Antarctic Bottom Water and Its Role in Climate Change
27.04.2010 - Atmosphere & Space, Water & Oceans, Antarctic
A team of oceanographers led by Yasushi Fukamachi of Japan's Hokkaido University has found a new factor in climate change as they measured a system of powerful currents off Antarctica according to a new study published in the journal Nature Geoscience.
The system under study, the Antarctic Bottom Water (AABW), is generated in clockwise movement in four big sea shelves that border Antarctica. During the process, the extremely cold water sinks to the bottom of the shelves and heads out northwards along the continental shelf while some of the water mixes with the Antarctic Circumpolar Current (ACC) at the edges of the ice shelf. What remains of the AABW then reaches up into the southern latitudes of the Indian, Pacific, and Atlantic Oceans.
In their study, the scientists used eight seabed sensors anchored at a depth of 3,500 metres for two years over 175 kilometres on the Kerguelen Plateau, to the east of Antarctica. The team found that about eight million cubic meters of extremely cold water (below 0.2°C) were transported northwards over this narrow section. This represents an amount four times the previous record documented in an AABW flow in the Weddell Sea on the other side of Antarctica.
These findings are important since currents are major players in climate change. Not only are they responsible for heat circulation, they also help determine the success of oceans as a storage place for carbon dioxide (CO2), the most abundant greenhouse gas. Once the phytoplankton has taken in the CO2 and die, they bring the carbon with them. However, whether these reach the ocean bottom or are swept back up to the surface is determined by the currents.
