Abstract
Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth’s atmosphere. Several rapid
14
C increases in the past, such as the 775 CE and 994CE
14
C spikes, have ...been reported to originate from extreme solar proton events (SPEs). Another rapid
14
C increase, also known as the ca. 660 BCE event in German oak tree rings as well as increases of
10
Be and
36
Cl in ice cores, was presumed similar to the 775 CE event; however, as the
14
C increase of approximately 10‰ in 660 BCE had taken a rather longer rise time of 3–4 years as compared to that of the 775 CE event, the occurrence could not be simply associated to an extreme SPE. In this study, to elucidate the rapid increase in
14
C concentrations in tree rings around 660 BCE, we have precisely measured the
14
C concentrations of earlywoods and latewoods inside the annual rings of Japanese cedar for the period 669–633 BCE. Based on the feature of
14
C production rate calculated from the fine measured profile of the
14
C concentrations, we found that the
14
C rapid increase occurred within 665–663.5 BCE, and that duration of
14
C production describing the event is distributed from one month to 41 months. The possibility of occurrence of consecutive SPEs over up to three years is offered.
Carbon‐14 in tree rings have suggested there had been multiple extreme solar proton events (SPEs) in the past. While the largest events such as in 774–775 CE can be significantly detected by the ...typical precision of accelerator mass spectrometry, smaller but possibly more frequent events have been difficult to be detected. Thus, the frequency or any characteristics of such relatively smaller events are still largely unknown. In this paper, we report that large SPEs had occurred in 1261–1262, 1268–1269, and 1279–1280 CE before the onset of the Wolf minimum based on high‐precision carbon‐14 analyses. It is suggested that they had occurred at the maximum and the declining phase of solar cycles, and that they had occurred during the transition time of solar activity into a deep minimum. We propose that this episode may provide a unique opportunity to elucidate a potential interaction between the solar dynamo and extreme solar flares.
Plain Language Summary
The Sun is a magnetically active star and occasionally cause intense bursts that sometimes accompany the ejection of energetic protons, described as the solar proton events. In this paper, we report that there were three intense solar proton events in the thirteenth century, just before the onset of the Wolf grand minimum. We propose that these events may be related to the weakening of solar activity during that time.
Key Points
Multiple abrupt increases in carbon‐14 content were found during the transition time of solar activity into the grand minimum state
They occurred at solar activity maximum or at the declining phase of solar cycles, suggesting that they originate from solar proton events
The Wolf minimum may provide a unique opportunity to potentially deepen the understanding of the solar dynamo
In 2009, Yamagata University installed a compact 14C accelerator mass spectrometry (YU-AMS) system and an automated graphitization line. The YU-AMS system is based on a 0.5 MV pelletron accelerator ...(1.5SDH-1) developed by National Electrostatics Corporation (NEC). A second automated graphitization line and an additional ion source of the YU-AMS system were installed in 2014. Approximately 2,000 samples have been measured per year using the system since 2010. The long-term stability of the system from 2010 to 2021 was assessed by measuring the IAEA-C6 and IAEA-C7 standard samples graphitized by the automated graphitization line.
Proxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such ...long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.
The spring Arctic Oscillation (AO) significantly affects the subsequent summer rainfall in the East Asian summer monsoon (EASM) region, and analysis of meteorological data indicates this ...teleconnection strength varied on interdecadal timescales during the late 20th century. Tree‐ring records may be able to extend the relatively short observational record, but the extent to which these proxy reconstructions correspond to AO variability has yet to be explored in this region. Therefore, we present new tree‐ring cellulose oxygen isotope (δ18O) records from northeastern Japan (Akita, northern limit of EASM), spanning a.d. 1950 to 2003 which overlaps with the instrumental record. Tree‐ring δ18O is used for reconstructing the past hydroclimate variability and allows us to consider whether tree‐ring δ18O has the potential to clarify the longer‐term interdecadal changes in the spring AO‐EASM relationship. Measurements and analyses show that our tree‐ring δ18O data sets have a significant negative correlation with May‐June‐July relative humidity, and the tree‐ring δ18O in northeastern Japan also significantly correlates with the summer EASM index. Temporal comparisons between our record and observed monthly AO index indicate that reconstructed following early summer relative humidity significantly correlates to the previous March‐April‐May AO. This linkage changes on interdecadal timescales, and the linkage is relatively strong during early 1970s through early 1990s. Similar results are also obtained using a separate tree‐ring δ18O record from a separate location about 200 km to the southeast, suggesting that tree‐ring cellulose δ18O in northeastern Japan is indeed useful for better understanding the long‐term teleconnection between the spring AO and EASM.
