While not understood until
recent years, there has always been a zonal (east to west) “throughflow” in the
Indonesian Seas from the Pacific to the Indian Ocean. This system of surface
currents flowing from the Pacific through the Indonesian seas is the only flow
between ocean basins at low latitudes and, consequently, plays an important
role in the meridional (north to south) transport of heat in the climate
system, all the more so since this transport originates from the warm-pool of
the Pacific and enters into the colder waters of the South Equatorial Current of
the Indian Ocean.
This flow of water is
governed by strong pressure gradient from the Pacific to the Indian Ocean, and
blows continually from the east to the west, through all of Indonesia. Measurements
of the volume transport of this throughflow has proven to be difficult due to
the extremely complex coastline and topography of the Indonesian Seas, as well
as the highly variable nature of currents in the throughflow region. The
maximum net, relative transport through Indonesia is 12 Sverdrup (Sv = 106
m3.s-1). The winds driving this throughflow are strong, whirling, and
treacherous.
Any wind-driven vessel
trying to sail through Indonesia is faced with opposing winds against them all
the way and whirling rip-currents, eddies, and swift currents, especially in
channels of the Malacca, Sonda and Lombok Straits—the only three entrances from
the Indian Ocean through Indonesia—which provide the greatest danger.
Local wind patterns,
however, can greatly modify these general wind patterns, especially in the
islands of central Maluku--Seram, Ambon, and Buru. This oscillating seasonal
pattern of wind and rain is related to Indonesia's geographical location as an
archipelago between two large continents. This is partly the reason why early
sea traders in the area had to have oars for throughflow navigation.
Prevailing wind patterns
interact with local topographic conditions to produce significant variations in
rainfall throughout the archipelago. In general, western and northern parts of
Indonesia experience the most precipitation, since the north- and
westward-moving monsoon clouds are heavy with moisture by the time they reach
these more distant regions. Western Sumatra, Java, Bali, the interiors of
Kalimantan, Sulawesi, and Irian Jaya are the most predictably damp regions of
Indonesia, with rainfall measuring more than 2,000 millimeters per year. The
city of Bogor, near Jakarta, lays claim to having the world's highest number of
rainstorms per year--322. To complicate the situation, some of the islands of
the southern Malukus experience highly unpredictable rainfall patterns,
depending on local wind currents.
Thus it would be extremely
difficult, if not impossible, for a deep ocean sailing vessel “driven forth
before the wind” to move from the Indian Ocean through Indonesia and out into
the Pacific since it would be sailing against the winds all the way. In
addition, there would be opposing currents and swift eddies all moving in treacherously swirling
directions.
(See the next post, “Driven Forth Before the Wind – The Prevailing Westerlies,” to see how the Lehi Colony actually reached the Western Hemisphere by being driven forth before the wind in their sailing ship)
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