The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations

Abstract

The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long‐range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite‐based estimate of dust deposition into the Amazon Basin using three‐dimensional (3‐D) aerosol measurements over 2007–2013 from the Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7 year average of dust deposition into the Amazon Basin is estimated to be 28 (8–48) Tg a−1 or 29 (8–50) kg ha−1 a−1. The dust deposition shows significant interannual variation that is negatively correlated with the prior‐year rainfall in the Sahel. The CALIOP‐based multiyear mean estimate of dust deposition matches better with estimates from in situ measurements and model simulations than a previous satellite‐based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3‐D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006–0.037) Tg P of phosphorus per year, equivalent to 23 (7–39) g P ha−1 a−1 to fertilize the Amazon rainforest. This out‐of‐basin phosphorus input is comparable to the hydrological loss of phosphorus from the basin, suggesting an important role of African dust in preventing phosphorus depletion on timescales of decades to centuries.

Long-term observations of cloud condensation nuclei in the Amazon rain forest – Part 2: Variability and characteristic differences under near-pristine, biomass burning, and long-range transport conditions

“…However, the regionally and biogenically dominated background state of the atmosphere is frequently perturbed by the episodic advection of 5 long-range transport (LRT) aerosols from Africa in air masses that bypass the major rain fields and, therefore, 'survive' the intense scavenging (Moran-Zuloaga et al, 2017). The frequent intrusion of LRT aerosols is a characteristic feature during the Amazonian wet season and represents a strong and important impact on the Amazonian ecosystem (e.g., Chen et al, 2009;Bristow et al, 2010;Baars et al, 2011;Abouchami et al, 2013;Yu et al, 2015;Rizzolo et al, 2016). These LRT plumes mostly comprise a complex mixture of Saharan dust, African 10 biomass burning smoke, and marine aerosols from the transatlantic air passage (e.g., Talbot et al, 1990;Swap et al, 1992;Glaser et al, 2015).…”

“…The African continent is of significant importance for the Amazonian atmospheric composition as it represents a major source of desert dust and pollution aerosols (e.g., Swap et al, 1992;Andreae et al, 1994;Yu et al, 2015;Rizzolo et al, 2016). A systematic overview of the properties and relevance of LRT plume arrival in the ATTO region during the Amazonian wet season can be found in Moran-Zuloaga et al (2017).…”

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

“…The Bodélé Depression (north-central Africa) is Earth's most prolific dust producer and may be key component to the global radiative budget of the atmosphere as well as to long-range nutrient transport to the Amazon rainforest (e.g., Prospero et al, 2002;Washington et al, 2003;Giles, 2005;Goudie and Middleton, 2006;Warren et al, 2007;Bristow et al, 2009Bristow et al, , 2010Hudson-Edwards et al, 2014;Yu et al, 2015). The Bodélé dust-source region consists mainly of diatomaceous lake beds overridden by dunes and other aeolian deposits (e.g., Warren et al, 2007;Bristow et al, 2009), which are driven by dominant northeasterly winds (Washington and Todd, 2005;Washington et al, 2006).…”

Comparison of aerosol optical depth from satellite (MODIS), sun photometer and broadband pyrheliometer ground-based observations in Cuba

“…All of these processes play a key role at a global and regional scales due to the high spatio-temporal variability of aerosol properties. Aerosols can also affect the biosphere and, in particular, humans in several ways: for example, the Saharan dust transported to America across the Atlantic supplies nutrients to the Amazon forest (Swap et al, 1992;Yu et al, 2015). Moreover, in the Caribbean, in addition to aerosols of local origin, dust makes the amount of aerosol exceed air quality standards associated with human health (Prospero and Lamb, 2003;Prospero et al, 2014).…”