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1. Variation and Change of Upwelling Dynamics Detected in the World’s Eastern Boundary Upwelling Systems

   https://doi.org/10.3389/fmars.2021.626411  

   Abrahams, Amieroh; Schlegel, Robert W.; Smit, Albertus J. (February 2021, Frontiers in Marine Science)

   Global increases in temperature are altering land-sea temperature gradients. Bakun (1990) hypothesized that changes within these gradients will directly affect atmospheric pressure cells associated with the development of winds and will consequently impact upwelling patterns within ecologically important Eastern Boundary Upwelling Systems (EBUS). In this study we used daily time series of NOAA Optimally Interpolated sea surface temperature (SST) and ERA 5 reanalysis wind products to calculate a series novel of metrics related to upwelling dynamics. We then use these to objectively describe upwelling signals in terms of their frequency, intensity and duration throughout the four EBUS during summer months over the last 37 years (1982–2019). We found that a decrease (increase) in SST is associated with an increase (decrease) in the number of upwelling “events,” a decrease (increase) in the intensity of upwelling, and an increase (decrease) in the cumulative intensity of upwelling, with differences between EBUS and regions within EBUS. The Humboldt Current is the only EBUS that shows a consistent response from north to south with a general intensification of upwelling. However, we could not provide clear evidence for associated changes in the wind dynamics hypothesized to drive the upwelling dynamics. 

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2. Polar Upwelling at Three Sunspot Minima

   https://doi.org/10.3847/2515-5172/ac905f  

   Ulrich, Roger K; Tran, Tham; Boyden, John E (September 2022, Research Notes of the AAS)

   Abstract We summarize the analysis methods used to derive differential rotation leading to the Torsional Oscillations (TO) and a new method for determining Meridional Circulation (MC). The new MC results show a reversal of the flow direction at near-polar latitudes with the time of reversal corresponding closely to the time of sunspot Minima. 

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3. Testing the intermittent upwelling hypothesis: comment

   https://doi.org/10.1002/ecy.2476  

   Menge, Bruce A.; Menge, Duncan N. L. (August 2018, Ecology)
4. Coastal upwelling generates cryptic temperature refugia

   https://doi.org/10.1038/s41598-022-23717-5  

   Salois, Sarah L.; Gouhier, Tarik C.; Helmuth, Brian; Choi, Francis; Seabra, Rui; Lima, Fernando P. (November 2022, Scientific Reports)

   Abstract Understanding the effects of climate-mediated environmental variation on the distribution of organisms is critically important in an era of global change. We used wavelet analysis to quantify the spatiotemporal (co)variation in daily water temperature for predicting the distribution of cryptic refugia across 16 intertidal sites that were characterized as ‘no’, ‘weak’ or ‘strong’ upwelling and spanned 2000 km of the European Atlantic Coast. Sites experiencing weak upwelling exhibited high synchrony in temperature but low levels of co-variability at monthly to weekly timescales, whereas the opposite was true for sites experiencing strong upwelling. This suggests upwelling generates temporal thermal refugia that can promote organismal performance by both supplying colder water that mitigates thermal stress during hot Summer months and ensuring high levels of fine-scale variation in temperature that reduce the duration of thermal extremes. Additionally, pairwise correlograms based on the Pearson-product moment correlation coefficient and wavelet coherence revealed scale dependent trends in temperature fluctuations across space, with a rapid decay in strong upwelling sites at monthly and weekly timescales. This suggests upwelling also generates spatial thermal refugia that can ‘rescue’ populations from unfavorable conditions at local and regional scales. Overall, this study highlights the importance of identifying cryptic spatiotemporal refugia that emerge from fine-scale environmental variation to map potential patterns of organismal performance in a rapidly changing world. 

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5. Climate Change Impacts on Eastern Boundary Upwelling Systems

   https://doi.org/10.1146/annurev-marine-032122-021945  

   Bograd, Steven J.; Jacox, Michael G.; Hazen, Elliott L.; Lovecchio, Elisa; Montes, Ivonne; Pozo Buil, Mercedes; Shannon, Lynne J.; Sydeman, William J.; Rykaczewski, Ryan R. (January 2023, Annual Review of Marine Science)

   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. 

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