Subjects -> EARTH SCIENCES (Total: 771 journals)
    - EARTH SCIENCES (527 journals)
    - GEOLOGY (94 journals)
    - GEOPHYSICS (33 journals)
    - HYDROLOGY (29 journals)
    - OCEANOGRAPHY (88 journals)

OCEANOGRAPHY (88 journals)

Showing 1 - 77 of 77 Journals sorted by number of followers
Deep Sea Research Part II: Topical Studies in Oceanography     Hybrid Journal   (Followers: 29)
Deep Sea Research Part I : Oceanographic Research Papers     Hybrid Journal   (Followers: 23)
Estuaries and Coasts     Hybrid Journal   (Followers: 23)
Limnology and Oceanography     Hybrid Journal   (Followers: 22)
Progress in Oceanography     Hybrid Journal   (Followers: 21)
Journal of Marine Biology & Oceanography     Hybrid Journal   (Followers: 19)
New Zealand Journal of Marine and Freshwater Research     Hybrid Journal   (Followers: 18)
Journal of Physical Oceanography     Hybrid Journal   (Followers: 18)
Frontiers in Marine Science     Open Access   (Followers: 17)
Journal of Marine Sciences     Open Access   (Followers: 17)
Coastal Engineering     Hybrid Journal   (Followers: 15)
Advances in Oceanography and Limnology     Open Access   (Followers: 15)
Journal of Oceanography     Hybrid Journal   (Followers: 14)
Maritime Studies     Open Access   (Followers: 13)
International Journal of Oceanography     Open Access   (Followers: 12)
Advances in Statistical Climatology, Meteorology and Oceanography     Open Access   (Followers: 11)
Atmospheric and Oceanic Science Letters     Open Access   (Followers: 10)
Bulletin of Marine Science     Full-text available via subscription   (Followers: 9)
Fisheries Oceanography     Hybrid Journal   (Followers: 8)
Journal of Oceanography and Marine Science     Open Access   (Followers: 7)
Open Journal of Marine Science     Open Access   (Followers: 6)
Limnology and Oceanography: Methods     Hybrid Journal   (Followers: 6)
Journal of Operational Oceanography     Hybrid Journal   (Followers: 6)
Physical Oceanography     Hybrid Journal   (Followers: 6)
Paleoceanography and Paleoclimatology     Full-text available via subscription   (Followers: 5)
Marine Science     Open Access   (Followers: 5)
Limnology and Oceanography: Fluids and Environments     Full-text available via subscription   (Followers: 5)
Ocean Yearbook Online     Hybrid Journal   (Followers: 4)
Journal of Oceanology and Limnology     Hybrid Journal   (Followers: 4)
Limnology and Oceanography Letters     Open Access   (Followers: 4)
Journal of Marine Science and Engineering     Open Access   (Followers: 4)
African Journal of Marine Science     Hybrid Journal   (Followers: 4)
Oceanology     Hybrid Journal   (Followers: 3)
Journal of Aquatic Sciences     Full-text available via subscription   (Followers: 3)
Limnology and Oceanography e-Lectures     Open Access   (Followers: 3)
Journal of Coastal Development     Open Access   (Followers: 3)
Ciencias Marinas     Open Access   (Followers: 3)
Journal of Marine Science and Application     Hybrid Journal   (Followers: 3)
Journal of Ocean Engineering and Marine Energy     Hybrid Journal   (Followers: 3)
Tropical Oceanography     Open Access   (Followers: 2)
Indian Journal of Geo-Marine Sciences     Open Access   (Followers: 2)
Mediterranean Marine Science     Open Access   (Followers: 2)
Regional Studies in Marine Science     Hybrid Journal   (Followers: 2)
Annals of Marine Science     Open Access   (Followers: 2)
Limnology and Oceanography: Bulletin     Hybrid Journal   (Followers: 2)
Annals of Limnology and Oceanography     Open Access   (Followers: 2)
Development and Applications of Oceanic Engineering     Open Access   (Followers: 2)
Journal of Ocean Engineering and Technology     Open Access   (Followers: 1)
Ocean Life     Open Access   (Followers: 1)
Marine Systems & Ocean Technology     Hybrid Journal   (Followers: 1)
Journal of Ocean University of China (English Edition)     Hybrid Journal   (Followers: 1)
Marine Life Science & Technology     Hybrid Journal   (Followers: 1)
Journal of Ocean Engineering and Science     Open Access   (Followers: 1)
Coastal Engineering Proceedings : Proceedings of the International Conference on Coastal Engineering     Open Access   (Followers: 1)
Marine Technology Society Journal     Full-text available via subscription   (Followers: 1)
Scientia Marina     Open Access   (Followers: 1)
Western Indian Ocean Journal of Marine Science     Open Access   (Followers: 1)
Asian Journal of Fisheries and Aquatic Research     Open Access  
Thalassas : An International Journal of Marine Sciences     Hybrid Journal  
Oceans     Open Access  
Aquatic Research     Open Access  
Jurnal Kelautan Tropis     Open Access  
Acta Aquatica : Aquatic Sciences Journal     Open Access  
Depik Jurnal Ilmu-Ilmu Perairan, Pesisir dan Perikanan     Open Access  
Journal of Agricultural and Marine Sciences     Open Access  
Turkish Journal of Maritime and Marine Sciences     Open Access  
Arquivos de Ciências do Mar     Open Access  
Scientific Drilling     Open Access  
Jurnal Kelautan : Indonesian Journal of Marine Science and Technology     Open Access  
Oceanologia     Open Access  
Revista de Gestão Costeira Integrada     Open Access  
Revista Ciencias Marinas y Costeras     Open Access  
Egyptian Journal of Aquatic Research     Open Access  
China Ocean Engineering     Hybrid Journal  
Revista de Biología Marina y Oceanografía     Open Access  
Latin American Journal of Aquatic Research     Open Access  
Acta Oceanologica Sinica     Hybrid Journal  
Similar Journals
Journal Cover
Journal of Oceanography
Journal Prestige (SJR): 0.989
Citation Impact (citeScore): 2
Number of Followers: 14  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1573-868X - ISSN (Online) 0916-8370
Published by Springer-Verlag Homepage  [2467 journals]
  • The island mass effect: a study of wind-driven nutrient upwelling around
           reef islands

