A bibliography of physical, chemical, and biological studies of rings in the world's oceans

This bibliography marks the end of several years of sporadic attempts to put together a set of references on rings. The scope of the effort encompasses the chemistry, biology, and physics of the long-lived, coherent features which are commonly referred to as rings after Fuglister (1972). There is a vast literature on the mesoscale eddy field in different parts of the world. The present set of references includes a subset of this body of work. The basic criterion used in the compilation of this bibliography is fairly narrow compared to the range of eddies found in the world's oceans. The emphasis here is on the highly nonlinear features formed due to the instability processes in boundary currents and in the planetary scale jet which surrounds the Antarctic. The nomenclature "ring", refers to the strong encircling current which forms a kinematic trap in which the core of the ring is embedded

The concentrating of organisms at fronts: A cold-water fish and a warm-core Gulf Stream ring

Net hauls made in and around a warm-core Gulf Stream ring in April and June 1982 suggest a concentrating of the mesopelagic fish Benthosema glaciale (family Myctophidae) in the frontal zone at the east edge of the ring. In April, Benthosema was found in very small numbers in the two-month old ring, as was to be expected from the subpolar-temperate distribution of this fish and the warm-water origin and age of the ring. By June, age-0 fish had been recruited to the population susceptible to capture by the midwater trawl. These young fish were about five times as abundant at the frontal zone of the ring and about twice as abundant in the ring center as in the adjacent Slope Water. It is proposed that the increased abundance at the ring front results from a concentrating of the original Slope Water population by convergence. The increase of B. glaciale in the center of the ring may be associated with the inwardly spiralling streamers observed in satellite images.A simple advection/diffusion model for both the fish and a passive tracer of the fluid is used to consider a mechanism that might have concentrated the fish at the ring edge. It is assumed that the fish can counter the vertical flow in order to maintain their preferred depth. Swimming in the horizontal is assumed to be random. The result of this behavior is that the fish and the passive tracer are affected differently in flow fields such as those in rings. Solutions to the model equations lead to the conclusion that the abundance of fish at the ring front can be accounted for by convergence. The model and the divergence pattern in the ring, calculated from hydrographic data, show the time necessary to effect the hundred-fold increase in abundance that was observed in the ring front between April and June to be on the order of two weeks to a month. We suggest that the concentrating mechanism described is widely applicable to a variety of frontal phenomena and to a variety of planktonic plants and animals

Lagrangian statistics in the South Atlantic as derived from SOS and FGGE drifters

Daily averaged positions obtained from satellite-tracked drifting buoys launched during the First GARP Global Experiment (FGGE) and those launched as part of the ONR sponsored Southern Ocean Studies (SOS) are used to analyze eddy diffusivity due to mesoscale motions and its parameterization in some regions of the South Atlantic Ocean, significantly extending the energy range for which this type of estimations are available. Diffusion coefficients, Lagrangian integral time scales and velocity variances are calculated, and Taylor\u27s (1921) Theorem which relates eddy diffusivity estimates with the dispersion of particles from a fixed origin is tested. In all of the cases analyzed here, the anisotropy of the statistics appears as an outstanding feature, with zonal values being larger than meridional ones. Although the conditions of stationarity and homogeneity of the statistics required by Taylor\u27s Theorem are not fulfilled, a positive test for relation was observed for small lags. However, for later times, diffusion and dispersion curves have a tendency to diverge due to the influence of mean current shear. This interpretation is evident in the large differences between diffusion and dispersion in the Brazil/Malvinas extension where there is substantial current shear and a very close agreement between the curves in the gyre interior where the shear is small. The relationship between the diffusion coefficients and eddy velocity statistics for different regimes in the gyre are explored with the conclusion that it is impossible to decide between the hypothesis that the diffusion is proportional to the eddy velocity, i.e. mixing-length theory applies, and the alternate case of the diffusion scaling with the velocity variance or eddy energy. The implications this has to any global parameterization of eddy diffusion is discussed

Exchange processes and watermass modifications along the subarctic front in the North Pacific: Oxygen consumption rates and net carbon flux

Exchange processes along the subarctic front and the modification of subpolar water in the North Pacific are investigated using tracer data from World Ocean Circulation Experiment P14N and P17N lines. The North Pacific Current transports water on both sides of the subarctic front from the western to eastern North Pacific. During this transport, subpolar water from the western subpolar gyre becomes warmer and saltier through the main thermocline via isopycnal mixing with subtropical water. It is shown that this modified subpolar water of western origin is the primary source of well-ventilated water to the eastern subpolar gyre. The isopycnal mixing along the subarctic front is quantified with a two end-member linear mixing analysis using potential temperature, which allowed estimates of oxygen consumption and nitrate remineralization on intermediate layers. Based on the oxygen consumption estimates and temporal information from transient tracers, the vertically integrated oxygen consumption rate is calculated to be 2.1 ± 0.4 M m-2y-1 in the 132-706 m depth range. This implies a net carbon flux of approximately 19 ± 4 gC m-2y-1 out of the euphotic zone

Seascape Genetics: A Coupled Oceanographic-Genetic Model Predicts Population Structure of Caribbean Corals

