Jonaotaro Onodera

Jonaotaro Onodera
Japan Agency for Marine-Earth Science Technology | JAMSTEC · Research Institute for Global Change

D.Sc.

About

94
Publications
10,190
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
2,809
Citations
Citations since 2017
19 Research Items
991 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150

Publications

Publications (94)
Article
Full-text available
The recent influx of microplastics into the Arctic Ocean may increase environmental stress on the western Arctic marine ecosystem, which is experiencing significant sea-ice loss due to global warming. Quantitative data on microplastics in the western Arctic Ocean are very limited, and the microplastic budget of the water column is completely unknow...
Article
Full-text available
The processes of seafloor sediment transport from the Chukchi shelf to the western Arctic basin were investigated using a pan‐Arctic sea ice‐ocean model and sediment‐trap measurements at four mooring stations: North of Barrow Canyon, North of Hanna Canyon, Northwind Abyssal Plain, and Chukchi Abyssal Plain. The available sediment‐trap data verified...
Article
Full-text available
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...
Article
Full-text available
Time series monitoring of hydrography and marine settling particles supplies a large amount of information regarding the marine lower‐trophic ecosystem with respect to the changing Arctic Ocean. To investigate the interannual relationship between the settling particles and hydrographic conditions of the western Arctic Ocean, bottom‐tethered sedimen...
Article
Full-text available
During Heinrich Stadial 1 (HS1, 18.0–14.7 kyr ago), the Bering and Okhotsk Seas in the western Subarctic Pacific (SAP) exhibited boundary conditions that enhanced intermediate water convection. However, little is known about the quantitative contribution of the intermediate waters from the Bering and Okhotsk Sea (BSIW and OSIW) to ventilation in th...
Article
Full-text available
We studied time‐series fluxes of radiolarian particles collected by two sediment traps deployed at the eastern (Sta. NAP12t) and western (Sta. CAP12t) sides of the Chukchi Borderland in the Chukchi Sea from 04 October 2012 to 18 September 2013. In order to elucidate the contribution of radiolarian skeletons to the biogenic silica flux, a three‐dime...
Article
Full-text available
Biosynthesis of hydrocarbons is a promising approach for the production of alternative sources of energy because of the emerging need to reduce global consumption of fossil fuels. However, the suitability of biogenic hydrocarbons as fuels is limited because their range of the number of carbon atoms is small, and/or they contain unsaturated carbon b...
Article
We investigated the transport and heat loss of the Pacific Summer Water (PSW) along the Chukchi Sea northern slope using the temperature, salinity, and velocity data of the mooring time series obtained in 2003–2005 (Period 1) and 2015–2019 (Period 2). The PSW at Stations HSN/NHC on the Chukchi Sea northern slope was warmer and fresher in Period 2 t...
Article
Full-text available
Ocean observation research theme under ArCS project, “Theme 4: Observational research on Arctic Ocean environmental changes”, aimed to elucidate the status and trends of ongoing Arctic Ocean environmental changes and to evaluate their impacts on Arctic marine ecosystem and the global climate system. For these purposes, we conducted field observatio...
Article
The Arctic Ocean is characterized as the greatly variable oceanic environment both seasonality and regionally. Such environmental variability would affect regional differences in the respective copepod community structures, though it has not been reported so far. In this study, we analyzed time-series zooplankton samples with focus on large copepod...
Article
Full-text available
The shallow Chukchi Sea is a gateway to the Arctic Ocean for Pacific‐origin waters. While a substantial portion of the Pacific‐origin waters flows through Barrow Canyon in the northeast corner of the Chukchi Sea, little is known on the hydrography of the surrounding regions in winter. We present profiles of wintertime hydrography on the Chukchi slo...
Article
In this study, intra-annual variation of near-inertial internal wave (NIW) in the Arctic Ocean is examined using year-round mooring in the Northwind Abyssal Plain. Our emphasis is on dynamical responses of NIW to local sea-ice variables such as concentration, draft, and drift. We obtained those using a coupling system of ice profiling sonar (IPS) a...
