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  • 1
    Publication Date: 2019-01-17
    Description: We present a new near-global coupled biogeochemical ocean-circulation model configuration. The configuration features a horizontal discretization with a grid spacing of less than 11km in the Southern Ocean and gradually coarsens in meridional direction to more than 200km at 64°N where the model is bounded by a solid wall. The underlying code framework is GFDL's Modular Ocean Model coupled to the Biology Light Iron Nutrients and Gasses (BLING) ecosystem model of Galbraith et al. (2010). The configuration is cutting-edge in that it features both a relatively equilibrated oceanic carbon inventory and a realistic representation of eddy kinetic energy – a combination that has, to-date, been precluded by prohibitive computational cost. Results from a simulation with climatological forcing and a sensitivity experiment with increasing winds suggest that the configuration is suited to explore Southern Ocean Carbon uptake dynamics on decadal timescales. Further, the fidelity of simulated bottom water temperatures off and on the Antarctic Shelf suggest that the configuration may be used to provide boundary conditions to ice-sheet models. The configuration is dubbed MOMSO a Modular Ocean Model Southern Ocean configuration.
    Type: Article , NonPeerReviewed
    Format: text
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  • 2
    Publication Date: 2014-05-05
    Repository Name: EPIC Alfred Wegener Institut
    Type: PANGAEA Documentation , NonPeerReviewed
    Format: application/zip
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  • 3
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    In:  [Talk] In: EGU General Assembly, 15.04, Vienna, Austria .
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 4
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    In:  [Talk] In: DYNAMITE-meeting, 07.02, Bologna, Italy .
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 5
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    In:  (Doctoral thesis/PhD), Christian-Albrechts-Universität, Kiel, Kiel, 98 pp
    Publication Date: 2018-11-02
    Description: Die Nordatlantische Oszillation (NAO) ist das dominierende Muster der atmosphärischen Zirkulation im Bereich des Nordatlantiks. Diese erklärt auf Zeitskalen von über einem Monat, besonders im Winter, einen Großteil der Varianz der atmosphärischen Zirkulation in diesem Gebiet. Eine bisher unbeantwortete Frage in diesem Kontext ist, ob die NAO ein rein zufälliges atmosphärische Phänomen ist oder ob sie auf bestimmten Zeitskalen durch andere Prozesse kontrolliert wird. In der vorliegenden Arbeit wird der Zusammenhang zwischen der NAO und dem Ozean näher untersucht. Der Zustand des Ozeans wird dabei durch die Meeresoberflächentemperatur (SST) repräsentiert. Von Interesse ist vor allem eine mögliche Rückwirkung von SST-Anomalien auf die NAO. Ein wichtiger Aspekt dieser Arbeit ist zudem ein verbessertes Verständnis des NAO-Musters. Es wird nachgewiesen, dass die Verteilung der synoptischen Systeme hinreichend ist, das NAO-Muster zu generieren, und auch dekadische Schwankungen hiermit erklärt werden können. Dies führt zu der Auffassung, dass die NAO hauptsächlich eine Verschiebung der Zyklonenzugbahnen widerspiegelt. Dieses deutlichere Bild der NAO gibt Anhaltspunkte für mögliche Mechanismen der Einwirkung von SST-Anomalien.
    Type: Thesis , NonPeerReviewed
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  • 6
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    American Meteorological Society, AMS
    In:  Monthly Weather Review, 133 (10). pp. 2894-2904.
    Publication Date: 2019-01-23
    Description: The North Atlantic Oscillation (NAO) represents the dominant mode of atmospheric variability in the North Atlantic region. In the present study, the role of the synoptic systems (cyclones and anticyclones) in generating the NAO pattern is investigated. To study the intermonthly variations of the NAO, NCEP–NCAR reanalysis data are used, and for the interdecadal variations the results of a 300-yr control integration under present-day conditions of the coupled model ECHAM4/OPYC3 are analyzed. A filtering method is developed for the sea level pressure anomalies. Application of this method to each grid point yields the low-frequency variability in the sea level pressure field that is due to the synoptic systems. The low-frequency variability of the filtered and the original data are in high agreement. This indicates that the low-frequency pressure variability, and with it the variability of the NAO, is essentially caused by the distribution of the synoptic systems. The idea that the distribution of the synoptic systems is the cause of the variation of the NAO is confirmed by high correlation between the latitudinal position of the polar front over the North Atlantic and the NAO index. Since most of the low-frequency variability in sea level pressure can be explained through the distribution of the synoptic systems, the NAO seems to be a reflection of the distribution of the synoptic systems, rather than the source for variations in the cyclone tracks.
    Type: Article , PeerReviewed
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  • 7
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    Elsevier
    In:  Ecological Modelling, 222 (8). pp. 1376-1386.
    Publication Date: 2017-02-21
    Description: Pelagic, coupled ocean circulation-ecosystem models, are widely used in climate research. These tools aim to quantify fluxes of nutrients and carbon in the ocean and are, increasingly, the base of future projections. For this purpose it is crucial to quantify and identify the sources of uncertainties. In contrast to physical models, the underlying equations for ecosystem models are derived from empirical relationships rather than based on first principles. This resulted in the development of a multitude of different ecosystem models – different in respect to both, underlying principles and complexity. Clearly, the question arises, to what extent the sensitivities of these models are comparable. This study focuses on the intrinsic dynamics of some widely used, simple (containing 2–3 prognostic variables) ecosystem models in a 0-D framework (i.e., comprising only the well-mixed oceanic surface layer). A suite of differing model approaches is tuned such that their behavior is similar. The setup resembles the well-mixed oceanic surface layer in the Baltic proper. It is illustrated that strong differences between the model approaches appear due to exemplary, anticipated changes in the external nutrient and light conditions. Herewith, we demonstrate the well-known, but rarely demonstrated fact that, apparent consistency between modeled prognostic variables with today's data bases is not necessarily a good measure of forecast skill. The causes which lead to the different sensitivities are illustrated by considering the steady state solutions. It is pointed out, that apparently small changes in the model formulations can result in very different dynamical behavior and an enormous spread between the model approaches, despite the feasibility to tune a common behavior in a limited range of light and nutrient supply. In our examples, the sensitivity is mainly a function of the formulation of the loss rate of phytoplankton. It is thus, in particular, the formulation of highly unknown heteorotrophic processes that determines the model sensitivity.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 8
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    In:  [Talk] In: 5. SAFEWIN assembly meeting, 26.-27.10.2011, St. Petersburg, Russia .
    Publication Date: 2012-08-06
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 9
    Publication Date: 2018-01-15
    Description: On the basis of integrations of an eddy-permitting coupled physical-biological model of the tropical Pacific we explore changes in the simulated mean circulation as well as its intraseasonal to interannual variability driven by the biologically modulated vertical absorption profiles of solar radiation. Three sensitivity ocean hind-cast experiments, covering the period from 1948 to 2003, are performed. In the first one, simulated chlorophyll affects the attenuation of light in the water column, while in the second experiment, the chlorophyll concentration is kept constant in time by prescribing an empirically derived spatial pattern. The third experiment uses a spatially and temporally constant value for the attenuation depth. The biotically induced differential heating is generated by increased absorption of light in the surface layers, leading to a surface warming and subsurface cooling. The effect is largest in the eastern equatorial Pacific. However, the initial vertical redistribution of heat leads to considerable changes of the near-surface ocean circulation subsequently influencing the near-surface temperature structure. In general, including biophysical coupling improves the model performance in terms of temperature and ocean circulation patterns. In particular, the upwelling in the eastern equatorial Pacific is enhanced, the mixed layer becomes shallower, the warm bias in the eastern Pacific is reduced, and the zonal temperature gradient increases. This leads to stronger La Niña events and an associated increase in the variability of the Niño3 SSTA time series. Furthermore, the eddy kinetic energy (EKE) associated with mesoscale eddies in the eastern equatorial Pacific increases by almost 100% because of enhanced EKE production due to enhanced horizontal and vertical shear of the mean currents.
    Type: Article , PeerReviewed
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  • 10
    Publication Date: 2012-08-06
    Description: Climate model results for the Baltic Sea region from an ensemble of eight simulations using the Rossby Centre Atmosphere model version 3 (RCA3) driven with lateral boundary data from global climate models (GCMs) are compared with results from a downscaled ERA40 simulation and gridded observations from 1980-2006. The results showed that data from RCA3 scenario simulations should not be used as forcing for Baltic Sea models in climate change impact studies because biases of the control climate significantly affect the simulated changes of future projections. For instance, biases of the sea ice cover in RCA3 in the present climate affect the sensitivity of the model's response to changing climate due to the ice-albedo feedback. From the large ensemble of available RCA3 scenario simulations two GCMs with good performance in downscaling experiments during the control period 1980-2006 were selected. In this study, only the quality of atmospheric surface fields over the Baltic Sea was chosen as a selection criterion. For the greenhouse gas emission scenario A1B two transient simulations for 1961-2100 driven by these two GCMs were performed using the regional, fully coupled atmosphere-ice-ocean model RCAO. It was shown that RCAO has the potential to improve the results in downscaling experiments driven by GCMs considerably, because sea surface temperatures and sea ice concentrations are calculated more realistically with RCAO than when RCA3 has been forced with surface boundary data from GCMs. For instance, the seasonal 2 m air temperature cycle is closer to observations in RCAO than in RCA3 downscaling simulations. However, the parameterizations of air-sea fluxes in RCAO need to be improved.
    Type: Article , PeerReviewed
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