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      Abstract: Abstract Using the method of process-oriented modelling, this study explores wind-driven upwelling features around reef islands of the tropical Pacific Ocean. The three-dimensional hydrodynamic model is coupled to a nutrient-phytoplankton (NP) model to simulate the creation of phytoplankton blooms initiated by the wind-driven upwelling of nutrients into the euphotic zone. Findings demonstrate that short-lived wind events of 2–5 days in duration, which are typical of tropical regions, can lead to significant phytoplankton blooms near reef islands. This finding agrees with observational evidence. Comparison studies reveal that the total phytoplankton production increases for higher wind speeds, longer durations of wind events and larger reef islands, and that it decreases with stronger static stability of the pycnocline. Overall, our findings indicate that wind-driven nutrient upwelling supports the ecosystem functioning around larger tropical reef islands.
      PubDate: 2022-12-03
       
  • Quality control of potentiometric pH measurements with a combination of
           NBS and Tris buffers at salinities from 20 to 40 and pH from 7.2 to 8.6

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      Abstract: Abstract Seawater pH is a valuable parameter to describe ocean acidification. However, pH measurements are often subject to large uncertainty and the results of the pH comparison from different laboratories are not convincing. We assessed the potentiometric method for pH measurement on seawater samples with salinities from 20 to 40 and pH ranging from 7.2 to 8.6. pH glass electrodes were calibrated using both commercially available NBS buffers and the equimolal Tris (2‐amino‐2‐hydroxymethyl‐1,3‐propanediol) buffer (prepared in synthetic seawater at a salinity of 35). The results demonstrated that the uncertainty in pH measurements was within ± 0.01 in the entire salinity range and was better than ± 0.003, when the sample salinity was close to that of equimolal Tris buffer (salinity difference within ± 2.5), regardless of the sample pH. This study suggests that if the electrode calibration is performed properly, the potentiometric method can fulfill the “weather” goal (± 0.02) of the Global Ocean Acidification Observing Network in pH measurements; it might even meet the “climate” goal (± 0.003) if the difference between the salinity of the samples and the Tris buffer is small.
      PubDate: 2022-12-01
       
