The circulation over the Ross Sea continental shelf facilitates the exchange between the Southern Ocean and the Ross Ice Shelf cavity. Here transport and mixing processes control the access of oceanic heat from the Southern Ocean to the ice shelf base, the formation of sea ice, and the production of High Salinity Shelf Water (HSSW) in polynyas and hence the subsequent formation of Antarctic Bottom Water. A climatological ocean‐ice shelf coupled model of the Ross Sea Sector including the cavity, with prescribed sea ice fluxes, was used to examine the details of currents and their seasonal variability over the continental shelf. A system of two cyclonic and three anticyclonic persistent circulation features has been identified. Transports steadily increase throughout winter, with individual currents carrying up to 2 Sv, nearly doubling their minimum. The seasonal modulation is driven by lateral differences in density and subsequent baroclinic pressure gradients, induced through dense shelf water formation in the Ross Sea and the Terra Nova Bay Polynas. Wind plays a minor role in ocean momentum variability. Sensitivity experiments suggest a weakening of transports with increasing wind stress. Horizontal density variations at the ocean surface are smoothed by the wind. The source of momentum in the cavity is the gravity‐driven bottom flow of HSSW, produced in the Ross Sea Polynya as part of the thermohaline overturning circulation. Tracer experiments suggest that HSSW forming in the Terra Nova Bay Polynya has no cavity access, but instead is the main contributor to Antarctic Bottom Water formed in the northwest slope.

High‐resolution measurements of the air‐ice‐ocean system during an October 2015 event in the Beaufort Sea demonstrate how stored ocean heat can be released to temporarily reverse seasonal ice advance. Strong on‐ice winds over a vast fetch caused mixing and release of heat from the upper ocean. This heat was sufficient to melt large areas of thin, newly formed pancake ice; an average of 10 MJ/m² was lost from the upper ocean in the study area, resulting in ∼3–5 cm pancake sea ice melt. Heat and salt budgets create a consistent picture of the evolving air‐ice‐ocean system during this event, in both a fixed and ice‐following (Lagrangian) reference frame. The heat lost from the upper ocean is large compared with prior observations of ocean heat flux under thick, multiyear Arctic sea ice. In contrast to prior studies, where almost all heat lost goes into ice melt, a significant portion of the ocean heat released in this event goes directly to the atmosphere, while the remainder (∼30–40%) goes into melting sea ice. The magnitude of ocean mixing during this event may have been enhanced by large surface waves, reaching nearly 5 m at the peak, which are becoming increasingly common in the autumn Arctic Ocean. The wave effects are explored by comparing the air‐ice‐ocean evolution observed at short and long fetches, and a common scaling for Langmuir turbulence. After the event, the ocean mixed layer was deeper and cooler, and autumn ice formation resumed.

Mesoscale cyclonic eddies are known to be highly productive. Less well‐known are the dynamics and productivity of smaller cyclonic eddies, known as frontal eddies, that form on the landward side of western boundary currents. In this study, we investigate the physical and biogeochemical properties of two contrasting cyclonic eddies in the East Australian Current (EAC). The first (“Murphy”), a mesoscale cyclonic eddy that formed at ∼28°S with a diameter of ∼160 km and high surface chlorophyll‐a concentrations, which lived ∼47 days. The second (“Freddy”), a smaller frontal eddy (∼35 km diameter) that formed from a shelf water billow ∼7 days prior to sampling at ∼31.5°S and was advected off the shelf along the EAC front (from ∼200 m to 4000 m of water). Both eddies were at least 1000 m deep with a similar steric height anomaly. We introduce and employ “the method of closest approach” using shipboard ADCP velocities to estimate the eddy centers, which reveals significant tilting through the water column. We estimate rotation rates of 4–10 days and 1–9 days and Rossby numbers 0.25–0.1 and 0.6–0.1, from the surface to 600 m for Murphy and Freddy, respectively. High‐resolution altimetry measurements from the SARAL/AltiKA satellite provide estimates of the ageostrophic component of rotation. Our results show that the frontal eddy is significantly more ageostrophic, energetic, and productive than the mesoscale cyclone, despite its small size and short life (∼4 weeks). We suggest that frontal eddies have potential to contribute significantly to the net productivity of the Tasman Sea region.

