The recent studies’ findings indicate that tectonic changes, particularly the closing of the Central American Seaway, have greatly influenced the global overturning circulations.
Deep-Water Circulation and Ocean Gateways
Deep-Water Circulation (DWC) pertains to the movement of water in the deep ocean. This movement is prompted by the differences in the density of water masses due to variations in salinity and temperature. The phenomenon of DWC, as well as the nuances of the Central American Seaway and the Antarctic Bottom Water (AABW), plays a pivotal role in global climate dynamics, heat exchanges, and the functioning of diverse ocean currents.
The Central American Seaway once acted as a water barrier between North and South America. It is now believed that its closure and other tectonic shifts led to the formation of two distinct water bodies: the Northern component water in the North Atlantic Ocean and AABW in the Southern Ocean. Consequently, these changes could have triggered large-scale variations in the DWC across the world’s oceans.
Significance of Deep-Water Circulation
DWC serves several crucial functions in maintaining the Earth’s climate stability and the health of marine ecosystems.
Its foremost role lies in heat distribution. DWC helps disseminate heat around the globe, regulating the Earth’s temperature and preventing regions from becoming excessively hot or cold. Further, it also plays a key role in managing levels of atmospheric carbon dioxide by transporting carbon from the surface to the deep ocean for long-term storage. This circulation pattern, known as the thermohaline circulation, significantly influences the formation of various ocean currents and the resultant circulation patterns within the world’s oceans. These currents, in turn, impact marine ecosystems, weather patterns, and coastal areas. Lastly, DWC influences sea levels, as warmer water (being less dense than cold water) can contribute to sea level rise through thermal expansion.
Indian Ocean’s Deep-Water Circulations
The Indian Ocean, unlike other oceans, does not generate its own deep water but receives it from outside sources, such as the North Atlantic and Antarctic. The northern region of the Indian Ocean, remote from areas creating deep water and ocean routes, provides an ideal location for studying the repercussions of changes in ocean circulation.
Investigations have been conducted using records from iron-manganese crusts and the authigenic neodymium isotope composition of sediment cores. However, these records have limitations. For instance, iron-manganese crusts are only found at greater depths and solely provide information about the AABW. Meanwhile, authigenic neodymium isotope records are exclusive to the Bay of Bengal region. These records may not be completely accurate due to interference from neodymium particulates carried by Himalayan rivers into the Bay.
Recent scientific breakthroughs have produced an authigenic neodymium isotope record from the Arabian Sea. This milestone has allowed researchers to reconstruct the DWC history of the Indian Ocean, spanning from 11.3 million years ago (the Miocene era) to 1.98 million years ago (the Pleistocene era).
UPSC Civil Services Examination Previous Year Questions
Understanding the impact and role of different forces on ocean currents is crucial for several fields including marine life conservation and fishing industry. In previous examination questions for UPSC civil services, candidates were asked to explain the impact of ocean currents and water masses on marine life and coastal environment (2019) and discuss the forces influencing ocean currents and their role in the world’s fishing industry (2022).
