Climatic Modulation of Atmospheric and Oceanographic Variability Along the Brazilian Amazon Coast

The Brazilian Amazon coast is characterized by pronounced seasonal hydroclimatic variability and may also reflect remote Pacific and Atlantic climate signals. This study investigated associations between large-scale climate variability and atmospheric and oceanographic conditions using monthly data from 1995 to 2024. Pacific variability was classified as El Niño, La Niña, or neutral, whereas Atlantic variability was evaluated using drought-related and neutral conditions. Climatic associations were assessed using seasonally adjusted multivariate and univariate analyses, restricted-permutation tests, Spearman correlations, lagged correlations, and multiple regression. El Niño–Southern Oscillation (ENSO) phase showed a significant but modest multivariate association with environmental conditions, supported by restricted-permutation analysis (R2 = 0.036, p = 0.0015). Wind speed and mean wave period showed the clearest ENSO-related differences, with higher winds and shorter wave periods during El Niño. Atlantic drought-related conditions showed an event-consistent increase in salinity, whereas the monthly wind-speed difference was more event-dependent. FDR-adjusted Spearman correlations revealed persistent wind–wave covariation, particularly during the dry season. ONI–SST correlations showed a broad positive pattern at lags of 4–9 months, with the largest observed coefficient at lag 6 (r = 0.348, nominal p = 0.012); however, no individual lag remained significant after false-discovery-rate correction (lag 6: q = 0.066), and the lagged pattern was therefore interpreted as exploratory. Overall, regional seasonality predominated, with climate signals acting as secondary, variable-specific modulators.