Faculty Profiles - MIYAKE Fusa

No signature of extreme solar energetic particle events in high-precision 14C data from the Alaskan tree for 1844–1876 CE Invited Reviewed Open Access

Fusa Miyake, Masataka Hakozaki, Hisashi Hayakawa, Naruki Nakano, Lukas Wacker

Journal of Space Weather and Space Climate Vol. 13 2023.12

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：EDP Sciences

Cosmogenic nuclides—14C from tree rings and 10Be & 36Cl from ice cores serve as an effective proxy for past extreme solar energetic particle (SEP) events. After identifying the first signature of an extreme SEP event in 774 CE, several candidates have been found in these proxy archives, such as 993 CE, 660 BCE, and 7176 BCE. Their magnitudes have been estimated to be tens of times larger than that of the largest SEP event ever observed since 1950s. Although a detailed survey of such extreme SEP events is ongoing, the detection of intermediate-sized SEP events that bridge the gap between modern observations and extreme events detected in cosmogenic nuclides has not progressed sufficiently, primarily because of the uncertainties in cosmogenic nuclide data. In this study, we measured 14C concentrations in tree rings in the 19th century (1844–1876 CE) to search for any increases in 14C concentrations corresponding to intermediate-size extreme SEP events. We utilized Alaskan tree-ring samples cut into early and latewoods to suppress the potential seasonal variations in intra-annual 14C data. Notably, no significant 14C variations were observed between early and latewoods (0.0 ± 0.3‰), and the annual resolution 14C data series displayed an error of ~0.8‰. Over the entire study period, no significant increase in 14C concentrations characterized by other candidates of extreme SEP events such as the 774 CE event was detected in the annual 14C data. The present result imposes a constraint on the SEP fluence when the largest-class of recorded solar storms occurred (especially those in 1859 CE and 1872 CE).

DOI： 10.1051/swsc/2023030

Extreme Solar Events: Setting up a Paradigm Reviewed Open Access

Ilya Usoskin, Fusa Miyake, Melanie Baroni, Nicolas Brehm, Silvia Dalla, Hisashi Hayakawa, Hugh Hudson, A. J. Timothy Jull, Delores Knipp, Sergey Koldobskiy, Hiroyuki Maehara, Florian Mekhaldi, Yuta Notsu, Stepan Poluianov, Eugene Rozanov, Alexander Shapiro, Tobias Spiegl, Timofei Sukhodolov, Joonas Uusitalo, Lukas Wacker

Space Science Reviews Vol. 219 ( 8 ) 2023.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Springer Science and Business Media LLC

Abstract

The Sun is magnetically active and often produces eruptive events on different energetic and temporal scales. Until recently, the upper limit of such events was unknown and believed to be roughly represented by direct instrumental observations. However, two types of extreme events were discovered recently: extreme solar energetic particle events on the multi-millennial time scale and super-flares on sun-like stars. Both discoveries imply that the Sun might rarely produce events, called extreme solar events (ESE), whose energy could be orders of magnitude greater than anything we have observed during recent decades. During the years following these discoveries, great progress has been achieved in collecting observational evidence, uncovering new events, making statistical analyses, and developing theoretical modelling. The ESE paradigm lives and is being developed. On the other hand, many outstanding questions still remain open and new ones emerge. Here we present an overview of the current state of the art and the forming paradigm of ESE from different points of view: solar physics, stellar–solar projections, cosmogenic-isotope data, modelling, historical data, as well as terrestrial, technological and societal effects of ESEs. Special focus is paid to open questions and further developments. This review is based on the joint work of the International Space Science Institute (ISSI) team #510 (2020–2022).

