Temperature and Freshwater Fluxes by Individual Eddies in the North Atlantic Ocean

This study investigates the temperature and freshwater fluxes by individual eddies in the North Atlantic between 40 degrees-55 degrees N and 60 degrees-10 degrees W for the period January 1993 to April 2014. Focus is on a zonal section along 47 degrees N, roughly at the boundary between the subpolar and the subtropical gyres. The main question is to what extent eddies are responsible for the variability and mixing in the region and how the anomalies of temperature and freshwater carried by eddies contribute to the overall fluxes across 47 degrees N. Almost 37000 eddies with a lifetime longer than one week are detected from surface geostrophic velocity fields derived from satellite-altimetry. First, only surface temperature fluxes based on collocating detected eddies with sea surface temperature observations from satellites are analyzed. The results are compared to two model simulations spanning the period from 2002 to 2013 with different horizontal resolution (1/4 degree and 1/12 degree), allowing to assess the impact of different resolution on the results. The analysis is then extended to three dimensional temperature and freshwater fluxes. The temperature and salinity fields used for the calculation of the fluxes stem from a new product that was derived from dynamic height using the Gravest Empirical Mode (GEM) technique. Using this new product allows for the first time to relate every detected eddy to profiles of temperature and freshwater and to analyze the respective fluxes across 47 degrees N. Since the 1/12 degree model configuration shows the more realistic results for the surface temperature fluxes, the comparison of the observed temperature and freshwater fluxes is confined to this configuration. The highest number of eddies is found along the pathway of the North Atlantic Current (NAC), roughly following the 4000 m isobath, and on the Grand Banks of Newfoundland. The typical vertical extent is around 1400 m, with anti-cyclonic eddies on average 200 m deeper than cyclonic eddies. Relating the observed eddies to the top-to-bottom velocity distribution from ship observations shows that the highest fluxes are linked to the fastest and most pronounced current branches in the western Newfoundland Basin. The time series of surface temperature fluxes by eddies crossing 47 degrees N reveal that single isolated eddies with large SST signatures contribute about 25% to the surface temperature flux. Similarly, about 15-35% of the three dimensional temperature and freshwater fluxes across 47 degrees N stem from eddies with large temperature and freshwater anomalies. The largest contribution to the flux by individual eddies stems from cold and fresh eddies originating from the Western Boundary Current moving northward with the NAC. While the fluxes by individual eddies are very small compared to the basin-wide integrated total fluxes, eddies induce a large part of the variability of the total flux. The effect of fluxes by individual eddies is regionally confined, but eddies contribute to the cooling of the NAC in the region around the Grand Banks of Newfoundland, to the local recirculation in the Newfoundland Basin, and in part to the interior southward pathway of subpolar water

Making big steps in trajectories

We consider the solution of initial value problems within the context of hybrid systems and emphasise the use of high precision approximations (in software for exact real arithmetic). We propose a novel algorithm for the computation of trajectories up to the area where discontinuous jumps appear, applicable for holomorphic flow functions. Examples with a prototypical implementation illustrate that the algorithm might provide results with higher precision than well-known ODE solvers at a similar computation time

Recirculation of Canada Basin Deep Water in the Amundsen Basin, Arctic

It is evident from hydrographic profiles in the Arctic Ocean that relatively warm and salty Canada Basin Deep Water (CBDW) flows over the Lomonosov Ridge into the Amundsen Basin, in the Eurasian Arctic. However, oceanographic data in the deep Arctic Ocean are scarce, making it difficult to analyze the spatial extent or the dynamics of this inflow. Here we present new hydrographic data from two recent expeditions as well as historical data from previous expeditions in the central Arctic. We use an end-member analysis to quantify the presence of CBDW in the Amundsen and Nansen Basins and infer new circulation pathways. We find that the inflow of CBDW is intermittent, and that it recirculates in the Amundsen Basin along the Gakkel Ridge. Although the forcing mechanisms for the inflow of CBDW into the Amundsen Basin remain unclear owing to the lack of continuous observations, we demonstrate that density-driven overflows, even intermittent, and the pressure gradient across the Lomonosov Ridge are unlikely drivers. We also find multiple deep eddies with a CBDW content of up to 600 g kg-1 and a vertical extent of up to 1200 m in the Amundsen Basin. The high CBDW content of these eddies suggests that they can efficiently trap CBDW and transport its heat and salt over long distances

Computational Complexity of Iterated Maps on the Interval (Extended Abstract)

The exact computation of orbits of discrete dynamical systems on the interval is considered. Therefore, a multiple-precision floating point approach based on error analysis is chosen and a general algorithm is presented. The correctness of the algorithm is shown and the computational complexity is analyzed. As a main result, the computational complexity measure considered here is related to the Ljapunow exponent of the dynamical system under consideration

Nonclassical Light Generation from III-V and Group-IV Solid-State Cavity Quantum Systems

In this chapter, we present the state-of-the-art in the generation of nonclassical states of light using semiconductor cavity quantum electrodynamics (QED) platforms. Our focus is on the photon blockade effects that enable the generation of indistinguishable photon streams with high purity and efficiency. Starting with the leading platform of InGaAs quantum dots in optical nanocavities, we review the physics of a single quantum emitter strongly coupled to a cavity. Furthermore, we propose a complete model for photon blockade and tunneling in III-V quantum dot cavity QED systems. Turning toward quantum emitters with small inhomogeneous broadening, we propose a direction for novel experiments for nonclassical light generation based on group-IV color-center systems. We present a model of a multi-emitter cavity QED platform, which features richer dressed-states ladder structures, and show how it can offer opportunities for studying new regimes of high-quality photon blockade.Comment: 64 pages, 32 figures, to appear as Chapter 3 in Advances in Atomic Molecular and Optical Physics, Vol. 6

