Without ocean currents, life on Earth would be radically different than it has been for the past billions of years. With much attention these days focused on the issue of global climate change, it is appropriate that we contemplate the role of the oceans in establishing climate, as that role is dominant. Over 70 percent of the Earth’s surface is covered by water, and most of that, needless to say, involves the major oceans and seas. The currents that guide those oceans, in particular, have a great deal of influence on the planet’s climate.
Appreciation of the role of ocean currents in establishing climate is a relatively recent development. It was only in the 19th Century that the connection between ocean currents and climate began to be made, and it wasn’t until the middle of the 20th Century that the full extent of that relationship was completely understood. Previously, it was believed that the earth’s atmosphere was primarily responsible for climate; now it is understood that ocean currents are the more important fact, although the relationship of the Earth’s atmosphere to the ocean currents and, consequently, to the Earth’s climate is clearly part of the larger equation. For example, whether the winds affected ocean currents or the other way around was only recently determined, with the prevalent role of the currents being the answer. It turned out that chemical and salinity levels in the oceans played a larger role than scientists had earlier anticipated.
Part of the reason for the very late appreciation for the significance of ocean currents was the simple lack of adequate technological means to study the oceans’ depths in detail, and the lack of resources and interest. As oceanographers and meteorologists developed the ability to dig deeper into the ocean floors and analyze the sediments brought to the surface, however, a greater understanding of the oceans’ role in establishing climate was the result. Additionally, by monitoring ocean temperature levels at various depths, starting, of course, at the surface, it was possible to extrapolate on the interaction between ocean, Sun, and climate. As the extent of the Sun’s warmth affected surface temperatures of the oceans became increasingly understood, greater knowledge of the role of various ocean depths began to be better understood, all of which affects climate.
In short, absent ocean currents, the Earth would be vastly different. Ice regions, for example, the poles, arid regions, and so on, would all be different than they currently are, and the status of the Earth’s climate would essentially be unknowable.