Phenomena

Following the Flow

Iceberg A-68A (outlines) swerves around South Georgia Island (white) thanks to local ocean currents (arrows).

In early December 2020, the world’s largest iceberg — roughly 135 km long by 44 km wide — was heading straight for South Georgia Island. Luckily for the island, iceberg A-68A was being carried by ocean surface currents that approach the island before turning sharply southward. The enormous iceberg followed, rotating nearly 90 degrees and drifting away on faster currents.

Scientists track these large-scale — 50 to 100 km wide — currents using satellites that measure the ocean height. Currents of this size actually generate a measurable tilt to the ocean surface, which scientists measure and use as input into models that estimate the surface currents’ speed and direction. (Image credit: L. Dauphin and J. Stevens; via NASA Earth Observatory)

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