A new method to quantify and compare the multiple components of fitness-A study case with kelp niche partition by divergent microstage adaptations to Temperature

Point 1 Management of crops, commercialized or protected species, plagues or life-cycle evolution are subjects requiring comparisons among different demographic strategies. The simpler methods fail in relating changes in vital rates with changes in population viability whereas more complex methods lack accuracy by neglecting interactions among vital rates. Point 2 The difference between the fitness (evaluated by the population growth rate.) of two alternative demographies is decomposed into the contributions of the differences between the pair-wised vital rates and their interactions. This is achieved through a full Taylor expansion (i.e. remainder = 0) of the demographic model. The significance of each term is determined by permutation tests under the null hypothesis that all demographies come from the same pool. Point 3 An example is given with periodic demographic matrices of the microscopic haploid phase of two kelp cryptic species observed to partition their niche occupation along the Chilean coast. The method provided clear and synthetic results showing conditional differentiation of reproduction is an important driver for their differences in fitness along the latitudinal temperature gradient. But it also demonstrated that interactions among vital rates cannot be neglected as they compose a significant part of the differences between demographies. Point 4 This method allows researchers to access the effects of multiple effective changes in a life-cycle from only two experiments. Evolutionists can determine with confidence the effective causes for changes in fitness whereas population managers can determine best strategies from simpler experimental designs.CONICYT-FRENCH EMBASSADY Ph.D. gran

Mixing and Circulation in the Tropical Atlantic Cruise No. M98

July 01 – July 28, 2013 Fortaleza (Brazil) – Walvis Bay (Namibia

Yale Global Tic Severity Scale (YGTSS): Psychometric Quality of the Gold Standard for Tic Assessment Based on the Large-Scale EMTICS Study

The Yale Global Tic Severity Scale (YGTSS) is a clinician-rated instrument considered as the gold standard for assessing tics in patients with Tourette's Syndrome and other tic disorders. Previous psychometric investigations of the YGTSS exhibit different limitations such as small sample sizes and insufficient methods. To overcome these shortcomings, we used a subsample of the large-scale “European Multicentre Tics in Children Study” (EMTICS) including 706 children and adolescents with a chronic tic disorder and investigated convergent, discriminant and factorial validity, as well as internal consistency of the YGTSS. Our results confirm acceptable convergent and good to very good discriminant validity, respectively, indicated by a sufficiently high correlation of the YGTSS total tic score with the Clinical Global Impression Scale for tics (rs = 0.65) and only low to medium correlations with clinical severity ratings of attention deficit/hyperactivity symptoms (rs = 0.24), obsessive–compulsive symptoms (rs = 27) as well as internalizing symptoms (rs = 0.27). Internal consistency was found to be acceptable (Ω = 0.58 for YGTSS total tic score). A confirmatory factor analysis supports the concept of the two factors “motor tics” and “phonic tics,” but still demonstrated just a marginal model fit (root mean square error of approximation = 0.09 [0.08; 0.10], comparative fit index = 0.90, and Tucker Lewis index = 0.87). A subsequent analysis of local misspecifications revealed correlated measurement errors, suggesting opportunities for improvement regarding the item wording. In conclusion, our results indicate acceptable psychometric quality of the YGTSS. However, taking the wide use and importance of the YGTSS into account, our results suggest the need for further investigations and improvements of the YGTSS. In addition, our results show limitations of the global severity score as a sum score indicating that the separate use of the total tic score and the impairment rating is more beneficial

Lack of Association of Group A Streptococcal Infections and Onset of Tics: European Multicenter Tics in Children Study

Background and objectives: The goal of this work was to investigate the association between group A streptococcal (GAS) infections and tic incidence among unaffected children with a family history of chronic tic disorders (CTDs). Methods: In a prospective cohort study, children with no history for tics who were 3 to 10 years of age with a first-degree relative with a CTD were recruited from the European Multicentre Tics in Children Study (EMTICS) across 16 European centers. Presence of GAS infection was assessed with throat swabs, serum anti-streptolysin O titers, and anti-DNAse titers blinded to clinical status. GAS exposure was defined with 4 different definitions based on these parameters. Cox regression analyses with time-varying GAS exposure were conducted to examine the association of onset of tics and GAS exposure during follow-up. Sensitivity analyses were conducted with Cox regression and logistic regression analyses. Results: A total of 259 children were recruited; 1 child was found to have tic onset before study entry and therefore was excluded. Sixty-one children (23.6%) developed tics over an average follow-up period of 1 (SD 0.7) year. There was a strong association of sex and onset of tics, with girls having an ≈60% lower risk of developing tics compared to boys (hazard ratio [HR] 0.4, 95% confidence interval [CI] 0.2-0.7). However, there was no statistical evidence to suggest an association of any of the 4 GAS exposure definitions with tic onset (GAS exposure definition 1: HR 0.310, 95% CI 0.037-2.590; definition 2: HR 0.561, 95% CI 0.219-1.436; definition 3: HR 0.853, 95% CI 0.466-1.561; definition 4: HR 0.725, 95% CI 0.384-1.370). Discussion: These results do not suggest an association between GAS exposure and development of tics. Classification of evidence: This study provides Class I evidence that group A streptococcal exposure does not associate with the development of tics in children with first-degree relatives with chronic tic disorder

Temperature Effects on Gametophyte Life-History Traits and Geographic Distribution of Two Cryptic Kelp Species

A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29–30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (λ) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed