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Ichiro Yasuda - One of the best experts on this subject based on the ideXlab platform.
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impact of the astronomical lunar 18 6 yr Tidal Cycle on el nino and southern oscillation
Scientific Reports, 2018Co-Authors: Ichiro YasudaAbstract:Even though El-Nino and Southern Oscillation (ENSO) has a tremendous impact on global climate and society, its long-term forecast remains difficult. In this study, we discovered a statistically significant relationship between ENSO timing and the 18.6-year period lunar Tidal Cycle in the mature-phase (December–February) ENSO time-series during 1867–2015 and extending back to 1706 with proxy data. It was found that El-Nino tended to occur in the 1st, 10th, and 13th years after the maximum diurnal tide in the 18.6-yr Cycle, and La-Nina tended to occur in the 3rd, 12th, and 16th years. These tendencies were also confirmed by corresponding sea-surface temperature (SST) and sea-level pressure (SLP) distributions; particularly Pacific SST and SLP spatial patterns in the third La-Nina and the tenth El-Nino year well resemble those of Pacific Decadal Oscillation (PDO). These findings contribute to understanding and forecasting long-term ENSO variability.
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numerical study on the impact of the 18 6 year period nodal Tidal Cycle on water masses in the subarctic north pacific
Journal of Geophysical Research, 2012Co-Authors: Satoshi Osafune, Ichiro YasudaAbstract:[1] A series of numerical experiments is performed to test the hypothesis that temporal variations in localized strong Tidal mixing related to the 18.6-year period nodal Tidal Cycle induce water mass variations. It is suggested that enhanced mixing around the Bering Sea, as that around the Okhotsk Sea, have an impact on water masses broadly in the North Pacific including the Bering Sea and the Okhotsk Sea. Oscillatory Tidal mixing with a 18.6-year period reproduces water mass variations in salinity and isopycnal potential temperature around the subarctic North Pacific that are qualitatively consistent with observed variations. When the amplitude of oscillatory vertical diffusivity is 15% of the long-term mean (and even when the amplitude is as small as 3 cm2/s, as obtained for a long-term mean of 20 cm2/s), the amplitude of the salinity variation near regions of strong mixing is smaller than but on the same order of magnitude as that observed. The induced salinity anomaly spreads broadly, over a distance of several hundreds of kilometers, by mean currents with a short lag time of less than 3 years, and is suggested to influence the model winter mixed layer over broad regions. These results support the hypothesis stated above and suggest that it is necessary to clarify spatial and temporal variations in Tidal mixing to reproduce both the mean states of and temporal variations in water masses of the subarctic North Pacific.
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Bidecadal variability in the Bering Sea and the relation with 18.6 year period nodal Tidal Cycle
Journal of Geophysical Research, 2010Co-Authors: Satoshi Osafune, Ichiro YasudaAbstract:[1] Bidecadal variations are investigated in the Bering Sea, especially in the southeastern basin adjacent to the Aleutian passes, where vertical mixing may be strong because of the diurnal tide. Those variations found in this region are synchronized with the 18.6 year period nodal Tidal Cycle, and the temporal patterns are similar to ones around the northwestern subarctic Pacific near the Kuril Straits reported by a previous study. Salinity and density in the upper layer are high in the periods when the diurnal tide is strong. In the intermediate layer, layer thickness is large, and isopycnal potential temperature and apparent oxygen utilization are low in the same periods. It is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing, and a simple two-dimensional model, assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current, succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer.
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the 18 6 year period moon Tidal Cycle in pacific decadal oscillation reconstructed from tree rings in western north america
Geophysical Research Letters, 2009Co-Authors: Ichiro YasudaAbstract:[1] Time-series of Pacific Decadal Oscillation (PDO) reconstructed from tree-rings in Western North America is found to have a statistically significant periodicity of 18.6-year period lunar nodal Tidal Cycle; negative (positive) PDO tends to occur in the period of strong (weak) diurnal tide. In the 3rd and 5th (10th, 11th and 13rd) year after the maximum diurnal tide, mean-PDO takes significant negative (positive) value, suggesting that the Aleutian Low is weak (strong), western-central North Pacific in 30-50°N is warm (cool) and equator-eastern rim of the Pacific is cool (warm). This contributes to climate predictability with a time-table from the astronomical Tidal Cycle.
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possible explanation linking 18 6 year period nodal Tidal Cycle with bi decadal variations of ocean and climate in the north pacific
Geophysical Research Letters, 2006Co-Authors: Ichiro Yasuda, Satoshi Osafune, Hiroaki TatebeAbstract:[1] Bi-decadal climate variation is dominant over the North Pacific on inter-decadal timescale; however the mechanism has not been fully understood. We here find that the bi-decadal variations in the North Pacific climate and intermediate waters possibly relate to the 18.6-year period modulation of diurnal tide. In the period of strong diurnal tide, tide-induced diapycnal mixing makes surface salinity and density higher and the upper-layer shallower along the Kuril Islands and the east coast of Japan. Simple model results suggest that the coastal depth adjustment by baroclinic Kelvin waves enhances the thermohaline circulation, the upper-layer poleward western boundary current and associated heat transport by about 0.05PW. This could also explain the warmer SST in the Kuroshio-Oyashio Extension regions, where positive feedback with Aleutian Low might amplify the bidecadal variations. The 18.6-year Tidal Cycle hence could play a role as a basic forcing for the bi-decadal ocean and climate variations.
