The Leeuwin Current is an oddity. Flowing south along Australia’s western shore, unlike most currents that flow along the western shores of continents, it flows toward the pole (away from the equator), carrying warm tropical water into what would otherwise be a cold ocean.
Though invisible to the naked eye, the warm current stands out in measurements of the temperature of the ocean’s surface, as shown in the left image acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite on June 6, 2014. Warmer water is orange and pink, while cooler water is purple.
The current hugs the coast, curving south and then east with the coastline. It is the world’s longest coastal current, extending 5,500 kilometers (3,400 miles) from the North West Cape to the west coast of Tasmania—roughly equivalent to the distance between San Francisco and Miami.
The heat the current transfers to southern Australia moderates the climate, making it hospitable to marine species normally found much closer to the equator. Its warmth also encourages rain to form and fall over western Australia, saving it from the extreme dryness found on the southwestern shores of the other southern continents. Without the current, western Australia might resemble South America’s Atacama desert or southern Africa’s Namib desert.
NASA Earth Observatory images by Jesse Allen, using MODIS data provided by NASA’s Ocean Color web. Caption by Holli Riebeek with review from Norman Kuring and Lachlan McKinna. This image is based on SST and chlorophyll originally published on NASA’s Ocean Color Web.
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