Monsoons and Wind and Ocean Currents – Part IV

Continuing with a reader’s submission about our being wrong regarding the winds and currents in the Indian Ocean and not being able to sail from Arabia to Indonesia, specifically the Malay Peninsula, in 600 B.C. Having shown some of the errors in the article submitted in the previous post, we return to the main point of showing Lehi’s course forced by these monsoon winds.

Air over land heats and rises drawing moist air in from tropical oceans creating the monsoons, which is a seasonal shift in the prevailing wind direction

    First of all, a monsoon is a large-scale sea breeze, that is a cool breeze blowing from the sea toward the land and is a seasonal shift in the prevailing kind direction, that usually brings with it a different kind of weather. In Physical Geography, a wind blowing from the sea to the land, especially during the day when the land surface is warmer. It is a thermally produced wind blowing from a cool ocean surface onto adjoining warm land, which is caused by a convection current during the day.
    In the area of the India-Indian Ocean monsoons, that breeze can escalate into not only very strong winds, but quite destructive weather fronts over the land mass of India, and adjoining regions. During the northeast (wind out of the northeast) monsoon, a persistent and large high pressure zone over Asia drives cool, dry air southward toward the tropics. This provides the monsoon region with its dry season. Then, during the southwest (wind out of the southwest) the summer monsoon arrives with persistent southerly wind flow driven by a warm air mass with low pressure at the surface that forms over southern Asia as it is warmed by the sun. Air from the relatively higher pressure air mass over the Indian and tropical western Pacific Ocean flows northward toward the low pressure over land, bring with it torrential rains. A late arrival of the monsoon can be bad for agriculture, as the monsoon rains are necessary for summer crops
    When the air mass over land heats up it rises drawing in the cooler air overlying the sea, creating a breeze, which occurs when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These Southwest monsoon winds are called 'Nairutya Maarut' in India, which is the reversal of winds that start taking place over the India sub-continent during the summer season, when cold and dry continental northeasterly winds are replaced by warm and moist southwesterly winds (Forecast Update for Monsoon 2015 in India,” Skymet Weather Services, India). These are extremely wet or dry events within the monsoon period (Stephanie Paige Ogburn, “Indian Monsoons Are Becoming More Extreme,” Scientific American, 2014), that based on a new study, have increased since 1980 (Quirin Schiermeier, “Extreme Monsoons on the Rise in India,” Nature International Journal, 30 November 2006).

The India Monsoon Current refers to the seasonally varying ocean current regime found in the tropical regions of the northern Indian Ocean. During winter, the flow of the upper ocean is directed westward from the Bay of Bengal near the Indonesian Archipelago to the Arabian Sea, which by the way precludes any sailing vessel “driven by the wind” from moving toward Indonesia from Arabia.

During the summer, the direction reverses, with eastward flow extending from Somalia into the Bay of Bengal—not into Indonesia. The seasonally reversing open ocean currents that pass south of India are referred to as the Winter Monsoon Current and the Summer Monsoon Current, or the Northeast Monsoon Current and the Southwest Monsoon Current.
    With this in mind, it is important to know that in the northern hemisphere (that includes the northern half of Sumatra, all of the Malay Peninsula, all of the South China Sea, the Sunda Shelf, Strait of Malacca, all of India, Bay of Bengal and Sri Lanka, all of Arabian Peninsula, and all of Somalia) tropical regions of the Atlantic and Pacific oceans, surface winds blow predominantly from the northeast year round, with westward-flowing ocean currents underneath.

Everything north of the Equator is in the Northern Hemisphere and the winds and currents are predominantly from the northeast year round, with westward-flowing ocean currents underneath

    Once we understand all of this, then it makes sense to recognize that sailing from Arabia to the east will not reach Indonesia and the Pacific Ocean, which half that distance would lie south of the Equator, but end up in the Bay of Bengal, not the Malay Peninsula.

Top: Uninformed historians and scholars would have Lehi sailing as shown by the red arrow against the predominant winds and currents out of the northeast; Bottom: In reality, any ship “driven forth before the wind” would be turned by those predominant northeast winds and currents to sail toward the south, where they would pick up the eastward curving South Indian Ocean Gyre

    Now, when Lehi left the area of Khor Rori along the Salalah Plain, his ship would have been blown southwest along the winds coming off the mainland as has been shown. The Winter Monsoon Current extends from the Bay of Bengal, around India and Sri Lanka, and across the Arabian Sea at a latitude of approximately 8 degrees North.
    Currents flow to the southwest along the coast of Somalia to the equator (Stefan Hastenrath and Lawrence Greischar, 1991: “The Monsoonal Current Regimes of the Tropical Indian Ocean: Observed Surface Flow Fields and Their Geostrophic and Wind-Driven Components,” Journal of Geophysical Research, Vol. 96, No. C7, 1991, pp12,619–12,633;).

 Lehi’s Course, began under the Monsoon Winds coming off the coast and blowing him southwest, then picked up the South Equatorial Counter Current below the Equator (the Indian Ocean Gyre) that turned him southeast, and then into the Southern Ocean east bound current south of Australia and New Zealand and across toward South America

    Although Mariners have been aware of the existence of the Monsoon current for nearly a thousand years, a detailed understanding did not emerge until after the International Indian Ocean Expedition of the 1960s (D. Shankar, P. N. Vinayachandran and A. S. Unnikrishnan, “The monsoon current in the north Indian Ocean,” Progress In Oceanography, Volume 52, Issue 1, 2002, pp63–120). The World Ocean Circulation Experiment of the mid 1990s permitted detailed measurement of these currents through an extensive field campaign (Friedrich A. Schott and Julian P. McCreary, Jr., "The monsoon circulation of the Indian Ocean," Progress In Oceanography, Volume 51, Issue 1, 2001, pp1–123).
    The point is, and we cannot overemphasize this enough, the movement of ocean currents and the monsoon winds do not blow from the west into Indonesia, but into the Bay of Bengal when the southwest winds are blowing. In trying to move into Indonesia, a vessel “sailing forth before the wind” as did Nephi’s ship, would not have been able to withstand the Pacific Ocean currents blowing across Indonesia and into the Indian Ocean, through the Indonesian through flow (ocean currents coming off the Pacific and through Indonesia and into the Indian Ocean), which would have caused a headwind for any such vessel trying to move past India and Beyond the Bay of Bengal toward Indonesia. Today, that is not a problem with diesel engines and modern sailing techniques and ships designed to sail in that manner, with very experienced crews able to maneuver such vessels extremely well. Lehi’s crew simply would not have been able to do that even if they had a ship that could manage it, which Nephi tells us they did not.