Pub Date : 2020-12-01DOI: 10.22449/1573-160x-2020-6-559-572
M. Koshlyakov, V. Belokopytov
The paper is aimed at reviewing the studies of mesoscale eddies in the open ocean carried out by the Soviet and foreign institutions during the experiments in the specified geographical regions. The eddy-current effects are known since the 1930ies, and just the experiments “Polygon-67” in the Arabian Sea, “Polygon-70”, MODE , POLYMODE, Tourbillon , “Mesopolygon” in the tropical Atlantic, “Megapolygon” in the northwestern Pacific Ocean have advanced our knowledge about physical nature of the ocean eddy dynamics. Long-term complex measurements including current meters at the moored buoy arrays accompanied by a series of hydrographic surveys have provided the required experimental data for developing the theory of mesoscale variability. It explained arising and evolution of the eddies in the ocean as a result of interaction between various physical processes: baroclinic instability of a large-scale current, transformation of geostrophic turbulence in the Rossby wave field, barotropization of eddies and others. Later on, the studies of the ocean mesoscale variability evolved from the oceanographic surveys and special-purpose experiments at the polygons performed due to the research vessel cruises to the satellite altimetry methods and the drifter technologies. All the modern global estimates of eddy formations published in the last decade confirm the previous summaries, particularly those describing spatial distribution of the eddy kinetic energy in the World Ocean. They also represent new or the improved assessments of the eddies’ various characteristics: their size, drift velocity and direction, sign of rotation, nonlinearity, trajectory shear and others. eddy dynamics within the whole World Ocean. It seems perspective to resume in future special-purpose experiments in the key regions of the World Ocean based on modern technologies. Acknowledgments: the work was carried out within the framework of the state task of IO RAS on theme No. 0149-2019-0004, RAS No. 0827-2018-0001.
{"title":"Mesoscale Eddies in the Open Ocean: Review of Experimental Investigations","authors":"M. Koshlyakov, V. Belokopytov","doi":"10.22449/1573-160x-2020-6-559-572","DOIUrl":"https://doi.org/10.22449/1573-160x-2020-6-559-572","url":null,"abstract":"The paper is aimed at reviewing the studies of mesoscale eddies in the open ocean carried out by the Soviet and foreign institutions during the experiments in the specified geographical regions. The eddy-current effects are known since the 1930ies, and just the experiments “Polygon-67” in the Arabian Sea, “Polygon-70”, MODE , POLYMODE, Tourbillon , “Mesopolygon” in the tropical Atlantic, “Megapolygon” in the northwestern Pacific Ocean have advanced our knowledge about physical nature of the ocean eddy dynamics. Long-term complex measurements including current meters at the moored buoy arrays accompanied by a series of hydrographic surveys have provided the required experimental data for developing the theory of mesoscale variability. It explained arising and evolution of the eddies in the ocean as a result of interaction between various physical processes: baroclinic instability of a large-scale current, transformation of geostrophic turbulence in the Rossby wave field, barotropization of eddies and others. Later on, the studies of the ocean mesoscale variability evolved from the oceanographic surveys and special-purpose experiments at the polygons performed due to the research vessel cruises to the satellite altimetry methods and the drifter technologies. All the modern global estimates of eddy formations published in the last decade confirm the previous summaries, particularly those describing spatial distribution of the eddy kinetic energy in the World Ocean. They also represent new or the improved assessments of the eddies’ various characteristics: their size, drift velocity and direction, sign of rotation, nonlinearity, trajectory shear and others. eddy dynamics within the whole World Ocean. It seems perspective to resume in future special-purpose experiments in the key regions of the World Ocean based on modern technologies. Acknowledgments: the work was carried out within the framework of the state task of IO RAS on theme No. 0149-2019-0004, RAS No. 0827-2018-0001.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41578818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/1573-160x-2020-6-631-658
E. Stanev, M. Ricker, S. Grayek, B. Jacob, V. Haid, J. Staneva
emil.stanev@hzg.de Purpose. The study addresses rotational motion of geophysical fluids in the horizontal and vertical planes. It is aimed mainly at tracing the development of high-resolution numerical modeling of the ocean, as well as at demonstrating new physical processes due to more correct consideration both of the tides in the eddy-resolving numerical models and sub-mesoscale dynamics in the models of the sea straits. Methods and Results. The ocean eddies and their interaction with tides are studied using numerical simulations by four NEMO models for the European North-West shelf with the resolutions ranging from 7 to 1.5 km. The vertical characteristics of motion in the Bosporus Strait were studied using numerical simulations with SCHISM , the unstructured grid model with the ultra-fine model resolution (less than 100 m). The barotropic tidal forcing resulted in substantial flattening of the slopes of the spectral curves. The most important difference between the spectral features of four models occurs in the motion rotational component. In the model with the 1.5 km resolution, the magnitude of the vorticity power spectral density at the scales ~ 70 km is by an order