Article
In recent years, marine ecosystems have changed due to the drastic sea ice reduction in the Arctic Ocean, but the relationship between copepod phenology and environmental drivers is unclear. To reveal the relationship, seasonal changes in the flux (abundance of swimmers), population structure, lipid accumulation and gonad maturation of four dominan...
Article
Full-text available
The recent increasing of atmospheric turbulence has had considerable impact on the oceanic environment and ecosystems of the Arctic. To understand its effect on phytoplankton community structure, a Eulerian fixed-point observation (FPO) was conducted on the Chukchi shelf in fall 2013. Temporal and vertical distributions of the phytoplankton communi...
Article
Full-text available
Our understanding of the paleoceanography of the Bering Sea has been considerably advanced by IODP Expedition 323. The expedition aimed to create a high-resolution record of changes in paleoceanography since the Pliocene in a relatively high-latitude region of the North Pacific, subject to polar amplification. The expedition recovered 660 cores, ma...
Article
Winter subsurface transport of the Pacific-origin warm water toward the Arctic Chukchi Borderland located west of the Canada Basin was investigated by mooring measurements and modeling analyses. In mid-winter or spring of 2011-2014, subsurface warming signals under sea ice were detected by the multi-year bottom-tethered mooring data in the Chukchi...
Article
Late Pliocene-Pleistocene fossil diatom assemblages from Ocean Drilling Program (ODP) Leg 145 Hole 884B in the western subarctic Pacific were investigated to improve the diatom biostratigraphy. Moreover, the paleoceanographic records at Hole 884B were compared with those in Integrated Ocean Drilling Program (IODP) Expedition 323 Holes U1341B and U1...
Article
Full-text available
Spatial and temporal variations in major phytoplankton populations such as diatoms in the changing Arctic Ocean have been well studied, whereas only a few monitoring studies have been conducted on minor siliceous flagellates. To discern the relationship between hydrographic conditions and the spatio-temporal distribution of silicoflagellates, ebrid...
Article
To examine seasonal changes in the mesozooplankton community, analyses were made on the swimmer samples (>1 mm) collected by a sediment trap mooring at 184 m depth on the Northwind Abyssal Plain in the western Arctic Ocean during October 2010–September 2011. The zooplankton swimmer flux ranged from 5 to 44 ind. m−2 day−1 and was greater during July...
Article
Full-text available
Seasonal and interannual variability in the biogenic particle sinking flux was recorded using multi-year bottom-tethered sediment trap mooring systems in the Northwind Abyssal Plain (Station NAP: 75° N, 162° W, 1975 m water depth) of the western Arctic Chukchi Borderland. Trapped particle flux at a median depth of 184 m had an obvious peak and domi...
Article
The future conditions of Arctic sea ice and marine ecosystems are of interest not only to climate scientists, but also to economic and governmental bodies. However, the lack of widespread, year-long biogeochemical observations remains an obstacle to understanding the complicated variability of the Arctic marine biological pump. Here we show an earl...
Article
Full-text available
Warming of high northern latitudes in the Pliocene (5.33-2.58 Myr ago) has been linked to the closure of the Central American Seaway and intensification of North Atlantic Deep Water. Subsequent cooling in the late Pliocene may be related to the effects of freshwater input from the Arctic Ocean via the Bering Strait, disrupting North Atlantic Deep W...
Article
Full-text available
Winter ice cover of the Arctic Ocean makes year-round zooplankton sampling by plankton net a difficult task. Therefore, the collection of copepods with a sediment trap can be a powerful tool. In the present study, we analysed the seasonal changes in the population structures of five dominant planktonic copepods (Oncaea parila, Calanus hyperboreus,...
Article
Full-text available
An increase in atmospheric turbulence in the Chukchi Sea due to the recent drastic sea-ice reduction during summer months has been reported. The importance of the effects of this atmospheric turbulence on the marine ecosystem in this region, however, is not fully understood. To evaluate the effects of atmospheric turbulence on the marine ecosystem,...
