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Sea-Bird Scientific SBE 41CP CTDs are used on autonomous floats in the global Argo ocean observing program to measure the temperature and salinity of the upper ocean. While profiling, the sensors are subject to dynamic errors as they profile through vertical gradients. Applying dynamic corrections to the temperature and conductivity data reduces these errors and improves sensor accuracy. A series of laboratory experiments conducted in a stratified tank are used to characterize dynamic errors and determine corrections. The corrections are adapted for Argo floats, and recommendations for future implementation are presented.

Summer and fall hydrographic sections in the northeastern Chukchi Sea frequently capture 5–20 m thick intrapycnocline lenses or horizontal plumes of warm, moderately salty summer Bering Sea Water flowing northward from Bering Strait. These features occur within the shallow (~20 m depth) pycnocline separating cold, dilute, surface meltwater from near-freezing, salty, winter-formed waters beneath the pycnocline. An idealized numerical model suggests that the features arise from eddies and meanders generated by instability of the surface front separating meltwater from Bering Sea Water. Warm Bering Sea Water is transported across the front and into the pycnocline by the cross-frontal velocities associated with the instabilities. The accompanying lateral eddy heat fluxes may be important both in summer for promoting ice melt and in fall by delaying the onset of ice formation over portions of this shelf. Lateral heat flux magnitudes depend upon the stratification of the Bering Sea Water.

The evolution of the near-inertial internal wavefield from ice-free summertime conditions to ice-covered wintertime conditions is examined using data from a yearlong deployment of six moorings on the Beaufort continental slope from August 2008 to August 2009. When ice is absent, from July to October, energy is efficiently transferred from the atmosphere to the ocean, generating near-inertial internal waves. When ice is present, from November to June, storms also cause near-inertial oscillations in the ice and mixed layer, but kinetic energy is weaker and oscillations are quickly damped. Damping is dependent on ice pack strength and morphology. Decay scales are longer in early winter (November–January) when the new ice pack is weaker and more mobile, decreasing in late winter (February–June) when the ice pack is stronger and more rigid. Efficiency is also reduced, as comparisons of atmospheric energy available for internal wave generation to mixed layer kinetic energies indicate that a smaller percentage of atmospheric energy is transferred to near-inertial motions when ice concentrations are >90%. However, large kinetic energies and shears are observed during an event on 16 December and spectral energy is elevated above Garrett–Munk levels, coinciding with the largest energy flux predicted during the deployment. A significant amount of near-inertial energy is episodically transferred to the internal wave band from the atmosphere even when the ocean is ice covered; however, damping by ice and less efficient energy transfer still leads to low Arctic internal wave energy in the near-inertial band. Increased kinetic energy below 300 m when ice is forming suggests some events may generate internal waves that radiate into the Arctic Ocean interior.

Observations of breaking internal tides on the Oregon continental slope during a 40-day deployment of 5 moorings along 43°12′N are presented. Remotely generated internal tides shoal onto the slope, steepen, break, and form turbulent bores that propagate upslope independently of the internal tide. A high-resolution snapshot of a single bore is captured from lowered acoustic Doppler current profilers (LADCP)/CTD profiles in a 25-h time series at 1200 m. The bore is cold, salty, over 100 m tall, and has a turbulent head where instantaneous dissipation rates are enhanced (ε > 10−6 W kg−1) and sediment is resuspended. At the two deepest slope moorings (1452 and 1780 m), similar borelike phenomena are observed in near-bottom high-resolution temperature time series. Mean dissipation rates and diapycnal diffusivities increase by a factor of 2 when bores are present ( W kg−1 and m s−1) and observed internal tides are energetic enough to drive these enhanced dissipation rates. Globally, the authors estimate an average of 1.3 kW m−1 of internal tide energy flux is directed onto continental slopes. On the Oregon slope, internal tide fluxes are smaller, suggesting that it is a relatively weak internal tide sink. Mixing associated with the breaking of internal tides is therefore likely to be larger on other continental slopes.

The linear transfer of tidal energy from large to small scales is quantified for small tidal excursion over a near-critical continental slope. A theoretical framework for low-wavenumber energy transfer is derived from “flat bottom” vertical modes and evaluated with observations from the Oregon continental slope. To better understand the observations, local tidal dynamics are modeled with a superposition of two idealized numerical simulations, one forced by local surface-tide velocities and the other by an obliquely incident internal tide generated at the Mendocino Escarpment 315 km southwest of the study site. The simulations reproduce many aspects of the observed internal tide and verify the modal-energy balances. Observed transfer of tidal energy into high-mode internal tides is quantitatively consistent with observed turbulent kinetic energy (TKE) dissipation. Locally generated and incident simulated internal tides are superposed with varying phase shifts to mimic the effects of the temporally varying mesoscale. Altering the phase of the incident internal tide alters (i) internal-tide energy flux, (ii) internal-tide generation, and (iii) energy conversion to high modes, suggesting that tidally driven TKE dissipation may vary between 0 and 500 watts per meter of coastline on 3–5-day time scales. Comparison of observed in situ internal-tide generation and satellite-derived estimates of surface-tide energy loss is inconclusive.