SummaryPopulation genetics is a powerful tool for measuring important larval connections between marine populations [1–4]. Similarly, oceanographic models based on environmental data can simulate particle movements in ocean currents and make quantitative estimates of larval connections between populations possible [5–9]. However, these two powerful approaches have remained disconnected because no general models currently provide a means of directly comparing dispersal predictions with empirical genetic data (except, see [10]). In addition, previous genetic models have considered relatively simple dispersal scenarios that are often unrealistic for marine larvae [11–15], and recent landscape genetic models have yet to be applied in a marine context [16–20]. We have developed a genetic model that uses connectivity estimates from oceanographic models to predict genetic patterns resulting from larval dispersal in a Caribbean coral. We then compare the predictions to empirical data for threatened staghorn corals. Our coupled oceanographic-genetic model predicts many of the patterns observed in this and other empirical datasets; such patterns include the isolation of the Bahamas and an east-west divergence near Puerto Rico [3, 21–23]. This new approach provides both a valuable tool for predicting genetic structure in marine populations and a means of explicitly testing these predictions with empirical data (Figure 1)

A numerical study of layer formation due to fingers in double-diffusive convection in a vertically-bounded domain

The evolution of fingers in a double-diffusive system is investigated using numerical integration of two-dimensional equations of motion for an incompressible, Boussinesq fluid. The computational domain is periodic in the horizontal direction and is closed with no-flux boundary conditions in the vertical direction. The main result of this study is the evolution of the system from initially linear profiles for both fast and slow diffusing components to a layered state characterized by a finger zone sandwiched between two mixed layers. The horizontal boundaries in this system play an important role in the development of the layered state. At the top and bottom boundaries, light and heavy finger fluxes accumulate leading to the formation of mixed layers exhibiting larger-scale eddies. In the quasi-equilibrium state, the finger zone is characterized by broken wiggly fingers which do not extend across the entire interface. The salinity flux at the mid-depth of the domain is approximately proportional to the 4/3 power of the salinity difference between the mixed layers, except for the initial phase and for the run-down phase

Dynamics of the Makassar Strait

Data collected as part of the Arlindo Project ( Arlindo is an acronym for Arus Lintas Indonesia, meaning throughflow in Bahasa Indonesia) from October 1996 to March 1998 are analyzed to study the characteristics of the flow through the Makassar Strait. Analysis of inverted echo sounders (IES) and bottom pressure data (PIES) combined with TOPEX/POSEIDON satellite-derived sea height anomaly suggest that a minimum of three-layer approximation is necessary to explain the dynamics of the flow in the Makassar Strait. The simple two-layer model used in several studies of the throughflow is rejected based on total incompatibility with the data sets. A three-layer model with significant contributions by the middle layer provides a consistent interpretation of PIES and satellite data. Results are interpreted in the framework of the large-scale circulation

Inertial gyre solutions from a primitive equation ocean model

A numerical exploration of inertial equilibrium states obtained with a primitive equation ocean model suggests that they can be described using statistical mechanics theory developed in the framework of quasi-geostrophy. The performance of the numerical model is first assessed with respect to the quasi-geostrophic model considering a series of experiments in the quasi-geostrophic range, in a closed basin with flat bottom and varying Rossby numbers. The results show that our model is consistent with the quasi-geostrophic model even in terms of dependence from boundary conditions and eddy viscosity values, and that the free surface contribution is negligible. As in the quasi-geostrophic experiments, a tendency toward Fofonoff flows is observed. This tendency remains in a second series of experiments performed outside the quasi-geostrophic range, namely with flows with higher Rossby numbers and with steep topography, characterized by sloping boundaries with an order one fractional change in the depth. It is only close to the boundaries that ageostrophic effects modify the flows. In conclusion, the fact that statistical mechanics theory, initially developed in the framework of quasi-geostrophy, holds for more realistic flows with steep topography supports development of subgrid scale parameterizations based on statistical mechanics theory, to be used in realistic general circulation models

The Role of Long Distance Dispersal Versus Local Retention in Replenishing Marine Populations

Early models and evidence from genetics suggested that long distance dispersal of larvae is likely a common event leading to considerable population connectivity among distant populations. However, recent evidence strongly suggests that local retention is more the rule, and that long distance transport is likely insufficient to sustain marine populations over demographic timescales. We build on earlier model results to examine the probability of larval dispersal to downstream islands within different regions of the Caribbean at varying distances from source populations. Through repeated runs of an ocean circulation model (MICOM), coupled with a random flight model estimating larval sub-grid turbulent motion, we estimate the likelihood of particular circulation events transporting large numbers of larvae to within 9km radii of downstream populations, as well as account for total accumulations of larvae over each year. Further, we incorporate realistic larval behavior and mortality estimates and production variability into our models. Our results are consistent with the hypothesis that marine populations must rely on mechanisms enhancing self-recruitment rather than depend on distant ‘source’ populations

Recipe for Banda Sea water

Water from the western Pacific flows through the Indonesian Seas following different pathways and is modified by various processes to form the uniquely characterized isohaline Banda Sea Water. The processes contributing to the isohaline structure are studied using data from three ARLINDO cruises in 1993, 1994, and 1996. An inverse-model analysis using salinity and CFC-11 data is applied to a vertical section along the main path of flow, from the Makassar Strait to the Flores Sea and Banda Sea. The model reproduces the seasonal and interannual variability of the throughflow and shows reversals of flow in the vertical structure. The model solutions suggest strong baroclinic flows during the southeast monsoon of 1993 and 1996 and a small, more barotropic flow during the northwest monsoon of 1994. The isohaline structure can be accounted for by isopycnal mixing of different source waters and by vertical exchanges, which are significant in this region. A downward flux equivalent to a downwelling velocity of 5 × 10-7 m/s is estimated for the section. The total balance also suggests that seasonally and possibly interannually variable backflushing of water from the Banda Sea into the Straits contribute to the isohaline structure of Banda Sea water