of magnitude higher than in the other three models. Although most of the tidal flattening is associated with the internal tides, beyond a certain horizontal resolution, the eddy dynamics become affected by the barotropic tides. The shelf of the Biscay Bay and the shallows around the Faroe Islands are the most sensitive areas to adding of the barotropic tides to the model forcing. Due to the grid ultra-fine resolution, new elements of physical motion emerged in the Bosporus region. The lateral circulation is dominated by the systems of multiple circulation cells with the scales ~ 1 km. In some areas, the lateral flow magnitude exceeds 0.5 m/s, which is comparable with the magnitude of the axial flow. This reveals importance of the helical elements of the strait circulation for overturning of water masses in the Bosporus. Conclusions. Without proper resolution, the models of tidal oceanic dynamics simulate the ocean general circulation, but do not describe correctly the energy cascades at the eddy scales including interaction between the tides and the mesoscale eddies. Absence of this sub-mesoscale dynamics in the models can largely affect their capability to simulate the two-layer
{"title":"Numerical Eddy-Resolving Modeling of the Ocean: Mesoscale and Sub-Mesoscale Examples","authors":"E. Stanev, M. Ricker, S. Grayek, B. Jacob, V. Haid, J. Staneva","doi":"10.22449/1573-160x-2020-6-631-658","DOIUrl":"https://doi.org/10.22449/1573-160x-2020-6-631-658","url":null,"abstract":" emil.stanev@hzg.de Purpose. The study addresses rotational motion of geophysical fluids in the horizontal and vertical planes. It is aimed mainly at tracing the development of high-resolution numerical modeling of the ocean, as well as at demonstrating new physical processes due to more correct consideration both of the tides in the eddy-resolving numerical models and sub-mesoscale dynamics in the models of the sea straits. Methods and Results. The ocean eddies and their interaction with tides are studied using numerical simulations by four NEMO models for the European North-West shelf with the resolutions ranging from 7 to 1.5 km. The vertical characteristics of motion in the Bosporus Strait were studied using numerical simulations with SCHISM , the unstructured grid model with the ultra-fine model resolution (less than 100 m). The barotropic tidal forcing resulted in substantial flattening of the slopes of the spectral curves. The most important difference between the spectral features of four models occurs in the motion rotational component. In the model with the 1.5 km resolution, the magnitude of the vorticity power spectral density at the scales ~ 70 km is by an order of magnitude higher than in the other three models. Although most of the tidal flattening is associated with the internal tides, beyond a certain horizontal resolution, the eddy dynamics become affected by the barotropic tides. The shelf of the Biscay Bay and the shallows around the Faroe Islands are the most sensitive areas to adding of the barotropic tides to the model forcing. Due to the grid ultra-fine resolution, new elements of physical motion emerged in the Bosporus region. The lateral circulation is dominated by the systems of multiple circulation cells with the scales ~ 1 km. In some areas, the lateral flow magnitude exceeds 0.5 m/s, which is comparable with the magnitude of the axial flow. This reveals importance of the helical elements of the strait circulation for overturning of water masses in the Bosporus. Conclusions. Without proper resolution, the models of tidal oceanic dynamics simulate the ocean general circulation, but do not describe correctly the energy cascades at the eddy scales including interaction between the tides and the mesoscale eddies. Absence of this sub-mesoscale dynamics in the models can largely affect their capability to simulate the two-layer","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47352402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/0233-7584-2020-6-691-719
E. V. Stanev, Marcel Ricker, S. Grayek, B. Jacob, V. Haid, Joanna Staneva
Purpose. The study addresses rotational motion of geophysical fluids in the horizontal and vertical planes. It is aimed mainly at tracing the development of high-resolution numerical modeling of the ocean, as well as at demonstrating new physical processes due to more correct consideration both of the tides in the eddy-resolving numerical models and sub-mesoscale dynamics in the models of the sea straits. Methods and Results. The ocean eddies and their interaction with tides are studied using numerical simulations by four NEMO models for the European North-West shelf with the resolutions ranging from 7 to 1.5 km. The vertical characteristics of motion in the Bosporus Strait were studied using numerical simulations with SCHISM , the unstructured grid model with the ultra-fine model resolution (less than 100 m). The barotropic tidal forcing resulted in substantial flattening of the slopes of the spectral curves. The most important difference between the spectral featurws of four models occurs in the motion rotational component. In the model with the 1.5 km resolution, the magnitude of the vorticity power spectral density at the scales ~70 km is by an order of magnitude higher than in the other three models. Although most of the tidal flattening is associated with the internal tides, beyond a certain horizontal resolution, the eddy dynamics become affected by the barotropic tides. The shelf of the Biscay Bay and the shallows around the Faroe Islands are the most sensitive areas to adding of the barotropic tides to the model forcing. Due to the grid ultra-fine resolution, new elements of physical motion emerged in the Bosporus region. The lateral circulation is dominated by the systems of multiple circulation cells with the scales ~ 1 km. In some areas, the lateral flow magnitude exceeds 0.5 m/s, which is comparable with the magnitude of the axial flow. This reveals importance of the helical elements of the strait circulation for overturning of water masses in the Bosporus. Conclusions. Without proper resolution, the models of tidal oceanic dynamics simulate the ocean general circulation, but do not describe correctly the energy cascades at the eddy scales including interaction between the tides and the mesoscale eddies. Absence of this sub-mesoscale dynamics in the models can largely affect their capability to simulate the two-layer inter-basin exchange.