Key Points
New tree‐ring cellulose oxygen isotope chronologies in northeastern Japan are reported
Tree‐ring oxygen isotope record significantly correlates to the Spring Arctic Oscillation
Tree‐ring cellulose oxygen isotope in northeastern Japan can be applied to better understand the long‐term spring AO‐EASM relationship
Status of the AMS system at Yamagata University Moriya, Toru; Takeyama, Mirei; Sakurai, Hirohisa ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
01/2019, Letnik:
439
Journal Article
Recenzirano
An accelerator mass spectrometry (AMS) system and an automated graphitization line were installed at Yamagata University (YU) in 2009. Approximately 2000 samples are measured per year using the ...YU-AMS system. The long-term stability of the system was assessed by measuring the standard sample IAEA-C7 graphitized by the automated graphitization line. In March 2014, a second automated graphitization line and an additional ion source for the YU-AMS system were installed to meet the requirement of 14C measurement for pharmacological and medical applications. A phosphoric acid treatment system was also developed for the radiocarbon dating of calcium carbonate (CaCO3) in shell and coral samples. Performance tests on the new YU-AMS system were carried out by measuring the C-series standard samples (C1-C9) and oxalic acid II (HOxII) obtained from IAEA and NIST, respectively. The results of the 14C concentration pMC are in good agreement with the consensus values. Performance tests for medical applications were also carried out by measuring the 14C concentration of 14C-glucose in human plasma.
We present a large-scale dendroclimatic reconstruction of July temperatures from 42–52°N to 140–145°E in the Northwest Pacific region for the period from 1800 to 1996. A multiple regression model ...with principal components (PCs) of a tree-ring chronology network was used for the reconstruction, which accounted for 31.7% of the temperature variance in the calibration period (1901–1996). The reconstructed spatially-averaged July temperatures show large fluctuations, which are comparable to previously published dendroclimatic reconstruction of spring temperatures in northeast Asia. It also shows stable relationships with other datasets, notably sea surface temperatures (SSTs) in a wide area of the North Pacific and the Pacific Decadal Oscillation (PDO), indicating atmospheric–oceanic interaction in the Northwest Pacific region since AD 1800.
•July temperature was reconstructed for the NW pacific region using tree-ring network.•The reconstruction model demonstrated satisfactory predictive skills.•Our study is the first reconstruction for spatial climate information in the region.•The reconstruction showed generally good agreements with other studies.•Our study suggests a large scale atmospheric–oceanic interaction in the region.
•Approach to providing a chronological framework of the ancient Nara, Japan.•Ancient tree-ring chronology was developed for magemono (wooden containers).•We compared the tree-ring dates with ...documented dates on mokkan (wooden slips).•Time differences between the tree-ring dates and documented dates were fairly small.•Magemono’s tree-ring dates complemented the documented dates on mokkan.
Written dates on mokkan (wood slips used as writing supports common in the 8th century) excavated at the ancient capital site have played an important role to build a chronological framework for the Nara period (CE 710–794). However, they are not always found during excavations, and alternative means to date accurately archaeological features of the historical period needed to be developed. Here we report how tree-ring dating of wooden containers known as magemono can be used in the absence of mokkan to determine the period of use of archaeological features at the historic site of Nara in Japan.
Out of 120 magemono, 90 (75 %) were successfully crossdated, resulting in a 696-year-long tree-ring chronology for Nara (CE 95–790). It consisted of 89 Hinoki and one Sawara cypress. The developed tree-ring chronology for magemono can be considered the longest, well-replicated ancient chronology in Japan. It showed strong teleconnections with many other tree-ring series obtained from Nara and adjacent regions up to 210 km away. Furthermore, we compared the tree-ring dates of the magemono with the dates written on mokkan for each of six archaeological features where both types of artefacts were present. Our analysis revealed that the timespans between the end dates of the magemono with sapwood or bark and the dates written on the mokkan were fairly small. End dates on magemono showed they were 1–25 years younger than mokkan (going by the dates written on the mokkan), with one exception being 60 years younger. This comparison demonstrated that tree-ring dates of magemono can be alternative keys to the precise estimation of archaeological sites or features where documentary records are not found. Our approach to chronological study by tree-ring dating of magemono has shown very promising results and can be applied elsewhere among Japanese archaeological sites.
Chloroplast DNA polymorphism in four oak species (Quercus serrata, Q. mongolica var. crispula, Q. dentata and Q. aliena) was studied using collections from a total of 127 localities in Japan and ...South Korea on the basis of five intergenic spacers (trnD-trnT, trnT-trnL, rps14-psaB, trnS-trnT and trnQ-trnS). Although no variation existed in sequences among the four species, a single nucleotide (T/C) substitution in the trnQ-trnS intergenic spacer was found in all the four species, resulting in two haplotypes (T- and C-type). Phylogenetic analyses of the four species and related species showed that the C-type is derived and even likely of monophyletic origin, while the T-type is ancestral. Geographically, the T-type is widespread from South Korea to Japan, whereas the C-type is restricted to eastern Japan with rare exceptions. "Eastern Japan" approximately coincides with the distribution range of the boreal conifer forest during the last glacial maximum. Overall evidence suggests that the mutation from T- to C-type occurred in an individual of one of the four oak species and then was transferred to all the species by hybridization in eastern Japan, and that the Kanto District provided individuals with the C-type with a refugium during the last glacial maximum.
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