Yusuke Yokoyama

The University of Tokyo | Todai · Atmosphere and Ocean Research Institute

One of the remaining issues regarding the Anthropocene is the lack of stratigraphic evidence indicating when the cumulative human pressure from the early Holocene began to fundamentally change the Earth system. Herein, we compile anthropogenic fingerprints from various high-precision-dated proxy records for 137 global sites to determine the age of...

Yakushima is a small, mountainous island off southern Kyushu, Japan. Its proximity to active volcanos and subduction zones leaves Yakushima vulnerable to large megathrust earthquakes and tsunamis, in addition to powerful typhoons and storm surges. These hazardous events deposit beach boulders: large rocks moved above sea-level by powerful waves. By...

Cold seeps, where geofluids containing methane and other hydrocarbons originating from the subseafloor seeps through the sediment surface, play important roles in the elemental and energy flux between sediment and seawater. These seep sites often harbor communities of endemic animals supported by chemolithoautotrophic bacteria, either through symbi...

East Asia is a major source of dust accounting for 20% of the global dust emission. Work on reconstructing past changes in dust transport in East Asia is complicated by difficulties in distinguishing local sedimentation from aerial material and lack of suitable material for age determination. Here, we address these issues and present a new dust pro...

Uranium-series dating provides radiometric age for the 10–10⁵ year timescales, which is used as a powerful dating method for the geological, climatological, and archeological research. In this paper, we review the methodology and its history of U/Th dating, and the recent climatological researches based on the U/Th dating of carbonate samples.

Trace elements and stable isotope ratios in otoliths have been used as proxies for the migration history of teleosts; however, their application in oceanic fishes remains limited. This study reports the first use of radiocarbons in otoliths to evaluate the horizontal migration histories of an oceanic fish species, the walleye pollock Gadus chalcogr...

Sea surface temperature (SST) across the Coral Sea is tightly coupled to the regional and larger‐scale ocean circulation and climate. Continuous records that reflect past changes in Coral Sea SST in high resolution are missing, however. Here, we present Mg/Ca‐ and alkenone‐based SST reconstructions from the northwestern Coral Sea that cover the pas...

Radiocarbon (¹⁴C) in corals can be used as a relatively high‐sensitivity indicator of vertical and horizontal advection of water masses, which contributes to the understanding of ocean circulation. In this study, we reconstruct Kuroshio and Ryukyu current transport with a seasonal resolution Δ¹⁴C record spanning 1947–2009. This record covers the be...

Kuroshio is an important western boundary current system in the North Pacific subtropical gyre. Mesoscale eddies play an important role in Kuroshio path variations, which significantly affect fisheries, marine navigation, and climate in regions along the Kuroshio path. However, the direct physical impacts of the Kuroshio variabilities on mixing dyn...

Deep‐sea hydrothermal vents host exceptional ecosystems with lush animal communities primarily relying on organic matter (OM) produced by chemoautotrophic microbes. Though energy sources and food webs at vents have been extensively studied, the exact carbon sources of chemosynthetic primary production, such as methane (CH4) and carbon dioxide (CO2)...

Geological evidence, such as tsunami deposits, is crucial for studying the largest rupture zone of the Kuril Trench in Hokkaido, Japan, due to its poor historical record. Although 17th-century tsunami deposits are widely distributed across Hokkaido, the presence of multiple wave sources during that period, including the collapse of Mt. Komagatake,...

At the Intertropical Convergence Zone (ITCZ), the northern and southern Tradewinds converge, and this region is characterized by low atmospheric pressure and high precipitation. The climate in the Timor Sea is characterized by seasonal precipitation changes driven by meridional migrations of the ITCZ and the monsoonal front. The ITCZ shifts in resp...

In this study, we investigate the distribution of radiocarbon and uranium in the calcified opercula of Turbo sp. collected from Ryukyu region and Chiba, Japan, to explore the potential of U/Th dating using mollusks collected from the Japanese archipelago. We acquired high-resolution radiocarbon and uranium concentration measurements using single-st...

The Jiroft Valley, southeastern Iran, was a West Asian hub for human settlement during the Chalcolithic and the Early Bronze Ages, ca. 7000-2200 BCE. The absence of detailed regional Holocene paleoclimate records, however, has obscured regional hydroclimate variability and its effects on Jiroft and adjacent region societal trajectories. Here, we pr...

