Das Projekt "Schwerpunktprogramm (SPP) 1158: Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Bereich Infrastruktur - Antarktisforschung mit vergleichenden Untersuchungen in arktischen Eisgebieten, Eddy-driven transports in the Antarctic Circumpolar Current" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: IFM-GEOMAR Leibniz-Institut für Meereswissenschaften.In the Southern Ocean, eddy-driven transports can be as large as mean transports. In particular the meridional, cross frontal transports are affected or even controlled by meso-scale eddy activity. On the other hand, these transports set the role of the Southern Ocean as a major oceanic sink in the global carbon cycle. In ocean models, such variability has to be adequately resolved or parameterised. The parameterisation by Gent and McWilliams (1990) is currently used to account for such eddy-driven transports, in which the so-called thickness diffusivity K has to be specified. Only a rough order of I magnitude is currently known for ', but, in particular in the Southern Ocean, the choice of K strongly affects meridional transports of mass and tracers and is therefore of crucial importance to quantify the role of the Southern Ocean in the climate system and the global carbon cycle. It is proposed to estimate the thickness diffusivity K in the Southern Ocean from synthetic data of an existing realistic eddy-resolving ocean model. While previous attempts highlight the problem of rotational eddy fluxes which complicate the estimation procedure, it has been recently shown that the definition and use of physically meaningful rotational fluxes reduces this problem. Therefore, reliable estimates of K in the Southern Ocean appear possible for the first time. Furthermore, it is proposed to estimate relations between mean quantities predicted by ocean models and thickness diffusivity, necessary in order to build a self-consistent eddy parameterisation.
Das Projekt "Schwerpunktprogramm (SPP) 1158: Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Bereich Infrastruktur - Antarktisforschung mit vergleichenden Untersuchungen in arktischen Eisgebieten, Cenozoic Antarctic glaciation: An integrated atmosphere - Ocean - Ice Sheet Model Approach" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft. Es wird/wurde ausgeführt durch: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung - Fachbereich Klimawissenschaften.The widespread glaciation of Antarctica and the associated shift towards colder temperatures at the Eocene-Oligocene boundary (about 35 million years ago) represents one of the most fundamental reorganisations of global climate in the earth s history. During the same time, the opening of the Southern Ocean gateways, the Drake Passage and the Tasman Gateway, led to the formation of the Antarctic Circumpolar Current and hence to the isolation of the Antarctic continent. Apart from the oceanic regime, other global phenomena such as the declining atmospheric carbon dioxide concentration and the orbital configuration, contributed to the onset of a persistent Antarctic glaciation. With this project we address the impact of each of these processes on the formation of the Antarctic Ice Sheet. We put special emphasis on the ocean circulation, latent heat transport as well as on ice sheet dynamics in an integrated modelling approach. Shifts in atmospheric circulation, temperature changes, and snow accumulation over Antarctica and their forcing factors will be analysed in detail. The identification of thresholds for the Antarctic ice sheet development will yield novel views for palaeoclimatic records at the Eocene-Oligocene transition.
Das Projekt "Paläoklima Südamerikas und Paläozeanographie des Südostpazifiks" wird/wurde gefördert durch: Deutsche Forschungsgemeinschaft / GeoForschungsZentrum Potsdam. Es wird/wurde ausgeführt durch: Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum.Das Klima Südchiles wird maßgeblich von der südhemisphärischen Westwindzone und dem antarktischen Zirkumpolarstrom bestimmt. Damit ist dieses Gebiet für die Rekonstruktion von Klimaveränderungen auf der Südhemisphäre besonders wichtig und geeignet. Untersuchungen an marinen und terrestrischen Archiven aus dieser Region haben gezeigt, dass die Breitenverlagerung der atmosphärischen und ozeanischen Systeme als wichtiger Teil dieser Veränderungen zu verstehen ist. Ziel dieses Projekts ist es, für diese Region in einem breiten methodischen Ansatz Änderungen in z.B. der Temperatur, dem Niederschlag und der Vegetation während des Spätglazials und des Holozäns zu erfassen.