3D X-ray computed tomography gray value and age model datasets of coral cores Baler 2 and 3 (Philippines)

The datasets here contain the 3D X-ray computed tomography (3DXCT) gray values and age models of coral cores Baler 2 and 3, taken from Baler, Aurora, Philippines. 3DXCT was used to analyze 5 mm-thick slabs of the coral cores. From the resulting 3DXCT images, gray values were determined per pixel from top to bottom of the slabs. The gray value profiles across the length of the slabs were then matched with records of sea surface temperature (SST) of the Baler site to construct the age model of the coral cores. Daily SST records from October 2018 to February 1982 were from the Optimum Interpolation Sea Surface Temperature or OISST [1,2], while monthly SST records from February 1982 to May 1945 were from the Extended Reconstructed Sea Surface Temperature or ERSST [3]. The gray value datasets of coral cores Baler 2 and 3 present historical records of the corals' response to changing environments through the years and may be used in studies related to such. An example of this can be seen in the relationship between coral gray values and SST. Furthermore, the age model datasets of Baler 2 and 3 serve as the basis for interpretation for all current and future studies on these coral cores. These datasets were originally produced for the research work titled “A historical record of the impact of nuclear activities based on ¹²⁹I in coral cores in Baler, Philippines: an update” [4].

A historical record of the impact of nuclear activities based on 129I in coral cores in Baler, Philippines: An update

In a previous study in 2016, we presented how ¹²⁹I in coral cores from the east (Baler) and west (Parola) sides of the Philippines recorded the impacts of human nuclear activities, including nuclear weapons testing, nuclear fuel reprocessing, and nuclear accidents. However, the 2016 Baler dataset only had a two-year time resolution and a crude age model based on growth band counting. Here we present a new 2020 Baler ¹²⁹I/¹²⁷I atomic ratio dataset that features at least annual time resolution and a more accurate age model constructed using 3D X-ray Computed Tomography. Results show that the bomb peaks in Baler primarily came from the Pacific Proving Grounds or PPG with a time lag of about 1.8 years (or more specifically, between 1.3 and 2.4 years). Moreover, a review of the Parola dataset shows that PPG signals may have been transported to Parola in the West Philippine Sea via two pathways: the northward and southward bifurcations of the North Equatorial Current, reaching Parola about 4.5 and 8.5 years after detonation, respectively. Moreover, a prominent peak in the year 2014.7 in Baler possibly came from the 2011 Fukushima Accident, transported by the Kuroshio Recirculation Gyre and the North Pacific Mode Waters with a 3.5-year time lag. This study contributes to the understanding of the impact and transport of human-made radionuclides to the Philippines and the relevant oceanographic processes in the Western Equatorial Pacific region.