{"title":"Примеры мезомасштабного и субмезомасштабного численного вихреразрешающего моделирования океана","authors":"E. V. Stanev, Marcel Ricker, S. Grayek, B. Jacob, V. Haid, Joanna Staneva","doi":"10.22449/0233-7584-2020-6-691-719","DOIUrl":"https://doi.org/10.22449/0233-7584-2020-6-691-719","url":null,"abstract":"Purpose. The study addresses rotational motion of geophysical fluids in the horizontal and vertical planes. It is aimed mainly at tracing the development of high-resolution numerical modeling of the ocean, as well as at demonstrating new physical processes due to more correct consideration both of the tides in the eddy-resolving numerical models and sub-mesoscale dynamics in the models of the sea straits. Methods and Results. The ocean eddies and their interaction with tides are studied using numerical simulations by four NEMO models for the European North-West shelf with the resolutions ranging from 7 to 1.5 km. The vertical characteristics of motion in the Bosporus Strait were studied using numerical simulations with SCHISM , the unstructured grid model with the ultra-fine model resolution (less than 100 m). The barotropic tidal forcing resulted in substantial flattening of the slopes of the spectral curves. The most important difference between the spectral featurws of four models occurs in the motion rotational component. In the model with the 1.5 km resolution, the magnitude of the vorticity power spectral density at the scales ~70 km is by an order of magnitude higher than in the other three models. Although most of the tidal flattening is associated with the internal tides, beyond a certain horizontal resolution, the eddy dynamics become affected by the barotropic tides. The shelf of the Biscay Bay and the shallows around the Faroe Islands are the most sensitive areas to adding of the barotropic tides to the model forcing. Due to the grid ultra-fine resolution, new elements of physical motion emerged in the Bosporus region. The lateral circulation is dominated by the systems of multiple circulation cells with the scales ~ 1 km. In some areas, the lateral flow magnitude exceeds 0.5 m/s, which is comparable with the magnitude of the axial flow. This reveals importance of the helical elements of the strait circulation for overturning of water masses in the Bosporus. Conclusions. Without proper resolution, the models of tidal oceanic dynamics simulate the ocean general circulation, but do not describe correctly the energy cascades at the eddy scales including interaction between the tides and the mesoscale eddies. Absence of this sub-mesoscale dynamics in the models can largely affect their capability to simulate the two-layer inter-basin exchange.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"36 1","pages":"691-719"},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46122632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/0233-7584-2020-6-613-627
М. Н. Кошляков, В Н Белокопытов
The paper is aimed at reviewing the studies of mesoscale eddies in the open ocean carried out by the Soviet and foreign institutions during the experiments in the specified geographical regions. The eddy-current effects are known since the 1930ies, and just the experiments “Polygon-67” in the Arabian Sea, “Polygon-70”, MODE , POLYMODE, Tourbillon , “Mesopolygon” in the tropical Atlantic, “Megapolygon” in the northwestern Pacific Ocean have advanced our knowledge about physical nature of the ocean eddy dynamics. Long-term complex measurements including current meters at the moored buoy arrays accompanied by a series of hydrographic surveys have provided the required experimental data for developing the theory of mesoscale variability. It explained arising and evolution of the eddies in the ocean as a result of interaction between various physical processes: baroclinic instability of a large-scale current, transformation of geostrophic turbulence in the Rossby wave field, barotropization of eddies and others. Later on, the studies of the ocean mesoscale variability evolved from the oceanographic surveys and special-purpose experiments at the polygons performed due to the research vessel cruises to the satellite altimetry methods and the drifter technologies. All the modern global estimates of eddy formations published in the last decade confirm the previous summaries, particularly those describing spatial distribution of the eddy kinetic energy in the World Ocean. They also represent new or the improved assessments of the eddies’ various characteristics: their size, drift velocity and direction, sign of rotation, nonlinearity, trajectory shear and others. Despite of the progress in remote sensing and regular launching of great amount of drifters and profiling floats, it is still difficult to obtain a comprehensive pattern of eddy dynamics within the whole World Ocean. It seems perspective to resume in future special-purpose experiments in the key regions of the World Ocean based on modern technologies.
