Tomohisa Irino

Hokkaido University | Hokudai · Faculty of Environmental Earth Science

Discriminating shelf sediment provenances using sediment trace metal and rare earth element (REE) concentration and isotope ratios and clay mineral contents has several unavoidable hurdles, such as the effect of sediment grain size on metal concentrations, ubiquitous inclusion of REE-rich heavy minerals in sediments, and meager and inconsistent com...

The Last Interglacial (LIG: 130,000–115,000 years ago) was a period of warmer global mean temperatures and higher and more variable sea levels than the Holocene (11,700–0 years ago). Therefore, a better understanding of Antarctic ice-sheet dynamics during this interval would provide valuable insights for projecting sea-level change in future warmin...

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...

In order to clarify the compound composition of the water-soluble organic nitrogen (WSON) in aerosols, simultaneous measurements of the WSON, free amino acids (FAA), combined amino acids (CAA), amines, and urea in the total suspended particles (TSP) were conducted at a remote coastal site located in the northern tip of Japan. About 15% of the water...

Japan sea sediments consist of various detrital materials of eolian and riverine origin. Understanding the provenance of eolian dust is vital for reconstructing the variability of wind patterns and monsoons in the past. New and complete eolian accumulation rates from Taklimakan, Gobi, and Ordos are reconstructed at Integrated Ocean Drilling Program...

Fossil benthic foraminifera from five cores in the Nakdong River Delta (southeast Korea) were investigated to reveal paleoenvironmental changes across the middle/late Holocene transition, particularly focusing on ∼4 ka climatic event. Based on multi-dimensional scaling, benthic foraminifera are divided into (1) Marine taxa, (2) Bay taxa, and (3) Op...

Little is known about the dynamics of marine food chains spanning primary to higher trophic levels on centennial and longer timescales, especially where the supply of dissolved iron limits primary productivity. To elucidate the long-term dynamics of biological productivity in the Coastal Oyashio (CO), which is a major pathway for transporting disso...

Climate and vegetation in Japan are strongly influenced by the East Asian Monsoon (EAM) and the ocean environment of the Japan Sea. This study discusses the findings from a new pollen record from Integrated Ocean Drilling Program Site U1427, situated off the northern coast of the Honshu Island in western Japan, which allows for direct comparisons w...

Rebun is a small island located northwest of Hokkaido Island where hunter-fisher-gatherer cultural traditions continued until the 19th century CE. In this study, we quantified polycyclic aromatic hydrocarbons (PAHs), pentacyclic triterpene methyl ethers (PTMEs), n-fatty acids, and glycerol dialkyl glycerol tetraethers (GDGTs) in sediments from Lake...

The summer climate of northern Japan since the last glacial period has likely been determined by atmospheric and oceanic dynamics, such as changes in the North Pacific High, the position of the westerlies, the Kuroshio Current, the Tsushima Warm Current (TWC), and the East Asian summer monsoon. However, it is unclear which factor has been most impo...

Tsunamis are generally considered to disturb the seafloor, rework surface sediments, and change seafloor environments. However, the response of the seafloor to such extreme wave events has not been fully elucidated. Herein, we compare the surface sediments before and after the 2011 Tohoku-oki tsunami on the Sendai shelf and demonstrate that both sa...

The Aleutian Low (AL) is one of the major atmospheric systems that determines environmental conditions during winter in the North Pacific Ocean, with impacts that affect the climates of both Asia and North America from mid- to high latitudes. However, the multi-centennial and longer scale behavior of the AL during the Holocene is not fully understo...

Deep-sea turbidite deposits are useful tools for submarine paleoseismology. It is fundamental to understand what kind of disturbance occurred owing to the earthquake and which event-induced deposits were formed in a particular area. The 2011 Tohoku-oki earthquake and tsunami were the most destructive geohazards in Japanese history. To understand th...

The inner shelf sediments of the East China Sea (ECS) preserve valuable information regarding climatic changes on land through detrital material discharged from large rivers, particularly the Yangtze River. In this paper, we examine the provenance changes of fine-grained detrital quartz preserved in the sediment of the MD06-3040 core retrieved from...

