HIGH AND LOW RESOLUTION STABLE ISOTOPE PROFILES OF HOLOCENE BIVALVE SHELLS FROM THE DOMINICAN REPUBLIC

The mean ITCZ does not extend beyond 10 N in the Caribbean ocean today, but there is increasing evidence that the character of the seasonal oscillation has changed as a result of orbital forcing. Changes in position of the mean ITCZ are important to document because its location and intensity essentially define the hydrologic budget in the tropics and have significant effects on atmospheric circulation and atmosphere-ocean interactions (Waliser and Gautier 1993). The generally observed trend is that the ITCZ occupied a more northward mean position during the Holocene thermal maximum between 10 and 5 ka,, when summer insolation was greater in the northern hemisphere than the southern hemisphere (Koutavas and LynchStieglitz, 2004). Curtis and Hodell (1993) linked the intensity of the seasonal cycle to evidence for a wetter climate in the Caribbean region between 7 k.a. and 3.2 k.a. This finding has recently been corroborated by bivalve d18O values from Florida that provide evidence for increased seasonality at ~5 k.a. (Jones et al., 2005). Both studies conclude that the further northward migration of the ITCZ is related to increased seasonality throughout the northern tropics during this period.