An invisible river in the sea
In the 1760s, Benjamin Franklin, then Deputy Postmaster General for the American colonies, noticed a strange inefficiency in the mail. Ships carrying mail from England to America took several weeks longer than merchant ships sailing east. He consulted his cousin Timothy Folger, a Nantucket whaling captain, who was familiar with a powerful current that whalers knew to avoid. This "Gulph Stream," as Franklin would name it, was an immense river of warm water flowing from the Florida coast, up past Newfoundland, and across the Atlantic. The British mail packet captains were unwittingly fighting this current on their westward journeys.
Working with Folger's firsthand knowledge and data from other ship captains, Franklin produced the first chart of the Gulf Stream around 1769-1770. It was a piece of physical oceanography based on simple tools: ship logs and thermometers. Franklin hypothesized, and later confirmed on his own transatlantic voyages in 1775 and 1776, that the Gulf Stream's water was significantly warmer than the surrounding ocean, providing a way for sailors to detect its presence. During the American Revolutionary War, Franklin, then serving as a diplomat in France, had the chart printed in Paris and distributed to French naval captains to aid the American cause. Brest, as France's primary Atlantic naval port, was central to this maritime effort.
Brest's legacy of ocean science
Brest's role in maritime exploration and science predates Franklin's era. The city is the historic site of the French Navy's hydrographic and oceanographic office. Known today as Shom (Service hydrographique et océanographique de la Marine), this organization is one of the oldest of its kind in the world. Its origins trace back to the Dépôt des cartes et plans de la Marine, created on November 19, 1720. For over three centuries, this institution has been responsible for producing the nautical charts and marine data for safe navigation, a mission that follows from the practical science of Franklin's map. Shom's work involves detailed descriptions of the marine physical environment, including seabed depths, currents, water temperatures, and salinity.
Today, Brest remains a global center for ocean science. It hosts the main campus of Ifremer (French Research Institute for Exploitation of the Sea), established in 1984 through a merger of two earlier institutions. Ifremer operates a significant portion of the French oceanographic fleet, including submersibles like the Nautile, and conducts research on everything from deep-sea ecosystems and fishery resources to marine pollution and climate change. The concentration of institutions like Shom and Ifremer in Brest creates one of the highest densities of oceanographers and marine technologists in the world.