Pacific by Simon Winchester

Author:Simon Winchester
Language: eng
Format: epub
Publisher: HarperCollins Publishers
Published: 2015-09-22T04:00:00+00:00

The Pacific Ocean is broiled by the sun, whatever the season. Given the tilt of the planet, the 23.5 degrees offset from vertical of the axis around which the world spins, the ocean’s northern parts are broiled in the northern summer, and the southern parts in the southern summer. The immense region of sea that lies between the Tropics of Cancer and Capricorn are being broiled all the time.

The heat, the thermal energy, that blasts endlessly down on the planet is dealt with differently depending on whether it strikes solid or liquid below. When intense sunshine radiates down onto the solid earth, the rocks become very hot very quickly—but then, because of the immutable physics of solids, they release this heat equally fast, return it to the atmosphere, and retain little. To a wanderer in the desert, a rock at nighttime can be blessedly cool.

It is different when the same intense heat is radiated down onto the ocean. Initially the water warms slowly, but then, and crucially, it retains the heat it has absorbed for some long while. Because it is a liquid, mobile entity, it then shifts this captured heat about, three-dimensionally. Under the influence of its currents and its surface winds, it drives the captured thermal energy either laterally, from east to west, or from north to south. Or else, by way of a pattern known as thermohaline circulation, it shifts the heat deep downward into its depths. Since the Pacific is by far the deepest ocean as well as the broadest and longest, the amount of heat it can incorporate within is almost beyond imagination.

Heat, in immeasurable quantities, is stored in the world’s oceans generally. The Pacific, which occupies one-third of the planet’s entire surface area, is responsible, then, for storing a very great deal of it. Much of this stored heat then warms the atmosphere. It does so most especially where the sea is subject to the most intense solar heating, along that wide band of ocean between the tropics and along the equator, a band that shifts to the north and the south as the seasons change.

Within this well-defined area, the intense heat causes the seawater to evaporate and the warm air above it to rise—so gigantic banks of cloud form and billow skyward. As they do so, they lower the air pressure in the void they leave behind them. Cooler and heavier air then pours into the low-pressure zone, from the north and the south. Thanks to the west-to-east spinning of the earth, this air tracks in a more or less westerly direction as it cascades inward: the air from the north heading toward the southwest, the air from the south tracking to the northwest. Since it is the custom to name winds for the direction from which they are coming (whereas currents, confusingly, are named according to where they are traveling to), these inrushings of cool air become the famous trade winds: the northeast trades in the Northern Hemisphere, the southeast trades below the equator.

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