A Fracturing Iceberg in the Polar Night 

When a massive iceberg first broke away from Antarctica’s Larsen C ice shelf sometime between July 10-12, 2017, scientists knew it would eventually start breaking apart. That’s the normal life cycle of a drifting iceberg, which is at the mercy of the ocean’s battering currents, tides, and winds. Already those forces have turned A-68 into two named bergs, A-68A and A-68B, as well as a handful of pieces too small to be named by the U.S. National Ice Center. 

The fractured berg and shelf are visible in these images, acquired on July 21, 2017, by the Thermal Infrared Sensor (TIRS) on the Landsat 8 satellite. The false-color view shows the relative warmth or coolness across the region. White indicates where the ice or water surface is warmest, most notably in the widening strip of mélange between the main iceberg and the remaining ice shelf. Dark grays and blacks are the coldest areas of ice. 

So far, the calving and fracturing has taken place under the dark cover of polar night during Antarctica’s austral winter. That makes thermal imagery from satellites a critical tool for “seeing” the action. Adrian Luckman of the UK-based Project MIDAS first saw the berg break away in thermal data from the Moderate Resolution Imaging Spectroradiometer (MODIS), before Sentinel radar data became available later on July 12. 

Scientists will have to wait until August—the end of polar night in Antarctica—to get their first natural-color images since the long-growing Larsen C rift became a complete break. 



Credits: NASA Goddard/UMBC JCET, Christopher A. Shuman 

For more information, visit: 
earthobservatory.nasa.gov/IOTD/view.php?id=90627 
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