What Is the Gulf Stream? (2/3)

A meandering mass of warm water, moving 300 times stronger than the flow of all the rivers emptying into the Atlantic Ocean---a mysterious force more powerful than a million nuclear plants---just what is this, and why is it so important?

Temperature readings

In April 1775, Franklin again sailed across the Atlantic. Along the way, he decided to do some scientific research. On April 29, in the company of two of his grandchildren, he carefully lowered a thermometer into the ocean at 8 a.m. He noted an 11-degree jump in water temperatures, from 60 degrees 14 hours earlier to 71 degrees. He knew he was in the Gulf Stream. Franklin took his measurements four to six times a day, until May 2. He would take similar readings every time he crossed the big current.

Princely efforts

The Guff Stream’s true identity would be slow to unfold; key insights came through a series of impressive efforts in the 20th century.

The returns were startling. The trails of the bottles revealed that the Gulf Stream was part of a wild system of spinning [-----1-----].

Father of modern oceanography

In 1948, the brilliant Henry Stommel explained that, despite its name, the Gulf Steam is not exactly [-----2-----]. It is the western flank of an enormous circle of water, or [-----3-----], in the Atlantic. The center of the gyre, however, is well west of the center of the ocean.

Stommel explained why western side of an ocean [-----4-----] is different from the eastern side. The planet’s spin creates forces that drive currents toward the west. The Gulf Stream is forced through a narrow [-----5-----] between the gyre’s center and the continent, so it flows rapidly. The water to the east of the center, with more room to spread out, leisurely drifts to the south.