X-ray fluorescence (XRF) scanning of marine sediment has the potential to yield near-continuous and high-resolution records of elemental abundances, which are often interpreted as proxies for paleoceanographic processes over different time scales. However, many other variables also affect scanning XRF measurements and convolute the quantitative cal...

The distribution and characteristics of marine surface sediments are a basic marine geological information. Large river floods are a frequent natural hazard that transport substantial terrigenous sediments into the marine environment. In August 2003, TY ETAU (0310) caused heavy rainfall in the southern coast of Hokkaido, north Japan, where some mou...

Major river flooding is a typical geohazard frequently characterized by the transportation of large quantities of terrigenous material from the land to the sea. However, the types and patterns of flood material deposition and the influence on seafloor environments differ because of the diversity in geological and climatic conditions. In September 2...

High-resolution studies of sedimentary sequences have reconstructed paleoceanographic changes in the Atlantic and southern and equatorial Pacific Oceans during the Late Miocene and Pliocene, but comparable analyses are lacking for the North Pacific Ocean. However, continuous samples of hemipelagic sequences covering this time interval were obtained...

A field study was conducted to clarify sources of atmospheric black carbon and related carbonaceous components at Rishiri Island, Japan. We quantified equivalent black carbon (eBC) particle mass and the absorption Ångström exponent (AAE), atmospheric CO and CH4, in addition to levoglucosan in total suspended particles, a typical tracer of biomass b...

Integrated Ocean Drilling Program Expedition 346 “Asian Monsoon” obtained sediment successions at seven sites in the Japan Sea (Sites U1422–U1427 and U1430) and at two closely located sites in the northern East China Sea (Sites U1428 and U1429). The Quaternary sediments of the Japan Sea are characterized by centimeter- to decimeter-scale dark–light...

Establishment of sedimentary sequence is essential for the interpretation of the sedimentary records. Integrated Ocean Drilling Program (IODP) Expedition (Exp.) 346 drilled high-quality sediment archives with more than three holes each at nine sites that enable us to establish continuous sedimentary sequences through splicing technique. After exten...

The burning of trees and grasses produces charred particles, such as charcoal and soot, that can be transported over long distances via winds and rivers to coastal, deltaic, and ocean environments, where they are preserved in sediments. Charcoal contained in sediments has been widely used as a proxy for biomass burning and human activities as well...

The Quaternary hemipelagic sediments of the Japan Sea are characterized by centimeter-to decimeter-scale alternation of dark and light clay to silty clay, which are bio-siliceous and/or bio-calcareous to a various degree. Each of the dark and light layers are considered as deposited synchronously throughout the deeper (> 500 m) part of the sea. How...

Submarine landslides triggered by earthquakes can generate turbidity currents. Recently, several studies have reported that the remobilization of surface sediment triggered by earthquakes can also generate turbidity currents. Such sedimentary processes may be influenced by sediment characteristics, seafloor morphology and seismic motions. Here, we...

Microbial nitrification is a key process in the nitrogen cycle in the continental shelf ecosystems. The genotype compositions and abundance of the ammonia monooxygenase gene, amoA, derived from ammonia-oxidizing archaea (AOA) and bacteria (AOB) in two size fractions (2–10 and 0.2–2 µm), were investigated in the East China Sea (ECS) in May 2008 usin...

Lower Cretaceous lacustrine oil shales are widely distributed in southeastern Mongolia. Due to the high organic carbon content of oil shale, many geochemical studies and petroleum exploration have been conducted. Although most of the oil shales are considered to be Early Cretaceous in age, a recent study reveals that some were deposited in the Midd...

The Asian summer monsoon exerts a strong influence on the hydrologic cycle in East Asia. Moreover, the distribution of heavy precipitation in the Yangtze River basin, which covers a large area of South China, is sensitive to changes in monsoon intensity. Thus, the paleo-distribution of heavy precipitation in the Yangtze basin is key in reconstructi...

Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st-century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard–Oeschger (D–O) cycles dur...

The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz ∕ feldspar and chlorite ∕ illite ratios in three sediment cores from the northern Chukchi Sea, providing insights into the long-term dynamic...

Paleorecords of pelagic fish abundance could better define the nature of fishery productivity dynamics and help understand responses of pelagic fish stocks to long-term climate changes. We report a high-resolution record of sardine and anchovy scale deposition rates (SDRs) from Beppu Bay, Southwest Japan, showing multidecadal and centennial variabi...

Reliable estimates of evolutionary rates of mitochondrial DNA might allow us to build realistic evo- lutionary scenarios covering broad time scales based on phylogenetic inferences. In the present study, we sought to obtain estimates of evolutionary rates in murine rodents using calibrations against historical biogeographic events. We first assumed...

In order to clarify the production process for the particulate WSON in the maritime atmosphere, measurements of the WSON and the associated species in the aerosols were conducted at the coastal site on Rishiri Island near the northern tip of Japan. The mean concentration of the WSON in the aerosols was 0.077 μg m⁻³, which was within the previous me...

We conducted an organic carbon analysis of flood sediments from the 2003 typhoon no. 10 off Hidaka, southern Hokkaido. Flood-induced sediments from the river mouth, inner shelf, outer shelf, and upper slope are rich in terrigenous organic carbon. Four years after the typhoon, flood sediments were found preserved in a topographic depression on the i...

The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz/feldspar and chlorite/illite ratios in three sediment cores from the northern Chukchi Sea providing insights into the long-term dynamics of...

Quaternary records provide an opportunity to examine the nature of the vegetation and fire responses to rapid past climate changes comparable in velocity and magnitude to those expected in the 21st century. The best documented examples of rapid climate change in the past are the warming events associated with the Dansgaard-Oeschger (D-O) cycles dur...

In the densely populated region of East Asia, it is important to know the mechanism, scale, and frequency of heavy precipitation brought about during the monsoons and typhoons. However, observational data, which cover only several decades, are insufficient to examine the long-term trend of extreme precipitation and its background mechanism. In humi...

The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz/feldspar and chlorite/illite ratios in two sediment cores from the northern Chukchi Sea providing insights into the long-term dynamics of th...

The 2011 Tohoku-oki earthquake and tsunami was the most destructive geohazard in Japanese history. However, little is known of the past recurrence of large earthquakes along the Japan Trench. Deep-sea turbidites are potential candidates for understanding the history of such earthquakes. Core samples were collected from three thick turbidite units o...

This paper describes the distribution of detrital minerals and sediment color in the surface sediments of the western Arctic Ocean and the northern Bering Sea and investigates the relationship between mineral composition and sediment provenance. This relationship was used to determine the provenance of western Arctic Ocean sediments deposited durin...

Rebun Island with Hamanaka and Funadomari among the 43 documented archaeological sites and the environmental archive stored in the Lake Kushu sediment proves to be one of the key areas to study the interplay between ecology, climate and human activities. This paper focuses on the potential of palaeobotanical records from Rebun Island for improving...

Asian dust has a significant impact on the natural environment. Its variability on multiple timescales modulates the ocean biogeochemistry and climate. We demonstrate that temporal changes in the deposition flux of Aeolian dust recorded in sediments from Lake Suigetsu, central Japan, during the last century exhibit a continuous decreasing trend and...

Equivalent black carbon (BC) in surface air was measured using an aethalometer on Rishiri Island, northern Japan (45°07ʹ N, 141°12ʹ E), to examine temporal variations in BC between May 15, 2012 and May 8, 2013. Based on the negative relationship observed between BC and 222Rn during the diurnal cycle, the dry deposition velocity of BC was estimated...

Integrated Ocean Drilling Program (IODP) Expedition 346 (29 July–27 September 2013) drilled seven sites covering a wide latitudinal range in the body of water bordered by the Eurasian continent, the Korean Peninsula, and the Japanese Islands, as well as two closely spaced sites in the East China Sea. This expedition recovered 6135.3 m of core with...