Satoshi Osafune - One of the best experts on this subject based on the ideXlab platform.
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numerical study on the impact of the 18 6 year period nodal Tidal Cycle on water masses in the subarctic north pacific
Journal of Geophysical Research, 2012Co-Authors: Satoshi Osafune, Ichiro YasudaAbstract:[1] A series of numerical experiments is performed to test the hypothesis that temporal variations in localized strong Tidal mixing related to the 18.6-year period nodal Tidal Cycle induce water mass variations. It is suggested that enhanced mixing around the Bering Sea, as that around the Okhotsk Sea, have an impact on water masses broadly in the North Pacific including the Bering Sea and the Okhotsk Sea. Oscillatory Tidal mixing with a 18.6-year period reproduces water mass variations in salinity and isopycnal potential temperature around the subarctic North Pacific that are qualitatively consistent with observed variations. When the amplitude of oscillatory vertical diffusivity is 15% of the long-term mean (and even when the amplitude is as small as 3 cm2/s, as obtained for a long-term mean of 20 cm2/s), the amplitude of the salinity variation near regions of strong mixing is smaller than but on the same order of magnitude as that observed. The induced salinity anomaly spreads broadly, over a distance of several hundreds of kilometers, by mean currents with a short lag time of less than 3 years, and is suggested to influence the model winter mixed layer over broad regions. These results support the hypothesis stated above and suggest that it is necessary to clarify spatial and temporal variations in Tidal mixing to reproduce both the mean states of and temporal variations in water masses of the subarctic North Pacific.
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Bidecadal variability in the Bering Sea and the relation with 18.6 year period nodal Tidal Cycle
Journal of Geophysical Research, 2010Co-Authors: Satoshi Osafune, Ichiro YasudaAbstract:[1] Bidecadal variations are investigated in the Bering Sea, especially in the southeastern basin adjacent to the Aleutian passes, where vertical mixing may be strong because of the diurnal tide. Those variations found in this region are synchronized with the 18.6 year period nodal Tidal Cycle, and the temporal patterns are similar to ones around the northwestern subarctic Pacific near the Kuril Straits reported by a previous study. Salinity and density in the upper layer are high in the periods when the diurnal tide is strong. In the intermediate layer, layer thickness is large, and isopycnal potential temperature and apparent oxygen utilization are low in the same periods. It is shown that these variations are consistent with the patterns expected from the nodal modulation of vertical mixing, and a simple two-dimensional model, assuming a balance between anomalous vertical mixing and advection of anomaly by the mean current, succeeds to some extent in explaining the variations of the upper layer salinity and isopycnal temperature and apparent oxygen utilization in the intermediate layer.
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possible explanation linking 18 6 year period nodal Tidal Cycle with bi decadal variations of ocean and climate in the north pacific
Geophysical Research Letters, 2006Co-Authors: Ichiro Yasuda, Satoshi Osafune, Hiroaki TatebeAbstract:[1] Bi-decadal climate variation is dominant over the North Pacific on inter-decadal timescale; however the mechanism has not been fully understood. We here find that the bi-decadal variations in the North Pacific climate and intermediate waters possibly relate to the 18.6-year period modulation of diurnal tide. In the period of strong diurnal tide, tide-induced diapycnal mixing makes surface salinity and density higher and the upper-layer shallower along the Kuril Islands and the east coast of Japan. Simple model results suggest that the coastal depth adjustment by baroclinic Kelvin waves enhances the thermohaline circulation, the upper-layer poleward western boundary current and associated heat transport by about 0.05PW. This could also explain the warmer SST in the Kuroshio-Oyashio Extension regions, where positive feedback with Aleutian Low might amplify the bidecadal variations. The 18.6-year Tidal Cycle hence could play a role as a basic forcing for the bi-decadal ocean and climate variations.
D Eisma - One of the best experts on this subject based on the ideXlab platform.
