Mixing of the Storfjorden overflow (Svalbard Archipelago) inferred from denstity overturns

Observations were made of the dense overflow from Storfjorden from a survey conducted at closely spaced stations in August 2002. The field data set consists of conventional conductivity-temperature-depth profiles and short-term moored current meters and thermistor strings. Finestructure estimates were made by calculating Thorpe scales over identified overturns using 0.1-dbar vertically averaged density profiles. Dissipation rate of turbulent kinetic energy per unit mass, e, is estimated assuming proportionality between Thorpe and Ozmidov length scales. Vertical eddy diffusivity Kz is estimated using Osborn’s model assuming a constant mixing efficiency. Survey-averaged profiles suggest enhanced mixing near the bottom with values of Kz and e, when averaged within the overflow, equal to 10 x 10-4 m2 s-1 and 3 x 10-8 W kg-1, respectively. Kz is found to decrease with increasing buoyancy frequency as N-1.2 (±0.3), albeit values of N covered only 0.5–8 cph (1 cph = 2p/3600 s-1). Values of heat flux obtained using Kz suggest that the plume gains a considerable amount of heat, 45 ± 25 W m2, when averaged over the thickness of the plume, from overlying waters of Atlantic origin. This value is lower than but, considering the errors in estimates of Kz, comparable with 100 W m2, the rate of change of heat in the overflow derived from sections across the sill and 80 km downstream.publishedVersio

Transitioning remote Arctic settlements to renewable energy systems – A modelling study of Longyearbyen, Svalbard

As transitioning away from fossil fuels to renewable energy sources comes on the agenda for a range of energy systems, energy modelling tools can provide useful insights. If large parts of the energy system turns out to be based on variable renewables, an accurate representation of their short-term variability in such models is crucial. In this paper, we have developed a stochastic long-term energy model and applied it to an isolated Arctic settlement as a challenging and realistic test case. Our findings suggest that the stochastic modelling approach is critical in particular for studies of remote Arctic energy systems. Furthermore, the results from a case study of the Norwegian settlement of Longyearbyen, suggest that transitioning to a system based on renewable energy sources is feasible. We recommend that a solution based mainly on renewable power generation, but also including energy storage, import of hydrogen and adequate back-up capacity is taken into consideration when planning the future of remote Arctic settlements.publishedVersio

A revised ocean glider concept to realize Stommel's vision and supplement Argo floats

This paper revisits Stommel's vision for a global glider network and the Argo design specification. A concept of floats with wings, so-called slow underwater gliders, is explored. An analysis of the energy or power consumption shows that, by operating gliders with half the vehicle volume at half the speed compared to present gliders, the energy requirements for long-duration missions can be met with available battery capacities. Simulation experiments of slow gliders are conducted using the horizontal current fields from an eddy-permitting ocean reanalysis product. By employing a semi-Lagrangian, streamwise navigation whereby the glider steers at right angles to ocean currents, we show that the concept is feasible. The simulated glider tracks demonstrate the potential for efficient coverage of key oceanographic features and variability.publishedVersio

Ocean science, data, and services for the UN 2030 Sustainable Development Goals

Relating the Sustainable Development Goal (SDG) 14 for Ocean and Life Below Water to the 16 remaining SDGs in the UN 2030 sustainable development agenda. A holistic approach that embraces sustainable Ocean stewardship informed by best available science, data and services to support society and the economy is required to create the ‘Future We Want’. The UN Decade of Ocean Science for Sustainable Development is an essential foundation to achieve this objective

Atlantic Water Pathways Along the North-Western Svalbard Shelf Mapped Using Vessel-Mounted Current Profilers

A large amount of warm Atlantic water (AW) enters the Arctic as a boundary current through Fram Strait (West Spitsbergen Current [WSC]) and is the major oceanic heat source to the Arctic Ocean. Along the north‐western Svalbard shelf, the WSC splits into the shallow Svalbard Branch, the Yermak Branch that follows the slope of the Yermak Plateau, and the Yermak Pass Branch flowing across the plateau. The WSC has previously been studied using moorings, dedicated oceanographic transects, and models. In this study, we mapped the circulation patterns and AW flow around Svalbard using Vessel‐Mounted Acoustic Doppler Current Profiler data from multiple surveys during four consecutive summers (2014–2017). Despite the scattered nature of this compiled data set, persistent circulation patterns could be discerned. Spatial interpolation showed a meandering boundary current west of Svalbard and a more homogeneous AW flow, centered around the 1,000‐m isobath north of Svalbard. In all summers, we observed a northward jet between 79 and 80°N and the 1,000‐ and 500‐m isobaths, before the WSC divided into the three branches. North of Svalbard, the shallow Svalbard Branch reunited with the Yermak Pass Branch between 10 and 15°E and a part of the AW circulated within Hinlopen Trench. The calculated volume transport of 2 Sv in the upper 500 m compares well with model results and previous observations. Our results further show that the Yermak Pass Branch can be as important as the Svalbard Branch in transporting AW across the Yermak Plateau during summer.publishedVersio

