Reconstructing Caribbean Salinity Changes Over Time Utilizing

A J Waite
RCF Abstract
2007 Citizen’s Board Research and Creativity Forum
In an effort to better understand the interaction between salinity, water masses, and
temperature in the Atlantic and Caribbean, a number of coral cores (Montastraea
faveolata and Siderastrea sidereal) were acquired from the Lesser Antilles. The cores,
which span the region from Barbuda to Union Island, were collected under the objectives
of the CAribbean Salinity Experiment (CASE) in 2002. Here, stable isotopes and the
trace element composition of the coral skeletons are utilized as a multi-proxy approach to
the reconstruction of regional climate, water mass flow, and riverine (Amazon and
Orinoco) inputs. Since instrumental records from all of the collection locations
demonstrate similar variations in water temperature, changes between the oxygen
isotopic signatures of the corals at the individual localities should principally reflect
differing salinity conditions. Early findings from Bequia, Union Island, Guadaloupe, and
St. Croix specimens exhibit differences in oxygen isotope composition, with the
specimens originating from more southerly islands possessing values more negative than
their northern counterparts. This implies the presence of less saline waters around the
southern portion of the Lesser Antilles. On a local scale, some corals demonstrate less
pronounced cyclicity in oxygen isotopes, while maintaining a clear annual carbon cycle;
this seems to suggest that runoff from land may be both amplifying the carbon isotopic
signature and masking that of the oxygen. Ultimately, the observed isotopic differences
will allow for the quantification of salinity changes experienced in the Caribbean over
more than 150 years, providing a clearer picture of the regional oceanographic conditions
through time.