  • Sea level variability along the Japanese coast forced by the Kuroshio and
           its extension

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      Abstract: Abstract Sea level variability along the Japanese coast and its relation to the Kuroshio-Kuroshio Extension (KE) are investigated using ocean reanalysis data. The first mode of an empirical-orthogonal-function for the coastal sea-level represents a simultaneous sea-level change along the whole Japanese coast, which is synchronized with sea levels in the KE region , the Japan Sea and the East China Sea. The second mode is characterized by an east–west dipole pattern at the south coast. The first mode is correlated with the Kuroshio variations around the Izu–Ogasawara Ridge (IOR) and tends to be in a positive phase when the Kuroshio takes a nearshore path around IOR. The Kuroshio’s position around IOR is closely related to the KE dynamic state. When the KE jet is in a stable (unstable) state, a nearshore (meandering) Kuroshio path is formed around IOR. A composite analysis suggests that the sea level along the Japanese coast becomes high due to propagation of coastal trapped waves when the Kuroshio takes a nearshore path around IOR. That is why the first mode is synchronized with the KE decadal variability. The second mode has a close relation with the Kuroshio Large Meander (LM). The eastern positive anomaly at the coast between the Izu and Kii Peninsulas is formed by warm Kuroshio water brought by a westward branch flow along the coast. The western negative anomaly is attributed to a southward shift in the Kuroshio south of the Kii Peninsula associated with the LM.
      PubDate: 2022-12-01
       
  • Distribution characteristics of pycnocline in the northern South China Sea
           based on an improved vertical gradient method

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      Abstract: Abstract Pycnocline is a widespread marine phenomenon across the world, which plays an important role in ocean engineering, oceanic meteorology, and biological applications. In this study, based on actual density data, statistical characteristics of complex density profiles are analyzed. It is found that the pycnocline interval \(d\) in multilayer structures conforms to the three-parameter Weibull distribution. To describe the multilayer structure more accurately, a dimensionless parameter \(\alpha\) is proposed, which takes into account scale effects and the relative position of layers. Then, the probability density distribution of \(\alpha\) is analyzed, from which the clustering phenomena are found. Therefore, clustering analysis is carried out to obtain a method for determining the location of pycnocline in complex density profiles. Based on this method, the statistical research of pycnocline distribution in the northern South China Sea is carried out including the key properties of pycnocline depth, pycnocline thickness, and pycnocline intensity. The result shows that the pycnocline distribution changes periodically with seasons, in which heat flux and monsoon are the main influencing factors. As the temperature increases, the formation of the pycnocline is encouraged, with the consequent decrease in pycnocline depth and increase in pycnocline thickness and intensity, vice versa. The monsoon influences the distribution of the pycnocline by affecting vertical mixing and Ekman wind-driven mechanism.
      PubDate: 2022-12-01
       
  • Superposition of coastal-trapped waves and Kuroshio warm water intrusions
           caused unusually high sea levels around the southern coasts of Japan in
           early September 1971

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      Abstract: Abstract Unusually high sea level (UHSL) in early September 1971, which caused coastal flooding around the southern coasts of Japan despite no severe weather conditions, is examined using a coastal assimilation system with 2-km resolution. The observed duration of high sea-level anomalies (SLAs) for the UHSL was successfully represented by assimilation results. Through sensitivity experiments, we investigated the contribution of two factors, the wind and the Kuroshio effects, as suggested by previous research. The northeasterly winds associated with Typhoon 7123 induced coastal-trapped waves (CTWs) along the Kashima-nada Sea. The CTWs propagated clockwise along the coast at a speed of about 2.3 m/s and caused the sea level to increase by about 15 cm in Sagami and Tokyo Bays. A cold eddy associated with a Kuroshio meander was formed, and as a result, the warm Kuroshio water intruded into the Enshu-nada Sea due to the northward flow in the eastern flank of the eddy. The warm water intrusion significantly contributed to the duration of SLAs of about 30 cm around the Enshu-nada and Kumano-nada Seas. It was also shown that the high SLAs for the UHSL were quantitatively explained by the sum of the two factors. Thus, we conclude that the UHSL event was caused by the superposition of the wind-induced CTWs and the Kuroshio-induced warm water intrusions.
      PubDate: 2022-12-01
       