To examine the behaviour of ozone (O-3) in the seasonal snowpack, measurements were taken of O-3 and CO2 in the interstitial air on Rishiri Island, which is located in northern Japan, during the 2010/11 winter season. Exhibiting variation on timescales ranging from several minutes to several days, the atmospheric O-3 in the surface air generally in...

The response of the monsoon climate on the inner shelf of the East China Sea (ECS) to abrupt climate changes events within the monsoonal Yangtze River drainage is contentious. Repositioning of the monsoon front is thought to have been responsible for the changes in hydroclimate over the Yangtze River drainage, which has exerted great impact on the...

Integrated Ocean Drilling Program (IODP) Expedition 346 (29 July–27 September 2013) drilled seven sites covering a wide latitudinal range in the body of water bordered by the Eurasian continent, the Korean Peninsula, and the Japanese Islands, as well as two closely spaced sites in the East China Sea. This expedition recovered 6135.3 m of core with...

Although it is accepted that large tsunami waves impact the sea floor, the response of surface sediments to tsunami is not yet fully understood. Tsunami by the 2011 off the Pacific coast of Tohoku earthquake caused considerable damage to Northeast Japan. Surface sediments on the outer shelf of Sendai Bay also show evidence of strong ground motion a...

Isoprenoid glycerol dialkyl glycerol tetraethers(GDGTs) and alkenones were analyzed in sediment samples retrieved from Ocean Drilling Program Site 1241 covering the last 150000 years to understand the hydrological evolution of the eastern Pacific warm pool (EPWP). GDGT and alkenone concentrations showed higher values in marine isotope stage (MIS)-2...

We analyzed the lithology, magnetic susceptibility, bulk density, and X-ray radiographs of 14 sediment cores (1-9 m long) from Beppu Bay in the western Seto Inland Sea, Japan, to establish the late Holocene stratigraphy in the deepest part of the bay and to develop an age-depth model for the sediments there. The cores contained 18 thick (major even...

The oxygen isotopic composition (δ18O) of planktonic foraminiferal shells in seafloor sediment provides information on past surface oceanography. Knowledge of seasonal and depth habitat, as well as the δ18O disequilibrium (vital effect), is essential to constrain the interpretation of sedimentary δ18O. Here, we present a 1-year time series of plank...

The aragonitic micro-bivalve Carditella iejimensis, which is less than 3.5 mm in height and length, inhabits the sediment surface in a submarine cave off the Okinawa Islands, Japan. To evaluate the use of this species as a quantitative paleoceanographic proxy, we analyzed the delta O-18 values of 50 living C. iejimensis specimens collected from the...

TEXH86 - and UK37′-derived paleotemperatures, and isoprenoid glycerol dialkyl glycerol tetraether (GDGT), and alkenone concentrations were examined for ODP Site 1239 in the eastern equatorial Pacific (EEP) for the last 430 kyr. We propose that the difference between TEXH86- and UK 37′-derived temperatures (ΔT) and the abundance ratio of GDGTs to al...

We investigated the spatial distribution of glycerol dialkyl glycerol tetraethers (GDGTs), alkenones, and polyunsaturated fatty acids in particulate organic matter collected at four sites along a depth transect from the continental shelf to the Okinawa Trough in the East China Sea during the spring bloom in 2008. The maximum alkenone concentration...

The Japan Sea is connected with the Okhotsk Sea and Northwest Pacific through three straits, viz. Mamiya (Tartarskiy), Soya and Tsugaru, and with the East China Sea through Tsushima Strait, all having sill depths of 18OPF) of the planktonic foraminifera. The δ18OPF exhibits extremely low values (∼0.5‰ vs. Belemnite from Pedee formation, South Carol...

Two gravity sediment cores (GH99-1239 and GH99-1246) obtained from the north-eastern Japan Basin in the East Sea/Japan Sea were analyzed for the orbital- and millennial-scale paleoceanographic changes. Chronostratigraphically, core GH99-1239 represents a continuous sedimentary record since 32 ka, based on correlation of distinct lithological marker...

