Under Pressure: Climate Change, Upwelling, and Eastern Boundary Upwelling Ecosystems

Abstract

The IPCC AR5 provided an overview of the likely effects of climate change on Eastern Boundary Upwelling Systems (EBUS), stimulating increased interest in research examining the issue. We use these recent studies to develop a new synthesis describing climate change impacts on EBUS. We find that model and observational data suggest coastal upwelling-favorable winds in poleward portions of EBUS have intensified and will continue to do so in the future. Although evidence is weak in data that are presently available, future projections show that this pattern might be driven by changes in the positioning of the oceanic high-pressure systems rather than by deepening of the continental low-pressure systems, as previously proposed. There is low confidence regarding the future effects of climate change on coastal temperatures and biogeochemistry due to uncertainty in the countervailing responses to increasing upwelling and coastal warming, the latter of which could increase thermal stratification and render upwelling less effective in lifting nutrient-rich deep waters into the photic zone. Although predictions of ecosystem responses are uncertain, EBUS experience considerable natural variability and may be inherently resilient. However, multi-trophic level, end-to-end (i.e., "winds to whales") studies are needed to resolve the resilience of EBUS to climate change, especially their response to long-term trends or extremes that exceed pre-industrial ranges.

High CO2 Under Nutrient Fertilization Increases Primary Production and Biomass in Subtropical Phytoplankton Communities: A Mesocosm Approach

“…Mcgillicuddy et al, 2007;Sangrà et al, 2009) and export fluxes (Omand et al, 2015) in the ocean. Under an scenario of an acidified and warmer ocean, leading to an intensification of cross-shore wind gradients and eddy kinetic energy across eastern boundary regions (Bakun, 1990;Sydeman et al, 2014;García-Reyes et al, 2015), mesoscale variability would increase mixing and upwelling of deeper nutrient-rich water into the euphotic zone (Renault et al, 2016;Xiu et al, 2018). Our data suggest that a patchy nutrient pumping in a more acidified ocean would increase primary productivity in subtropical warm regions.…”

“…Nevertheless, it has been predicted that the heterogeneous warming of oceans and continents, may enhance upwelling-favorable winds in Eastern Boundary Current Systems (Bakun, 1990;Sydeman et al, 2014;García-Reyes et al, 2015). Stronger cross-shore wind gradients would lead to an intensification of the eddy kinetic energy fields across eastern boundary regions of the subtropical Gyres, favoring the upward pumping of nutrients driven by upwelling processes.…”

Extreme Marine Warming Across Tropical Australia During Austral Summer 2015–2016

“…MHWs occurring post‐summer coral bleaching can have implications for coral recovery and susceptibility to disease (e.g., Bruno et al, ; Ward et al, ) and so this cool‐season warm period may have exacerbated the effects of the summertime MHWs. Furthermore, near‐surface warming increases the stratification, reducing vertical mixing with deeper oceanic waters, and potentially changing the depth of upwelling waters and nutrient sources (García‐Reyes et al, ). For 2016, in the Central GBR, typical upwelling events appeared to have been suppressed during the peak of the MHW, compared with past years during the same month (Benthuysen et al, ).…”

Atmospheric Inputs of Iron and Manganese to Coastal Waters of the Southern California Current System: Seasonality, Santa Ana Winds, and Biogeochemical Implications

“…During spring and summer, the NPHP system is located at its northernmost position (Halliwell & Allen, ), establishing a pressure gradient with the Continental Low Pressure (CLP) center located in northwestern Mexico‐southwestern of the United States. This condition generates strong and persistent coastal winds, whose mean direction is from the northwest (Figure ), which in turn are responsible for inducing an offshore advection of surface water (Bakun, ; García‐Reyes et al, ; Huyer, ; Nelson, ). This advected water is replaced by the upwelling of subsurface water, characterized by lower temperature and high concentrations of nutrients and trace metals that, eventually, boost primary production during this period of the year.…”