  • Identification of Kuroshio meanderings south of Japan via a topological
           data analysis for sea surface height

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      Abstract: Abstract This study proposes an algorithm to identify stable Kuroshio meanderings by extracting topological features from a sea surface height (SSH) gridded dataset in 1993–2020. Based on the mathematical theory of topological classifications for streamline patterns, the algorithm provides a unique symbolic representation and a discrete graph structure, which is referred to as the partially cyclically ordered rooted tree (COT) representation and the Reeb graph, respectively, to structurally stable Hamiltonian vector fields. We have confirmed that the temporal variations in the Kuroshio southernmost position south of the Tokai district captured by the algorithm are well consistent with the existing results by the Japan Meteorological Agency (JMA). The algorithm based on the topology detects five meandering periods: The three of them correspond to large meandering events detected by the JMA, while the two of them are offshore non-large meandering events. The topological data analysis reveals that a large cyclonic eddy inside of the meandering is split into two small eddies near the termination of the most meandering events.
      PubDate: 2022-12-01
       
  • Long-term sea-level variability along the coast of Japan during the 20th
           century revealed by a 1/10 $$^{\circ }$$ OGCM

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      Abstract: Abstract We explore long-term sea-level variability along the coast of Japan during the 20th century, using a 1/10 \(^{\circ }\) ocean general circulation model driven by two 20th century atmospheric reanalysis data. The modeled sea level anomalies along the coast of Japan (JPN-SLAs) show a consistent upward trend throughout the 20th century, which is comparable to global-mean sea-level rise, whereas no trend is obvious for the observed JPN-SLAs based on tide gauge data carefully selected by the Japan Meteorological Agency (JMA). We point out that the major difference between the model results and the tide gauge data may be due to the vertical land movements (VLMs) at the tide gauge stations, despite the JMA’s assumption that the VLMs are relatively small there. If this is correct, the estimates from our model combined with the barystatic component by a recent study would yield a linear trend of 1.79 [0.89 \(\sim\) 2.28] mm \(\hbox {yr}^{-1}\) for JPN-SLAs without VLMs from 1900 to 2010, which is close to the global average SLAs estimated in recent studies. The empirical orthogonal function (EOF) analysis shows that the first mode of the modeled JPN-SLAs is almost spatially uniform with a peak in the 1950s. The peak is created by coastal trapped waves (CTWs), which are excited when positive sea level anomalies produced by change in wind stress, propagate westward as baroclinic Rossby waves and reach Japan. From idealized experiments, we find that the first EOF mode is well reproduced by the CTWs excited east of Hokkaido.
      PubDate: 2022-11-29
       
  • Particle-tracking experiments of coastal-origin sea ice that could induce
           high biological productivity in the Sea of Okhotsk

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      Abstract: Abstract In the southwestern Sea of Okhotsk, a large spring phytoplankton bloom occurs after the sea ice melts. A suggested scenario is that sea ice with materials such as iron-containing sediment or ice algae is transported from the north and melted with release of them, inducing a prominent bloom. We hypothesize that sea ice containing materials that could enhance spring bloom originates from active coastal polynyas in the upstream region. To verify this hypothesis and identify which coastal areas generate sea ice that is further transported to the bloom area, we simulated the transport of sea ice produced in the coastal polynyas by a particle-tracking method. Sea ice production and drift velocity were derived from satellite microwave data. For regions near the coast, where ice drift data derived from the satellite are inaccurate, we combined ice drift data derived from the wind using the wind factor and the turning angle obtained from mooring data. Further, we used the apparent wind factor that expresses enhancement of the alongshore component of ice drift by the ocean current. The simulations suggest that most of the sea ice that melts in the western Kuril Basin originates from the Terpenia Bay and Sakhalin polynyas. The area where high net community production occurs after the sea ice melts corresponds well to the area where sea ice originating from these polynyas melts. The simulation of frazil ice suggests the importance of melt ice originating from the Terpenia Bay polynya with a higher rate of frazil ice production.
      PubDate: 2022-11-28
       