A complex superposition of locally forced and shoaling remotely generated semidiurnal internal tides occurs on the Oregon continental slope. Presented here are observations from a zonal line of five profiling moorings deployed across the continental slope from 500 to 3000 m, a 24-h expendable current profiler (XCP) survey, and five 15–48-h lowered ADCP (LADCP)/CTD stations. The 40-day moored deployment spans three spring and two neap tides, during which the proportions of the locally and remotely forced internal tides vary. Baroclinic signals are strong throughout spring and neap tides, with 4–5-day-long bursts of strong cross-slope baroclinic semidiurnal velocity and vertical displacement . Energy fluxes exhibit complex spatial and temporal patterns throughout both tidal periods. During spring tides, local barotropic forcing is strongest and energy flux over the slope is predominantly offshore (westward). During neap tides, shoaling remotely generated internal tides dominate and energy flux is predominantly onshore (eastward). Shoaling internal tides do not exhibit a strong spring–neap cycle and are also observed during the first spring tide, indicating that they originate from multiple sources. The bulk of the remotely generated internal tide is hypothesized to be generated from south of the array (e.g., Mendocino Escarpment), because energy fluxes at the deep mooring 100 km offshore are always directed northward. However, fluxes on the slope suggest that the northbound internal tide is turned onshore, most likely by reflection from large-scale bathymetry. This is verified with a simple three-dimensional model of mode-1 internal tides propagating obliquely onto a near-critical slope, whose output conforms fairly well to observations, in spite of its simplicity.

[1] An internal partly standing wave in Mamala Bay, Hawaii is studied using new observations and the Princeton Ocean Model (POM). Previous work suggested a convergence in the bay of east- and westbound waves emanating from Kaena Ridge and Makapuu Point, respectively. New energy flux measurements with shipboard ADCP/CTD confirm that Makapuu Point is the eastern source. After validating the POM results against observations, the model output is modally decomposed and compared with the expected theoretical patterns of kinetic and available potential energy, energy flux, and group velocity for a partly standing wave. Agreement is seen for the first baroclinic mode, which also contains most of the energy. The results confirm previous suggestions of standing wave dynamics in Mamala Bay.

[1] Two deep ocean hotspots of turbulent mixing were found over the Oregon continental slope. Thorpe-scale analyses indicate time-averaged turbulent energy dissipation rates of e > 10−7 W/kg and eddy diffusivities of Kρ ∼ 10−2 m2/s at both hotspots. However, the structure of turbulence and its generation mechanism at each site appear to be different. At the 2200-m isobath, sustained >100-m high turbulent overturns occur in stratified fluid several hundred meters above the bottom. Turbulence shows a clear 12.4-h periodicity proposed to be driven by flow over a nearby 100-m tall ridge. At the 1300-m isobath, tidally-modulated turbulence of similar intensity is confined within a stratified bottom boundary layer. Along-slope topographic roughness at scales not resolved in global bathymetric data sets appears to be responsible for the bulk of the turbulence observed. Such topography is common to most continental slopes, providing a mechanism for turbulence generation in regions where barotropic tidal currents are nominally along-isobath.

Online science outreach is paradoxically both easy and difficult. While anyone can start a blog and post updates to Twitter, it can be extremely challenging to establish a long-term following and demonstrate solid measures of success. A daunting number of online tools and platforms exist, and choosing where to start can be a difficult task in itself (for an explanation and guide to online tools, see [1]). As practicing scientists who have contributed to the highly visited marine science blog Deep-Sea News (DSN) for up to nine years, we provide guidance on how scientists, who often have minimal excess time and more pressing priorities, can maximally utilize new media tools. Here, we describe ten rules for conducting effective online outreach, so that other scientists can also enjoy the advantages of disseminating their knowledge and expertise through social media.

"Can I really do this?!" Enthusiasm and doubt surrounded the junior women at the opening reception of the Pattullo Conference. As in other science and engineering fields, real and perceived challenges prevent many women from continuing careers in physical oceanography after graduate school, and we were gathered with senior scientists in the field to debunk the myths surrounding academic careers and help junior women understand the real challenges. Topics at the conference ranged from balancing work and family life to successfully funding research proposals. In this article, we—junior scientist attendees—share some of our personal revelations, surprises, and perspectives about women in physical oceanography gained from this conference. We hope this article will provide insight into the benefits of a gender-specific mentoring event such as the Pattullo Conference, inform senior scientists about what they can do to strengthen the field for junior scientists, and provide guidance to our peers in all geosciences about their chosen careers.