Article
Site U1341 in the southern Bering Sea was drilled and cored down to 600 meters below sea-floor (mbsf) during Integrated Ocean Drilling Program (IODP) Expedition 323, covering a nearly complete record of the last 4.3 million years (Myrs). Analyses of the biogenic opal content of sediments at the site provide detailed and useful information on past b...
Article
Full-text available
Seasonal and interannual variability in sinking flux of biogenic particles was reported by the multi-year bottom-tethered sediment trap measurements in the Northwind Abyssal Plain (Station NAP: 75° N, 162° W, 1975 m water depth) of the western Arctic Chukchi Borderland. Whereas the trapped particle flux had an obvious peak with the dominance of sea...
Article
Full-text available
The vertical distribution of radiolarians was investigated using a vertical multiple plankton sampler (100– 0, 250–100, 500–250, and 1000–500 m water depths, 62 µm mesh size) at the Northwind Abyssal Plain and southwestern Canada Basin in September 2013. To investigate seasonal variations in the flux of radiolarians in relation to sea ice and water...
Article
Full-text available
We studied time-series fluxes of diatom particles from 4 October 2010 to 18 September 2012 using bottom-tethered moorings with two sediment traps deployed at 180 and 1300 m depths at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. This paper discusses on the relationship of time-series diatom fluxes to satellite-based s...
Article
Full-text available
The vertical distribution of radiolarians was investigated using a vertical multiple plankton sampler (100–0, 250–100, 500–250 and 1000–500 m water depths, 62 μm mesh size) at the Northwind Abyssal Plain and southwestern Canada Basin in September 2013. To investigate seasonal variations in the flux of radiolarians in relation to sea-ice and water m...
Article
Full-text available
We studied time-series fluxes of diatom particles and their relationship to hydrographic variations from 4 October 2010 through 18 September 2012 using bottom-tethered sediment trap moorings deployed at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. We observed clear maxima of the diatom valve flux in November–December...
Article
Full-text available
The future conditions of Arctic sea ice and marine ecosystems are of interest not only to climate scientists, but also to economic and governmental bodies. However, the lack of widespread, year-long biogeochemical observations remains an obstacle to understanding the complicated variability of the Arctic marine biological pump. Here we show an earl...
Article
Full-text available
To examine seasonal changes in the mesozooplankton community, analyses were made on the swimmer samples (>1 mm) collected by a sediment trap mooring at 184 m depth on the Northwind Abyssal Plain in the western Arctic Ocean during October 2010–September 2011. The zooplankton swimmer flux ranged from 5 to 44 ind. m−2 day−1 and was greater during July...
Article
The biogeographic characteristics and interannual variation of diatom and silicoflagellate floral fluxes are outlined in the western North Pacific, the Bering Sea, and the Arctic Ocean, based on the time-series sediment trap studies at Stations NAP10t, AB, SA, 50N, K2, KNOT, 40N, and S1. In this paper, two paleoceanographic studies are also introdu...
Article
The biostratigraphy and datum levels of diatoms, silicoflagellates, and ebridians are presented at Site U1341 drilled by the IODP Expedition 323 on the western slope of Bowers Ridge in the Bering Sea. Identified biostratigraphic diatom zones were from the Neodenticula seminae Zone to the Thalassiosira oestrupii Subzone. Silicoflagellate and ebridia...
Article
Full-text available
PARLUX type sediment traps were moored at 600 m above the sea-floor at Station SA (water depth: 5,406 m) in the central subarctic Pacific and at Station AB (water depth: 3,788 m) in the Aleutian Basin of the Bering Sea. The time-series flux samples were obtained during 1990-2010 for nineteen years. This allowed us to characterize primary fluxes of...
Article
To determine the influence of oceanographic conditions on silicoflagellate assemblages, sinking fluxes and composition of silicoflagellates were studied from August 1990 to July 1994 at two long-term monitoring sites: Station AB in the Bering Sea (53.5°N, 177°W) and Station SA in the northern subarctic Pacific Ocean (49°N, 174°W). Total silicoflage...
Article
Full-text available
We reconstructed the ventilation record of deep water at 2100 m depth in the mid-latitude western North Pa-cific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sedi-ment with a high sedimentation rate. The 14 C data on frag-ile and robust planktic foraminiferal shells were concordant wi...