Vertical mixing is a key issue in ocean circulation modeling today. Mixing, particularly tidal mixing, is poorly represented in ocean and climate models, which generally ignore critical latitude effects. Critical latitude is the latitude where the inertial frequency equals the tidal frequency and differs for each tidal constituent. Critical latitudes strongly influence generation and propagation of internal tides. Using a model, latitude effects on tidal interactions with a seamount were examined by varying the latitude from 20° to 38°, through the range of the diurnal critical latitudes. The diurnal critical latitudes were found to strongly influence propagation of the diurnal internal tides, the magnitude of the semidiurnal tides, the energy in the harmonic and higher frequencies, the barotropic mean flow, and the diffusivities. The strongest effects occurred between the K₁ and O₁ critical latitudes. Here the semidiurnal tides, harmonics, and high frequencies were enhanced, barotropic mean velocities weakened, energy at the harmonics and higher frequencies increased, and diffusivities increased. Spectral techniques indicate that most of these impacts are the result of nonlinear wave‐wave interactions and resonant phenomena with the prominent mechanism harmonic transfers. There was no evidence of parametric subharmonic instabilities. The semidiurnal tides indicated a resonant response at 20°S, which is near the latitude for the combined M₂ and K₁ tidal period, ∼19°S.

The deformation and evolution of internal solitary waves (ISWs) beneath an ice keel can enable potential diapycnal mixing and facilitate upper ocean heat transport, despite a poor understanding of the underlying physics and energetics of ISWs in Polar environments. This study aims to understand the dynamic processes and mixing properties during the evolution of ISWs beneath ice keels in the Arctic Ocean using high‐resolution, non‐hydrostatic simulations. Ice keels can destabilize ISWs through overturning events. Consequently, the initial ISW disintegrates and transfers its energy into secondary smaller‐scale waves. During the ISW‐ice interaction, ISW‐induced turbulent mixing can reach O(10⁻³) W/kg with a magnitude of resultant heat flux of O(10)W/m. Sensitivity experiments demonstrated that the ISW‐ice interaction weakened as the ice keel depth decreased, and consequently, the resultant turbulent mixing and upward heat transfer also decreased. The ice keel depth was critical to the evolution and disintegration of an ISW beneath the ice keel, while the approximate ice keel shape had little effect. Our results provide an important but previously overlooked energy source for upper ocean heat transport in the Arctic Ocean.

Internal tides are energetic in the Mariana arc, but their three‐dimensional radiation and dissipation remain unexplored, particularly the trench‐arc‐basin impacts. Here, the generation, propagation and dissipation of M₂ internal tides over the Mariana area are examined using a series of observation‐supported high‐resolution simulations. The M₂ barotropic to baroclinic conversion rate amounts to 8.35 GW, of which two arc‐shaped ridges contribute ∼81% of the generated energy. The contributions to generation by the Mariana basin and deep trench are weak. Nevertheless, they are important in modulating the energy radiation and dissipation, since tidal beams can spread to these areas. The Mariana ridges radiate the westward‐focused and eastward‐spreading tidal beams. This is very consistent with the altimetric measurements. The resonance in the ridge center enhances the westward converging beam, which can travel across the Palau Ridge, 800 km away. In contrast, the eastward beams propagate over a limited lateral range, but can radiate and dissipate significant energy in the deep water column, reaching even to the abyssal Mariana trench. The direct estimation from the model results reveals the dissipation's multilayer vertical profile in the entire water column, and is well consistent with the finescale parameterization estimate based on vertical strain. However, the estimate of an oft‐used energy balance method, which typically assumes an exponentially decaying vertical structure function for the dissipation rate based on distance above the seafloor, is largely inconsistent with the measurements. Our findings highlight the complexity of three‐dimensional radiation paths and dissipation map of internal tides in the Mariana area.