Scale-dependent response diversity of seabirds to prey in the North Sea

Functional response diversity is defined as the diversity of responses to environmental change among species that contribute to the same ecosystem function. Because different ecological processes dominate on different spatial and temporal scales, response diversity is likely to be scale dependent. Using three extensive data sets on seabirds, pelagic fish, and zooplankton, we investigate the strength and diversity in the response of seabirds to prey in the North Sea over three scales of ecological organization. Two-stage analyses were used to partition the variance in the abundance of predators and prey among the different scales of investigation: variation from year to year, variation among habitats, and variation on the local patch scale. On the year-to-year scale, we found a strong and synchronous response of seabirds to the abundance of prey, resulting in low response diversity. Conversely, as different seabird species were found in habitats dominated by different prey species, we found a high diversity in the response of seabirds to prey on the habitat scale. Finally, on the local patch scale, seabirds were organized in multispecies patches. These patches were weakly associated with patches of prey, resulting in a weak response strength and a low response diversity. We suggest that ecological similarities among seabird species resulted in low response diversity on the year-to-year scale. On the habitat scale, we suggest that high response diversity was due to interspecific competition and niche segregation among seabird species. On the local patch scale, we suggest that facilitation with respect to the detection and accessibility of prey patches resulted in overlapping distribution of seabirds but weak associations with prey. The observed scale dependencies in response strength and diversity have implications for how the seabird community will respond to different environmental disturbances

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

Decreasing intensity of open-ocean convection in the Greenland and Iceland seas

The air–sea transfer of heat and fresh water plays a critical role in the global climate system. This is particularly true for the Greenland and Iceland seas, where these fluxes drive ocean convection that contributes to Denmark Strait overflow water, the densest component of the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). Here we show that the wintertime retreat of sea ice in the region, combined with different rates of warming for the atmosphere and sea surface of the Greenland and Iceland seas, has resulted in statistically significant reductions of approximately 20% in the magnitude of the winter air–sea heat fluxes since 1979. We also show that modes of climate variability other than the North Atlantic Oscillation (NAO) are required to fully characterize the regional air–sea interaction. Mixed-layer model simulations imply that further decreases in atmospheric forcing will exceed a threshold for the Greenland Sea whereby convection will become depth limited, reducing the ventilation of mid-depth waters in the Nordic seas. In the Iceland Sea, further reductions have the potential to decrease the supply of the densest overflow waters to the AMOC

Temporal Variability of Diapycnal Mixing in Shag Rocks Passage

Diapycnal mixing rates in the oceans have been shown to have a great deal of spatial variability, but the temporal variability has been little studied. Here we present results from a method developed to calculate diapycnal diffusivity from moored Acoustic Doppler Current Profiler (ADCP) velocity shear profiles. An 18-month time series of diffusivity is presented from data taken by a LongRanger ADCP moored at 2400 m depth, 600 m above the sea floor, in Shag Rocks Passage, a deep passage in the North Scotia Ridge (Southern Ocean). The Polar Front is constrained to pass through this passage, and the strong currents and complex topography are expected to result in enhanced mixing. The spatial distribution of diffusivity in Shag Rocks Passage deduced from lowered ADCP shear is consistent with published values for similar regions, with diffusivity possibly as large as 90 × 10-4 m2 s-1 near the sea floor, decreasing to the expected background level of ~ 0.1 × 10-4 m2 s-1 in areas away from topography. The moored ADCP profiles spanned a depth range of 2400 to 1800 m; thus the moored time series was obtained from a region of moderately enhanced diffusivity. The diffusivity time series has a median of 3.3 × 10-4 m2 s-1 and a range of 0.5 × 10-4 m2 s-1 to 57 × 10-4 m2 s-1. There is no significant signal at annual or semiannual periods, but there is evidence of signals at periods of approximately fourteen days (likely due to the spring-neaps tidal cycle), and at periods of 3.8 and 2.6 days most likely due to topographically-trapped waves propagating around the local seamount. Using the observed stratification and an axisymmetric seamount, of similar dimensions to the one west of the mooring, in a model of baroclinic topographically-trapped waves, produces periods of 3.8 and 2.6 days, in agreement with the signals observed. The diffusivity is anti-correlated with the rotary coefficient (indicating that stronger mixing occurs during times of upward energy propagation), which suggests that mixing occurs due to the breaking of internal waves generated at topography