  • Occurrence patterns of larval mesopelagic fishes in the mouth of highly
           eutrophic Tokyo Bay, central Japan

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      Abstract: Abstract The estimated biomass of mesopelagic fishes has been revised recently, indicating the importance of their roles in oceanic ecosystems and global biogeochemical cycling. This study clarified the occurrence patterns of larval mesopelagic fish species in the surface layers of the highly eutrophic Tokyo Bay. Oceanographic observations and larval fish sampling were conducted across four seasons in 2003 and 2005–06 from the inner area to the mouth of the bay. The number of mesopelagic fishes sampled was 2,276 individuals of 78 species (14 families), accounting for 0.4% of total specimens and 25.4% of the total species number. Myctophidae comprised the largest number of species, with 43 species/morphotypes, followed by Gonostomatidae (seven species). Most larvae in Tokyo Bay were found to belong to tropical/subtropical species. The number of mesopelagic species was negatively correlated with the distance from the Kuroshio Current axis to the mouth of the bay, suggesting that these species were transported by the Kuroshio Current. A thermohaline front likely functions as a barrier preventing mesopelagic fish larvae from entering the inner bay area. Species in the outer bay and mouth of the bay clearly differed, likely due to the differing vertical distributions innate to each species. On the other hand, some species occurred in surface layers penetrated by inner bay water. In addition, the abundances of a myctophid species and copepods, which are potential food items for larvae, were positively correlated, suggesting that some mesopelagic larvae actively approach productive coastal waters due to the advantage of food availability.
      PubDate: 2022-11-09
       
  • Decadal changes in the basin-wide heat budget of the mid-latitude North
           Pacific Ocean

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      Abstract: Abstract Research has indicated that the meridional heat transport (MHT) in the North Pacific Ocean (NP) across 24°N increased in the 1980s and 1990s, resulting in different heat distributions: the ocean heat content (OHC) increased in the 1980s, while the net surface heat release was strengthened in the 1990s; however, the reasons for these differences remained unclear. The authors revisited the investigation of the heat budget in the NP mainly using hydrographic observations to understand why the heat distribution was different between these 2 decades and extend the analysis to the 2010s. The OHC in the upper 700 m north of 24°N and east of 137°E exhibited sharp increases around 1990 as well as in the 2010s, while it was nearly stable in between. The northward retreat of the subarctic gyre boundary coincided with the spin-up of the subtropical gyre in the late 1980s, thereby allowing warm anomaly from the subtropics to propagate northeastward. Meanwhile, the concurrent weakening of the wintertime westerlies resulted in the suppression of the surface heat loss in the western NP. In contrast, the southward shift of the subarctic front suppressed the OHC rise, despite the MHT increase in the late 1990s. In the 2010s, unprecedented warming occurred in the eastern NP. The MHT estimation based on hydrographic observations indicates that the net surface release must have been suppressed since the MHT did not increase; however, the latest atmospheric reanalysis datasets failed to reproduce this.
      PubDate: 2022-10-28
       