Various marine proxies has been used intensively in the reconstruction of paleoclimate and paleoceanography in the Eastern Equatorial Pacific (EEP). In this study, we discussed the sea surface temperatures (SSTs) produced by TEX86, UK’37 and Mg/Ca in Ocean Drilling Program (ODP) Leg 202 sites 1239, 1237 and the nearby cores during the last glacial...

High-resolution pollen records from Taiwan, Japan and Sakhalin document regional vegetation changes during Dansgaard-Oeschger (D-O) cycles during the last glacial. During the period from the cold phase (GS 18/19) to warm phase (D-O 19), the biome shift from temperate conifer forest to cold/cool conifer forest in Japan and from subtropical forest to...

Dispersion and deposition of terrestrial organic matter by flooding on the inner shelf were studied using C/N ratios, δ13C, and Δ14C values of sedimentary organic matter. Surface sediment samples (top 2 cm) were collected from coastal areas near the Saru River in southwestern Hokkaido, northern Japan, 1 yr after a flood event in 2006. Riverine susp...

The micro-bivalve Carditella iejimensis inhabits the sediment surface within submarine caves at Ie Island, Okinawa, Japan. A comparison of the δ18O values (δ18Oaragonite) of empty and living shells indicates that the shell is formed over several seasons, and that the main cause of mortality is low water temperature. According to this hypothesis, it...

We investigated centennial-scale temperature variations in sea surface temperature (SST) in Core KY07-04 PC-1 and PL-1 taken from the northern East China Sea during the last 5000 years by the application of UK37' and TEX86 paleothermometry. We also investigated the concentrations of glycerol diphytanyl glycerol tetraethers (GDGTs), which is used fo...

No abstract available. doi:10.2204/iodp.sd.8.08.2009

Scientific drilling on land and sea has played a key role in advancing our knowledge of climate change. It has helped to demonstrate the effects of orbital variations on climate, revealed evidence for extreme warm events in the past and for the timing of Antarctic ice growth, and provided insights into the hydrologic balance of lake systems around...

Suborbital climate variability during the last glacial period was characterized by a periodicity of 1,470 years, but the expression and spatial distribution of the ~1,500-year oscillation during interglacials are not clear. Here we generated a multi-decade-resolution record of alkenone sea-surface temperatures (summer SST) off central Japan in the...

In order to reconstruct past variations in the aeolian dust (Kosa) contribution to the Japan Sea, and to establish a direct link between terrestrial and marine climatic records, we have applied statistical procedures to distinguish and quantify detrital subcomponents within the detrital fraction of the late Quaternary hemipelagic sediments in the J...

Suborbital climate variability during the last glacial period is suggested to have involved a 1500-year pacing cycle, but the expression and spatial distribution of the ~1500-year oscillation during interglacials remains unclear. We generated a multidecade resolution record of alkenone sea surface temperature (SST) in the northwestern Pacific off c...

We measured the δ18O values of the whole shells of the cavernicolous micro-bivalvia Carditella iejimensis obtained from sediments within a submarine cave (31 m water depth) at Ie Island (Okinawa Island, Japan) in the subtropical Northwest Pacific. Our results show no significant millennial-scale trend in the δ18O record, implying that both springti...

To understand the main controlling factors of coral skeletal carbon isotope ratio (δ13Cc), we undertook high-temporal-resolution (∼1.5 d) measurements of δ13Cc for Porites lutea collected from the east coast of Hainan Island, China. The results were compared with factors that have previously been proposed to control coral δ13Cc: skeletal extension...

We propose skeletal δ18O of Platygyra, a hermatypic reef building massive coral, as a potential paleo-SST proxy in midlatitude regions, where the commonly used massive Porites corals are rare. Skeletal δ18O ratio (δ18Oc) of a Platygyra and Porites corals collected from Ishigaki Island, Japan, shows a clear seasonality corresponding to SST variation...