The impact of salinity perturbations on the future uptake of heat by the Atlantic Ocean

Anthropogenic ocean heat uptake is a key factor in determining climate change and sea-level rise. There is considerable uncertainty in projections of freshwater forcing of the ocean, with the potential to influence ocean heat uptake. We investigatethis by adding either -0.1 Sv or +0.1 Sv freshwater to the Atlantic in global climate model simulations, simultaneously imposing an atmospheric CO2 increase. The resulting changes in the Atlantic meridional overturning circulation are roughly equal and opposite (±2Sv). The impact of the perturbation on ocean heat content is more complex, although it is relatively small (~5%) compared to the total anthropogenic heat uptake. Several competing processes either accelerate or retard warming at different depths. Whilst positive freshwater perturbations cause an overall heating of the Atlantic, negative perturbations produce insignificant net changes in heat content. The processes active in our model appear robust, although their net result is likely model- and experiment-dependent

Spatial variability of mixing in the Southern Ocean

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 32 (2005): L18603, doi:10.1029/2005GL023568.Strain variance from standard hydrographic profiles in the southern hemisphere oceans shows that turbulent mixing is vertically and spatially non-uniform. In the South Atlantic, Indian and South Pacific Oceans, enhanced diffusivities are found over rough topography. Consistent with internal tide generated mixing, the water column diffusivity returns to background levels 500 m to 1000 m off the sea floor. In the Southern Ocean, enhanced diffusivities throughout the entire water column below 1500 m are found in the Antarctic Circumpolar Current over complex topography. Differences in the vertical extent of enhanced diffusivity profiles in the Antarctic Circumpolar Current between the parameterizations based on tidal models and topography and of the present estimate of strain variance imply that elevated vertical diffusivity profiles in the Southern Ocean are due to the interaction between the mean geostrophic current and bottom topography.BMS was supported by the Ocean and Climate Change Institute at the Woods Hole Oceanographic Institution

Zonal circulation across 52°W in the North Atlantic

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 109 (2004): C11008, doi:10.1029/2003JC002103.In July–August 1997, a hydrographic/Acoustic Doppler Current Profiler (ADCP)/tracer section was occupied along 52°W in the North Atlantic as part of the World Ocean Circulation Experiment Hydrographic Program. Underway and lowered ADCP (LADCP) data have been used to reference geostrophic velocities calculated from the hydrographic data; additional (small) velocity adjustments provided by an inverse model, constraining mass and silicate transports in 17 neutral density layers, yield the absolute zonal velocity field for 52°W. We find a vigorous circulation throughout the entire section, with an unusually strong Gulf Stream (169 Sv) and southern Deep Western Boundary Current (DWBC; 64 Sv) at the time of the cruise. At the northern boundary, on the west side of the Grand Banks of Newfoundland, we find the westward flowing Labrador Current (8.6 Sv), whose continuity from the Labrador Sea, east of our section, has been disputed. Directly to the south we identify the slopewater current (12.5 Sv eastward) and northern DWBC (12.5 Sv westward). Strong departures from strictly zonal flow in the interior, which are found in the LADCP data, make it difficult to diagnose the circulation there. Isolated deep property extrema in the southern portion, associated with alternating bands of eastward and westward flow, are consistent with the idea that the rough topography of the Mid-Atlantic Ridge, directly east of our section, causes enhanced mixing of Antarctic Bottom Water properties into overlying waters with distinctly different properties. We calculate heat and freshwater fluxes crossing 52°W that exceed estimates based on air-sea exchanges by a factor of 1.7.This work was supported by NSF grants OCE95-29607, OCE 95-31864, OCE98-18266, and OCE-0219644

Reduced Antarctic meridional overturning circulation reaches the North Atlantic Ocean

