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About The Southern Annular Mode

Context:

Recently, the Indian National Centre for Ocean Information Services (INCOIS) discovered that the Southern Annular Mode (SAM), an important climate pattern, plays a pivotal role in shaping sea conditions across the Indian Ocean.

Relevance:

GS I: Geography

Dimensions of the Article:

  1. Southern Annular Mode (SAM): Understanding Antarctic Oscillation
  2. Significance

Southern Annular Mode (SAM): Understanding Antarctic Oscillation

  • Definition: The Southern Annular Mode (SAM) refers to the north-south movement of Southern Westerly Winds occurring over timescales of 10s to 100s of years.
  • Other Name: Also known as the Antarctic Oscillation.
  • Geographical Range: These winds persistently blow in the mid- to high-latitudes of the southern hemisphere.
Characteristics:
  • Definition Basis: SAM is typically defined as the difference in the zonal mean sea level pressure at 40°S (mid-latitudes) and 65°S (Antarctica).
SAM Modes:

Positive SAM:

  • Lower anomalous air pressure over Antarctica.
  • Higher anomalous air pressure over the mid-latitudes.
  • Strengthens and contracts the belt of strong westerly winds towards Antarctica.

Negative SAM:

  • Belt of strong Southern Westerly Winds expands northwards towards the equator.
  • Results in cold, wet weather in Patagonia, glacier advance, and decreased Circumpolar Deep Water upwelling on the Antarctic Continental Shelf.

Significance:

  • Wave Predictions: Advances in SAM understanding contribute to more accurate wave predictions, aiding in identifying fair-weather windows.
  • Beneficiaries: Fishing communities, as well as stakeholders in the blue economy like shipping, maritime boards, and the oil industry, stand to benefit from improved operations at sea.

-Source: The Hindu


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