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5th September 2023 (10 Topics)

'Atlantification' of the Arctic Ocean

Context

In a recent study published in the journal Science, an international team of scientists has shed new light on the “Atlantification” of the Arctic Ocean. This phenomenon explains the trend in Arctic Ocean sea ice loss that seems to have plateaued since 2007.

Key-highlights of the Study

Arctic Dipole

  • The Arctic dipole, also known as the Dipole Anomaly, is a relatively recent climate pattern characterized by atmospheric pressure variations in the Arctic region. 
  • It has garnered increased attention due to its pronounced impact on the sea ice extent and its potential linkage with mid-latitude weather patterns. 
  • The study delves into the multifaceted influence of the Arctic dipole on the Arctic Ocean climate.
  • The researchers discovered that the Arctic dipole follows an approximately 15-year cycle. They surmise that we’re nearing the end of the present regime.
  • When broken down, the current “positive” regime of the Arctic dipole, which has persisted since 2007, is characterized by high pressure centered over the Canadian sector of the Arctic producing clockwise winds, and low pressure over the Siberian Arctic, with counterclockwise winds. 
  • This specific wind configuration affects upper ocean currents and has a wide-ranging influence, from air temperatures to sea-ice drift, heat exchanges, and even ecological implications.
  • Switchgear mechanism: The research also unveils a “switchgear mechanism” responsible for the alternating changes in the Fram Strait and the Barents Sea. These alterations, triggered by the Arctic dipole mechanisms, have profound effects. 
  • An influx of warmer Atlantic water to the Arctic is changing the makeup of this ocean stratification. 
  • Driven by climate change, the Arctic Ocean is seeing
    • sea ice reductions
    • weakening of the halocline
    • reduction in the depth of the Atlantic warm waters
    • Atlantic water is having an increasing influence on the Arctic Ocean

Major Layers of the Arctic Ocean

  • The Arctic Ocean is formed of numerous water layers that remain in place due to the differences in salt concentration, which affect the buoyancy of the water.
    • Top Layer: The top layer is freshwater with a low salinity, held at near freezing point, which comes from the melting of sea ice and from Arctic rivers that release into the ocean.
    • Layer of Salt: Beneath this layer comes a layer of saltier and warmer water from the Atlantic.
    • Arctic halocline: In between these two layers, there is an intermediate layer known as the Arctic halocline where the warm, salty water mixes with the cold, fresh surface layer above.
    • Arctic deep water: Beyond the warm and salty Atlantic layer, there is another water mass of cold and slightly saltier water, known as Arctic deep water.

What factor is responsible for maintaining the layered structure?

  • Thermohaline circulation, also known as the "Great Ocean Conveyor Belt," is a key factor in maintaining the layered structure of the Arctic Ocean.
  • It involves the movement of ocean water based on differences in temperature (thermo) and salinity (haline).
  • In the Arctic Ocean, cold and dense water sinks beneath warmer and less dense water, creating a layered structure that helps in retaining the various water layers in place.

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