Otosaka, S.; Hou, Y.; Wakita, M.; Yamashita, Y.; Nishioka, J.; Obata, H.; Miyairi, Y.; Yokoyama, Y., and Ogawa, H., 2023. Origin and transport of dissolved organic matter in the northwestern margin of the North Pacific inferred from radiocarbon signatures. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.),...

Analysis of the chronological data and observation of a lagoonal sediment core reveal sand washover events between around 2.4 to 2.5 cal. ky BP in the Isumi River lowland. We conducted radiocarbon dating with AMS and constructed an age-depth model using the latest calibration curve and appropriate model routine. In the middle to lower part of the c...

Radiocarbon (¹⁴C) has been widely used to understand the ages in archeology and paleo-environmental sciences. In marine environments, the dissolved inorganic radiocarbon (expressed as DIC Δ¹⁴C) of seawater has been used as a reliable tracer in the research of carbon cycling and studies in global to regional water mixing. Here, we present the first...

Identifying invisible tsunami deposits in the geological record is challenging and requires multiproxy analyses. In particular, geochemical signatures provide useful information for identifying paleo-tsunami deposits, as well as for reconstructing the paleoenvironment history, even when other proxies are equivocal. In addition, geochemical proxies...

Corals have been used as geochemical proxies since the 1970's and they play prominent roles in paleoclimatology. However, it has not been well elucidated how minerals in seawater are transported and precipitated in aragonite coral skeleton. There are no foundational methods to differentiate and quantify biogenic and abiogenic effects during skeleta...

The Rowley Shelf, the southern half of the tropical, carbonate-dominated, North West Shelf of Australia, is covered with linear ridges that can be tracked parallel to the coast over 1100 km between the modern coast and the 140 m isobath. Here, we investigate the origin and nature of these ridges based on the integration of extensive borehole data,...

The mechanisms underlying stabilization of soil organic matter (SOM) in coastal ecosystems, including mangrove forests, are poorly understood, limiting our ability to predict the consequences of disturbances. Here, we introduce density fractionation to mangrove soils to identify the distribution and properties of the functional components of SOM wi...

Reliable records of past volcanic activities are essential for assessing future eruption probabilities and establishing effective volcanic disaster mitigation plans. We integrated the lacustrine and terrestrial sequences of tephra deposits at the northeastern foot of Mt. Fuji based on high-resolution radiocarbon (14 C) dating to elucidate its erupt...

The rapidly melting Totten Glacier of East Antarctica drains a basin containing ~3.5 m sea-level rise equivalent of ice, but the Totten Glacier dynamics and interaction with the Southern Ocean since the Last Glacial Maximum is not well understood. To better understand the response of the glacier to present and future climate changes, an accurate re...

1. Otoliths have been widely studied as natural recorders of the entire life cycle of aquatic teleosts. Trace elements and stable isotope rations in otoliths are well understood and used as proxies of migration histories, however few elements have shown the potential to reconstruct the migration history of oceanodromous fish. 2. This study reports...

Ancient DNA (aDNA) from mollusc shells is considered a potential archive of historical biodiversity and evolution. However, such information is currently lacking for mollusc shells from the deep ocean, especially those from acidic chemosynthetic environments theoretically unsuitable for long-term DNA preservation. Here, we report on the recovery of...

Onshore and offshore site investigations along the dryland tide-dominated De Grey River delta (northwestern Australia) led to the unexpected discovery of the largest yet-known marine ooid shoals in the Indo-Pacific region. Ooids exhibit up to 60 tangential aragonitic laminae that were formed around fluvial sediment grains during the late Holocene....

Rising sea levels and associated coastal topography changes are expected to increase coastal vulnerability to tsunamis. Reliable records of the periodicity of the most damaging tsunamis, with recurrence intervals of several centuries, are often incomplete. To understand the likelihood of coastal disasters that would be worsened by sea-level rise, a...

The Great Barrier Reef (GBR) located along the northeastern margin of Australia is the largest coral reef system in the world. Modern climatic alterations are quickly changing the GBR ecosystem. To understand the implications of these changes it is important to reconstruct the geological history of GBR. Here we use geochemical and magnetic proxies...