DOI： 10.1007/s11214-023-01018-1

Other Link： https://link.springer.com/article/10.1007/s11214-023-01018-1/fulltext.html

Regional Differences in Carbon-14 Data of the 993 CE Cosmic Ray Event Reviewed Open Access

Fusa Miyake, Masataka Hakozaki, Katsuhiko Kimura, Fuyuki Tokanai, Toshio Nakamura, Mirei Takeyama, Toru Moriya

Frontiers in Astronomy and Space Sciences Vol. 9 2022.7

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers Media SA

Cosmogenic nuclides such as 14C from tree rings and 10Be and 36Cl from ice cores are excellent proxies for the past extremely large solar energetic particle (SEP) events, which are dozens of times larger than the largest SEP event in the history of observation. So far, several rapid 14C increases have been discovered, which are considered to have originated from extreme SEP events (or set of successive SEP events) from verifications using multiple cosmogenic nuclide analyses in natural archives. Although these events are characterized by a rapid increase in cosmogenic nuclide concentrations, 14C data recorded worldwide do not always show similar variations, especially during the 993 CE event, where a rapid increase was recorded in either 992–993 CE or 993–994 CE in several records. We present new 14C data of the Japanese cedar sample for the 993 CE event. Although the latest data show no significant increase in 1 year, an overall increase pattern is consistent with the previously reported 14C data of the Japanese cedar, which supports that a significant 14C increase occurred from 993 to 994 CE in the Japanese sample. Given the dominant 14C production in high latitudes by SEPs, the difference in timing of increase may be a transport effect in the atmosphere. Moreover, the difference in the timing of the 14C increase can cause a 1-year age-determination error using the 993 CE radiocarbon spike. Compared with the 14C data between tree samples from high latitude and midlatitude, including Japan, high-latitude data can capture 14C changes originating from SEP events more quickly and clearly and may be more suitable for a SEP event exploration in the past.

DOI： 10.3389/fspas.2022.886140

A Single-Year Cosmic Ray Event at 5410 BCE Registered in 14C of Tree Rings. Reviewed International coauthorship International journal Open Access

F Miyake, I P Panyushkina, A J T Jull, F Adolphi, N Brehm, S Helama, K Kanzawa, T Moriya, R Muscheler, K Nicolussi, M Oinonen, M Salzer, M Takeyama, F Tokanai, L Wacker

Geophysical research letters Vol. 48 ( 11 ) page： e2021GL093419 2021.6

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal)

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411-5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481-5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.

DOI： 10.1029/2021GL093419

PubMed

THE INTCAL20 NORTHERN HEMISPHERE RADIOCARBON AGE CALIBRATION CURVE (0-55 CAL KBP) Reviewed International coauthorship International journal Open Access

Paula J. Reimer, William E. N. Austin, Edouard Bard, Alex Bayliss, Paul G. Blackwell, Christopher Bronk Ramsey, Martin Butzin, Hai Cheng, R. Lawrence Edwards, Michael Friedrich, Pieter M. Grootes, Thomas P. Guilderson, Irka Hajdas, Timothy J. Heaton, Alan G. Hogg, Konrad A. Hughen, Bernd Kromer, Sturt W. Manning, Raimund Muscheler, Jonathan G. Palmer, Charlotte Pearson, Johannes van der Plicht, Ron W. Reimer, David A. Richards, E. Marian Scott, John R. Southon, Christian S. M. Turney, Lukas Wacker, Florian Adolphi, Ulf Buentgen, Manuela Capano, Simon M. Fahrni, Alexandra Fogtmann-Schulz, Ronny Friedrich, Peter Koehler, Sabrina Kudsk, Fusa Miyake, Jesper Olsen, Frederick Reinig, Minoru Sakamoto, Adam Sookdeo, Sahra Talamo

RADIOCARBON Vol. 62 ( 4 ) page： 725 - 757 2020.8

Language：English Publishing type：Research paper (scientific journal) Publisher：UNIV ARIZONA DEPT GEOSCIENCES

