Interannual Arctic-Tropical Coupling in Boreal Summer: Beaufort Sea Ice Variability and Its Association with Tropical North Atlantic SST

The relationship between the Arctic and the Tropical North Atlantic (TNA) is a critical, yet relatively underexplored aspect of climate variability, particularly in light of the rapid changes occurring in the Arctic. Despite its potential significance, the interannual linkage remains insufficiently understood, limiting a comprehensive understanding of broader climate dynamics. In this study, we investigate the variability of the interannual relationship between Beaufort Sea Ice Concentration (SIC) and TNA Sea Surface Temperature (SST) over the period 1979–2023. Our results reveal a statistically significant negative correlation between Beaufort SIC and TNA SST. Increased Beaufort SIC appears to induce notable local radiative cooling through reduced upward longwave radiation and enhanced shortwave reflection, which may trigger anomalous vertical circulation and a Rossby wave source over the Arctic. The resulting stationary wave train, originating from the Beaufort region, tends to propagate southeastward across Canada and the northern United States, extending toward the western and subtropical North Atlantic and eventually into the TNA. This circulation pattern is associated with atmospheric conditions favorable for the development of negative SST anomalies over the TNA. Associated turbulent heat flux responses over the TNA further suggest that Arctic-induced atmospheric circulation changes can modulate local air-sea heat exchange, providing an energetic pathway through which Beaufort SIC variability may influence TNA SST anomalies. The NCAR Community Atmosphere Model version 5.3 (CAM5.3) is able to reproduce the observed mechanisms to a reasonable extent, offering additional support for the proposed dynamical pathway.