Dynamic shifts in eastern boundary upwelling systems: climate-change driven impacts on frequency, intensity and spatial patterns of upwelling.

Global temperatures and atmospheric carbon dioxide (CO₂) have been rising since the industrial period due to increased anthropogenic activities. The adverse impact of this warming and changing climate systems significantly reflects on Eastern Boundary Upwelling Systems (EBUS) in the global ocean. Here, we investigate the influence of climate change on EBUS by analysing the long-term changes in upwelling and productivity within these ecologically crucial regions. Based on the Bakun's (1990) hypothesis, which suggests that modifications in land-sea thermal gradients affect atmospheric pressure cells and subsequently influence upwelling patterns in EBUS, we analyse the daily time series data of wind and sea surface temperature (SST). Furthermore, we assess the impact of changes in these upwelling patterns on productivity.

We employ a set of matrices to objectively characterise upwelling dynamics, focusing on frequency, intensity and duration across four EBUS. Our findings reveal a compelling relationship between SST changes and upwelling events, demonstrating a decrease in SST associated with increased upwelling frequency and reduced intensity. Interestingly, variations emerge among EBUS and regions within them, notably an intensification of upwelling in the Humboldt Current systems. Despite this observed response, clear evidence supporting the associated changes in wind dynamics that drive upwelling remains elusive.

This study enhances our understanding of how shifts in global temperatures impact EBUS, which are crucial systems in regulating fisheries and marine ecosystems. Consistent changes in the timing, intensity and spatial heterogeneity of coastal upwelling are evident in most EBUS. The spatially variable yet subtle changes are observed in accordance with climate change patterns. These findings provide valuable insights into the complex interplay between climate-driven shifts and the dynamic nature of EBUS, suggesting implications for marine ecosystems and coastal communities.