The Peaceful Pacific Ocean

The posting below this one is titled "The Atlas Barrier". It is about a phenomenon that I noticed concerning the formation of barrier islands on the coasts of the U.S. and lands around the Caribbean Sea. These barrier islands are formed by hurricanes over time.

The thing that puzzled me was why the U.S. states of North Carolina and Florida are known for their barrier islands while the two states with a coastline between these two, South Carolina and Georgia, have far less barrier island along their coasts.

The answer lay across the ocean in north Africa. Hurricanes depend on the dust that is swept out over the ocean by the east wind across the Sahara desert. This dust in the air provides condensation nuclei for a vast amount of the water that evaporates from the warm ocean to condense upon, thus building the foundation of a hurricane.

I pointed out that the circular motion of a hurricane counteracts the earth's gravity so that they rotate eastward with the earth less than the sorrounding air without this circular momentum. The result is that hurricanes seem to be moving westward because it is actually the earth which is rotating eastward into them. Hurricanes also tend to be pulled away from the equator because the earth has more spin away from the equator and this pulls the hurricane along.

The reason for the gap in barrier islands along the coasts of South Carolina and Georgia, in comparison with North Carolina to the north and Florida to the south, is that the Atlas Mountains in Morocco block the east wind and thus the dust that would be otherwise carried out over the Atlantic Ocean. The dust that gets out immediately south of these mountains form hurricanes that go to Florida and southward and the same for the dust to the north to North Carolina.

I would like to expand on this concept to explain something else about global geography that I have not seen pointed out anywhere. Consider the Pacific Ocean, it is the world's largest ocean by far and could cover all of the land on earth with plenty of room to spare. It also gets much deeper than the other oceans, the Marianas Trench drops down about 11 kilometers.

Yet, the very term "pacific" means peaceful. It originates with the same root word as "pacify" or "pacifist". The Pacific Ocean is not completely peaceful, as far as weather goes, but it generally lacks the hurricanes of the Atlantic Ocean and the Monsoons of the Indian Ocean.

Now, keeping the Atlas Barrier scenario in mind, I would like to speculate that the reason that this vast ocean is so peaceful compared with the others is that is is virtually sorrounded by mountains. If you look at a map showing the Pacific Ocean in a world atlas or on http://www.maps.google.com/ it is easy to see that virtually wherever this ocean meets land, there are mountains. These mountain ranges around the perimeter of the ocean block most dust that would be carried out over the ocean and would serve as condensation nuclei for storm clouds in the same way as does the Atlas Mountains.

The Pacific Ocean is situated on a large tectonic plate all it's own and the mountain ranges that virtually sorround it were formed by tectonic collision or volcanism. It is truly a paradox that the so-called "Ring of Fire" around the Pacific, referring to volcanoes and the mountains thus formed, actually make the ocean more peaceful in terms of weather compared with the other oceans so that it is given a name meaning "peace".

There is little dust from land over the wide expanse of water and so storm clouds do not form as easily. The other two major oceans have no such shielding. There is a fourth ocean, the Arctic Ocean but it is virtually covered by ice.

There is one major exception to this, that of Australia. This is a largely dry continent that does contribute dust to the air. Australia is south of the equator and circular storms are guided by the earth's rotation but it affects weather in the northern hemisphere because winds from equatorial hadley cells pull Australian dust north of the equator.

The result is the typhoons of southeast Asia, particularly the South China Sea and the legendary Monsoons of India and Bangladesh. Both head west due to the eastward rotation of the earth and are also pulled northward by it's spin.

A hadley cell is the meteorological process where hot air rises from around the equator across the world, this creates a low pressure area that draws in air from the south and north and the air which originally rose from around the equator descends to take it's place. Thus a vertical circuit of air is formed. The hadley cells at the equator operate in this way between about 30 degrees latitude to the north and south.

A ferrell cell is the opposite of a hadley cell, where some of the descending air moves further north or south. These cells skew the prevailing winds, easterlies around the equator, westerlies further north and south, and easterlies again around the poles, to make up the earth's general patterns of wind.

We can presume that if Australia was wet and green, and so did not contribute much dust, that there would not be Monsoons or typhoons in Asia. The obvious reason that there are not hurricanes in South America like there are in North America and the Gulf of Mexico is that central Africa is green and does not give off enough dust. Southern Africa is drier but it is too far from the equator and the water offshore too cold to form hurricanes.

This concept also operates in reverse. It seems to me that the reason Australia is relatively dry is that the easterlies which might bring rain are largely blocked by the Great Dividing Range along the east coast of Australia.

Prevailing wind direction can make all the difference in the climate of an region. Have you ever wondered why the Mediterranean area is relatively dry? Spain and Portugal are just as close to water as are Britain and Ireland. But you can see in the satellite imagery that rural areas in Britain or Ireland have that lush green color (colour) while Spain and Portugal are obviously much drier. It is because the prevailing west wind in northern Europe brings water that has evaporated from the Atlantic Ocean, while the east wind of the Mediterranean brings dry air that has passed over mostly land.

The intense storms produced by abundant dust leave drought to the west of where they dump most of their water. The thought came to me that if not for the Monsoons that drench south Asia, the water would be carried as far west as the Arabian Peninsula. This area is, of course, one of the driest on earth but the reason it does not seem to be a major source of storm dust is that it is blocked from getting to the Mediterranean area by highland and mountains around the western part of Saudi Arabia.

This explanation of the peacefulness of the Pacific Ocean is unrelated to my posting on this blog, "The Wave Pressure Hypothesis" about why the ocean has such favorable (favourable) surfing waves.