Cool harvest: frost on sea ice may boost atmosphere's bromine.Frost flowers Frost flowers is the name commonly given to a condition in which thin layers of ice are extruded from long-stemmed plants in autumn or early winter. The thin layers of ice are often formed into exquisite patterns that curl into "petals" that resemble flowers. , the delicate crystals that sometimes grow atop fresh sea ice, can be a substantial source of ozone-destroying bromine bromine (brō`mēn, –mĭn) [Gr.,=stench], volatile, liquid chemical element; symbol Br; at. no. 35; at. wt. 79.904; m.p. –7.2°C;; b.p. 58.78°C;; sp. gr. of liquid 3.12 at 20°C;; density of vapor 7. in the lower atmosphere near the poles, researchers suggest. Over tropical and temperate seas, salt spray from breaking waves provides most of the low-altitude atmospheric bromine. The origin of bromine over ice-bound oceans has remained a mystery, but several lines of evidence now point to frost flowers as culprits. These arrangements of needle-like ice crystals often grow on the new ice that forms rapidly in frigid conditions. When winds are calm and the humidity just above the fresh ice is high, a dense crop of frost flowers sprouts. The fragile structures can reach heights of 2 centimeters or so. If the air temperature is about -40[degrees]C, for example, frost flowers can accumulate over as much as 50 percent of the fresh ice in just 5 days. When seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. freezes, many dissolved salts and ions, including bromine, concentrate in briny pools atop the new ice. The frost flowers act as wicks, drawing the liquid into their petal-like Adj. 1. petal-like - resembling a petal petallike leafy - having or covered with leaves; "leafy trees"; "leafy vegetables" crystals. There, the concentrations of dissolved ions can reach about triple what's normally found in the ocean, says Georg C. Heygster, a physicist at the University of Bremen The University of Bremen (German Universität Bremen) is a university of approximately 23,500 people are currently studying, teaching, researching and working from 126 countries in Bremen, Germany. It was founded in 1971. in Germany. What's more, he notes, the brine-soaked crystals provide a large surface area where chemical reactions can take place. The team's new analyses of ground-based weather data bolster this notion by showing that some polar air masses containing elevated concentrations of bromine monoxide (BrO) had on the previous day passed over areas of fresh sea ice, which probably sported frost flowers. Heygster and his colleagues report this finding in the Aug. 28 Geophysical Research Letters Geophysical Research Letters is a publication of the American Geophysical Union. GRL is the organization's only letters journal. Since its introduction in 1974, GRL has published only short research letters, typically 3-5 pages long, which focus on a specific discipline or . The reactions that produce BrO and other brominated gases are typically driven by sunlight. Satellite data of the polar-ocean region indicate that BrO shows up in especially large quantifies only after sunshine returns to polar regions in the spring, the researchers point out. "Until recently, frost flowers seemed like just a very pretty, but not especially important, phenomenon," says Eric W. Wolff of the British Antarctic Survey Based in Cambridge, the British Antarctic Survey (BAS) is the United Kingdom's national Antarctic operator and has an active role in Antarctic affairs. BAS is part of the Natural Environment Research Council and has over 450 staff. in Cambridge, England. The new research provides, "for the first time, some real evidence that the areas where frost flowers are likely to occur are also the areas where [scientists] find high levels of BrO" in the lower atmosphere, Wolff notes. Ice covered with frost flowers reflects radar differently than smooth ice does, says Mark R. Drinkwater of the European Space Agency European Space Agency (ESA), multinational agency dedicated to the promotion, for exclusively peaceful purposes, of cooperation among European states in space research and technology. in Noordwijk, the Netherlands. Scientists might next use high-resolution radar observations from satellites to more definitively link BrO plumes to patches of ice covered with frost flowers. |
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