Quantitative analysis of the influence of dust sea surface forcing on the primary production of the subtropical Atlantic Ocean using a ten-year time series of satellite observations

Abstract

Dust aerosols that are not deposited over oceans are able to significantly reduce the solar energy available at the sea surface. Here, the impact of dust aerosols on the photosynthetically available radiation (PAR) at the sea surface and on the associated oceanic primary production (PP) is quantified over the subtropical Atlantic Ocean based on a ten-year time series of satellite observations. The ten-year average value of the attenuation of both PAR and PP due to dust aerosols is high (∼15%). The comparisons with predictions suggested that the decrease of PP might be ∼35% in the case of intense episodic events (i.e., dust aerosols optical depth>0.6). Therefore, dust aerosol events could significantly alter the organic carbon budget of the underlying oceanic ecosystems. The analysis of the interannual variations of the relative reduction of primary production (PP/PP) due to dust aerosols showed that the evolution of PP/PP does not exhibit any major trend of variation within the entire study area over the decade. However, a significant tendency (0.22% per year) is found near Africa in summer. Thus, dust aerosol events might induce a major decrease of the marine productivity the next centuries. The radiative forcing of dust aerosols on the sea surface needs to be accounted for in coupled atmosphere-ocean models for calculating correctly the primary production. A more extensive analysis of the aerosol radiative budget is also required to better understand the link between the atmospheric and oceanic processes driving the primary production over dust aerosol areas. © 2012. American Geophysical Union. All Rights Reserved.