{"title":"Синоптические вихри открытого океана: обзор экспериментальных исследований","authors":"М. Н. Кошляков, В Н Белокопытов","doi":"10.22449/0233-7584-2020-6-613-627","DOIUrl":"https://doi.org/10.22449/0233-7584-2020-6-613-627","url":null,"abstract":"The paper is aimed at reviewing the studies of mesoscale eddies in the open ocean carried out by the Soviet and foreign institutions during the experiments in the specified geographical regions. The eddy-current effects are known since the 1930ies, and just the experiments “Polygon-67” in the Arabian Sea, “Polygon-70”, MODE , POLYMODE, Tourbillon , “Mesopolygon” in the tropical Atlantic, “Megapolygon” in the northwestern Pacific Ocean have advanced our knowledge about physical nature of the ocean eddy dynamics. Long-term complex measurements including current meters at the moored buoy arrays accompanied by a series of hydrographic surveys have provided the required experimental data for developing the theory of mesoscale variability. It explained arising and evolution of the eddies in the ocean as a result of interaction between various physical processes: baroclinic instability of a large-scale current, transformation of geostrophic turbulence in the Rossby wave field, barotropization of eddies and others. Later on, the studies of the ocean mesoscale variability evolved from the oceanographic surveys and special-purpose experiments at the polygons performed due to the research vessel cruises to the satellite altimetry methods and the drifter technologies. All the modern global estimates of eddy formations published in the last decade confirm the previous summaries, particularly those describing spatial distribution of the eddy kinetic energy in the World Ocean. They also represent new or the improved assessments of the eddies’ various characteristics: their size, drift velocity and direction, sign of rotation, nonlinearity, trajectory shear and others. Despite of the progress in remote sensing and regular launching of great amount of drifters and profiling floats, it is still difficult to obtain a comprehensive pattern of eddy dynamics within the whole World Ocean. It seems perspective to resume in future special-purpose experiments in the key regions of the World Ocean based on modern technologies.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"36 1","pages":"613-627"},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46261732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/1573-160x-2020-6-659-676
G. Reznik, S. Kravtsov
Purpose. This paper briefly reviews the theory of singular vortices (SV) on a beta-plane. Methods and Results : The primary focus of the paper is on a long-term evolution of an individual SV: the governing equations and integrals of motion are given, the algorithm of numerical implementation of these equations for investigation of such an evolution is described, and the results of some numerical experiments are presented. It is shown that the vortex evolution consists of two stages. At an initial (quasi-linear) stage, the near-field radiation of Rossby waves by the vortex produces, near the vortex, a non-stationary secondary dipole – the beta-gyres – which forces the vortex to move (a cyclone drifts northwestward, an anticyclone – southwestward). At the next (nonlinear) stage, the far-field radiation of Rossby waves and self-interactions within the regular component of the motion become of importance. A singular cyclone (anticyclone) migrates slowly into the anticyclonic (cyclonic) beta-gyre; the SV and the beta-gyre form a compact vortex pair which continues to move northwestward (southwestward). As this process takes place, the cyclonic (anticyclonic) beta-gyre gradually drifts away from and ceases to affect the SV, while the SV starts to interact with the Rossby waves it radiated previously, which results in oscillations of its translation speed. The duration of the quasi-linear stage rapidly increases with an increasing intensity of the SV; for vortices of small or moderate intensity, this stage ends rapidly and gives way to the nonlinear stage. The first phenomenological description of the nonlinear stage of a singular monopole’s evolution appeared in our recent work on the dynamics of the SV on a beta-plane. Conclusions : The theory of singular vortices on a beta-plane developed here significantly broadens our understanding of the evolution and dynamics of localized geophysical vortices which play an important role in the large-scale circulation of the ocean and atmosphere.
