We use the 20th Century Reanalysis database to assess the influence of oceanic and terrestrial atmospheric pressure systems on winter and summer upwelling-favorable winds in Eastern Boundary Upwelling Systems. The analysis provides baseline information regarding the roles of continental thermal low (CTL) and oceanic high (OH) pressure systems in driving seasonal upwelling modes, which have high biological relevance. We show that variability in upwelling-favorable winds is dominated by OH, particularly in winter, and only weakly influenced by CTL, except at annual time scales. This is most pronounced in the California system given that the North Pacific High dominates wind variability. In contrast, CTL and OH equally influence Benguela upwelling-favorable winds during summer. This work underscores the need to understand how OH systems are likely to respond to climate change and how this might impact coastal winds that drive upwelling and productivity in these ecosystems.
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