Glacio-eustatic sea-level fluctuations and subsequent paleoceanographic changes in the East Sea (Sea of Japan) have been identified by unique sedimentary features and their geochemical properties throughout the late Quaternary sediments. These events were synchronous basin wide. The effect of sea-level change in the East Sea is fundamental to the a...

For better understanding of carbon isotope systematic of coral skeleton, two different coral species growing next to each other, Porites sp. and Platygyra ryukyuensis, were collected at a site from Ishigaki Island, Japan, and analyzed for oxygen and carbon isotope ratios. Oxygen isotope ratios of both corals show seasonal variations well matching e...

本研究は，鹿島沖から採取された長さ約46 mのMD01-2421コアに介在する23枚のテフラについて，岩石学的記載と火山ガラスの主元素組成分析を行い，既知のテフラとの対比を試みたものである．その結果，九州起源のATとAso-4，御岳山を給源とし中部～東北地方に広く分布するOn-Pm1，北関東に分布するAg-KP，南関東に分布するHk-TP，立山カルデラ起源のTt-D，福島県南部と茨城県北部で対比されているNm-Tgが同定された．また，本コアで得られている高分解能の底生有孔虫の酸素同位体層序を使用して，各テフラの噴出年代を算出し，SPECMAP年代に伴う誤差も合わせて示した．対比された7枚のテフラの噴出年代を，報告されている放射年代や花粉分析や海水準変動史から予想されていた噴出年代と比較して議...

Flood event is an event to supply large amount of terrigenous materials to marine environments. Thus, it is very important process for sea bottom environments, material cycles in the ocean, and strata formation. Mode of dispersion and deposition of flood sediments and its controlling factor is not fully clarified yet. In August 2003, hard rain by t...

An important part of global organic carbon cycle is the flux of terrestrial organic carbon from the continents to the oceans. The potential importance of coastal systems in global and regional organic budgets is still unclear because of the inherent complexity and variability of rivers, estuaries and coastal zones. Therefore, it is important to und...

We carried out a marine geological survey on the shelf off Hidaka, southern Hokkaido in 2005 and 2006, and 2 and 3 years after the severe flood in August, 2003. Bottom water turbidity based on sea-bottom photographs generally decreases offshore. It is higher in front of each river mouth than the surrounding area on the inner to middle shelf, showin...

The difference between benthic and planktonic foraminifera radiocarbon (B–P 14C) age differences in core PC6 (40° 23.89′ N, 143° 29.87′ E) retrieved from the northwestern North Pacific provide a clue to the reconstruction of deep water circulation during the last deglaciation and the early Holocene (15-5 cal. kyr B.P.). The observed B–P 14C age dif...

Paleoceanographic conditions in the Japan Sea changed drastically during the Late Quaternary in association with orbital and suborbital cycles and glacio-eustatic sea level changes. However, few studies have examined long-term sediment records older than 160 ka because of the lack of long and continuous cores and the difficulty in constructing high...

Orbital- and millennial-scale variations in the Asian monsoon and its probable association with the Dansgaard–Oeschger (D–O) Cycles have been demonstrated by previous studies. However, the origin and nature of such variations are poorly understood. The Japan Sea is located down wind of the arid areas of the Eurasian continent, and thus receives sig...

A sediment layer (43 cm thick) and surface sediments (5 cm thick) in a submarine limestone cave (31 m water depth) on the fore-reef slope of Ie Island, off Okinawa mainland, Japan, were examined by visual, mineralogical and geochemical means. Oxygen isotope analysis was performed on the cavernicolous micro-bivalve Carditella iejimensis from both co...

Holocene suborbital climate variability is a recent topic. Here we present a multi-decadal resolution record of alkenone sea surface temperature (summer SST) from Cores MD01-2421, KR02-06 St. A, MC1 and MC2 off central Japan in the northwestern Pacific during the Holocene. SST increased by ~10°C from ~12 ka to ~8 ka (22.3°C) and decreased by ~6°C f...