Article
Full-text available
We reconstructed the ventilation record of deep water at 2100 m depth in the mid-latitude western North Pacific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sediment with a high sedimentation rate. The <sup>14</sup>C data on fragile and robust planktic foraminiferal shells were concor...
Article
The Bering Strait is the gateway between Pacific and Arctic, plays an important role in global freshwater cycle and eventually influences on climate change. The glacial Pacific Ocean had well-ventilated and nutrient-depleted glacial North Pacific Intermediate Water (GNPIW) above ~2000 m. GNPIW is a thicker and more deeply penetrating water mass tha...
Article
It is fundamental importance to understand the roles of oceanic biological export production and its response to the long-term global climate regime. Since 1990, we have continued observation of sinking particle using by T/S sediment trap at the Bering Sea Station AB: 53° 30 N, 177° W, sea- floor depth: 3788 m, trap depth: 3198m) and the central su...
Article
We studied microbially mediated diagenetic processes driven by carbon mineralization in subseafloor sediment of the northeastern Bering Sea Slope to a depth of 745 meters below seafloor (mbsf). Sites U1343, U1344 and U1345 were drilled during Integrated Ocean Drilling Program (IODP) Expedition 323 at water depths of 1008 to 3172 m. They are situate...
Conference Paper
IODP Exp 323 drilled 7 sites to study Bering Sea paleoceanography, and recovered 5741 m of high quality sediments with high sedimentation rates covering the last 5 myrs. The sites included hemipelagic Bowers Ridge and a N-S transect of slope sites proximal to the Bering shelf, covering water depths from 818 to 3174 m. The bulk of the cores were obt...
Conference Paper
We present records of benthic and planktonic foraminifera from deep-sea Sites U1340 and U1341, collected from Bowers Ridge in the southern Bering Sea, and Sites U1343 and U1344, collected from the northern Aleutian Basin. They comprise abundant calcareous benthic species that are indicative of reduced oxygen conditions (e.g. Bulimina, Globobulimina...
Data
The silicoflagellate and ebridian assemblages in early middle Eocene Arctic cores obtained by IODP Expedition 302 (ACEX) were studied in order to decipher the paleoceanography of the upper water column. The assemblages in Lithologic Unit 2 (49.7-45.1 Ma), one of the biosiliceous intervals, were usually endemic as compared to the assemblages that oc...
Article
The water masses of the central and western equatorial Pacific can be divided into two parts: the Western Pacific Warm Pool (WPWP) and the Equatorial Upwelling Region (EUR). The behavior of the WPWP plays a significant role in global climate changes such as the El Niño-Southern Oscillation (ENSO), and it drastically modifies the oceanographic condi...
Article
Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) obtained the first relatively continuous long sediment cores from the Lomonosov Ridge in the central Arctic Ocean in 2004. Preceding microfossil studies indicated the dominance of low salinity surface waters in the early to middle Eocene Arctic basin. The main p...
Article
Diatom sinking fluxes at Sites MT3-MT7 in the western Equatorial Pacific in 1999-2002 were studied in order to decipher the ecological relationships between the diatom fluxes and environmental conditions such as water temperature and salinity. As a supplement for those studies, this paper contains the compiled data tables of diatom fluxes at Sites...
Article
Long-term monitoring of diatom fluxes during 1990–1998 was conducted at Station AB in the Bering Sea and Station SA in the central subarctic Pacific in order to decipher the relationships between sinking diatom and the upper water mass environments. The total diatom flux at Station AB was generally twice as high as that at Station SA. The dominant...
Article
Diatoms were obtained on three different circumstances, sea-ice, sea-water, and diatom mat samples, at four different locations in the central Arctic Ocean during August and September 2004. One hundred twenty diatom taxa belonging to 38 genera, 14 of which were centric and 22 of which were pennate, were recognized in these samples. Even within the...
Article
The silicoflagellate taxa obtained in IODP Expedition 302 (ACEX) were identified and counted in order to establish the silicoflagellate biostratigraphy in the central Arctic Ocean. These microfossils in the ACEX samples were preserved in the Lithology Units 1/6 and 2, which are dark silty clay and biosiliceous ooze, respectively. The silicoflagella...
