Charting ocean currents
Mariners have studied ocean currents to find the best routes since ancient times. Benjamin Franklin was the first to chart the Gulf Stream in 1777, by measuring sea temperatures. He recommended following this warmer current to reduce trip times between New York and London.
First chart of the Gulf Stream in 1777. Credits: NOAA
In 1849, Matthew Maury published the first global charts of winds and currents compiled from data collected by ships. Exploration of the oceans for purely scientific purposes really began in 1872, when the first Challenger expedition surveyed the oceans for 42 months, gathering data from the surface to the sea floor.
From the 1970s, space technologies revolutionized the way scientists study the planet. The technique of satellite altimetry was first presented at a symposium in Athens in 1965 and subsequently used on the U.S. satellites GEOS 3 (1975), SEASAT (1978) and GEOSAT (1985). The first large-scale altimetry mission was the French-U.S. satellite TOPEX/POSEIDON (1992), followed by JASON-1 (2001) and ENVISAT (2002).
Altimetry missions. Credits: AVISO
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These missions have taken ocean science to new heights. Now, scientists can study the planet from a global perspective in which Earth is a unique system of elements—land masses, oceans, atmosphere and biosphere—that are constantly interacting. With satellites, they also have the capability to monitor natural phenomena in real time through repeat observations of the same point at regular intervals of only a few days. |
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