Long-range Transport of Saharan Dust Over the North Atlantic Ocean and Estimation of its Transport Amount

In order to investigate the long-range transport of the Saharan dust over the North Atlantic Ocean and to estimate its transport amount, atmospheric dust samples were collected at Bermuda Island and Barbados Island in the North Atlantic Ocean from February 1989 to February 1991. The dust samples were analyzed by X-ray fluorescence and atmospheric concentrations of major crustal elements such as Al, Si and Fe were measured. The annual mean concentrations of Al, Si and Fe were 140 ng/m³ (n=71), 380 ng/m³ (n=65) and 120 ng/m³ (n=65) at Bermuda Island and 830 ng/m³ (n=96), 1880 ng/m³ (n=90) and 550 ng/m³ (n=85) at Barbados Island, respectively. In Bermuda Island, the high concentrations of Al, Si and Fe were observed in the summer season. Air mass trajectory patterns in Bermuda and Barbados Islands were classified with the charts of back trajectory analysis. When the air mass came from the direction of the North African Continent, the mean atmospheric concentrations of Al, Si and Fe were the highest ones in all the trajectory patterns at both islands. The air mass from the North African Continent reached frequently both islands during the summer from July to September. Therefore, it was confirmed that the Saharan dust was transported to Bermuda and Barbados Islands in the North Atlantic Ocean. By use of data of mineral dust concentrations and Box model, an annual transport amount of Saharan dust over the North Atlantic Ocean was estimated to be 123 × 10⁶ t/y.