Radiocarbon (C-14) ages cannot provide absolutely dated chronologies for archaeological or paleoenvironmental studies directly but must be converted to calendar age equivalents using a calibration curve compensating for fluctuations in atmospheric C-14 concentration. Although calibration curves are constructed from independently dated archives, they invariably require revision as new data become available and our understanding of the Earth system improves. In this volume the international C-14 calibration curves for both the Northern and Southern Hemispheres, as well as for the ocean surface layer, have been updated to include a wealth of new data and extended to 55,000 cal BP. Based on tree rings, IntCal20 now extends as a fully atmospheric record to ca. 13,900 cal BP. For the older part of the timescale, IntCal20 comprises statistically integrated evidence from floating tree-ring chronologies, lacustrine and marine sediments, speleothems, and corals. We utilized improved evaluation of the timescales and location variable C-14 offsets from the atmosphere (reservoir age, dead carbon fraction) for each dataset. New statistical methods have refined the structure of the calibration curves while maintaining a robust treatment of uncertainties in the C-14 ages, the calendar ages and other corrections. The inclusion of modeled marine reservoir ages derived from a three-dimensional ocean circulation model has allowed us to apply more appropriate reservoir corrections to the marine C-14 data rather than the previous use of constant regional offsets from the atmosphere. Here we provide an overview of the new and revised datasets and the associated methods used for the construction of the IntCal20 curve and explore potential regional offsets for tree-ring data. We discuss the main differences with respect to the previous calibration curve, IntCal13, and some of the implications for archaeology and geosciences ranging from the recent past to the time of the extinction of the Neanderthals.

DOI： 10.1017/RDC.2020.41

Prolonged production of 14C during the ~660 BCE solar proton event from Japanese tree rings. Reviewed International journal Open Access

Hirohisa Sakurai, Fuyuki Tokanai, Fusa Miyake, Kazuho Horiuchi, Kimiaki Masuda, Hiroko Miyahara, Motonari Ohyama, Minoru Sakamoto, Takumi Mitsutani, Toru Moriya

Scientific reports Vol. 10 ( 1 ) page： 660 - 660 2020.1

Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Annual rings record the intensity of cosmic rays (CRs) that had entered into the Earth's atmosphere. Several rapid 14C increases in the past, such as the 775 CE and 994CE 14C spikes, have been reported to originate from extreme solar proton events (SPEs). Another rapid 14C increase, also known as the ca. 660 BCE event in German oak tree rings as well as increases of 10Be and 36Cl in ice cores, was presumed similar to the 775 CE event; however, as the 14C 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 14C concentrations in tree rings around 660 BCE, we have precisely measured the 14C concentrations of earlywoods and latewoods inside the annual rings of Japanese cedar for the period 669-633 BCE. Based on the feature of 14C production rate calculated from the fine measured profile of the 14C concentrations, we found that the 14C rapid increase occurred within 665-663.5 BCE, and that duration of 14C 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.

DOI： 10.1038/s41598-019-57273-2

10Be Signature of the Cosmic Ray Event in the 10th Century CE in Both Hemispheres, as Confirmed by Quasi‐Annual 10Be Data From the Antarctic Dome Fuji Ice Core Reviewed International journal Open Access

F. Miyake, K. Horiuchi, Y. Motizuki, Y. Nakai, K. Takahashi, K. Masuda, H. Motoyama, H. Matsuzaki

Geophysical Research Letters Vol. 46 ( 1 ) page： 11 - 18 2019.1

Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE Reviewed International journal Open Access