{"title":"Singular Vortices on a Beta-Plane: A Brief Review and Recent Results","authors":"G. Reznik, S. Kravtsov","doi":"10.22449/1573-160x-2020-6-659-676","DOIUrl":"https://doi.org/10.22449/1573-160x-2020-6-659-676","url":null,"abstract":"Purpose. This paper briefly reviews the theory of singular vortices (SV) on a beta-plane. Methods and Results : The primary focus of the paper is on a long-term evolution of an individual SV: the governing equations and integrals of motion are given, the algorithm of numerical implementation of these equations for investigation of such an evolution is described, and the results of some numerical experiments are presented. It is shown that the vortex evolution consists of two stages. At an initial (quasi-linear) stage, the near-field radiation of Rossby waves by the vortex produces, near the vortex, a non-stationary secondary dipole – the beta-gyres – which forces the vortex to move (a cyclone drifts northwestward, an anticyclone – southwestward). At the next (nonlinear) stage, the far-field radiation of Rossby waves and self-interactions within the regular component of the motion become of importance. A singular cyclone (anticyclone) migrates slowly into the anticyclonic (cyclonic) beta-gyre; the SV and the beta-gyre form a compact vortex pair which continues to move northwestward (southwestward). As this process takes place, the cyclonic (anticyclonic) beta-gyre gradually drifts away from and ceases to affect the SV, while the SV starts to interact with the Rossby waves it radiated previously, which results in oscillations of its translation speed. The duration of the quasi-linear stage rapidly increases with an increasing intensity of the SV; for vortices of small or moderate intensity, this stage ends rapidly and gives way to the nonlinear stage. The first phenomenological description of the nonlinear stage of a singular monopole’s evolution appeared in our recent work on the dynamics of the SV on a beta-plane. Conclusions : The theory of singular vortices on a beta-plane developed here significantly broadens our understanding of the evolution and dynamics of localized geophysical vortices which play an important role in the large-scale circulation of the ocean and atmosphere.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49219209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/1573-160x-2021-6-612-631
I. D. Rostov, E. Dmitrieva, N. Rudykh
Purpose. The aim of the study consists in identifying the spatial-temporal features of interannual changes in the surface air temperature Ta, the sea surface temperature (SST) and the upper 1000-meter water layer temperature Tw in the extratropical zone of the South Pacific Ocean over the past four decades, which are manifested as a result of the planetary changes and a shift in the climatic regime at the turn of the XX–XXI centuries. Besides, the revealed features’ trends and their possible cause-and-effect relationships with the processes in the atmosphere and on the ocean surface are planned to be assessed. Methods and Results. Based on the Global Meteorological Network and Reanalysis data (NOAA), regional features and trends of the water and air temperature interannual fluctuations, and their relation to variations in the pressure and wind fields, intensity of the atmosphere action centers (AAC) and climatic indices (CI) over the past 4 decades have been determined. Applied were the methods of the cluster, correlation and regression analysis, as well as the apparatus of empirical orthogonal functions (EOF). The positive trends in changes of the Ta and SST fields are manifested mainly in the northwestern part of the region, where they are statistically significant and reach their maximum 0.4–0.6°C over 10 years in the Tasman Sea region and to the northeast of New Zealand. The water areas with minimal, negative or insignificant values of the air and water temperature trends are located on the southern and eastern peripheries of the water area under study – in the areas of influence of cold currents. Over the entire investigated water area, the trends in the mean annual SST and Ta were ~ 0.04–0.06°C/10 years that are 2–3 times less than those in the subarctic region of the North Pacific Ocean. The features of spatial-temporal variability of the water temperature trends at different horizons differ significantly from the characteristics of the SST trends. The trends’ spatial distribution is already transformed within the upper 200-m layer; and deeper, maximums of this value are observed in the southeastern part of the water area. Conclusions. The results obtained made it possible to characterize the degree of heterogeneity of response of the atmosphere surface layer, SST and vertical distribution of Tw in the extratropical zone of the South Pacific to the ongoing global changes, to identify the isolated areas, to estimate quantitatively the warming rate in these water areas, and to compare these estimates with those of the other regions in the Pacific Ocean. It is shown that the individual phases of alternation of the warm and cold periods in the interannual temperature variation are consistent with the changes of the regional CI and the AAC state; this fact emphasizes the inhomogeneous nature of these processes in space and time.
