(ORDO NEWS) — Scientists from the international climate project CLOUD have found that one of the reasons for the rapid melting of Arctic ice is the formation of iodine-containing clouds over the Arctic Ocean. The nuclei of condensation for their formation are particles of iodine released from sea water. The research results are published in the journal Science.
Low solid clouds over the Arctic and Antarctic contribute to the warming of these regions, blocking the removal of long-wave heat from the Earth’s surface.
All clouds in the Earth’s atmosphere are formed by aerosols, which occur when water vapor is attached to suspended particles in the air. For the formation of clouds, it is not decisive what aerosol particles consist of – dust, salt crystals, molecules emitted by plants, or human activity products such as soot – their size is most important: aerosol particles become condensation nuclei of water droplets with a size of 70 nanometers and higher.
Researchers at the CLOUD (Cosmics Leaving OUtdoor Droplets) consortium, which includes 21 research institutions, are studying how new aerosol particles are formed from precursor gases and continue to grow in the atmosphere.
The authors found that, in addition to salt crystals formed from sea spray and sulfur compounds such as dimethyl sulfide released by phytoplankton, iodine compounds play an important role in the formation of atmospheric aerosols.
As the area of sea ice in the Arctic shrinks and the surface of open water increases, more iodine-containing vapors rise from the sea. Each liter of seawater contains 0.05 milligrams of iodine, and when it enters the atmosphere, sunlight and ozone form iodic acids there.
This creates a positive feedback loop: the accelerated formation of iodine particles leads to more clouds, which, in turn, promote faster ice melting.
In order to understand how aerosol particles are formed from iodine-containing vapors, scientists have constructed a special experimental chamber CLOUD at the European Center for Nuclear Research CERN in Geneva, in which the atmospheric conditions of middle and Arctic latitudes, including cosmic rays, simulated by a beam of elementary particles, have been reproduced.
The results showed that the formation of aerosol particles based on iodic acid occurs very quickly – much faster than particles of sulfuric acid or ammonia under similar conditions. In addition, the formation of particles is facilitated by cosmic ray ions. For the conversion of molecular iodine into iodine-containing acids, not even UV radiation is needed, but only a little daylight, scientists believe. In this pattern, very large amounts of aerosol can be generated quickly.
“Iodine aerosols are formed faster than almost all other types of aerosols known to us. If ions produced by cosmic rays are added, each collision leads to the growth of molecular clusters,” the words of one of the authors are quoted in a press release from the Goethe University in Frankfurt am Main research by Professor Joachim Curtius.
Due to the fact that global iodine emissions have tripled over the past 70 years, the authors fear a mutual increase in sea ice melting and cloud formation, which could accelerate warming in the Arctic and Antarctic.
“A vicious circle may have already started: the melting of pack ice increases the water surface area and more iodine is released into the atmosphere. This leads to more aerosol particles that form clouds, which further heat the poles,” explains Curtius.
Scientists hope the mechanism they have identified will become part of climate models.
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