  • Reviewers of manuscripts

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      PubDate: 2022-10-03
       
  • Oscillation and the resulting bait loss observed in pelagic longline hooks

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      Abstract: Abstract The oscillation cycle and intensity in each part of the pelagic longline were investigated in Sagami Bay, Japan, to evaluate the effect on bait loss. The results of three longline operations were analyzed. The longline consisted of 25 ordinary and 15 midwater float baskets, with six branch lines per basket. Acceleration loggers were attached to the upper end (main float) and lower end of the float line, and the hook of the first and third branch lines. A depth logger was attached to the upper and lower ends of the branch line (hook). A video logger was attached, facing downward at a position 0.6 m above the hook. The periodicity of the oscillation was clarified by autocorrelation analysis, and the sum of the absolute values of the dynamic acceleration of the three axes (ODBA) was compared. From the video footage and autocorrelation analyses, the oscillation cycle of the hooks was approximately 3 s, which is the same as that of the main float. The ODBA of the first hook was 1.9–2.3 m/s2, which was significantly larger than the main float (1.1–1.4 m/s2) and the third hook (0.2–1.8 m/s2, p < 0.001). Therefore, the oscillation of the hook was derived from the vertical movement of the main float due to the wave, and it decreased as the distance from the main float increased. The third hook in the midwater float basket had an unclear cycle, and the ODBA was significantly smaller than that of the ordinary baskets.
      PubDate: 2022-10-03
       
  • Decadal sea surface height modes in the low-latitude northwestern Pacific
           and their contribution to the North Equatorial Current transport variation
           

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      Abstract: Abstract Three decadal sea surface height (SSH) modes in the low-latitude northwestern Pacific over 1958 − 2018 were revealed by empirical orthogonal function analysis of decadal SSH anomalies derived from the Ocean Reanalysis System 4 provided by the European Centre for Medium-Range Weather Forecasts. The two leading SSH modes present large and small cyclonic signals in the northwestern tropical Pacific and a localized domain of (120 − 150 °E, 6 − 14 °N), respectively. In contrast, the third SSH mode demonstrates positive basin-scale signals from 7 to 21 °N. All three SSH modes enhance the NEC transport, with the most considerable contribution from the third mode. The temporal evolutions of the first and third modes are more relevant to the decadal NEC transport variation before 1976, whereas the second and third modes become more important after then. Further investigations suggest that the first and second SSH modes correlate well with the time series of the two leading EOFs of the Tropical Pacific Decadal Variability, and the third SSH mode moderately correlates with the Pacific Decadal Oscillation. Using a linear reduced gravity model, the three SSH modes are reproduced with the wind forcing patterns regressed against the climate indices. This study is a new attempt and deepens our understanding of the decadal variability of the NEC by revealing the linkages between multiple SSH modes and Pacific climate indices.
      PubDate: 2022-10-01
      DOI: 10.1007/s10872-022-00645-6
       
  • Seasonal dynamics of dinoflagellates with special emphasis on potentially
           harmful species in a tropical estuarine system along the southwest coast
           of India

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      Abstract: Abstract To understand seasonal variations of the dinoflagellate community in the estuarine waters of Cochin (Southwest coast of India), the abundance and species composition, in particular the harmful species, were investigated. The study records 43 species of dinoflagellates belonging to 6 orders and 19 genera, with the genus Protoperidinium (14 species) being the most diverse one, followed by the genus Tripos (5 species). Diversity and abundance of dinoflagellates were maximum during the pre-monsoon season (H′ 2.08 and 3.9 × 103 cells L−1, respectively). The numerical abundance correlated well with environment variables like surface water temperature (r = 0.89, p < 0.01), salinity (r = 0.64, p < 0.05), phosphate concentration (r = 0.70, p < 0.05) and turbidity (r = − 0.835, p < 0.01) suggesting their role in the growth and sustenance of dinoflagellates. The presence of 19 harmful dinoflagellate species, with Akashiwo sanguinea, Noctiluca scintillans and Peridinium quardidentatum forming their blooms in the region, also emphasizes potential risks for future HAB outbreaks along the southwest coast of India.
      PubDate: 2022-10-01
      DOI: 10.1007/s10872-022-00648-3
       
  • Dominant modes of winter SST variability in the Japan Sea and their
           influences on atmosphere