Article
Abundant and diversified ebridians recovered during IODP Expedition 302 (ACEX) have been identified and counted in order to establish their taxonomy and to decipher the biostratigraphic potential of ebridians in the central Arctic Ocean. In the ACEX samples these fossils are preserved in Lithologic Units 1/6 and 2, which consist mainly of dark silt...
Article
The Arctic Coring Expedition (ACEX) carried out in 2004 by the Integrated Ocean Drilling Program (IODP) afforded us the opportunity to obtain seawater and sea-ice samples at four different times and locations including the North Pole in the central Arctic Ocean. We performed taxonomic and census investigation on extant silicoflagellates in the samp...
Data
Integrated Ocean Drilling Program (IODP) Expedition 302 Arctic Coring Expedition (ACEX) obtained the first relatively continuous long sediment cores from the Lomonosov Ridge in the central Arctic Ocean in 2004. Preceding microfossil studies indicated the dominance of low salinity surface waters in the early to middle Eocene Arctic basin. The main p...
Article
IODP Exp. 302 (Arctic Coring Expedition - ACEX) revealed that the paleo-geography of the Arctic Ocean in the early middle Eocene was a semi-closed basin similar to the modern Black and the Baltic Seas, based on many paleoceanographic proxies. The primary composition of the microfossil assemblages of the middle Eocene ACEX cores included silicoflage...
Article
Full-text available
The silicoflagellate and ebridian assemblages in early middle Eocene Arctic cores obtained by IODP Expedition 302 (ACEX) were studied in order to decipher the paleoceanography of the upper water column. The assemblages in Lithologic Unit 2 (49.7-45.1 Ma), one of the biosiliceous intervals, were usually endemic as compared to the assemblages that oc...
Article
The early middle Eocene sediments from the central Arctic Ocean obtained by IODP Expedition 302 (ACEX) were studied for the siliceous microfossils of silicoflagellates and ebridians in order to establish the biostratigraphy and to decipher the paleoceanographic changes of the upper water column. Seven silicoflagellate taxa of the total of 56 taxa a...
Article
With the currently predicted drastically different future environments of the Arctic Ocean without perennial sea-ice cover, it is important to learn how the ice-free Arctic basin behaved in the past. The environmental reconstruction of the middle Eocene Arctic basin explored by the IODP Arctic Coring Expedition (ACEX) provides excellent opportunity...
Article
Full-text available
Diatom oxygen isotope measurements are commonly made on bulk mixed species assemblages due to the difficulty in purifying and separating individual taxa. As such, it is essential to understand processes in diatoms which may lead to isotope offsets both between and within individual species. Existing studies have suggested that mechanisms which may...
Article
The one hundred seventy two photomicrographs for major diatoms and siliceous flagellates in the pelagic northwestern subarctic Pacific are presented here as supplemental information for our previous publication on diatom and silicoflagellate flux studies at Stations 50N, KNOT, and 40N in the subarctic Pacific. As the siliceous flagellates, silicofl...
Article
The IODP Leg 302 Arctic Coring Expedition retrieved approximately 120 m long continuous Eocene section from the Lomonosov Ridge in the central Arctic for the first time. The Eocene section is lithologically classified into Unit 2 with the assigned age of ~49-44Ma below and Unit 1/6 with 44Ma above the unit boundary. Unit 2 consists of very dark gra...
Article
Diatom oxygen isotope measurements are commonly made on bulk mixed species assemblages due to the difficulty in purifying and separating individual taxa. As such, it is essential for vital effects in diatoms to be fully understood. Existing studies have suggested diatom oxygen isotope vital effects to be either non-existent or negligible. Here, we...
Article
The early middle Eocene Arctic samples, which were obtained by IODP Expedition 302 (ACEX), were studied for the siliceous microfossils of silicoflagellates and ebridians in order to decipher the paleoceanographic changes of the upper water column. The presence of low salinity waters in the Eocene Arctic is suggested from the co-occurrence of freshw...