{"title":"Interannual Variability of Thermal Conditions in the Extratropical Zone of the South Pacific at the Turn of the XX–XXI Centuries","authors":"I. D. Rostov, E. Dmitrieva, N. Rudykh","doi":"10.22449/1573-160x-2021-6-612-631","DOIUrl":"https://doi.org/10.22449/1573-160x-2021-6-612-631","url":null,"abstract":"Purpose. The aim of the study consists in identifying the spatial-temporal features of interannual changes in the surface air temperature Ta, the sea surface temperature (SST) and the upper 1000-meter water layer temperature Tw in the extratropical zone of the South Pacific Ocean over the past four decades, which are manifested as a result of the planetary changes and a shift in the climatic regime at the turn of the XX–XXI centuries. Besides, the revealed features’ trends and their possible cause-and-effect relationships with the processes in the atmosphere and on the ocean surface are planned to be assessed. Methods and Results. Based on the Global Meteorological Network and Reanalysis data (NOAA), regional features and trends of the water and air temperature interannual fluctuations, and their relation to variations in the pressure and wind fields, intensity of the atmosphere action centers (AAC) and climatic indices (CI) over the past 4 decades have been determined. Applied were the methods of the cluster, correlation and regression analysis, as well as the apparatus of empirical orthogonal functions (EOF). The positive trends in changes of the Ta and SST fields are manifested mainly in the northwestern part of the region, where they are statistically significant and reach their maximum 0.4–0.6°C over 10 years in the Tasman Sea region and to the northeast of New Zealand. The water areas with minimal, negative or insignificant values of the air and water temperature trends are located on the southern and eastern peripheries of the water area under study – in the areas of influence of cold currents. Over the entire investigated water area, the trends in the mean annual SST and Ta were ~ 0.04–0.06°C/10 years that are 2–3 times less than those in the subarctic region of the North Pacific Ocean. The features of spatial-temporal variability of the water temperature trends at different horizons differ significantly from the characteristics of the SST trends. The trends’ spatial distribution is already transformed within the upper 200-m layer; and deeper, maximums of this value are observed in the southeastern part of the water area. Conclusions. The results obtained made it possible to characterize the degree of heterogeneity of response of the atmosphere surface layer, SST and vertical distribution of Tw in the extratropical zone of the South Pacific to the ongoing global changes, to identify the isolated areas, to estimate quantitatively the warming rate in these water areas, and to compare these estimates with those of the other regions in the Pacific Ocean. It is shown that the individual phases of alternation of the warm and cold periods in the interannual temperature variation are consistent with the changes of the regional CI and the AAC state; this fact emphasizes the inhomogeneous nature of these processes in space and time.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49234060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/0233-7584-2020-6-740-756
G. G. Sutyrin
Purpose. The article is aimed at substantiating theoretically amazing longevity (up to 5 years) of the individual vortices in the World Ocean against the background of strong fluctuations of the ocean currents and regardless of the Rossby wave dispersion features. Methods and Results. Evolution of the baroclinic vortices is considered in a hybrid two-layer ocean model over a topographic slope on the beta-plane. In the upper layer with strong potential vorticity anomalies, the currents are assumed to be balanced; in the lower layer at week potential vorticity anomalies, the currents are described in the traditional quasi-geostrophic approximation. Slow evolving almost circular vortices embedded in a vertically sheared current typical of the subtropical part of the ocean are described analytically. The theory shows how a baroclinic vortex is followed by the lee Rossby waves. The vortex drift across the mean current is conditioned mainly by the baroclinic-dipole structure of the represented solution; at that the vortex energy loss related to the Rossby wave radiation can be compensated by the energy stored in the mean currents. Conclusions. The constructed model provides reasonable estimates of the energy drift and transfer typical of the ocean vortices with strong anomalies of potential vorticity. Direct support of long-lived vortices by the energy of the baroclinic mean flows irrespective of their stability, is of great importance for better understanding the physical mechanisms relating to significant longetivity of the geophysical vortices and the features of their movement.
