"Polarstern” begins new iron fertilization experiment
On January 21, 2004, the "Polarstern", research vessel of the Alfred-Wegener-Institute of Polar and Marine Research, will leave Cape Town for the third stage of the 21st expedition to Antarctica. Forty-nine scientists from nine countries will be aboard to investigate the effects of fertilizing the Southern Ocean on the carbon exchange between air and sea surface. Carbon in the form of carbon dioxide acts as a greenhouse gas, and plays a major role in global climate warming.
Planctonic algae consume carbon dioxid
In 2000, scientist aboard "Polarstern" were already able to demonstrate that fertilizing the Southern Ocean with iron sulphate causes a planktonic algal bloom. Planktonic algae consume dissolved carbon dioxide for growth. The deficit of carbon dioxide created in the upper layers of water during blooms, is replenished subsequently from atmospheric carbon dioxide. This is what makes the experiment interesting in the context of global climate research. The question is whether the greenhouse gas carbon dioxide, once it has been moved from the air into the water, remains in the ocean. Previously, "Polarstern" was never on site for long enough to observe the continuing process. This will be different on the current expedition:
“Ten weeks should be sufficient to observe what happens to the algae and the carbon they incorporate. If they are consumed by animals, they will be metabolically converted and the greater part of the carbon will transferred to the air through respiration and excretion” says expedition leader Prof. Dr.Victor Smetacek from the AWI. “If, in contrast, they die after the bloom and sink to the bottom, then carbon is removed from the atmosphere permanently”.
The experiment will be carried out at approximately latitude 50 degree South in the open ocean. Currently the AWI is selecting a suitable stable gyre using satellite images of the ocean surface. In the centre of this approximately 100 km wide gyre, the “Polarstern” will release iron sulphate solution over approximately 150 to 200 square kilometres. Scientists in helicopters using a laser measuring system (LIDAR) will observe algal growth over large areas. They will follow interactions among algae, bacteria and various small animals in the fertilized patch. The data will also provide important insights into the realm of plankton, the base of the oceanic food chain. Interdisciplinary project groups from the AWI investigate pathways of carbon, an important component of life on earth.
“Polarstern” will conclude this leg of the research expedition in Cape Town on March 25. Afterwards, she will proceed for 6 weeks to the Lazarew Sea in Antarctica to investigate how the ecologically most significant species in Antarctic waters, krill, survives the winter. “Polarstern” will not return to Bremerhaven before June 2, 2004.
Bremerhaven, 16.1.04
Sinking greenhouse gas into the Ocean
