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Tiny bits of iron may explain why some icebergs are green

Scientists may have finally figured out why some icebergs are green. Iron oxides could create the emerald hat Icebergs often appear mostly white because light bounces off air bubbles trapped inside the ice. But pure ice – ice without air bubbles that often form on a mountain's underside – appears blue because it absorbs longer light wavelengths (warm colors like red and orange) and reflects shorter ones (the cooler colors). Since the 1930s, though, mysterious capsized icebergs with green undersides, nicknamed "jade mountains," have been spotted around Antarctica. that the green came from microscopic carbon particles from dead organisms. When integrated into ice, these yellow carbon particles would absorb blue light leaving green. Later experiments, though, found that the amount of carbon in green icebergs was too low to create the emerald hue. "So we were left with this disturbing result," Warren says. Then in 201 6, researchers discovered iron oxides in a decades-old preserved green ice sample taken from the American ice shelf in Antarctica. Iron oxides such as rust reflect reds and oranges but absorb blue light. If these particles, possibly picked up from rocks crushed by the weight and friction of glaciers flowing towards the ocean, incorporated into ice forming underwater, the result would be a vibrant green, Warren and his colleagues report March 4 in the Journal of Geophysical Research: Oceans Warren hopes to return to Antarctica to collect samples to see if jade mountains are rich in iron. If so, that could both solve a…

Scientists may have finally figured out why some icebergs are green. Iron oxides could create the emerald hat

Icebergs often appear mostly white because light bounces off air bubbles trapped inside the ice. But pure ice – ice without air bubbles that often form on a mountain’s underside – appears blue because it absorbs longer light wavelengths (warm colors like red and orange) and reflects shorter ones (the cooler colors).

Since the 1930s, though, mysterious capsized icebergs with green undersides, nicknamed “jade mountains,” have been spotted around Antarctica.

that the green came from microscopic carbon particles from dead organisms. When integrated into ice, these yellow carbon particles would absorb blue light leaving green. Later experiments, though, found that the amount of carbon in green icebergs was too low to create the emerald hue.

“So we were left with this disturbing result,” Warren says.

Then in 201

6, researchers discovered iron oxides in a decades-old preserved green ice sample taken from the American ice shelf in Antarctica. Iron oxides such as rust reflect reds and oranges but absorb blue light. If these particles, possibly picked up from rocks crushed by the weight and friction of glaciers flowing towards the ocean, incorporated into ice forming underwater, the result would be a vibrant green, Warren and his colleagues report March 4 in the Journal of Geophysical Research: Oceans

Warren hopes to return to Antarctica to collect samples to see if jade mountains are rich in iron. If so, that could both solve a mystery and suggest a previously unknown role for this unusual ice cream: ferrying a scarce but essential nutrient to the microscopic plankton that the entire ocean food web relies on.

“I don’t know how important [green icebergs] are, “Warren says. “I’ll find out.”


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