May 11, 2011
MBARI News Release
Antarctic icebergs help the ocean take up carbon dioxide
|Icebergs such as this one carry iron-rich sediment from Antarctica out into the Southern Ocean. The darker parts of the ice contain higher concentrations of sediment. Image: Debbie Nail Meyer © 2009 MBARI|
The first comprehensive study of the biological effects of Antarctic icebergs shows that they fertilize the Southern Ocean, enhancing the growth of algae that take up carbon dioxide from the atmosphere and then, through marine food chains, transfer carbon into the deep sea. This process is detailed in 19 new research papers published electronically in a special issue of the journal Deep Sea Research Part II: Topical Studies in Oceanography.
The research team was led by MBARI marine biologist Ken Smith and funded by the National Science Foundation. Smith, along with researchers from more than a dozen other institutions, conducted three month-long cruises to the Weddell Sea in 2005, 2008, and 2009. By tracking individual icebergs and deploying remotely controlled aircraft and submersibles, as well as robotic drifters, the team was able to document a process that had previously been suspected, but never proven.
|Instead of avoiding icebergs, the research vessel Nathanial Palmer approached very closely to these floating "islands" of ice during this five-year research project. Image: Debbie Nail Meyer © 2009 MBARI|
During their three cruises, the team studied an area they called “iceberg alley” in the inhospitable and sometimes dangerous Southern Ocean. Instead of avoiding icebergs, they directed their research vessel to approach and follow drifting icebergs the size of small towns. To follow individual icebergs, they used satellites and GPS tracking devices that were dropped on the icebergs using a radio-controlled airplane. They also used three different robotic submersibles to study life on the undersides of the icebergs.
|Researchers programmed this Lagrangian sediment trap (the gray tube with white funnels) to sink 600 meters below the surface as a large iceberg drifted overhead. After collecting sinking debris for about three days, the trap rose to the surface. At that point, researchers and crew members used a small boat to lift the trap carefully out of the water and then hoisted it onto their research vessel. Image: Debbie Nail Meyer © 2009 MBARI|
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-kilometer (18.6-mile) radius of the iceberg, compared with an open-ocean “control” area.
Extrapolating their findings to the rest of the Weddell Sea, the researchers concluded that the icebergs (both large and small) were playing an important role in controlling how much carbon from the atmosphere was taken up by algae and ultimately transported into the deep sea. “The role of icebergs in removing carbon from the atmosphere may have implications for global climate models that need to be further studied,” said Smith.
In addition to the direct measurements of material sinking beneath the icebergs, the multidisciplinary research team performed a wide variety of physical, chemical, and biological studies around the icebergs. Many of these studies are detailed in the special issue of Deep-Sea Research. The 19 papers in this special issue describe:
- New methods and tools for tracking icebergs from a moving ship at sea
- Water-sampling and video surveys by remotely operated vehicles
- Aerial surveys and tracking of icebergs using radio-controlled aircraft
- The fresh water, iron, and sediment released by melting icebergs
- The design and operation of the Lagrangian sediment traps, and the amounts of debris, organic carbon, and other materials collected by these traps
- Populations of marine microbes, algae, marine animals, and seabirds around the icebergs
|Ken Smith (left), Alana Sherman (right), and other members of the research team examine a Lagrangian sediment trap after it was brought back on board the research vessel. Image: Debbie Nail Meyer © 2009 MBARI|
Note: The primary authors of papers in this special issue of Deep-Sea Research II are affiliated with the Monterey Bay Aquarium Research Institute (MBARI), the University of South Carolina, Scripps Institution of Oceanography, University of San Diego, Bigelow Laboratory for Ocean Sciences, Brigham Young University, University of Nevada Desert Research Institute, Leeds University (UK), Stanford University, the Universidad Nacional de La Plata (Argentina), the University of California at San Diego, and the University of Southampton (UK).
For additional information or images relating to this news release, please contact:
Kim Fulton-Bennett: (831) 775-1835, firstname.lastname@example.org
Ken Smith (ed.), Free-Drifting Icebergs in the Southern Ocean, Deep Sea Research Part II: Topical Studies in Oceanography, Volume 58, Issues 11-12, Pages 1277-1504 (June 2011).
- Gallery of photographs relating to this news release
- MBARI news release on the results of Ken Smith's 2005 cruise to the Southen Ocean
- Photographs from Ken Smith's 2005 cruise to the Southern Ocean
- News release from the National Science Foundation on a related paper describing parts of this research (includes photo gallery).
Short video describing this research (from MBARI's YouTube Channel):