Indian Ocean

• The Indian Ocean is the body of water located to the east of Africa, south of the Arabian Peninsular, Pakistan and India, and to the west of Australia, Indonesia, Myanmar and Thailand.
• It was known to the Romans as the Erythraean Sea, a name which included the Red Sea, the Arabian Sea and the Persian Gulf.

Geography of the Indian Ocean

• Cape Guardafui
• Great Whirl
• Horn of Africa
• Socotra
• Socotra Gyre

Africa

• Somali Current
• Menouthias Islands
• Azania
• Rhapta

India and the Island chains

• Muziris
• Taprobane
• Laccadives, Maldives and Chagos Islands
• Divi

Bay of Bengal

• Andaman and Nicobar Islands
• Straits of Malacca

Winds and Currents

• Monsoon
• Periplus of the Erythraean Sea.
• Tropical Cyclones

Winds and Currents in the Arabian Sea

• The Current in the Arabian Sea travels clockwise, north up the coast of Africa, east along southern Arabia, and south down the coast of India.
• The exception to this is the Somali Current which reverses between December to April, to become a southerly flow along the Somali coast.

• From May to November:
  • The Somali Current flows Northward in a band 30-60 miles wide, along the East Coast of Africa. During the Southwest Monsoon, between May and June, the Current is at its strongest flow. This intense Current produces two main Eddies, the Great Whirl and a secondary Eddy known as the Socotra Gyre.

• From December to April:
  • During the Northeast Monsoon, the Somali Current reverses to become a Southward Flow, starting from up to Latitude 10 degrees North, which includes most of the Somali Coastline. The Current is at its strongest in January.
  • However, the current flows north between Socotra and the Horn of Africa, before turning east along the South Arabian coastline.
  • The Monsoon winds blow from the Northeast, across the Arabian Sea, and down the Somali coast.
  • If a sailing vessel, returning from India to the Red Sea, failed to get into the Gulf of Aden, it would have been carried down the Somali coast, unable to turn back. The vessel would then have had to wait until May, for the return of the Southeast Monsoon and the reversal of the Somali Current, to get back to the Red Sea.
  • A Roman vessel returning from Muziris or Taprobane using the Northeast Monsoon winds, would have been going against the current for the first half of its journey.

Winds and Currents in the Bay of Bengal

• The East India Coastal Current flows Northeast from February to September, and is at its strongest between March to April. The Southwest Monsoon blows from June to September in the same direction.
• When the Monsoon reverses to become the Northeast Monsoon, the Current reverses to become Southeasterly between October to January, and is at its strongest during November.
• The Bay of Bengal has a clockwise Current during most of the year, but it becomes anticlockwise during November.

• Anticyclonic Flow in the Northern Hemisphere is clockwise.
• Cyclonic Flow in the Northern Hemisphere is anti-clockwise.

The Andaman Sea

• To the east of the Bay of Bengal lies the Andaman Sea. It is bounded in the west by the Andaman and Nicobar Islands and the Malay Peninsular and in the east by Myanmar and Thailand. Its southernmost point is Breueh Island off Banda Aceh, Sumatra.
• The Malacca Strait then connects the Andaman Sea with the South China Sea.