Variability of the Norwegian Atlantic Current and associated eddy field from surface drifters

The Norwegian Atlantic Current (NwAC) and its eddy field are examined using data from surface drifters. The data set used spans nearly 20 years, from June 1991 to December 2009. The results are largely consistent with previous estimates, which were based on data from the first decade only. With our new data set, statistical analysis of the mean fields can be calculated with larger confidence. The two branches of the NwAC, one over the continental slope and a second further offshore, are clearly captured. The Norwegian Coastal Current is also resolved. In addition, we observe a semipermanent anticylonic eddy in the Lofoten Basin, a feature seen previously in hydrography and in models. The eddy kinetic energy (EKE) is intensified along the path of the NwAC, with the largest values occurring in the Lofoten Basin. The strongest currents, exceeding 100 cm s−1, occur west of Lofoten. Lateral diffusivities were computed in five domains and ranged from 1–5 × 107 cm2 s−1. The Lagrangian integral time and space scales are 1–2 days and 7–23 km, respectively. The data set allows studies of seasonal and interannual variations as well. The strongest seasonal signal is in the NwAC itself, as the mean flow strengthens by approximately 20% in winter. The EKE and diffusivities on the other hand do not exhibit consistent seasonality in the sampled regions. There are no consistent indications of changes in either the mean or fluctuating surface velocities between the 1990s and 2000s

Increased Levels of Circulating Fatty Acids Are Associated with Protective Effects against Future Cardiovascular Events in Nondiabetics

Cardiovascular disease (CVD) is a major cause of morbidity and mortality worldwide, particularly in individuals with diabetes. The current study objective was to determine the circulating metabolite profiles associated with the risk of future cardiovascular events, with emphasis on diabetes status. Nontargeted metabolomics analysis was performed by LC–HRMS in combination with targeted quantification of eicosanoids and endocannabinoids. Plasma from 375 individuals from the IMPROVE pan-European cohort was included in a case-control study design. Following data processing, the three metabolite data sets were concatenated to produce a single data set of 267 identified metabolites. Factor analysis identified six factors that described 26.6% of the variability in the given set of predictors. An association with cardiovascular events was only observed for one factor following adjustment (p = 0.026). From this factor, we identified a free fatty acid signature (n = 10 lipids, including saturated, monounsaturated, and polyunsaturated fatty acids) that was associated with lower risk of future cardiovascular events in nondiabetics only (OR = 0.65, 0.27–0.80 95% CI, p = 0.030), whereas no association was observed among diabetic individuals. These observations support the hypothesis that increased levels of circulating omega-6 and omega-3 fatty acids are associated with protective effects against future cardiovascular events. However, these effects were only observed in the nondiabetic population, further highlighting the need for patient stratification in clinical investigations

Relative dispersion in the Nordic Seas

We examine the relative dispersion of surface drifters deployed in the POLEWARD experiment in the Nordic Seas during 2007–2008. The drifters were launched in pairs and triplets, yielding 67 pairs with an initial separation of 2 km or less. There were 26 additional pairs from drifters which subsequently came near one another. As these produced statistically identical dispersion to the original pairs, we used them as well, yielding 93 pairs. The relative dispersion exhibits three phases. The first occurs during the first two days, at spatial scales less than 10 km. The dispersion increases approximately exponentially during this period, with an e-folding time of roughly half a day. During the second phase, from 2 to roughly 10 days and scales of 10 to roughly 100 km, the dispersion increases as a power law, with r2 α t3. At the largest spatial and temporal scales, the dispersion increases linearly in time and the pair velocities are uncorrelated, consistent with diffusive spreading. We use a stochastic model with a representative mean flow to test the effect of the mean shear on dispersion. The model produces dispersion comparable to the observed during the second and third phases but fails to capture other statistics, such as the PDFs of the displacements. These statistics are instead suggestive of an inverse energy cascade, from the deformation scale up to 100 km

Surface circulation in the Nordic Seas from clustered drifters

We compare two methods for estimating mean velocities and diffusivities from surface drifter observations, using data from the Nordic Seas. The first is the conventional method of grouping data into geographical bins. The second relies on a "clustering" algorithm, and groups velocity observations according to nearest-neighbor distance. Capturing the spatial variability of the mean velocity requires using bins with a length scale of ˜50km. However, because many bins have few observations, the statistical significance varies substantially between bins. Clustering yields sets with approximately the same number of observations, so the significance is more uniform. At the densely sampled Svinøy section, clusters can be used to construct the mean flow field with <=10km resolution. Clustering also excels at the estimation of eddy diffusivities, allowing resolution at the 20 km scale in the densely sampled regions. Taking bathymetry into account in the clustering process further improves mean estimates where the data is sparse. Clustering the available surface drifter data, extended by recent deployments from the POLEWARD project, reveals new features in the surface circulation. These are a large anticyclonic vortex in the center of the Lofoten Basin and two anticyclonic recirculations at the Svinøy section. Clustering also yields maps of the eddy diffusivities at unprecedented resolution. Diffusivities are suppressed at the core of the Norwegian Atlantic Current, while they are elevated in the Lofoten Basin and along the Polar Front