Buntgen Ulf, Wacker Lukas, Galvan J. Diego, Arnold Stephanie, Arseneault Dominique, Baillie Michael, Beer Jurg, Bernabei Mauro, Bleicher Niels, Boswijk Gretel, Brauning Achim, Carrer Marco, Ljungqvist Fredrik Charpentier, Cherubini Paolo, Christl Marcus, Christie Duncan A, Clark Peter W, Cook Edward R, D'Arrigo Rosanne, Davi Nicole, Eggertsson Olafur, Esper Jan, Fowler Anthony M, Gedalof Ze'ev, Gennaretti Fabio, Griessinger Jussi, Grissino-Mayer Henri, Grudd Hakan, Gunnarson Bjorn E, Hantemirov Rashit, Herzig Franz, Hessl Amy, Heussner Karl-Uwe, Jull A. J. Timothy, Kukarskih Vladimir, Kirdyanov Alexander, Kolar Tomas, Krusic Paul J, Kyncl Tomas, Lara Antonio, LeQuesne Carlos, Linderholm Hans W, Loader Neil J, Luckman Brian, Miyake Fusa, Myglan Vladimir S, Nicolussi Kurt, Oppenheimer Clive, Palmer Jonathan, Panyushkina Irina, Pederson Neil, Rybnicek Michal, Schweingruber Fritz H, Seim Andrea, Sigl Michael, Churakova (Sidorova, Olga, Speer James H, Synal Hans-Arno, Tegel Willy, Treydte Kerstin, Villalba Ricardo, Wiles Greg, Wilson Rob, Winship Lawrence J, Wunder Jan, Yang Bao, Young Giles H. F

NATURE COMMUNICATIONS Vol. 9 ( 1 ) page： 3605 2018.9

Language：English Publishing type：Research paper (scientific journal) Publisher：NATURE PUBLISHING GROUP

Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the C-14 content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct C-14 excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved C-14 measurements are needed.

DOI： 10.1038/s41467-018-06036-0

SEARCH FOR ANNUAL C-14 EXCURSIONS IN THE PAST Reviewed International journal Open Access

Fusa Miyake, Kimiaki Masuda, Toshio Nakamura, Katsuhiko Kimura, Masataka Hakozaki, A. J. Timothy Jull, Todd E. Lange, Richard Cruz, Irina P. Panyushkina, Chris Baisan, Matthew W. Salzer

RADIOCARBON Vol. 59 ( 2 ) page： 315 - 320 2017.4

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：UNIV ARIZONA DEPT GEOSCIENCES

Two radiocarbon excursions (AD 774-775 and AD 993-994) occurred due to an increase of incoming cosmic rays on a short timescale. The most plausible cause of these events is considered to be extreme solar proton events (SPE). It is possible that there are other annual C-14 excursions in the past that have yet to be confirmed. In order to detect more of these events, we measured the C-14 contents in bristlecone pine tree-ring samples during the periods when the rate of C-14 increase in the IntCal data is large. We analyzed four periods every other year (2479-2455 BC, 4055-4031 BC, 4465-4441 BC, and 4689-4681 BC), and found no anomalous C-14 excursions during these periods. This study confirms that it is important to do continuous measurements to find annual cosmic-ray events at other locations in the tree-ring record.

DOI： 10.1017/RDC.2016.54

Large C-14 excursion in 5480 BC indicates an abnormal sun in the mid-Holocene Reviewed International journal Open Access

Fusa Miyake, A. J. Timothy Jull, Irina P. Panyushkina, Lukas Wacker, Matthew Salzer, Christopher H. Baisan, Todd Lange, Richard Cruz, Kimiaki Masuda, Toshio Nakamura

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Vol. 114 ( 5 ) page： 881 - 884 2017.1

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：NATL ACAD SCIENCES

Radiocarbon content in tree rings can be an excellent proxy of the past incoming cosmic ray intensities to Earth. Although such past cosmic ray variations have been studied by measurements of C-14 contents in tree rings with >= 10-y time resolution for the Holocene, there are few annual C-14 data. There is a little understanding about annual C-14 variations in the past, with the exception of a few periods including the AD 774-775 C-14 excursion where annual measurements have been performed. Here, we report the result of C-14 measurements using the bristlecone pine tree rings for the period from 5490 BC to 5411 BC with 1- to 2-y resolution, and a finding of an extraordinarily large C-14 increase (20 parts per thousand) from 5481 BC to 5471 BC (the 5480 BC event). The C-14 increase rate of this event is much larger than that of the normal grand solar minima. We propose the possible causes of this event are an unknown phase of grand solar minimum, or a combination of successive solar proton events and a normal grand solar minimum.

DOI： 10.1073/pnas.1613144114

The Solar and Geomagnetic Storms in 2024 May: A Flash Data Report

PubMed

Another rapid event in the carbon-14 content of tree rings Reviewed

F. Miyake, K. Masuda, T. Nakamura

Nature Communications 2013

A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan Reviewed

F. Miyake, K. Nagaya, K. Masuda, T. Nakamura

Nature page： 240-242 2012

Hayakawa, H; Ebihara, Y; Mishev, A; Koldobskiy, S; Kusano, K; Bechet, S; Yashiro, S; Iwai, K; Shinbori, A; Mursula, K; Miyake, F; Shiota, D; Silveira, MVD; Stuart, R; Oliveira, DM; Akiyama, S; Ohnishi, K; Ledvina, V; Miyoshi, Y

ASTROPHYSICAL JOURNAL Vol. 979 ( 1 ) 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Astrophysical Journal

In 2024 May, the scientific community observed intense solar eruptions that resulted in a great geomagnetic storm and auroral extensions, highlighting the need to document and quantify these events. This study mainly focuses on their quantification. The source active region (AR; NOAA Active Region 13664) evolved from 113 to 2761 millionths of the solar hemisphere between May 4 and 14. NOAA AR 13664’s magnetic free energy surpassed 1033 erg on May 7, triggering 12 X-class flares on May 8-15. Multiple interplanetary coronal mass ejections (ICMEs) were produced from this AR, accelerating solar energetic particles toward Earth. According to satellite and interplanetary scintillation data, at least four ICMEs erupted from AR 13664, eventually overcoming and combining each other. The shock arrival at 17:05 UT on May 10 significantly compressed the magnetosphere down to ≈5.04 R E and triggered a deep Forbush Decrease. GOES satellite data and ground-based neutron monitors confirmed a ground-level enhancement from 2 UT to 10 UT on 2024 May 11. The ICMEs induced exceptional geomagnetic storms, peaking at a provisional Dst index of −412 nT at 2 UT on May 11, marking the sixth-largest storm since 1957. The AE and AL indices showed great auroral extensions that located the AE/AL stations into the polar cap. We gathered auroral records at that time and reconstructed the equatorward boundary of the visual auroral oval to 29.°8 invariant latitude. We compared naked-eye and camera auroral visibility, providing critical caveats on their difference. We also confirmed global disturbances of the storm-enhanced density of the ionosphere.

DOI： 10.3847/1538-4357/ad9335

The Role of Deposition of Cosmogenic 10Be for the Detectability of Solar Proton Events Reviewed Open Access

K. Schaar, T. Spiegl, U. Langematz, T. Sato, F. Mekhaldi, M. Kunze, F. Miyake, S. Yoden

Journal of Geophysical Research: Atmospheres Vol. 129 ( 11 ) 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：American Geophysical Union (AGU)

Abstract

The manifestation of extreme solar proton events (SPEs) in Beryllium‐10 (10Be) ice core data contains valuable information about the strength and incidence of SPEs or local characteristics of the atmosphere. To extract this information, the signals of enhanced production of cosmogenic 10Be due to the SPEs have to be detected, hence distinguished from the variability of the background production by galactic cosmic rays (GCRs). Here, we study the transport and deposition of 10Be from GCRs, using the ECHAM/MESSy Atmospheric Chemistry climate model, and discuss the detectability of extreme SPEs (similar to the CE 774/775 SPE) in 10Be ice core data depending on the ice core location, seasonal appearance of the SPE, atmospheric aerosol size distribution and phase of the 11‐year solar cycle. We find that sedimentation can be a major deposition mechanism of GCR generated 10Be, especially at high latitudes, depending on the aerosols to which 10Be attaches after production. The comparison of our results to four ice core records of 10Be from Greenland and Antarctica shows good agreement for both 10Be from GCRs and solar energetic particles (SEP). From our results we deduce that the location of detection and the season of occurrence of the SPE have a considerable effect on its detectability, as well as the aerosol size distribution the produced cosmogenic nuclides meet in the atmosphere. Furthermore, we find that SPEs occurring in the phase of highest activity during the 11‐year solar cycle are more detectable than SPEs that arise in the phase of lowest activity.

