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Abstract
The acoustic properties of a cyclonic Gulf Stream ring have been studied with field data and ray computations. Cyclonic rings represent relatively low sound velocity regions with large horizontal gradients of sound velocity embedded in the Sargasso Sea. Ray computations have shown the development of deep sound-channel-axis propagation from a near-surface source within a cyclonic ring.
Abstract
The acoustic properties of a cyclonic Gulf Stream ring have been studied with field data and ray computations. Cyclonic rings represent relatively low sound velocity regions with large horizontal gradients of sound velocity embedded in the Sargasso Sea. Ray computations have shown the development of deep sound-channel-axis propagation from a near-surface source within a cyclonic ring.
Abstract
The mixing and entrainment processes present in a cyclonic ring are investigated by means of a parametric model which is fitted to serial temperature data for a North Atlantic ring. The physical model assumes an axially symmetric ring in which the temperature is presumed to be governed bywhere KA and KZ are the horizontal and vertical eddy diffusivity coefficients and J(ψT) is the (r,z) Jacobian of the transverse streamfunction ψ and the temperature T. Data from two cruises during the 1967 observation of a ring by the Woods Hole Oceanographic Institution provided estimates of the derivatives of the temperature. Regression analysis was used to determine the coefficients for polynomial representations of ψ(r,z) for selected combinations of Kh and Kz . The study indicates upper bounds on the order of magnitude for the diffusivities (Kh ,Kz )=(105,10) cm2 s−1 based upon near-minimum least-squares error estimates from the regression analysis. An important result is that little differentiation exists between a purely advective entrainment regime and those regimes including both entrainment and diffusion; i.e., the entrainment circulation appears to be the dominant mechanism in the temporal changes of the ring for a time scale of at least two months. The results provide streamline patterns for the transverse flow from the surface to 1000 m depth consistent with isotherm movement and changes in the ring water masses.
Abstract
The mixing and entrainment processes present in a cyclonic ring are investigated by means of a parametric model which is fitted to serial temperature data for a North Atlantic ring. The physical model assumes an axially symmetric ring in which the temperature is presumed to be governed bywhere KA and KZ are the horizontal and vertical eddy diffusivity coefficients and J(ψT) is the (r,z) Jacobian of the transverse streamfunction ψ and the temperature T. Data from two cruises during the 1967 observation of a ring by the Woods Hole Oceanographic Institution provided estimates of the derivatives of the temperature. Regression analysis was used to determine the coefficients for polynomial representations of ψ(r,z) for selected combinations of Kh and Kz . The study indicates upper bounds on the order of magnitude for the diffusivities (Kh ,Kz )=(105,10) cm2 s−1 based upon near-minimum least-squares error estimates from the regression analysis. An important result is that little differentiation exists between a purely advective entrainment regime and those regimes including both entrainment and diffusion; i.e., the entrainment circulation appears to be the dominant mechanism in the temporal changes of the ring for a time scale of at least two months. The results provide streamline patterns for the transverse flow from the surface to 1000 m depth consistent with isotherm movement and changes in the ring water masses.
Abstract
Sea surface flow derived from displacements of surface patterns in sequential NOAA-6 AVHRR (11 micron band) satellite images yield coherent nonuniform distributions of velocity vectors, An analytic representation of flow over the region of the distribution is obtained by performing a least-squares regression analysis for coefficients of a streamfunction expansion that is expressed in terms of trigonometric bash functions. Sea surface topography is estimated with the streamfunction by employing a geostrophic approximation. An application is made to a portion of the Oyashio Frontal Zone in the northwestern Pacific that includes the First and Second Oyashio Intrusions and an anticyclonic eddy. A horizontal map of a local rotational perturbation property is calculated for this region as a further example of the use of the streamfunction analysis.
Abstract
Sea surface flow derived from displacements of surface patterns in sequential NOAA-6 AVHRR (11 micron band) satellite images yield coherent nonuniform distributions of velocity vectors, An analytic representation of flow over the region of the distribution is obtained by performing a least-squares regression analysis for coefficients of a streamfunction expansion that is expressed in terms of trigonometric bash functions. Sea surface topography is estimated with the streamfunction by employing a geostrophic approximation. An application is made to a portion of the Oyashio Frontal Zone in the northwestern Pacific that includes the First and Second Oyashio Intrusions and an anticyclonic eddy. A horizontal map of a local rotational perturbation property is calculated for this region as a further example of the use of the streamfunction analysis.
Abstract
Eight cruises over a 10-month period in the North Atlantic have provided the Cyclonic Ring Experiment with observations of two rings. Life histories, structure and structural changes have been studied with emphasis on the effects of Stream interaction and spindown processes. Ring AL was generated in September 1976 with a central water mass composed of Slope and anticyclonic ring waters. Ring BOB separated from the Stream in March 1977 with a Shelf and Slope Water core. Both rings had a 7-month lifetime, interacted with the Gulf Stream and were regenerated. The Stream interaction altered the core structures, and in the case of BOB, cruise observations show significant changes in ring size and shape. BOB's spatial extent decreased with interaction and increased during spindown while eccentricity of the ring behaved in an opposite manner.
Abstract
Eight cruises over a 10-month period in the North Atlantic have provided the Cyclonic Ring Experiment with observations of two rings. Life histories, structure and structural changes have been studied with emphasis on the effects of Stream interaction and spindown processes. Ring AL was generated in September 1976 with a central water mass composed of Slope and anticyclonic ring waters. Ring BOB separated from the Stream in March 1977 with a Shelf and Slope Water core. Both rings had a 7-month lifetime, interacted with the Gulf Stream and were regenerated. The Stream interaction altered the core structures, and in the case of BOB, cruise observations show significant changes in ring size and shape. BOB's spatial extent decreased with interaction and increased during spindown while eccentricity of the ring behaved in an opposite manner.
Abstract
Field observations provide a data base that supports a comparison of ring structures in terms of the background Sargasso Sea environment. Five ring surveys, three from the 1967 sequence, a big baby ring and ring AL, were selected for this study. Anomalies of temperature, salinity, transport potential energy density, heat content and sound velocity have been examined using a reference which closely approximates Iselin's characteristic T-S relation for the western gyre.
The results for the 1967 sequence demonstrate an initial reduction in anomaly strengths followed by strong ring stability. Comparison of two different rings, possibly equal in age, show the effect of the initial water mass conditions on anomaly strengths. Comparison of a cyclonic ring and the big baby ring reveals similar anomaly strengths and sizes in the same geographical region for rings that are assumed to be two and eleven months in age, respectively. This suggests that big baby rings can initially represent more intense perturbations to the Sargasso Sea than cyclonic ring counterparts.
Abstract
Field observations provide a data base that supports a comparison of ring structures in terms of the background Sargasso Sea environment. Five ring surveys, three from the 1967 sequence, a big baby ring and ring AL, were selected for this study. Anomalies of temperature, salinity, transport potential energy density, heat content and sound velocity have been examined using a reference which closely approximates Iselin's characteristic T-S relation for the western gyre.
The results for the 1967 sequence demonstrate an initial reduction in anomaly strengths followed by strong ring stability. Comparison of two different rings, possibly equal in age, show the effect of the initial water mass conditions on anomaly strengths. Comparison of a cyclonic ring and the big baby ring reveals similar anomaly strengths and sizes in the same geographical region for rings that are assumed to be two and eleven months in age, respectively. This suggests that big baby rings can initially represent more intense perturbations to the Sargasso Sea than cyclonic ring counterparts.
