North Atlantic climate variability recorded in reef corals from Bermuda.

Abstract

Climate sensitive proxies can open windows into tines, for which instrumental observations are lacking. A strong tool for gaining insight into climate changes through the most recent geological period of the past several centuries, is the use of massive reef coral skeletons. The research reported in this thesis analyzes climate sensitive coral proxy records from Bermuda and is directed at characterizing seasonal, inter-annual and long-term climate fluctuations relevant to the western Sargasso Sea. The type of climate proxies used include skeletal growth parameters, i.e. annual growth rates and density, and the stable oxygen and carbon isotope composition (g18O and g13C, respectively) of coral skeletons. Chronologies of annual density and growth rate were analyzed m the skeletons of two colonies of Diploria labyrinthiformis. The records cover the last 150 years, a period where instrumental climate data are available for comparison and evaluation of the proxy records. Annual values of skeletal density and growth rate reveal response to changes in sea surface temperature and the sea surface convective activity near Bermuda, and large-scale North Atlantic atmospheric mass oscillations.