Past and present ocean dynamics in the western subtropical Atlantic

• Main Author: Mildner, Tanja Carolin
• Other Authors: Eden, Carsten (Prof. Dr.)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky 2013
• Subjects: 550 Geowissenschaften; 38.48 Marine Geologie; 38.90 Ozeanologie; Ozeanographie; Atlantic Ocean; Gulf of Mexico; Last Glacial Maximum; Loop Current; Florida Straits; Yucatan Channel; Caribbean; Gulf Stream; ddc:550; Atlantik; North Atlantic
• Online Access: http://nbn-resolving.de/urn:nbn:de:gbv:18-64014; https://ediss.sub.uni-hamburg.de/handle/ediss/5109

The main physical processes responsible for the past and present Loop Current variability in the Gulf of Mexico and its interconnection with both, the Caribbean Sea and the Florida Straits are investigated in this PhD thesis. The aim is to contribute to the understanding of ocean dynamics in the western part of the North Atlantic across the prominent transition from the Last Glacial Maximum to the Holocene during the last 25 kyr (kilo years). A combined approach using high resolution models, present day observations and paleo-proxies has helped to explore the past and the present spatial and temporal changes of Loop Current dynamics and to understand the relative contributions of different external forcing factors. This PhD thesis consists of three research papers: The first part of this thesis addresses the influence of atmospheric and internal ocean variability on the Loop Current and the associated Florida Straits transport on interannual to decadal scales. A clear relationship is found between different stages within a ring shedding cycle of the Loop Current in the Gulf of Mexico and transport minima in the Florida Current transport, both in observations and in model simulations. It is demonstrated that transport changes in Florida Straits have a significant influence on the transport variability on monthly to decadal time scales. Differences (and changes) between the ring shedding period and seasonal cycle lead to an interannual to decadal beat frequency, which explains large parts of the variability of the Florida Current transport in the model simulations, even exceeding atmospheric forcing variability on the considered time scales. Although additional trigger events might support the ring shedding process, the Florida Straits transport is influenced mainly by internal dynamics. The second part focuses on the influence of the Loop Current eddy shedding on the heat budget of the Gulf of Mexico at changing sea levels, different wind stress forcings and topographic effects. The model simulations imply that ...