| 1. |
- Olsen, Are, 1972, et al.
(författare)
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Overview of the Nordic Seas CARINA data and salinity measurements
- 2009
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Ingår i: Earth System Science Data Discussions. - 1866-3591. ; 2, s. 1-25
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Tidskriftsartikel (refereegranskat)abstract
- Water column data of carbon and carbon relevant hydrographic and hydrochemical parameters from 188 previously non-publicly available cruises in the Arctic, Atlantic, and Southern Ocean have been retrieved and merged into a new database: CARINA (CARbon IN the Atlantic). The data have been subject to rigorous quality control (QC) in order to ensure highest possible quality and consistency. The data for most of the parameters included were examined in order to quantify systematic biases in the reported values, i.e. secondary quality control. Significant biases have been corrected for in the data products, i.e. the three merged files with measured, calculated and interpolated values for each of the three CARINA regions; the Arctic Mediterranean Seas (AMS), the Atlantic (ATL) and the Southern Ocean (SO). With the adjustments the CARINA database is consistent both internally as well as with GLODAP (Key et al., 2004) and is suitable for accurate assessments of, for example, oceanic carbon inventories and uptake rates and for model validation. The Arctic Mediterranean Seas includes the Arctic Ocean and the Nordic Seas, and the quality control was carried out separately in these two areas. This contribution provides an overview of the CARINA data from the Nordic Seas and summarises the findings of the QC of the salinity data. One cruise had salinity data that were of questionable quality, and these have been removed from the data product. An evaluation of the consistency of the quality controlled salinity data suggests that they are consistent to at least 0.05.
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| 2. |
- Saether, Stein Are, et al.
(författare)
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Inferring local adaptation from QST-FST comparisons : neutral genetic and quantitative trait variation in European populations of great snipe
- 2007
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 20:4, s. 1563-1576
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Tidskriftsartikel (refereegranskat)abstract
- We applied a phenotypic QST (PST) vs. FST approach to study spatial variation in selection among great snipe (Gallinago media) populations in two regions of northern Europe. Morphological divergence between regions was high despite low differentiation in selectively neutral genetic markers, whereas populations within regions showed very little neutral divergence and trait differentiation. QST > FST was robust against altering assumptions about the additive genetic proportions of variance components. The homogenizing effect of gene flow (or a short time available for neutral divergence) has apparently been effectively counterbalanced by differential natural selection, although one trait showed some evidence of being under uniform stabilizing selection. Neutral markers can hence be misleading for identifying evolutionary significant units, and adopting the PST–FST approach might therefore be valuable when common garden experiments is not an option. We discuss the statistical difficulties of documenting uniform selection as opposed to divergent selection, and the need for estimating measurement error. Instead of only comparing overall QST and FST values, we advocate the use of partial matrix permutation tests to analyse pairwise QST differences among populations, while statistically controlling for neutral differentiation.
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| 3. |
- Are, Sasanka, et al.
(författare)
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Coarse-Grained Langevin Approximations and Spatiotemporal Acceleration for Kinetic Monte Carlo Simulations of Diffusion of Interacting Particles
- 2009
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Ingår i: Chinese Annals of Mathematics. Series B. - : Springer Science and Business Media LLC. - 0252-9599 .- 1860-6261. ; 30:6, s. 653-682
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Tidskriftsartikel (refereegranskat)abstract
- Kinetic Monte Carlo methods provide a powerful computational tool for the simulation of microscopic processes such as the diffusion of interacting paxticles oil a surface, at a detailed atomistic level. However such algorithms are typically computationally expensive and are restricted to fairly small spatiotemporal scales. One approach towards overcoming this problem was the development of coarse-gained Monte Carlo algorithms. In recent literature, these methods were shown to be capable of efficiently describing much larger length scales while still incorporating information on microscopic interactions and fluctuations. In this paper, a coarse-grained Langevin system of stochastic differential equations as approximations of diffusion of interacting particles is derived, based on these earlier coarse-grained models. The authors demonstrate the asymptotic equivalence of transient and long time behavior of the Langevin approximation and the underlying microscopic process, using asymptotics methods such as large deviations for interacting particles systems, and furthermore, present corresponding numerical simulations, comparing statistical quantities like mean paths, auto correlations and power spectra of the microscopic and the approximating Langevin processes. Finally, it is shown that the Langevin approximations presented here are much more computationally efficient than conventional Kinetic Monte Carlo methods, since in addition to the reduction in the number of spatial degrees of freedom in coarse-grained Monte Carlo methods, the Langevin system of stochastic differential equations allows for multiple particle moves in a single timestep.
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| 4. |
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| 5. |
- Pierrot, D., et al.
(författare)
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Recommendations for autonomous underway pCO2 measuring systems and data-reduction routines
- 2009
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Ingår i: Deep-Sea Research II. - : Elsevier BV. - 0967-0645. ; 56:8-10, s. 512-522
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Tidskriftsartikel (refereegranskat)abstract
- In order to facilitate the collection of high quality and uniform surface water pCO2 data, an underway pCO2 instrument has been designed based on community input and is now commercially available. Along with instrumentation, agreements were reached on data reduction and quality control that can be easily applied to data from these systems by using custom-made freeware. This new automated underway pCO2 measuring system is designed to be accurate to within 0.1 μatm for atmospheric pCO2 measurements and to within 2 μatm for seawater pCO2, targeted by the scientific community to constrain the regional air–sea CO2 fluxes to 0.2 Pg C year−1. The procedure to properly reduce the underway pCO2 data and perform the steps necessary for calculation of the fugacity of CO2 from the measurements is described. This system is now widely used by the scientific community on many different types of ships. Combined with the recommended data-reduction procedures, it will facilitate producing data sets that will significantly decrease the uncertainty currently present in estimates of air–sea CO2 fluxes.
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