Yusuke Yokoyama Lab Diary
東京大学大気海洋研究所 横山祐典研究室
Atmosphere and Ocean Research Institute, the University of Tokyo
Site Categories
10/13/2026
New Papers Nature (2026/10/05 - 2026/10/12)
10/12/2026
New Paper (ELSEVIER, 261005~261012)
Chemical Geology
1. High-precision laser ablation U-Pb geochronology using a Neptune PLUS equipped with two 1013 Ω amplifiers: Age mapping of Jack Hills detrital zircon
2. An assessment of the Zr/Hf ratio as a proxy of marine clay authigenesis
3. The late shoulder season modifies the mobility of iron and dissolved organic carbon in rivers from distinct permafrost regions
Geochimica et Cosmochimica Acta
4. Oxygen isotope exchange unravels million-year long hydrogeochemical evolution of a deep carbonate aquifer in the Swiss Molasse Basin
5. Two-stage Mg isotope behavior during silicate weathering and its implication for tracing continental weathering intensity
Palaeogeography, Palaeoclimatology, Palaeoecology
6. Sources of particulate and sedimentary organic matter in the middle Okinawa Trough since the Last Glacial Maximum: Implications for lateral transport across the East China Sea shelf
10/09/2026
Fieldwork in Kikaijima (9/29-10/2)
こんにちは!D2のYangerです!
I just got back from a field trip to Kikaijima with Professor Hirabayashi. Kikaijima is a small island in Kagoshima Prefecture, east of Amami. Besides being known for its sugar cane and sesame, the island is also famous for its uplifted coral reefs and was recently designated as a Japanese geopark. As we approached the island by air, we could clearly see the classic spur-and-groove formations of its coral reefs.

Our main mission this time was to survey limestone outcrops exposed during excavation for an underground dam. We were joined by Professor Marc Humblet from Nagoya University, an expert on coral and limestone assemblages. With his help, we identified fossils of corals, foraminifera, brachiopods, and other organisms preserved in the limestone. These fossils offered clues about the water depths and environments in which they originally lived. We even found a well-preserved barnacle fossil protruding from the rock face!

We spent two days at the site documenting and sampling the
specimens we found in the rock. After long days working under the sun, we were
rewarded with beautiful sunsets.

In addition to examining the outcrops, we also had the
chance to inspect rock cores collected before construction began. The cores
were stored in the gym of an old school, where rows upon rows of boxes filled
the space. As we examined the cores and identified sections containing corals,
foraminifera, and crustose coralline algae (CCA), we could trace how the
island's environment had changed over time.

On our final day, we drove around the island to sample
groundwater from springs. Professor Hirabayashi explained that our lab has been
regularly monitoring the geochemical composition of Kikaijima's groundwater for
several years. By using radiocarbon as a tracer, these measurements help us
understand how groundwater moves and changes beneath the island.

In just four days, I got a glimpse of the exciting research
being conducted on this coral island. A huge thank you to Professor Humblet for
helping us identify the various organisms preserved in the limestone and
explaining what they can tell us about the island's past environments. I'm also
very grateful to Professor Hirabayashi for organizing the trip and teaching me
so much about Kikaijima!
10/05/2026
New Papers (AGU, etc.) 2026/09/29~2026/10/05
Geochemistry, Geophysics, Geosystems
1. Pre-Eruptive Volatiles and Magma Storage Depth for the
2018 Eruption at Mount Veniaminof, Alaska
E. G. Huggins, P. Ruprecht, M. Loewen, M.
Gavrilenko, R. J. Bodnar, M. Harlaux
Geophysical Research Letters
2. Cosmogenic 10Be as a Tracer for Recent
Heliospheric Encounters With Interstellar Cold Clouds and Nearby Supernovae
Anna Nica, Merav Opher, Jesse A. Miller,
Jennifer L. Middleton, Joe Giacalone
3. Water Storage Capacity Dynamics in Drained Boreal
Peatlands: Responses to Rewetting and Climate Change
Shokoufeh Salimi, Behshid Khodaei, Hjalmar Laudon
4. Climate Change Induced Seasonal Amplification of the
Indian Ocean CO2 Sink
A. P. Joshi, Kunal Chakraborty, V. V. S.
S. Sarma, Prasanna Kanti Ghoshal, B. Sridevi, Zouhair Lachkar
5. Asynchronous Changes in Tempo-Spatial Patterns of the
Younger Dryas Hydroclimate in Northeastern China
Sihan Sun, Yukun
Zheng, Yue Wang, Jun Cheng, Yiyin Li, Hongyan Liu, Ulrike Herzschuh
6. Dead Sea Warming and the Origin of Salt Giants
E. Guillerm, T. K.
Lowenstein, V. Gardien, F. Bärenbold, D. Bouffard, A. Brauer, F. Caupin
7. Record-Breaking Humid Heat in Northern China During
Summer 2025 Driven by Kuroshio–Oyashio Extension SST Anomalies
Wenyue He, Huopo
Chen, Zhicong Yin, Fei Xie
8. Divergent Influences of Oceanic Western Boundary Currents
on Weak and Strong Tropical Cyclones
Wenting Lou, Tongya
Liu, Jiacheng Hong, Yi-Peng Guo, Han Zhang, Dake Chen
Paleoceanography and Paleoclimatology
9. Simulated Ocean Oxygen Under Miocene Boundary Conditions
James R. Berg,
David K. Hutchinson, Katrin J. Meissner, Benoît Pasquier, Mark Holzer,
Alexandra Auderset
10. Chemostratigraphic Constraints on Oligocene–Miocene
Sedimentation and Hiatus Formation at IODP Site U1516, Mentelle Basin:
Implications for Deep-Water Circulation in the Eastern Indian Ocean
Tianqi Sun,
Christophe Colin, Zhaokai Xu, Arnaud Dapoigny, Rosella Pinna-Jamme, Dhongil
Lim, Gang Hu, Fengming Chang, Hongjin Chen, Wei Wang, Qingchao Fan, Tiegang Li
Climate of the Past
11. Ocean warming caused by Late Ordovician glacial onset in
a coupled climate-ice sheet simulation
Yudong Sun,
Yonggang Liu, Jiacheng Wu, Kai Man, Haonan Yu, Shuai Yuan, Yizhang Liu, Yue
Liu, Qi Cui, Qiang Wei, and Yongyun Hu
12. Holocene-like summer climate during Marine Isotope Stage
11 in northwestern Greenland
John Michael N. Aguilar, Elizabeth K.
Thomas, Diana S. Aga, Paul R. Bierman, Jason P. Briner, Isla S. Castañeda, and
Andrew J. Christ
10/03/2026
Seawater, Sea Squirts, and Stories from Onagawa
こんにちは!D3のMiyaです!
I recently visited Onagawa to help Professor Tanaka and her students with fieldwork on hoya (sea squirts). Their research focuses mainly on cellulose analysis and DNA-based investigations, while my role was to help collect seawater for dissolved inorganic carbon (DIC), uranium/thorium (U/Th), and oxygen isotope (δ¹⁸O) analyses. I thought hoya is called sea pineapple, but realized only the commonly-eaten species マボヤ is called sea pineapple.
My first encounter with hoya was a few years ago, when I bought a sea pineapple at a supermarket in Otsuchi. It was my first time eating one, and I dissected it myself to prepare it. Cutting into it felt strangely like cutting into a heart—not that I’ve ever cut into one! This time in Onagawa, I got to see a wider variety of sea squirts as we sorted the different species by hand.
We sampled seawater both inside and outside the aquaculture farm, and the team also collected sediment samples. We even got to enjoy a bite of the fresh ones during sampling!
Alongside the sampling, we sorted different species of hoya by hand, including マボヤ, エボヤ, and 白ボヤ. Working through the specimens gave me a closer look at the variety of sea squirts living in the area—something quite different from my usual work with abalone shells.
One evening, we had dinner with people working at Tohoku University’s Onagawa Field Center, part of the Graduate School of Agricultural Science. Over dinner, they shared their memories of the 2011 earthquake and tsunami.
One person recalled being on a research cruise with the coastal research center when the earthquake struck. After seeing the tsunami, he decided to sail farther offshore rather than return to land. He and his colleague ended up staying offshore for three days.
Hearing this account directly from someone who experienced it made a strong impression on me. Our visit was centered on collecting samples, but the conversations over dinner also offered a glimpse into the experiences of the people who live and work along this coast.
Thank you to Professor Tanaka, her students, and everyone at the Onagawa Field Center for welcoming me and sharing both their research and their stories. Also thank you Yosuke and Shishi for helping me with preparation and Yusuke for sponsoring the trip!