The response of marine and terrestrial environments to global changes in atmospheric carbon dioxide (CO2) concentrations will likely be governed both by responses to the direct environmental forcing and by responses to Earth system feedbacks induced by that forcing. It has been proposed that anthropogenic greenhouse forcing will intensify coastal upwelling in eastern boundary current regions (1, 2). Focusing on the California Current, we show that biophysical land cover-atmosphere feedbacks induced by CO2 radiative forcing enhance the radiative effects of CO2 on land-sea thermal contrast, resulting in changes in eastern boundary current total-seasonal upwelling and upwelling seasonality. Specifically, relative to CO2 radiative forcing, land cover atmosphere feedbacks lead to a stronger increase in peak- and late-season near-shore upwelling in the northern limb of the California Current and a stronger decrease in peak and late-season near-shore upwelling in the southern limb. Such changes will impact both marine and terrestrial communities (2-4), and these and other Earth system feedbacks should be expected to play a substantial role in shaping the response of eastern boundary current regions to CO2 radiative forcing.

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