DOI： 10.1029/2023JD040463

TWO NEW MILLENNIUM-LONG TREE-RING OXYGEN ISOTOPE CHRONOLOGIES (2349–1009 BCE AND 1412–466 BCE) FROM JAPAN Reviewed

Exploring past solar eruptions using cosmogenic nuclides

Fusa Miyake

Abstracts of Annual Meeting of the Geochemical Society of Japan Vol. 71 ( 0 ) page： 101 2024

Masaki Sano, Katsuhiko Kimura, Fusa Miyake, Fuyuki Tokanai, Takeshi Nakatsuka

Radiocarbon Vol. 65 ( 3 ) page： 721 - 732 2023.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Cambridge University Press (CUP)

ABSTRACT

We present two new millennium-long tree-ring oxygen isotope chronologies for central and northern Japan, based on 9693 annually resolved measurements of tree-ring oxygen isotopes from 39 unearthed samples consisting mainly of Japanese cedar (Cryptomeria japonica). These chronologies were developed through cross-dating of tree-ring widths and δ18O data from multiple samples covering the periods 2349–1009 BCE (1341 yr) and 1412–466 BCE (947 yr) for central and northern Japan, respectively. In combination with our published chronology for central Japan, the tree-ring δ18O dataset currently available covers the past 4354 yr (2349 BCE to 2005 CE), which represents the longest annually resolved tree-ring δ18O dataset for Asia. Furthermore, the high-resolution temporal record of 14C contents independently developed by Sakurai et al. (2020) was reproduced by our 14C measurements of earlywood and latewood in annual rings for the period 667–660 BCE.

DOI： 10.1017/RDC.2023.29

Present status of the YU-AMS system and its operation over the past 10 years Reviewed

Mirei Takeyama, Toru Moriya, Hisako Saitoh, Hiroko Miyahara, Fusa Miyake, Motonari Ohyama, Rimi Sato, Rie Shitara, Hirohisa Sakurai, Fuyuki Tokanai

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Vol. 538 page： 30 - 35 2023.5

A WIGGLE-MATCHED 297-YR TREE-RING OXYGEN ISOTOPE RECORD FROM THAILAND: INVESTIGATING THE 14C OFFSET INDUCED BY AIR MASS TRANSPORT FROM THE INDIAN OCEAN Reviewed Open Access

Masaki Sano, Nathsuda Pumijumnong, Koji Fujita, Masataka Hakozaki, Fusa Miyake, Takeshi Nakatsuka

Radiocarbon Vol. 65 ( 2 ) page： 505 - 519 2023.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Cambridge University Press (CUP)

ABSTRACT

Regional offsets from Northern Hemisphere radiocarbon (14C) calibration curves are widely recognized for monsoon Asia and often hinder accurate 14C dating. In this paper, we explore the possible linkage between summer monsoon intensity and 14C offsets using tree-ring δ18O and 14C data from Thailand. We developed a 297-yr floating tree-ring δ18O chronology comprising seven teak log-coffin samples from the Ban Rai rock shelter site, northwestern Thailand. The outermost ring of our chronology was estimated to date from 358–383 CE, within a 95.4% (2σ) probability range, based on a total of 10 14C measurements that were wiggle-matched against a mixed calibration curve evenly weighted from the IntCal20 and SHCal20 curves. Backward trajectory analysis showed that an intensified (weakened) summer monsoon detected in a modern tree-ring δ18O chronology was most likely to be induced by increased (decreased) air mass transport from the tropical Indian Ocean, which is an area of intense upwelling where the 14C concentration is lower than the atmospheric 14C level. However, partly because of the limited sample size and dating uncertainty, the direct linkage between the tree-ring δ18O series and 14C records obtained from our teak log-coffin samples could not be statistically verified.

DOI： 10.1017/RDC.2023.14