Deep-Water Circulation

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16-Jan-2023: Studies indicate tectonically driven changes in the ocean gateways had a dramatic impact on the global overturning circulations

Deep-Water Circulation

  • Movement of water in the deep ocean
  • Driven by density differences caused by variations in temperature and salinity
  • Creates a circulation pattern known as the thermohaline circulation
  • Helps distribute heat around the globe
  • Controls atmospheric carbon dioxide levels
  • Shapes ocean currents and circulation patterns
  • Influences marine ecosystem, weather patterns, and coastal regions
  • Affects sea level by redistributing heat and thermal expansion

Impact of Tectonic Changes

  • Central American Seaway closing created two distinct water bodies
    1. Northern component water in North Atlantic Ocean
    2. Antarctic Bottom Water (AABW) in Southern Ocean
  • Large-scale changes in Deep-Water Circulation (DWC) across the world
  • Impacted global climate and heat exchanges

Deep-Water Circulations of Indian Ocean

  • Indian Ocean does not produce its own deep water. It receives it from other sources such as North Atlantic and Antarctic.
  • Northern part of Indian Ocean is good place to study ocean circulation changes as it is located far away from the areas where deep water is formed and ocean routes.
  • Studies done using records from iron-manganese crusts and authigenic neodymium isotope composition of sediment cores.

Limitations of records

  • Iron-manganese crusts are found at deeper depths and are only bathed by Antarctic Bottom Water (AABW), so they can only provide information about the history of AABW.
  • Authigenic neodymium isotope records are only available from the Bay of Bengal region, but they are also not accurate as the Himalayan rivers that flow into the Bay bring in a lot of neodymium particulates which can interfere with the results.
  • Despite all this, Scientists have generated an authigenic neodymium isotope record from the Arabian Sea and reconstructed the DWC record of the Indian Ocean for the period from 11.3 million years ago (Miocene era) to 1.98 million years ago (Pleistocene era).