Yes. Soil-derived aerosols, or dust, are abundant in our atmosphere. One source of dust is sandstorms over the Sahara. These storms whip small pieces of mineral dust from the desert into the atmosphere. Easterly winds then carry large plumes of Saharan dust away from the desert and over the Atlantic Ocean.
This weather system is referred to as a Saharan air layer, or SAL, and at times dust in the SAL has traveled to the Caribbean, Texas and Florida. Desert dust from the Sahara and Gobi deserts has been observed on the ice sheet of Greenland. Ice cores in Greenland provide a history of the dust deposition as it appears as layers in the ice.
This past July, satellites tracked a large plume of Saharan dust carried over the Atlantic Ocean. The incoming dust produces hazy-looking skies and causes red sunsets and sunrises. If rain should fall through the dust layer, the raindrops collect the soil particles. When the rain droplets hit objects on the ground, the water evaporates and leaves behind dry mud spots.
Dust plays a major role in Earth’s climate. The airborne dust particles absorb and reflect sunlight, thus reducing the amount of solar energy reaching the surface. Hurricane formation is very sensitive to several environmental factors including sea-surface temperature, vertical wind shear and even the SAL. The SAL is much drier than tropical air and can have a strong vertical wind shear. Both factors inhibit hurricane development. Dust can also promote or reduce cloud and storm formation, depending on other atmospheric conditions.
Dust from the Sahara impacts biological systems, as it is rich with iron and other minerals that plants and phytoplankton need. Dust transported out of the deserts is a natural fertilizer for ecosystems downwind. Iron and other nutrients in dust can lead to phytoplankton blooms as the dust settles into nutrient-limited waters.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
