Calving glacier

At first, you might hear a sharp crack or a rumble, and then, if you’re lucky, you’ll get to witness a tidewater glacier calving into the sea.  Photographer: Ray Boren

 Antarctic peninsula

In this instance, a glacier along Gerlache Strait of the Antarctic Peninsula made just such a report as a ship passed by. Huge chunks of ice fell from the glacier’s terminus (also called “toe” or “snout”). This was just the first part of the show. Shortly afterwards, an even larger area calved – click here to see an animation. During this encore, yet more of the glacier dropped into the icy rubble along its snout. The resulting segments were “growlers,” relatively small pieces of ice less than 3.3 ft (1 m) high and less than 16 ft long (5 m). When bigger sections of a tidewater glacier calve, very large icebergs may be created often over 245 ft (75 m) high and over 660 ft (200 m) long.

The Antarctic Peninsula has warmed about 1.2 degrees F (17 degrees C) since the 1950s. This warming is likely contributing to an increase in calving events. According to the British Antarctic Survey, using aerial photographs and satellite imagery, 87 percent of the peninsula’s glaciers have both dwindled in size and retreated poleward during the past seven decades. Photo taken On January 14, 2011, during the middle of the brief Antarctic summer season.  Photographer: Ray Boren