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      Abstract: Abstract The high-resolution spatial and long-term temporal variabilities of winter sea surface temperature (SST) in the Japan Sea and their influences on the atmosphere are investigated using a newly published satellite observation data set. The first and second principal components are characterized by the basin-wide and east–west dipole structure, respectively. Both the basin-wide and the dipole modes show the influence of ocean on the above atmosphere. Local atmospheric response of the basin-wide mode is constrained to the East Korea Bay, which can be explained through the vertical mixing mechanism, that the warm (cold) SST enhances (weakens) the wind speed. Moreover, the basin-wide mode shows a remote pattern over the eastern North Pacific that is enhanced by the divergence of transient eddy vorticity flux via downstream intensified storm track, even in the absence of strong Arctic Oscillation forcing.
      PubDate: 2022-10-01
      DOI: 10.1007/s10872-022-00643-8
       
  • Projected future changes in the contribution of Indo-Pacific sea surface
           height variability to the Indonesian throughflow

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      Abstract: Abstract The Indonesian throughflow (ITF) transports a significant amount of warm freshwater from the Pacific to the Indian Ocean, making it critical to the global climate system. This study examines decadal ITF variations using ocean reanalysis data as well as climate model simulations from the Coupled Model Inter-comparison Project Phase 5 (CMIP5). While the observed annual cycle of ITF transport is known to be correlated with the annual cycle of sea surface height (SSH) difference between the Pacific and Indian Oceans, ocean reanalysis data (1959–2015) show that the Pacific Ocean SSH variability controls more than 85% of ITF variation on decadal timescales. In contrast, the Indian Ocean SSH variability contributes less than 15%. While those observed contributions are mostly reproduced in the CMIP5 historical simulations, an analysis of future climate projections shows a 25–30% increase in the Indian Ocean SSH variability to decadal ITF variations and a corresponding decrease in the Pacific contribution. These projected changes in the Indian Ocean SSH variability are associated with a 23% increase in the amplitudes of negative zonal wind stress anomalies over the equatorial Indian Ocean, along with a 12º eastward shift in the center of action in these anomalies. This combined effect of the increased amplitude and eastward shift in the zonal wind stress increases the SSHA variance over the Indian Ocean, increasing its contribution to the ITF variation. The decadal ITF changes discussed in this study will be crucial in understanding the future global climate variability, strongly coupled to Indo-Pacific interactions.
      PubDate: 2022-10-01
      DOI: 10.1007/s10872-022-00641-w
       
  • On anomalously high sub-surface dissolved oxygen in the Indian sector of
           the Southern Ocean

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      Abstract: Abstract The Southern Ocean (SO) plays a critical role in global ocean productivity and carbon cycling. Bio-Argo floats deployed in the Indian sector of the Southern Ocean provides new insights into the biogeochemical processes. Here we report significantly higher dissolved oxygen(DO) (~ 310 μmol/kg) in summer of 2014–2015 for one float (F1) and winter of 2014 in other float (F2) at sub-surface layer in the subantarctic region of the SO. The summer DO peak in F1 was 10% higher than those during the summer of succeeding year, while the winter DO peak in F2 was 20% higher than those during the winter of succeeding year. Temperature and dynamic height structure show that cyclonic eddies play an important role in the observed increase in the dissolved oxygen: the high DO is a manifestation of the co-occurrence of a cold core eddy which transported the cold oxygen rich water from deep to the surface during winter, while, during summer, the high chlorophyll below the mixed layer depth (MLD) also contributed to the elevated DO. Low apparent oxygen utilisation suggests that the observed high oxygen concentration was due to high production rates over the consumption.
      PubDate: 2022-10-01
      DOI: 10.1007/s10872-022-00644-7
       
  • Cladoceran communities in offshore Suruga Bay, Japan: How are they
           formed'