Einstein-aether theory, violation of Lorentz invariance, and metric-affine gravity

We show that the Einstein-aether theory of Jacobson and Mattingly (J&M) can be understood in the framework of the metric-affine (gauge theory of) gravity (MAG). We achieve this by relating the aether vector field of J&M to certain post-Riemannian nonmetricity pieces contained in an independent linear connection of spacetime. Then, for the aether, a corresponding geometrical curvature-square Lagrangian with a massive piece can be formulated straightforwardly. We find an exact spherically symmetric solution of our model.Comment: Revtex4, 38 pages, 1 figur

Cost and value of multidisciplinary fixed-point ocean observatories

Sustained ocean observations are crucial to understand both natural processes occurring in the ocean and human influence on the marine ecosystems. The information they provide increases our understanding and is therefore beneficial to the society as a whole because it contributes to a more efficient use and protection of the marine environment, upon which human livelihood depends. In addition the oceans, which occupy 73% of the planet surface and host 93% of the biosphere, play a massive role in controlling the climate. Eulerian or fixed-point observatories are an essential component of the global ocean observing system as they provide several unique features that cannot be found in other systems and are therefore complementary to them. In addition they provide a unique opportunity for multidisciplinary and interdisciplinary work, combining physical, chemical and biological observations on several time scales. The fixed-point open ocean observatory network (FixO3) integrates the 23 European open ocean fixed-point observatories in the Atlantic Ocean and in the Mediterranean Sea. The programme also seeks to improve access to key installations and the knowledge they provide for the wider community, from scientists, to businesses, to civil society. This paper summarises the rationale behind open ocean observatories monitoring the essential ocean variables. It also provides an estimate of the costs to operate a typical fixed-point observatory such as those included in the FixO3 network. Finally an assessment of the type of data and services provided by ocean observations and their value to society is also given

Potential role of conventional and speckle-tracking echocardiography in the screening of structural and functional cardiac abnormalities in elderly individuals:Baseline echocardiographic findings from the LOOP study

BACKGROUND: Elderly individuals occupy an increasing part of the general population. Conventional and speckle-tracking transthoracic echocardiography may help guide risk stratification in these individuals. The purpose of this study was to evaluate the potential utility of conventional and speckle-tracking echocardiography in the screening of cardiac abnormalities in the elderly population. METHODS: Two cohorts of elderly individuals (sample size: 1441 and 944) were analyzed, who were part of a randomized controlled clinical trial (LOOP study) and of an observational study (Copenhagen City Heart Study), recruiting participants from the general population >70 years of age with cardiovascular risk factors (arterial hypertension, diabetes mellitus, heart failure, or prior stroke) and sinus rhythm. Participants underwent a comprehensive transthoracic echocardiographic examination, including myocardial speckle tracking. Cardiac abnormalities were defined according to the ASE/EACVI guidelines. RESULTS: Structural cardiac abnormalities such as left ventricular (LV) remodeling, mitral annular calcification (MAC), and aortic valve sclerosis (with or without stenosis) were highly prevalent in the LOOP study (40%, 39%, and 27%, respectively). Moreover, a high prevalence of functional cardiac alterations such as LV diastolic dysfunction (LVDD), abnormal LV longitudinal systolic strain (GLS), and abnormal left atrial (LA) reservoir strain was present in the LOOP study (27%, 18%, and 9%, respectively). Likewise, the rate of LVDD, abnormal GLS, and abnormal LA reservoir strain was comparable in the validation sample from the Copenhagen City Heart Study. In line with these findings, subjects with LV remodeling, MAC, and aortic valve changes had a higher prevalence of LVDD, abnormal GLS, and abnormal LA reservoir strain than those without structural cardiac alterations. CONCLUSION: The findings of this study highlight the potential clinical utility of conventional and speckle-tracking echocardiography in the screening of structural and functional cardiac abnormalities in the elderly population. Further studies are warranted to determine the prognostic relevance of these findings