{"title":"Каким образом океанические вихри могут быть столь долгоживущими","authors":"G. G. Sutyrin","doi":"10.22449/0233-7584-2020-6-740-756","DOIUrl":"https://doi.org/10.22449/0233-7584-2020-6-740-756","url":null,"abstract":"Purpose. The article is aimed at substantiating theoretically amazing longevity (up to 5 years) of the individual vortices in the World Ocean against the background of strong fluctuations of the ocean currents and regardless of the Rossby wave dispersion features. Methods and Results. Evolution of the baroclinic vortices is considered in a hybrid two-layer ocean model over a topographic slope on the beta-plane. In the upper layer with strong potential vorticity anomalies, the currents are assumed to be balanced; in the lower layer at week potential vorticity anomalies, the currents are described in the traditional quasi-geostrophic approximation. Slow evolving almost circular vortices embedded in a vertically sheared current typical of the subtropical part of the ocean are described analytically. The theory shows how a baroclinic vortex is followed by the lee Rossby waves. The vortex drift across the mean current is conditioned mainly by the baroclinic-dipole structure of the represented solution; at that the vortex energy loss related to the Rossby wave radiation can be compensated by the energy stored in the mean currents. Conclusions. The constructed model provides reasonable estimates of the energy drift and transfer typical of the ocean vortices with strong anomalies of potential vorticity. Direct support of long-lived vortices by the energy of the baroclinic mean flows irrespective of their stability, is of great importance for better understanding the physical mechanisms relating to significant longetivity of the geophysical vortices and the features of their movement.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"36 1","pages":"740-756"},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45928831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/1573-160x-2020-6-573-589
G. Shapiro, J. Gonzalez-Ondina
Purpose. The main goal of this study is to analyse the seasonal variability of meso-scale eddy activity in the north tropical Indian Ocean. The selected area coincides with the location of POLYGON-67 (P67) experiment where the mesoscale eddies of the open ocean were first discovered. Methods and results. The variability of mesoscale eddy kinetic energy in surface ocean layer, enstrophy of larger scale circulation, spatial and temporal patterns of surface currents and surface winds are jointly analysed using a 20-year long daily time series of eddy-resolving ocean reanalysis data obtained from EU Copernicus Marine Environment Monitoring Service and climatic wind data from US National Oceanographic and Atmospheric Administration. The fast mesoscale and slow large-scale processes are separated using a Savitsky – Golay filter with the cut-off time of 103 days which corresponds to a local minimum in the full kinetic energy power spectrum. In contrast to other parts of the tropical ocean, the seasonal variability of EKE exhibits 2 maxima – the largest being in April, and the secondary being in October which are related to the maxima in enstrophy of larger scale currents. Conclusions. The double peak variability in EKE corresponds to the seasonal variability of large scale enstrophy and monsoon wind circulation and supports a hypothesis that the main mechanism of EKE generation is barotropic instability of larger scale currents. The EKE variability within P67 is mostly controlled by advection of energy from neighbouring areas, and to a lesser extent by local generation.
{"title":"Seasonal Variability of Eddy Kinetic Energy in the Central Indian Ocean: POLYGON-67 Revised","authors":"G. Shapiro, J. Gonzalez-Ondina","doi":"10.22449/1573-160x-2020-6-573-589","DOIUrl":"https://doi.org/10.22449/1573-160x-2020-6-573-589","url":null,"abstract":"Purpose. The main goal of this study is to analyse the seasonal variability of meso-scale eddy activity in the north tropical Indian Ocean. The selected area coincides with the location of POLYGON-67 (P67) experiment where the mesoscale eddies of the open ocean were first discovered. Methods and results. The variability of mesoscale eddy kinetic energy in surface ocean layer, enstrophy of larger scale circulation, spatial and temporal patterns of surface currents and surface winds are jointly analysed using a 20-year long daily time series of eddy-resolving ocean reanalysis data obtained from EU Copernicus Marine Environment Monitoring Service and climatic wind data from US National Oceanographic and Atmospheric Administration. The fast mesoscale and slow large-scale processes are separated using a Savitsky – Golay filter with the cut-off time of 103 days which corresponds to a local minimum in the full kinetic energy power spectrum. In contrast to other parts of the tropical ocean, the seasonal variability of EKE exhibits 2 maxima – the largest being in April, and the secondary being in October which are related to the maxima in enstrophy of larger scale currents. Conclusions. The double peak variability in EKE corresponds to the seasonal variability of large scale enstrophy and monsoon wind circulation and supports a hypothesis that the main mechanism of EKE generation is barotropic instability of larger scale currents. The EKE variability within P67 is mostly controlled by advection of energy from neighbouring areas, and to a lesser extent by local generation.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49041823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-01DOI: 10.22449/0233-7584-2020-6-646-675
