annual data (Weighed mean ± larger of error of the mean or standard error of replicated data, when applicable) of the 77 *Cedrela odorata* tree rings from Eastern Equatorial Amazon, Brazil (1°S, 53°W; 1940-2016). Variables (columns from left to right) listed are described as follows:

1: “#” = The sample number.
2: “Calendar year AD” = Dendrochronological calendar dates were adjusted to the calendar’s sub-annual level of 0.34 yrs based on the climate diagram in Granato-Souza et al. (2020) and intra-annual Delta14C values of 1962 and 1963 rings.
3: “IRMS-delta13C” = Values of IRMS-delta13C were obtained from alpha-cellulose extracts produced at LDEO and KCCAMS/UCI only. M...