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 35 (2008): L22601, doi:10.1029/2008GL035619.We analyze abyssal temperature data in the western North Atlantic Ocean from the 1980s–2000s, showing that reductions in Antarctic Bottom Water (AABW) signatures have reached even that basin. Trans-basin oceanographic sections occupied along 52°W from 1983–2003 and 66°W from 1985–2003 quantify abyssal warming resulting from deepening of the strong thermal boundary between AABW and North Atlantic Deep Water (NADW), hence a local AABW volume reduction. Repeat section data taken from 1981–2004 along 24°N also show a reduced zonal gradient in abyssal temperatures, consistent with decreased northward transport of AABW. The reduction in the Antarctic limb of the MOC within the North Atlantic highlights the global reach of climate variability originating around Antarctica.NOAA and NSF supported the 2003 U.S. CLIVAR/CO2 Repeat Hydrography Program reoccupations of the 52 W and 66 W sections, led by Chief Scientists John Toole and Terrence Joyce, respectively. The U.K. National Environment Research Council supported the 2004 reoccupation of the 24 N section, led by Chief Scientist Stuart Cunningham. The hard work of all contributing to the collection and processing of data analyzed here is gratefully acknowledged. The NOAA Office of Oceanic and Atmospheric Research and the NOAA Climate Program Office supported the analysis

Risk Management – Maximum Effect of Minimization Measures

Na osnovi podataka iz pretkliničkih i kliničkih ispitivanja farmaceutska kompanija koja želi staviti lijek na tržište Europske unije predlaže plan upravljanja rizicima koji agencija za lijekove odobrava neposredno prije stavljanja lijeka na tržište. Plan upravljanja rizicima definira mjere koje kompanija poduzima pri praćenju i minimizaciji rizika povezanih s lijekom. Mjere praćenja lijeka na tržištu mogu biti osnovne, tj. rutinske (prijavljivanje nuspojava, pisanje periodičkih izvješća, detekcija i analiza signala) te dodatne (dodatne studije). Sigurnu primjenu lijeka koju provode zdravstveni djelatnici i pacijenti omogućavaju rutinske mjere minimizacije rizika (prenošenje informacije o lijeku putem sažetka ili upute o lijeku) te dodatne mjere (poput edukacijskih materijala, pisma liječnicima ili programa prevencije trudnoće). Plan upravljanja rizicima ažurira se tijekom životnog ciklusa lijeka na osnovi novih informacija kako bi se osigurao pozitivan omjer koristi i rizika od lijeka te njegova sigurna primjena koju provode zdravstveni djelatnici i pacijenti. Osim toga,farmaceutska kompanija i agencija za lijekove mogu poduzeti i druge mjere edukacije zdravstvenih djelatnika i pacijenata radi smanjenja rizika povezanih s lijekovima.Based on non-clinical and clinical findings pharmaceutical companies needs to agree on a Risk Management Plan (RMP) with the authority at the time of drug approval in the European Union. RMP defines measures that a company needs to implement to collect more information and mitigate risk related to drug use. Measures are defined as either routine pharmacovigilance (reporting of adverse events, periodic reports, safety signal detection) or as additional measures (post-authorization safety studies). Safe drug use by healthcare providers and patients is assured by routine risk minimization measures (communication of information through the summary of products characteristics and patient information leaflet) and additional measures (such as educational materials, letters to healthcare providers and pregnancy prevention programs). RMP is updated during product life-cycle based on new information to assure positive benefit/risk of the drug and safe drug use by healthcare providers and patients. Pharmaceutical companies and health authorities may also take other actions to educate healthcare professionals and patients in order to decrease risks related to drug use

Surface currents in operational oceanography: Key applications, mechanisms, and methods

This paper reviews physical mechanisms, observation techniques and modelling approaches dealing with surface currents on short time scales (hours to days) relevant for operational oceanography. Key motivations for this article include fundamental difficulties in reliable measurements and the persistent lack of a widely held consensus on the definition of surface currents. These problems are augmented by the fact that various methods to observe and model ocean currents yield very different representations of a surface current. We distinguish between four applicable definitions for surface currents; (i) the interfacial surface current, (ii) the direct wind-driven surface current, (iii) the surface boundary layer current, and (iv) an effective drift current. Finally, we discuss challenges in synthesising various data sources of surface currents - i.e. observational and modelling – and take a view on the predictability of surface currents concluding with arguments that parts of the surface circulation exhibit predictability useful in an operational context