The marine aerosol is injected into the atmosphere by waves breaking at shore, and by whitecaps when winds over open water exceed 15 knots. Out of Africa Magnesium and potassium inputs also follow their seawater ratios, but calcium substantially exceeds the amount in sea water. The excess calcium was attributed to trans-Atlantic transport of Sahara dust by McDowell et al. The results are translated into images, which may be viewed on Web . Screen shot from the NOAA Website.
Image is turned sideways so the dust cloud coming across the Atlantic ocean can be clearly seen.
The relationship is even stronger when we account for weeks in which there was not enough rain fall to remove all the dust from the air. In the continental U.S., only Midwestern farming areas receive this much calcium in rain, which comes from local sources in those areas. Sahara dust reaches the Caribbean from June through September, but the emission season begins earlier. One of the larger events occurred in February 2000, and was pictured in the September 2000 issue of National Geographic magazine. Dust from the early-season events is washed out of the atmosphere by rain falling over the Atlantic Ocean.