Abstract
The Pacific/North American (PNA) pattern is a dominant atmospheric pattern of climate variability in the extratropical Northern Hemisphere and strongly influences the winter climate of the southeast United States. The instrumental record used to characterize the PNA pattern does not exist prior to the mid-1940s. However, information about past variability in the PNA pattern is preserved in the skeletons of long-lived corals at the reefs of the Flower Garden Banks National Marine Sanctuary (NMS). The Flower Garden Banks NMS is located approximately 180 km south of the Texas/Louisiana border in the Gulf of Mexico and is the northernmost hermatypic reef on the United States continental shelf. It has previously been shown that linear coral extension rates at the Flower Garden Banks are highly correlated with winter air and sea surface temperatures. In addition, average winter temperatures in the southeastern United States are negatively correlated with the phase of the PNA pattern. During a positive phase of the PNA pattern, the southeast US experiences stronger and more frequent winter storms while a negative phase of the PNA pattern brings milder winters to the region. Thus, past coral extension rates at the Flower Garden Banks provide a means to reconstruct the history of temporal variations in the PNA pattern. We collected several long cores of skeletal material from long-lived Montastrea faveolata and Siderastrea siderea coral heads from the Flower Garden Banks NMS. Annual extension rates have been determined based on X- radiographic analysis of high/low density growth bands and are used to characterize interdecadal variability associated with changes in the PNA pattern. In addition, the presence of winter stress bands due to below average water temperatures indicate winters with more severe and/or frequent storms. Analysis of these results will contribute directly to our understanding of the temporal character of interannual and interdecadal variations of North American winter climate.