Abstract: The subpolar seas of the North Atlantic (e.g., the Nordic Seas, Irminger Sea, and Baffin Bay), connecting the Arctic and Atlantic Ocean, exhibit regional sea level variability influenced by multiple factors. Using altimetry, tide gauge data, and reanalysis products obtained over the past three decades, this study analyzed the long-term trend in sea level change and investigated the underlying mechanisms driven by the large-scale circulation. Results showed that heat flux dominated sea level trends, explaining 33.2% of the variability, while Ekman pumping primarily influenced interannual variations (explained variance: 10.9%). Freshwater flux contributed 8.8% to the long-term change in sea level. Regional differences in the long-term change in sea level arise from spatially heterogeneous responses of Ekman pumping and buoyancy flux under Arctic Oscillation (AO) modulation. During positive/negative AO phases, sea level pressure anomalies induced cyclonic/anticyclonic wind anomalies over the Irminger and Nordic seas, driving sea level divergence/convergence via Ekman pumping. Sea level pressure anomalies also modified vertical atmospheric motion, altering cloud cover and generating localized sensible/latent heat flux and precipitation anomalies, further impacting sea level in the subpolar North Atlantic. 

Key words: subarctic North Atlantic, sea level, heat flux, large-scale circulation