New Approaches for Air-Sea Fluxes in the Southern Ocean

Air-Sea Fluxes for the Southern Ocean: Strategies and Requirements for Detecting Physical and Biogeochemical Exchanges; Frascati, Italy, 21–23 September 201

Interpreting wind-driven Southern Ocean variability in a stochastic framework

A stochastic model is derived from wind stress and bottom pressure gauge data to examine the response of the Antarctic Circumpolar Current (ACC) transport to wind stress forcing. A general method is used to estimate the drift and diffusion coefficients of a continuous stationary Markovian system. As a first approximation, the response of the ACC to wind stress forcing can be described by a multivariate Ornstein-Uhlenbeck process: Gaussian red noise wind stress drives the evolution of the ACC transport, which is damped by a linear drag term. The model indicates that about 30(±10)% of ACC variability is directly driven by the wind stress. This stochastic model can serve as a null hypothesis for studies of wind driven ACC variability. A more accurate stochastic description of the wind stress over the Southern Ocean requires a multiplicative noise component. The variability of the wind stress increases approximately linearly with increasing wind stress values. A multiplicative stochastic process generates a power-law distribution rather than a Gaussian distribution. A simple stochastic model shows that non-Gaussian forcing could have a significant impact on the velocity (or transport) probability density functions (PDFs) of the wind-driven circulation. The net oceanic damping determines whether the distribution of the oceanic flow is Gaussian (small damping) or resembles the distribution of the atmospheric forcing (large damping)

Energetics of wind-driven barotropic variability in the Southern Ocean

This study addresses the energetics of the Southern Ocean, in response to high-frequency wind forcing. A constant-density, multi-layer model is forced with a band of stochastically varying wind stress. The focus is on the interplay between the surface layer and the interior circulation.In line with previous examinations, it is concluded that the interior ocean is not directly energized by the wind work, but rather through the work done by the pressure field. The spatial and temporal characteristics of these terms differ substantially. Although the wind work may be negative in extensive regions of the World Ocean, the pressure work energizes the interior circulation almost everywhere. For low-frequency variability, the total work done by the wind and pressure on the barotropic flow is comparable, but discrepancies may arise for high-frequency variability. A mechanism is identified through which kinetic energy can leak from the wind-driven surface layer to the barotropic flow

Evidence-based guiding principles to build public trust in personal data use in health systems

Objective: Public trust in health systems is pivotal for their effective and efficient functioning. In particular, public trust is essential for personal data use, as demonstrated in debates in many countries, for example, about whether data from COVID-19 contact tracing apps should be pooled or remain on individuals’ smartphones. Low levels of public trust pose a risk not only to health system legitimacy but can also harm population health. Methods: Synthesising our previous qualitative and theoretical research in the English National Health Service which enabled us to conceptualise the nature of public trust in health systems, we present guiding principles designed to rebuild public trust, if lost, and to maintain high levels of public trust in personal data use within the health system, if not. Results: To build public trust, health system actors need to not rush trust building; engage with the public; keep the public safe; offer autonomy to the public; plan for diverse trust relationships; recognise that trust is shaped by both emotion and rational thought; represent the public interest; and work towards realising a net benefit for the health system and the public. Conclusions: Beyond policymakers and government officials, the guiding principles address a wide range of actors within health systems so that they can work collectively to build public trust. The guiding principles can be used to inform policymaking in health and health care and to analyse the performance of different governments to see if those governments that operate in greater conformity with the guiding principles perform better

Dynamics of the Antarctic circumpolar current : evidence for topographic effects from altimeter data and numerical model output

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1995.Includes bibliographical references (leaves 209-216).by Sarah Tragler Gille.Ph.D

Physical Drivers of Phytoplankton Bloom Initiation in the Southern Ocean's Scotia Sea

Abstract: The Scotia Sea is the site of one of the largest spring phytoplankton blooms in the Southern Ocean. Past studies suggest that shelf‐iron inputs are responsible for the high productivity in this region, but the physical mechanisms that initiate and sustain the bloom are not well understood. Analysis of profiling float data from 2002 to 2017 shows that the Scotia Sea has an unusually shallow mixed‐layer depth during the transition from winter to spring, allowing the region to support a bloom earlier in the season than elsewhere in the Antarctic Circumpolar Current. We compare these results to the mixed‐layer depth in the 1/6° data‐assimilating Southern Ocean State Estimate and then use the model output to assess the physical balances governing mixed‐layer variability in the region. Results indicate the importance of lateral advection of Weddell Sea surface waters in setting the stratification. A Lagrangian particle release experiment run backward in time suggests that Weddell outflow constitutes 10% of the waters in the upper 200 m of the water column in the bloom region. This dense Weddell water subducts below the surface waters in the Scotia Sea, establishing a sharp subsurface density contrast that cannot be overcome by wintertime convection. Profiling float trajectories are consistent with the formation of Taylor columns over the region's complex bathymetry, which may also contribute to the unique stratification. Furthermore, biogeochemical measurements from 2016 and 2017 bloom events suggest that vertical exchange associated with this Taylor column enhances productivity by delivering nutrients to the euphotic zone