A. Mikaelyan, A. Zatsepin, A. Kubryakov
Different types of mesoscale eddy dynamics are considered in the paper from the viewpoint of their effect on the plankton (mainly phytoplankton) amount and its taxonomic structure. The eddy structures of all types, including cyclonic, anticyclonic, water-body anticyclonic and frontal ones, as well as the dipole structures, actively affect plankton. Theoretical schemes of the influencing mechanisms, which are illustrated by the examples of such an impact on the plankton in the Black Sea, are examined. The analyzed responses of the marine plankton ecosystems to the eddy dynamics and the scientific literature review unambiguously testify the important role of these processes in formation of biological productivity in the seas and oceans. A cyclonic eddy forms the isopycnals rise (a dome-like bend) in its core both in the thermocline and in the pycno-halocline that elevates nitrocline; it promotes bioproductivity increase. In the center of the anticyclonic eddy, the thermocline and pycno-halocline deepen (deflection) which negatively affects bioproductivity. At the same time, the rise of the isopycnals occurs at the eddy periphery that, on the contrary, contributes to increase in primary production. In contrast to a regular anticyclone, a water-body (or lens-like) eddy induces the water rise in a layer above the depth of the maximum orbital velocity of the eddy, in other words, in its upper part it often acts like a cyclone. Thus, in any eddy there are the areas where the thermocline rises to the surface and, therefore, the prerequisites for the bioproductivity increase are formed. Strong winds not only enhance the effect of the eddies on biota, but can completely change the nature of this impact. When exposed to wind, the intensity of the biogenic elements transport to the photic layer in the cyclones can decrease, whereas in the lens-like anticyclones it can increase. The important point is that the long-living eddies change the influencing mechanisms depending on the stage of their evolution. At last, the eddy structures often promote changing in the dominant phytoplankton species that can significantly alter the flow of organic matter to the bottom and affect the global carbon cycle.
{"title":"Effect of Mesoscale Eddy Dynamics on Bioproductivity of the Marine Ecosystems","authors":"A. Mikaelyan, A. Zatsepin, A. Kubryakov","doi":"10.22449/0233-7584-2020-6-646-675","DOIUrl":"https://doi.org/10.22449/0233-7584-2020-6-646-675","url":null,"abstract":"Different types of mesoscale eddy dynamics are considered in the paper from the viewpoint of their effect on the plankton (mainly phytoplankton) amount and its taxonomic structure. The eddy structures of all types, including cyclonic, anticyclonic, water-body anticyclonic and frontal ones, as well as the dipole structures, actively affect plankton. Theoretical schemes of the influencing mechanisms, which are illustrated by the examples of such an impact on the plankton in the Black Sea, are examined. The analyzed responses of the marine plankton ecosystems to the eddy dynamics and the scientific literature review unambiguously testify the important role of these processes in formation of biological productivity in the seas and oceans. A cyclonic eddy forms the isopycnals rise (a dome-like bend) in its core both in the thermocline and in the pycno-halocline that elevates nitrocline; it promotes bioproductivity increase. In the center of the anticyclonic eddy, the thermocline and pycno-halocline deepen (deflection) which negatively affects bioproductivity. At the same time, the rise of the isopycnals occurs at the eddy periphery that, on the contrary, contributes to increase in primary production. In contrast to a regular anticyclone, a water-body (or lens-like) eddy induces the water rise in a layer above the depth of the maximum orbital velocity of the eddy, in other words, in its upper part it often acts like a cyclone. Thus, in any eddy there are the areas where the thermocline rises to the surface and, therefore, the prerequisites for the bioproductivity increase are formed. Strong winds not only enhance the effect of the eddies on biota, but can completely change the nature of this impact. When exposed to wind, the intensity of the biogenic elements transport to the photic layer in the cyclones can decrease, whereas in the lens-like anticyclones it can increase. The important point is that the long-living eddies change the influencing mechanisms depending on the stage of their evolution. At last, the eddy structures often promote changing in the dominant phytoplankton species that can significantly alter the flow of organic matter to the bottom and affect the global carbon cycle.","PeriodicalId":43550,"journal":{"name":"Physical Oceanography","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68625117","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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