Icebergs that break off from Antarctica can stay afloat in the Southern Ocean for years. Some become stuck, while other drift in currents that circle the continent. Where those currents are interrupted by South Georgia Island, some bergs make a northern turn.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite captured this true-color image of South Georgia Island and several icebergs on November 27, 2015.

South Georgia Island sits in the Southern Ocean more than 1,000 miles (1,600 km) east-northeast of South American's southern tip. The icebergs appear extremely bright white compared to the dull clouds and slightly off-white snow and ice covering the island.

Two icebergs are especially large and, like the island, are trailed by visible waves - not in the ocean, but in the atmosphere. Just as a ship leaves behind a V-shaped wake in the water, tall obstacles such as mountains - and tall icebergs - can produce a similar wake in low-level clouds.

In both cases the movement is caused by turbulence behind an object. In the case of the ship, the ship is the object that pushes water aside as it moves forward. In the atmosphere, the blowing wind is moving against an immobile object.

When forward air flow is halted, the air is pushed aside to continue to flow around or above the object, creating turbulence. When the turbulent air is pushed upward high enough over an object, it rolls along on the lee side of the object, creating the distinct wave pattern seen here. Credit: Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC Click to enlarge.



Today's Weather Activity

Welcome to JetStream, the National Weather Service Online Weather School. This site is designed to help educators, emergency managers, or anyone interested in learning about weather and weather safety.

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