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concentration clay mineral composition and coulter counter size distribution of suspended sediment in the turbidity maximum of the jiaojiang river estuary zhejiang china
Journal of Sea Research, 1999Co-Authors: B G Li, D EismaAbstract:Abstract Measurements of current velocities, concentrations of suspended matter and Coulter counter size distributions of the suspended matter during the Tidal Cycle at the surface, at mid-depth and near to the bottom were carried out during spring and neap tide in the Jiaojiang river estuary, Zhejiang, China. The results indicate that a lutocline was present during most of the Tidal Cycle, except during the highest tides when the suspended-matter concentrations were approximately uniform over the entire water depth. Suspended-matter concentrations showed a relation with maximum flow velocities in the surface water and with increasing flow velocities in the bottom water, with regular deposition and resuspension during the Tidal Cycle. The clay mineral composition of the suspended matter indicated that most of the suspended matter was supplied by the Chang Jiang river. There was probably also some local supply and local sorting. The suspended-matter particle size, measured with a Coulter counter, became larger (with a larger standard deviation) when the suspended-matter concentration increased, and smaller when the suspended-matter concentration decreased. Size sorting during the Tidal Cycle indicated deflocculation and reflocculation processes; break-up of about 10 to 20% of the flocs in suspension is sufficient to produce the shift in the Coulter counter size distributions observed. This led to the conclusion that the trend in the smectite concentration in the estuary was the result of local sorting of smectite-containing particles after floc break-up.
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changes in suspended matter floc size during the Tidal Cycle in the dollard estuary
Netherlands Journal of Sea Research, 1993Co-Authors: D EismaAbstract:Abstract Measurements of in situ particle size of suspended matter in a Tidal channel in the Dollard (Dutch Wadden Sea) indicated systematic variations in floc size during the Tidal Cycle that can be explained by assuming settling during slack tide, resuspension during the early ebb and early flood, flocculation of fine particles into large ones during most of the tide, and deflocculation of large flocs into smaller particles during or after settling to the bottom. There was a characteristic difference in floc-size variation during ebb and during flood. During the ebb maximum floc size coincided with maximum suspended-matter concentration (maximum collision frequency); during the flood maximum floc size continued to increase towards high-water slack tide. The adjacent Tidal flats had a marked influence on floc size: where the flats were small, the highest percentages of large flocs (> F 128 μ m) occurred around slack tide when current velocities are low. Where the adjacent flats were broad and extensive, high percentages also occured during intermediate periods. Flocs of maximum size are probably not in equilibrium with the bulk of the suspended matter: they are mainly formed during periods of high suspended-matter concentrations of short duration.
Jef Huisman - One of the best experts on this subject based on the ideXlab platform.
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Dancing with the tides: fluctuations of coastal phytoplankton orchestrated by different oscillatory modes of the Tidal Cycle.
PloS one, 2012Co-Authors: A. Blauw, Elisa Benincà, Remi W. P. M. Laane, Naomi Greenwood, Jef HuismanAbstract:Population fluctuations are often driven by an interplay between intrinsic population processes and extrinsic environmental forcing. To investigate this interplay, we analyzed fluctuations in coastal phytoplankton concentration in relation to the Tidal Cycle. Time series of chlorophyll fluorescence, suspended particulate matter (SPM), salinity and temperature were obtained from an automated measuring platform in the southern North Sea, covering 9 years of data at a resolution of 12 to 30 minutes. Wavelet analysis showed that chlorophyll fluctuations were dominated by periodicities of 6 hours 12 min, 12 hours 25 min, 24 hours and 15 days, which correspond to the typical periodicities of Tidal current speeds, the semidiurnal Tidal Cycle, the day-night Cycle, and the spring-neap Tidal Cycle, respectively. During most of the year, chlorophyll and SPM fluctuated in phase with Tidal current speed, indicative of alternating periods of sinking and vertical mixing of algal cells and SPM driven by the Tidal Cycle. Spring blooms slowly built up over several spring-neap Tidal Cycles, and subsequently expanded in late spring when a strong decline of the SPM concentration during neap tide enabled a temporary “escape” of the chlorophyll concentration from the Tidal mixing regime. Our results demonstrate that the Tidal Cycle is a major determinant of phytoplankton fluctuations at several different time scales. These findings imply that high-resolution monitoring programs are essential to capture the natural variability of phytoplankton in coastal waters.
A Hierro - One of the best experts on this subject based on the ideXlab platform.
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trace metal partitioning over a Tidal Cycle in an estuary affected by acid mine drainage tinto estuary sw spain
Science of The Total Environment, 2014Co-Authors: A Hierro, M Olias, Carlos Ruiz Canovas, Julia Martin, J P BolivarAbstract:Abstract The Tinto River estuary is highly polluted with the acid lixiviates from old sulphide mines. In this work the behaviour of dissolved and particulate trace metals under strong chemical gradients during a Tidal Cycle is studied. The pH values range from 4.4 with low tide to 6.9 with high tide. Precipitation of Fe and Al is intense during rising tides and As and Pb are almost exclusively found in the particulate matter (PM). Sorption processes are very important in controlling the mobility (and hence bioavailability) of some metals and particularly affect Cu below pH 6. Above pH ~ 6 Cu is desorbed, probably by the formation of Cu(I)–chloride complexes. Although less pronounced than Cu, also Zn desorption above pH 6.5 seems to occur. Mn and Co are affected by sorption processes at pH higher than ca. 6. Cd behaves conservatively and Ni is slightly affected by sorption processes.
