Non-Stationary Interdecadal Variability in the North Atlantic Oscillation Revealed in a 185-Year Coral-Based Sea Surface Temperature Record from the Western Tropical North Atlantic

The North Atlantic Oscillation (NAO) is primarily a boreal winter climate phenomenon defined by fluctuations in atmospheric pressure between the Bermuda-Azores High and the Icelandic Low. The NAO is often characterized by a distinct tripole pattern of sea surface temperature (SST) anomalies across the North Atlantic, and significantly influences temperature and precipitation patterns, with far-reaching environmental and socioeconomic impacts. Previous studies on the NAO from paleo-archives and instrumental records reveal that the long-term variance of the NAO has been increasing since the 1800s, suggesting changes in its long-term behavior. However, our understanding of the NAO remains limited by short instrumental records. Moreover, most marine-based NAO reconstructions are in high-latitude or subtropical regions, or outside the Atlantic basin. Thus, highlighting the need for additional marine-based records from the tropical Atlantic. Here, we present a high-resolution 185-year Sr/Ca-based boreal winter (DJFM) SST reconstruction (1831-2015) in the western tropical North Atlantic from a massive Colpophyllia natans coral collected at Kelleston Drain, Tobago. We found that the coral-derived DJFM SST record significantly captures regional SST trends (p