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      Abstract: Abstract Although marine cladocerans are known as coastal zooplankton, they sometimes appear in offshore waters in large numbers. In Suruga Bay, located in the center of Japan and opens to the Pacific Ocean, cladocerans occur abundantly in offshore waters during the spring and summer seasons. However, the mechanisms by which these offshore populations form in the bay are still unknown. The aim of this study was to clarify the factors that explain these offshore cladoceran populations by combining field sampling and numerical experiments, using particle-tracking methods. Cladocerans showed different occurrence patterns in coastal and offshore areas. Abundance of Penilia avirostris, the dominant offshore species, was much higher in offshore than in coastal areas. The unique filter feeding of Pe. avirostris may enable it to survive in offshore Suruga Bay with less abundant food conditions. On the other hand, while Pleopis polyphemoides and Podon leuckartii occurred abundantly in coastal areas, they appeared in very small numbers in offshore areas. This suggests that offshore environments are unfavorable for them to maintain populations. Particle-tracking experiments demonstrated that particles released from the coast of Suruga Bay were transported to and accumulated at the inner offshore region of the Bay from March to August. Those patterns were not observed in other months. Our results suggest that a combination of transport of coastal populations by surface circulation currents and biological characteristics of the species to survive in oligotrophic and high-salinity offshore environments contribute to form periodic mass occurrences of cladocerans in offshore Suruga Bay.
      PubDate: 2022-09-24
      DOI: 10.1007/s10872-022-00662-5
       
  • Current observations on and around a deep-ocean island/reef: northern
           Palau and Velasco Reef

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      Abstract: Abstract Current and hydrographic measurements were made in the equatorial Pacific Ocean between the westward-flowing North Equatorial Current and the eastward-flowing North Equatorial Counter Current. Nine moorings containing current profilers and hydrographic sensors were deployed on and around Velasco Reef, just north of Palau Island, from May 2016 to March 2017, when the Pacific Ocean was relaxing after the 2015/16 El Niño. Currents and their interactions with this abrupt bathymetric feature are characterized on spatial scales of 10–30 km, and frequencies from semidiurnal to intraseasonal. Currents near the reef displayed a two-layer structure and were not stationary due to the shifting of the major currents and eddy passages. Energy was significant at tidal and inertial periods, and at periods longer than ten days. Tides and higher frequency currents were responsible for about half the energy on the reef but for only about 20% of the energy in the deep water. Cyclonic (anticyclonic) vorticity occurred on the western (eastern) side of the reef during westward (eastward) flows, indicating recirculation on the leeward side of the reef. Vorticity west of the reef was much stronger than vorticity on the east side. When the cyclonic vorticity was large, the divergence flow patterns supported strong upwelling in the upper layer. Differences in both vertical and horizontal velocity coherences and correlations between moorings indicated that the reef affected the currents. The reef seemed to significantly impact water exchange. Currents near the reef are difficult to be described, particularly at depth by satellite products, making their prediction problematic.
      PubDate: 2022-08-10
      DOI: 10.1007/s10872-022-00647-4
       
  • Phytoplankton and ice-algal communities in the seasonal ice zone during
           January (Southern Ocean, Indian sector)

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      Abstract: Abstract In the seasonal ice zone (SIZ), sea-ice algae have been hypothesized to influence phytoplankton species composition in seawater after melting from sea ice. However, information on ice-algal species composition during summer (December–February) was small particularly in the Indian sector of the Southern Ocean. We investigated sea-ice macronutrient concentrations and relationships between phytoplankton and ice-algal species composition in this region during January of 2018–2020. The species composition of ice algae each year (after weighted-averaged by sample volume for each sea ice) was dominated by the diatom Fragilariopsis cylindrus (78–89% of total cells). This result differed from ice-algal compositions in spring but consistent with those in summer, indicating seasonal changes in species composition of ice algae at East Antarctic SIZ. Using all years’ sea-ice data, we found nitrate + nitrite: phosphate ratio declined significantly with increased algal concentrations. Diatoms’ uptake ratio of macronutrients and remineralization of phosphorus from their products (e.g., dissolved organic matter) may result in this relationship, which indicates algal accumulation especially of diatoms in sea ice. At the ice-sampling stations, phytoplankton was dominated by F. cylindrus, while at the northern stations, higher proportions of F. kerguelensis, Pseudo-nitzschia prolongatoides/subcurvata, and Gymnodiniales were observed. The similarity index of sea-ice and phytoplankton composition was negatively correlated with days elapsed since sea-ice retreat and surface seawater temperature at each sampled station. This suggests that phytoplankton species composition might be influenced by release of ice algae where the influence of sea ice is strong during summer.
      PubDate: 2022-06-25
      DOI: 10.1007/s10872-022-00649-2
       
 
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