Wetland soils are among the largest carbon reservoirs in terrestrial ecosystems and are vulnerable to climate change. Here we elucidate the developmental history of a wetland soil located on the Konsen Plateau in Hokkaido, Japan, during the Holocene. Through radiocarbon dating of sediment samples, we revealed that continuous sedimentation persisted...

Plain Language Summary The East Australian Current (EAC) transports large amounts of heat out of the Western Pacific Warm Pool into the subtropics and subpolar regions, thereby regulating the local and global climate. The few existing reconstructions of past changes in transport and temperature of the EAC are contradictory resulting in a knowledge...

For assessment of the potential of the Beppu Bay sediments as a Global Boundaries Stratotype Section and Point (GSSP) candidate for the Anthropocene, we have integrated datasets of 99 proxies. The datasets for the sequences date back 100 years for most proxy records and 1300 years for several records. The cumulative number of occurrences of the ant...

A single stage Accelerator Mass Spectrometer (National Electrostatic Corporation, YS-AMS) at the Atmosphere and Ocean Research Institute (AORI), University of Tokyo has operated smoothly since 2013. The average annual operation hours exceeded 8000 h/year for the last two years, allowing for measurement of up to 2912 samples/year (including standard...

A high-precision age model is a critical component of coral skeletology. Here we propose a rapid and precise method, coupling coral growth band counting based on X-ray photo and Sr/Ca measurement using inductively coupled plasma atomic emission spectroscopy (ICP-AES) to establish the high-resolution age model. We measured Sr/Ca ratio of the Kikai c...

A precise age model of marine sediment core is crucial for environmental studies of the past such as paleoceanography, paleoclimatology, and paleo-hazard studies. Here the geochemical dataset is described that is used to determine the age model of marine sediment cores collected from Agulhas Ridge in the South Atlantic Ocean using piston coring and...

Reef communities at intermediate (10 to 30 m) and mesophotic (~ 30 to 150 m) depths occupy large areas of sea floor but little is known about their potential to accrete vertically, their response to sea-level change and other environmental perturbations. In this study, the authors have examined cores from two holes, M0040A and M0041A, drilled by th...

Understanding of global sea-level changes and coral reef development is poorly constrained during Marine Isotope Stage 3 (MIS 3; ~ 60 to 30 ka). Australia’s North West Shelf (NWS), at depths of ~ 50 to 120 m below present sea-level (mbsl), represents an ideal natural laboratory to address these knowledge gaps. In this study, the authors investigate...

The partial melting of Earth’s bi-polar ice sheets since the Last Glacial Maximum (LGM) has translated into a ~ 120 m amplitude stepwise sea-level rise punctuated by three major meltwater pulses that were tracked and recorded with some of the best accuracy by coral reefs. However, the initial meltwater pulse marking the end of the LGM, at 19 ka, is...

Malé, the capital of the Republic of Maldives, is established on an island of about 6.8 square kilometres, with a maximum relief of 2.7 m and a population of 236,000 inhabitants. It is amongst the most densely populated areas on Earth and located virtually at sea-level. This study focuses on the late Pleistocene-Holocene evolution of Malé island th...

There is growing interest in the use of pteropods as potential archives of past changes in ocean chemistry. However, pteropods have rarely been used in studies of millennial-scale sedimentary records, especially in shallow-marine environments. This study obtained core data for the last 16 kyr from the Northwest Shelf of Australia (NWS). Changes in...

Osaka Bay adjacent to the Kyoto–Osaka–Kobe metropolitan area was affected by severe metal pollution during the twentieth century; yet little is known about the trace metal sources and pre-industrial human activities. We have determined the elemental concentrations and zinc stable isotope ratios (δ66Zn) in bulk sediments and the trace metal concentr...

Submarine groundwater discharge is increasingly recognized as an important component of the oceanic geochemical budget, but knowledge of the distribution of this phenomenon is limited. To date, reports of meteoric inputs to marine sediments are typically limited to shallow shelf and coastal environments, whereas contributions of freshwater along de...

With their complex cycles and rupture modes, infrequent megathrust earthquakes require a high‐resolution spatiotemporal record of tsunami inundations over thousands of years to provide more accurate long‐term forecasts. The geological record suggests that Mw > 8 earthquakes in the Kuril Trench occurred at intervals of several hundred years. However...

