A detailed energy analysis of the barotropic and baroclinic M2 tides in the Monterey Bay area is performed. The authors first derive a theoretical framework for analyzing internal tide energetics based on the complete form of the barotropic and baroclinic energy equations, which include the full nonlinear and nonhydrostatic energy flux contributions as well as an improved evaluation of the available potential energy. This approach is implemented in the Stanford Unstructured Nonhydrostatic Terrain-Following Adaptive Navier–Stokes Simulator (SUNTANS). Results from three-dimensional, high-resolution SUNTANS simulations are analyzed to estimate the tidal energy partitioning among generation, radiation, and dissipation. A 200 km × 230 km domain including all typical topographic features in this region is used to represent the Monterey Bay area. Of the 152-MW energy lost from the barotropic tide, approximately 133 MW (88%) is converted into baroclinic energy through internal tide generation, and 42% (56 MW) of this baroclinic energy radiates away into the open ocean. The tidal energy partitioning depends greatly on the topographic features. The Davidson Seamount is most efficient at baroclinic energy generation and radiation, whereas the Monterey Submarine Canyon acts as an energy sink. Energy flux contributions from nonlinear and nonhydrostatic effects are also examined. In the Monterey Bay area, the nonlinear and nonhydrostatic contributions are quite small. Moreover, the authors investigate the character of internal tide generation and find that in the Monterey Bay area the generated baroclinic tides are mainly linear and in the form of internal tidal beams. Comparison of the modeled tidal conversion to previous theoretical estimates shows that they are consistent with one another.

A detailed energetics analysis of the Gulf Stream (GS) and associated eddies is performed using a highresolution multidecadal regional ocean model simulation. The energy equations for the time-mean and timevarying flows are derived as a theoretical framework for the analysis. The eddy-mean flow energy components and their conversions show complex spatial distributions. In the along-coast region, the cross-stream and cross-bump variations are seen in the eddy-mean flow energy conversions, whereas in the off-coast region, a mixed positive-negative conversion pattern is observed. The local variations of the eddy-mean flow interaction are influenced by the varying bottom topography. When considering the domain-averaged energetics, the eddy-mean flow interaction shows significant along-stream variability. Upstream of Cape Hatteras, the energy is mainly transferred from the mean flow to the eddy field through barotropic and baroclinic instabilities. Upon separating from the coast, the GS becomes highly unstable and both energy conversions intensify. When the GS flows into the off-coast region, an inverse conversion from the eddy field to the mean flow dominates the power transfer. For the entire GS region, the mean current is intrinsically unstable and transfers 28.26 GW of kinetic energy and 26.80 GW of available potential energy to the eddy field. The mesoscale eddy kinetic energy is generated by mixed barotropic and baroclinic instabilities, contributing 28.26 and 9.15 GW, respectively. Beyond directly supplying the barotropic pathway, mean kinetic energy also provides 11.55 GW of power to mean available potential energy and subsequently facilitates the baroclinic instability pathway.

[1] A detailed statistical study of the mesoscale eddy activity in the Gulf Stream (GS) region is performed based on a high-resolution multidecadal regional ocean model hindcast. An eddy detection and tracking method that can be used to capture eddy features from large datasets is presented. This method is applied to the 50 year model hindcast within a domain with the most energetic eddy activity along the GS. Detection results are then analyzed to investigate the kinematic properties and temporal variability of GS mesoscale eddies. The studied kinematic properties include the eddy size, duration, intensity, propagation, and spatial distribution. On average, cyclonic eddies are smaller in size but more energetic and remain coherent longer than anticyclonic ones. Cyclonic eddies generally travel further from the generation sites and have a strong tendency for westward propagation with a small equatorward deflection. Anticyclonic eddies remain near their generation locations and tend to propagate northward. The temporal evolution of eddy properties for long-lived eddies (lifetime >90 days) is also examined. For both cyclonic and anticyclonic eddies, the size increases rapidly to their maximum value within the first 20 days at which point they begin to slowly decay. In terms of intensity, cyclonic eddies show a quasi-linear decay while the anticyclonic ones reach a quasi-steady state after 3-4 months of a more rapid decay. Finally, the seasonal variability of the GS mesoscale eddies is explored. In autumn and winter, both types of eddies are more numerous and larger but less intense, while in spring they are more intense but less numerous and generally smaller. Several possible mechanisms, including the wind stress, thermal forcing, and topographic influence, are considered to explain the seasonal cycle of eddy variability.

The Mid‐Atlantic Bight (MAB) Cold Pool is a distinctive cold (lower than 10 °C) and relatively fresh (lower than 34 practical salinity unit) water mass. It is located over the middle and outer shelf of the MAB, below the seasonal thermocline, and is attached to the bottom. Following this definition, we put forward a method that includes three criteria to capture and quantify Cold Pool characteristics, based on a 50‐year (1958–2007) high‐resolution regional ocean model hindcast. The seasonal climatology of the Cold Pool and its properties are investigated during its onset‐peak‐decline cycle. Three stages of the Cold Pool event are defined according to its evolution and characteristics. The Cold Pool cores travel along the 60‐m isobath starting south of the New England shelf to the Hudson Shelf Valley at a speed of 2–3 cm/s. Furthermore, the northern extent of the Cold Pool retreats about 2.6 times faster than the southern extent during the summer progression. The heat balance of near‐bottom waters over the MAB and Georges Bank is computed and it is found that the heat advection, rather than vertical diffusion, dominates the resulting spatial patterns of warming. Possible origins of the Cold Pool are investigated by performing a lead‐lag correlation analysis. Results suggest that the Cold Pool originates not only from local remnants of winter water near the Nantucket Shoals, but has an upstream source traveling in the spring time from the southwestern flank of the Georges Bank along the 80‐m isobath.

A comparison of three common formulations for calculating the available potential energy (APE) in internal wave fields is presented. The formulations are the perturbation APE (APE 1 ), the exact local APE (APE 2 ), and its approximation for linear stratification (APE 3 ). The relationship among these formulations is illustrated through a graphical interpretation and a derivation of the energy conservation laws. Numerical simulations are carried out to quantitatively assess the performance of each APE formulation under the influence of different nonlinear and nonhydrostatic effects. The results show that APE 2 is the most attractive in evaluating the local APE, especially for nonlinear internal waves, since use of APE 2 introduces the smallest errors when computing the energy conservation laws. Larger errors arise when using APE 1 because of the large disparity in magnitude between the kinetic energy and APE 1 . It is shown that the disparity in the tendency of APE 1 is compensated by a large flux arising from the reference pressure and density fields. Because the tendency of the kinetic energy is close to that of APE 3 , computational errors arise when using APE 3 only in the presence of nonlinear stratification, and these errors increase for stronger flow nonlinearity.