Dullo, Wolf-Christian

Hetzinger, Steffen

Pfeiffer, Miriam

Ruprecht, Eberhard

English

OceanRep

Geophysical Research Abstracts, Vol. 7, 04678, 2005SRef-ID: 1607-7962/gra/EGU05-A-04678© European Geosciences Union 2005Tracking tropical Atlantic climate variability of the lastcentury using a 93-year monthly resolved δ18O andSr/Ca record from a Caribbean coralS. Hetzinger, M. Pfeiffer, W.-Chr. Dullo, E. RuprechtIFM-GEOMAR, Leibniz Institute of Marine Sciences at Kiel University, Wischhofstr. 1-3,24148 Kiel, Germany, contact: shetzinger@ifm-geomar.deA 93-year high resolution record of coral aragonite Sr/Ca and δ18O variations is pre-sented from a colony of the massive reef-building coral Diploria strigosa from Guade-loupe, Caribbean Sea. During seasonal flood-events, the Lesser Antilles are regularlyaffected by low-salinity plumes which are generated by the maximum seasonal dis-charge of the Orinoco river. The seasonal flood plume, and the corresponding sea-surface salinity (SSS) anomaly, generally propagate northwards along the coastlinetowards the Caribbean Sea due to advection by mean ocean currents and extend fromthe Venezuelan coast to Puerto Rico shortly after maximum discharge. Highest sea-sonal discharge during late boreal fall is expected to correlate with the precipitationmaximum associated with the Intertropical Convergence Zone (ITCZ).Using a paired analysis of two geochemical proxies (oxygen isotopes and Sr/Ca ele-mental ratios) it is possible to unlink the effects of SST and seawater δ18O compo-sition (δ18OSW ), which in turn is related to salinity, in the coral δ18O time series.Coral skeletal δ18O was measured in monthly resolution for the growth period be-tween 1907 and 2000. High precision Sr/Ca-ratios were measured using inductivelycoupled plasma optical emission spectroscopy (ICP-OES). Both proxy time series de-duced from the same subsamples of coral aragonite were combined with monthlyaveraged instrumental SSTs of a 1˚ by 1˚ gridded data set (NOAA NCEP, Reynolds etal. 2002) for a corresponding time period (1982-2000) to derive a Sr/Ca-SST calibra-tion. Our results indicate that monthly resolved Sr/Ca-ratios of Diploria strigosa, incontrast to other massive growing coral species sampled in the tropical Atlantic, cap-ture the full amplitude of the seasonal SST cycle. The coral δ18O, in contrast, showsa larger seasonal amplitude (approx. 0,2 per mil) than expected from SST alone, ow-ing to the large seasonal salinity change. Therefore, δ18OSW reconstructed from thecoral should provide evidence of past hydrologic balance, including information aboutprecipitation-evaporation cycles and riverine freshwater input. A multi-taper spectralanalysis indicates that significant interannual coral δ18O oscillations occur at aver-age periods near 4 – 5.5 years. Further, a shift towards lower δ18O values from themid-80‘s is observable. On interannual to centennial time scales, our reconstructionswill help to provide information on variability of past sea surface conditions in thetropical Atlantic and to establish an apparent link between Caribbean SSS extremesrecorded in the aragonitic skeletons of Diploria strigosa corals and the entrainment oflow-salinity plumes induced by seasonal Orinoco river discharge events.

Tracking tropical Atlantic climate variability of the last century using a 93-year monthly resolved δ<sup>18</sup>O and Sr/Ca record from a Caribbean coral

Tracking tropical Atlantic climate variability of the last century using a 93-year monthly resolved δ<sup>18</sup>O and Sr/Ca record from a Caribbean coral

Abstract

Similar works

Full text

Available Versions

OceanRep