Data from: A novel post-1950 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 notable increase in 14C from land-respired CO2 starting
in the 1970s, a decade earlier than previously predicted, followed by a
slight decrease after 2000, signaling a transition towards the fossil fuel
era. This shift is likely attributed to changes in reservoir sources or
global atmospheric dynamics. The EAB 14C record, when compared with a
shorter record from Muna Island, Indonesia, highlights regional
differences and contributes to a more nuanced understanding of global 14C
variations at low latitudes. This study not only fills critical spatial
gaps in existing 14C compilations but also aids in refining the
demarcation of 14C variations over South America. The extended tree-ring
14C record from the EAB is pivotal for reevaluating global patterns,
particularly in the context of the current global carbon budget, and
underscores the importance of tropical regions in understanding
carbon-climate feedbacks.

本研究基于亚马逊盆地东部（Eastern Amazon Basin, EAB）的77个西班牙雪松（Cedrela odorata）单树木年轮，构建了1940至2016年的完整大气放射性碳（¹⁴C）记录。该记录包含通过加速器质谱法（accelerator mass spectrometry, AMS）获得的175个高精度¹⁴C测量值，为公元（Common Era, CE）1950年后热带低压带（Tropical Low-Pressure Belt, TLPB）的¹⁴C波动提供了详尽年表。为保证准确性与可靠性，我们纳入了1962和1963年日历年内树木年轮的年内连续切片¹⁴C-AMS结果，并开展了实验室间比对。此外，1962和1963年单年切片的¹⁴C浓度亦有助于验证组织生长的季节性。这些树木位于亚马逊河及其河口区域上游的关键位置，避免了亚马逊盆地中部采矿与贸易活动产生的本地化石CO₂排放对¹⁴C记录的影响。研究结果显示，自20世纪70年代起，陆地呼吸释放CO₂中的¹⁴C显著增加——这比此前预测早了十年——随后在2000年后略有下降，标志着向化石燃料时代的过渡。这种转变可能源于储库来源的变化或全球大气动力学过程。将EAB的¹⁴C记录与印度尼西亚穆纳岛的较短记录对比，凸显了区域差异，有助于更细致地理解低纬度地区的全球¹⁴C变化。本研究不仅填补了现有¹⁴C数据集的关键空间空白，还助力于优化南美洲¹⁴C变化的划分。EAB的延长树木年轮¹⁴C记录对于重新评估全球模式——尤其是在当前全球碳收支背景下——至关重要，并强调了热带区域在理解碳-气候反馈中的重要性。