Search for: All records

Here, we present the data and MixSIAR code that corresponds to the manuscript “Interannual variability in the source location of North African dust transported to the Amazon.” African dust is seasonally transported to the western Tropical Atlantic Ocean (TAO) and South America (SA), including the Amazon Basin. Leading hypotheses suggest that either the Western North African potential source area (PSA) or the Central North African PSA (e.g., Bodélé Depression) is the main source of dust transported to the Amazon. However, these notions remain largely untested with geochemical data. Here, we present a more nuanced hypothesis: both PSAs contribute dust to SA with precipitation and wind patterns determining the dominant source. Our premise is based upon two years of isotopic measurements (strontium and neodymium) of African dust collected in SA integrated into a statistical model in a Bayesian framework. With this approach, we identified strong interannual variability: while the Central PSA supplied 48% in winter 2016, a region within the Western PSA, which we suggest may be located near Niger, Mali, and Algeria accounts for 54% of transport in winter 2014. We propose the variability is due to the strength of the Libyan High and differing amounts of precipitation in the Gulf of Guinea and TAO between the two years. We anticipate that our work will lead to better constraints of dust nutrient deposition and subsequent carbon sequestration in the TAO and Amazon as well as improved model predictions of dust transport. Due to the connection between dust, precipitation, and wind patterns, our work can be used to link changes in climate with past changes in the source and magnitude of dust transported to the Amazon and TAO. This data is associated with the article: Barkley, A.E., Pourmand, A., Longman, J., Sharifi, A., Prospero, J.M., Panechou, K., Bakker, N., Drake, N., Guioiseau, D., Gaston, C.J. Interannual variability in the source location of North African dust transported to the Amazon. Submitted to the Proceedings of the National Academy of Sciences ## Description of the datasets The `data/` folder contains three data sets. `ds01` contains the data collected in this study from 34 samples including the dates of collection and Sr and eNd isotopic ratios. ## Metadata of the trajectory file ds01 is a *csv* file that contain 12 columns. Column 1 presents the date in the format ‘MM:DD:YYYY’ (e.g., 01-30-2014) that sample collection was initiated. Column 2 presents the date ‘MM:DD:YYYY’ (e.g., 01-31-2014) sample collection ended. Column 3 shows the mean 87Sr/86Sr ratio (unitless) measured and Column 4 shows the 95% confidence interval (CI) for each sample run in triplicate. Column 5 shows the 143Nd/144Nd isotopic ratio reported as epsilon neodymium (unitless) and Column 6 presents the 95% CI of the mean epsilon Nd. Columns 7, 9, and 11 show the lead (Pb) isotopic ratios normalized to 204Pb with their corresponding 95% CI in Columns 8, 10, and 12. 

Abstract African dust is transported to South America (SA) every winter and spring. Hypotheses suggest that either Western or Central North Africa (e.g., Bodélé Depression) is the main source of transported dust, yet these notions remain largely untested with geochemical data. Using 2 years of isotopic measurements (strontium and neodymium) of African dust collected in SA integrated into a statistical model, we identified strong interannual variability in dust source region. Central North Africa supplied 44% of long‐range transported dust in winter 2016 while the Western region accounted for 53% of dust in winter 2014. We propose the variability is due to differences in the strength of the Libyan High and precipitation over the Gulf of Guinea and Atlantic Ocean between the 2 years. Our findings can improve constraints of dust nutrient deposition and predictions of how changes in climate impact the source and magnitude of dust transported to the Amazon. 

Abstract The equatorial North Atlantic Ocean (NAO) is a nutrient‐limited ecosystem that relies on the deposition of long‐range transported iron (Fe)‐containing aerosols to stimulate primary productivity. Using microscopy, we characterized supermicron and supercoarse mode African aerosols transported to the western NAO in boreal winter/spring. We detected three particle types including African dust, primary biological aerosol particles, and freshwater diatoms (FDs). FDs contained 4% Fe by weight due to surficial dust inclusions that may be susceptible to chemical processing and dissolution. FDs were typically larger than dust particles and comprised 38% of particles between 10 and 18 μm in diameter. The low density, high surface‐area‐to‐volume ratio, and large aspect ratios of FD particles suggest a mechanism by which they can be carried great distances aloft. These same properties likely increase the residence time of FDs in surface waters thereby increasing the time for Fe dissolution and their potential impact on marine biogeochemical cycles.