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Giant icebergs can provide nutrients for microscopic organisms. Credit: United States Antarctic Program, Patrick Rowe, NSF.
Giant icebergs in the Southern Ocean appear to be leaving much more than melted ice in their wakes. They’re providing a bounty of nutrients that feed “blooms” of microscopic organisms. And those organisms could help slow the rise in Earth’s temperature.
An iceberg forms when a glacier pushes out to sea and part of it breaks off. The bottom of the iceberg holds bits of nutrient-rich rock and dirt gouged out as the glacier scraped across land.
As the iceberg melts, it releases the nutrients, which can fuel blooms of the organisms known as phytoplankton. And a recent study found that giant icebergs — those that are as long as Manhattan Island or bigger — are particularly efficient at feeding these blooms.
Researchers looked at satellite photos of the ocean around giant icebergs. After the ’bergs passed, the ocean looked greener. The boost in color indicated a massive increase in the number of these organisms, which look green because they contain chlorophyll. The blooms extended up to hundreds of miles from the icebergs, and could last for a month or longer.
Phytoplankton take in carbon dioxide from the atmosphere — the molecule that’s responsible for much of Earth’s warming climate. When they die, they fall to the bottom, taking the CO2 with them.
More giant icebergs are likely to break off the Antarctic glaciers in the years ahead, perhaps leading to more giant blooms. That won’t stop global warming. But it shows how complicated our climate is — a fascinating interplay of water, air — and icebergs.
