Relevance:
A team of researchers from the Goa-based National Centre for Polar and Ocean Research and the School of Earth, Ocean, and Atmospheric Sciences in Goa University reconstructed the past deep-water circulations of the Indian Ocean.
News Summary:
- Global Overturning Circulation (GOC) is an equatorward transport of cold, deep waters and poleward transport of warm, near-surface waters.
- It is responsible for transport of carbon and heat among ocean basins and between ocean and atmosphere.
- GOC is a system of 2 connected overturning cells –
- Upper cell is linked to formation of North Atlantic Deep Water (NADW) and its shallower return flow to form Atlantic Meridional Overturning Circulation (AMOC).
- Lower cell (referred as Southern Ocean Meridional Overturning Circulation) is associated with formation of Antarctic Bottom Water (AABW) and its return flow as Pacific Deep Water (PDW).
- Studies have indicated that tectonically driven changes in ocean gateways such as closure of Central American Seaway (CAS), since late Miocene period, had impacted GOC.
- CAS is a body of water that once separated North America from South America.
Indian Ocean Deep water circulation:
- Indian Ocean does not have any major deep-water formations of its own. It acts only as a host for both GOC components.
- The northern parts of the Indian Ocean are located at one of the terminals ends of the GOC, far away from the deep-water formation regions and oceanic seaways.
- Few studies have been carried out in the Indian Ocean to reconstruct past deep water circulations based on iron-manganese crust records and authigenic neodymium isotope composition of sediment cores.
- But iron-manganese crusts are situated at deeper depths and are bathed only by AABW, making it suitable only for the reconstruction of the history of AABW, and authigenic neodymium isotope records are available only from the Bay of Bengal region.
- But they too cannot help as the Himalayan rivers that empty into the Bay also bring in substantial amounts of Neodymium particulates.
The most important fishing grounds of the world are found in the regions where: (2013)
- warm and cold atmospheric currents meet
- rivers drain out large amounts of fresh water into the sea
- warm and cold oceanic currents meet
- continental shelf is undulating
Reference: The Hindu
