Climate Change Impacts on Eastern Boundary Upwelling Systems

Abstract

The world's eastern boundary upwelling systems (EBUSs) contribute disproportionately to global ocean productivity and provide critical ecosystem services to human society. The impact of climate change on EBUSs and the ecosystems they support is thus a subject of considerable interest. Here, we review hypotheses of climate-driven change in the physics, biogeochemistry, and ecology of EBUSs; describe observed changes over recent decades; and present projected changes over the twenty-first century. Similarities in historical and projected change among EBUSs include a trend toward upwelling intensification in poleward regions, mitigatedwarming in near-coastal regions where upwelling intensifies, and enhanced water-column stratification and a shoaling mixed layer. However, there remains significant uncertainty in how EBUSs will evolve with climate change, particularly in how the sometimes competing changes in upwelling intensity, source-water chemistry, and stratification will affect productivity and ecosystem structure. We summarize the commonalities and differences in historical and projected change in EBUSs and conclude with an assessment of key remaining uncertainties and questions. Future studies will need to address these questions to better understand, project, and adapt to climate-driven changes in EBUSs.

Greenhouse Warming Weakens the Seasonal Cycle of the Eastern Boundary Upwelling

“…Moreover, the UI shows good consistency with the UI τ (Figures 1f–1i), which is consistent with previous studies (Bakun, 1973; Bograd et al., 2023; Ding et al., 2021; Dorantes‐Gilardi & Rivas, 2019; García‐Reyes et al., 2015; Jacox et al., 2018). Especially, their spatial‐temporal correlation coefficients and magnitude differences of all EBUSs are above 0.8 and less than 20%, respectively, suggesting the winds mainly account for the climatological seasonal cycle of UI.…”

“…In these regions, equatorward alongshore winds, combined with the Coriolis effect, induce offshore Ekman transport, bringing nutrient‐rich water from depth to the photic zone. This provides critical ecosystem services and substantial economic value for human society and coastal communities (Arístegui et al., 2009; Block et al., 2011; Bograd et al., 2023; García‐Reyes et al., 2015; Huyer, 1983; Rykaczewski & Checkley, 2008). Besides the mean‐state of upwelling, its annual cycle is also suggested to play a vital role in eastern boundary ecosystems functioning, impacting ecosystem processes from producers to predators since biological lives are differentially sensitive to distinct seasons (Abraham & Sydeman, 2004; Barth et al., 2007; Beare & McKenzie, 1999; Black et al., 2011; Bograd et al., 2009; Cushing, 1990; Schwing et al., 2006; Wells et al., 2008).…”

Uncertain future of sustainable fisheries environment in eastern boundary upwelling zones under climate change

“…Remote influences from the tropics, possibly driven by variations in the positions of atmospheric pressure systems or large-scale effects caused by e.g., the Pacific Decadal Oscillation or the El Niño-Southern Oscillation 42 , may produce changes in source water chemistry that affect nutrient supply to the upwelling waters. How these competing changes collectively affect future fisheries environment in EBUSs remains to be investigated 43 . Future studies need to include ocean biogeochemistry and fisheries components in the high-resolution model framework to assess the full impact of future upwelling changes on marine ecosystems and fisheries.…”

Evaluation of Different Bias Correction Methods for Dynamical Downscaled Future Projections of the California Current Upwelling System

“…A warmer upper‐ocean increases stability and may shoal the mixed layer, reducing the source depth of upwelled water and limiting nutrient supply to the surface mixed layer (e.g., Bograd et al., 2023). GFDL projects a ∼10 m shoaling of the MLD in the offshore region while there changes in the coastal region are small except for MLD shoaling (>15 m) near the southern coastal boundary and deepening (∼10 m) between 40 and 43°N (second row in Figure 5).…”