von Reumont, Jonas (2018) Coral-based reconstructions of reef- to regional-scale ocean surface conditions in the Atlantic Warm Pool since the late 19th century. (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, Germany, 188 pp.

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Abstract

Climate variability in the tropical Atlantic region produces numerous impacts on society and the environment of the surrounding continents. Understanding past tropical climate variability beyond the period of instrumental observations or within regions lacking instrumental data requires the use of climate proxies. The geochemistry of coral skeletons provides such proxies, recording environmental fluctuations in ambient seawater during growth. This thesis investigates seasonal-scale proxy records of surface ocean conditions in order to study past changes in tropical Atlantic climate variability and reef scale environmental variability extending beyond the period of instrumental data. Monthly resolved coral records from the central Caribbean (Cayman Islands) are generated using the massive growing hermatypic species Diploria strigosa. The potential of coral proxy time series to capture local environmental signals is assessed. These time series are used to examine how local environmental parameters may affect and be imprinted in the coral record and which may be specific for different reef environments. The isotopic and trace elemental composition of two coral cores drilled in adjacent but distinct reef environments (fore reef and lagoon) are examined. The measured geochemical proxies are compared to in situ and gridded SST data and used to reconstruct seasonal- to decadal-scale SST variations. Furthermore, the potential of Little Cayman Island as a qualified reference site for the investigation of past large-scale climate signals and of the influence of external climate modes on the Caribbean and regions beyond is assessed. For this purpose the geochemical record from the fore reef environment is analyzed for decadal to multidecadal signals of climate variability and examined in combination with coral proxy records from other Caribbean sites.

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