Antarctic icebergs help ocean absorb carbon dioxide
Washington: Antarctic icebergs may be instrumental in boosting the growth of algae that absorbs atmospheric carbon dioxide (CO2) and transfers it back into the deep sea through marine food chains.
Marine biologist Ken Smith from Monterey Bay Aquarium Research Institute, along with researchers from a dozen other institutions, conducted three month-long cruises to the Weddell Sea in 2005, 2008, and 2009.
Global climate change is causing Antarctic ice shelves to shrink and split apart, releasing thousands of free-drifting icebergs that are carried by currents into the nearby Weddell Sea, the journal Deep-Sea Research reports.
Their research vessel, Nathanial Palmer, very closely approached these floating islands of ice during this five-year research project, according to a Monterey Bay statement.
The new study suggests that these icebergs carry iron-rich sediment from the land out into the ocean. As these icebergs melt and drift across the ocean, some of the iron dissolves in the seawater, creating a trail of iron-rich meltwater that can be up to 19 km long. The iron in this water helps fertilise the growth of microscopic algae.
Monterey Bay engineers, led by Alana Sherman, developed a new robotic instrument that was programmed to sink 600 meters below the ocean surface while a large iceberg drifted overhead, then rise back to the sea surface after the iceberg had passed.
This instrument, called 'Lagrangian sediment trap', was used to collect particles of sediment, bits of dead algae, and other debris that drifted down from the waters under and around the iceberg.
This device allowed scientists to measure for the first time the amount of organic carbon sinking into the deep sea beneath a large (six-km-wide, 35-km-long, and 28-metres-high), free-floating iceberg.
The researchers compared the amount of carbon sinking down to 600 meters beneath the iceberg with the amount of carbon sinking in the open ocean nearby.
They found that about twice as much carbon sank into the deep sea within a 30-km radius of the iceberg, compared with an open-ocean "control" area.