West Africa warms but airborne dust keeps the Red Sea cool
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KAUST researchers reveal how the Red Sea’s location in a dust trap affects the regional climate.
The Red Sea is located between North Africa and the Arabian Peninsula, the world’s largest dust source regions. Summer winds pump dust from the Sahara and Arabian deserts down a narrowing mountain-fringed passage, causing it to accumulate over the southern Red Sea. Dust suspended as aerosol particles in the atmosphere can influence climate by altering the balance between sunlight absorbed at the Earth’s surface and heat energy radiated back to space. This is known as radiative forcing.
“We show that summer conditions over the Red Sea produce the world's largest aerosol radiative forcing, and yet the impact of dust on the Red Sea was never studied— it was simply unknown," says Sergey Osipov, postdoctoral fellow and coauthor with his supervisor Georgiy Stenchikov. Simulations reveal that dust cools and freshens the Red Sea, potentially protecting coral reefs against the damaging effects of ocean warming due to climate change.
A surprising finding relates to biological productivity. “Dust deposition adds nutrients,” explains Osipov. “However, we find that dust radiative forcing slows down the Red Sea circulation and reduces the main nutrient supply to the Red Sea through the Bab-el Mandeb strait. The net effect on overall bio-productivity remains to be established.”
Large volcanic eruptions, such as the 1991 eruption of Mount Pinatubo in the Philippines, inject vast amounts of sulfur dioxide into the upper atmosphere, where it is converted into tiny sulfate aerosol droplets. These sulphate aerosols spread around the globe, exerting a strong radiative forcing effect.
Osipov and Stenchikov previously showed that the Pinatubo eruption affected the regional climate of the Middle East and Red Sea. They have now compared its impact with that of airborne dust.
“We show the effects of Pinatubo and dust are greatest in the northern and southern Red Sea, respectively, having different effects on surface and deep-water cooling,” says Osipov.
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