Measurement of dissolved organic radiocarbon (DO¹⁴C) in seawater can provide information about the timescale of the dynamics of dissolved organic matter and its sources in the ocean. Despite the development of accelerator mass spectrometry, the DO¹⁴C analysis requires complicated processing techniques such as the use of UV irradiation, which emits...

The surface of intertidal estuarine sediments is covered with diatom biofilms excreting exopolymeric substances (EPSs) through photosynthesis. These EPSs are highly reactive and increase sediment cohesiveness notably through organo-mineral interactions. In most sedimentary environments, EPSs are partly to fully degraded by heterotrophic bacteria in...

Accurate understanding of changing population dynamics associated with climate change is critical for managing highly migratory fish species. However, long-term data on population dynamics and the resulting recruitment variability is still lacking for many species, making it difficult to predict and integrate the effects of ocean warming into manag...

Massive boulders in landslide and tsunami deposits are prominent geomorphic features in various landscapes. Tracking their movement history is important for reconstructing past geologic dynamics; however, the reworking movements of massive boulders remain unresolved. The boulder field on the Ishigaki Island was formed by repeated tsunamis. Although...

Plutonium (Pu) has been used as a mid-twentieth century time-marker in various geological archives as a result of atmospheric nuclear tests mainly conducted in 1950s. Advancement of analytical techniques allows us to measure 239Pu and 240Pu more accurately and can thereby reconstruct the Pacific Pu signal that originated from the former Pacific Pro...

Normal fault scarps, as classical topographic features and geomorphological markers along mountain range-fronts, form in consolidated bedrock due to faulting in extensional settings. They generally preserve more complete records of paleo-earthquakes than fault scarps in unconsolidated sediments. The reconstruction of paleo-seismic history from a be...

Stable and radiocarbon isotope analyses provide valuable insights into carbon dynamics in hydrosphere ecosystems. A lake containing seeps of deep methane (CH4) may provide an ideal environment for elucidating such dynamics, including the involvement of deep carbon in the surface ecosystem and its food web. In this study, we performed carbon isotope...

The primary Antarctic contribution to modern sea-level rise is glacial discharge from the Amundsen Sea sector of the West Antarctic Ice Sheet. The main processes responsible for ice mass loss include: (1) ocean-driven melting of ice shelves by upwelling of warm water onto the continental shelf; and (2) atmospheric-driven surface melting of glaciers...

Cold-water corals (CWCs) are the engineers of complex ecosystems forming unique biodiversity hotspots in the deep sea. They are expected to suffer dramatically from future environmental changes in the oceans such as ocean warming, food depletion, deoxygenation, and acidification. However, over the last decades of intense deep-sea research, no extin...

Methane (CH4) associated with marine and terrestrial sites of serpentinization has been proposed to be abiotic in origin. However, the source of carbon and the depth and temperature of CH4 synthesis often remain inconclusive. We measured the radiocarbon (¹⁴C), bulk stable isotope ratios (δ13C and δD) and isotopologue abundance (Δ13CH3D) of CH4, and...

This Data in Brief paper comprises dataset obtained for sediment cores collected from Lake Selina, located in the West Coast Range of Tasmania, Australia. Datasets include radiocarbon and optically stimulated luminescence age estimates, elemental composition, beryllium isotopes, magnetic properties and the paleomagnetic record measured on the cores...

The Adélie Basin is a relatively small (∼1600 km²), semi-enclosed continental shelf bathymetric depression located adjacent to the Wilkes Subglacial Basin, a basin underlying a sector of the East Antarctic Ice Sheet that contains ∼3–4 meters sea level equivalent of ice. Located within the Adélie Basin is a ∼184 m thick laminated sediment deposit, t...

Corals do not all grow near the sea surface. Different species favour different ranges in depth and can survive at different depths from 0 to 5 m to over 0–100 m. Fossil corals, as markers of sea level, are the preferred choice in radiometric dating. Timing and magnitude of sea-level variations are determined from the location and age of a set of i...

Estimating paleotsunami frequency and size is an important requirement for assessing future tsunami risks. However, several issues such as ground soil erosion by subsequent tsunami waves and the preservation potential of tsunami deposits make it difficult to ascertain the paleotsunami history accurately based solely on tsunami deposits. This study...