Iceberg B31, the large iceberg which broke free of the Pine Island Glacier in November, 2013 continues to drift away from Pine Island Bay, despite the late fall freeze-up of sea ice in Antarctica. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured a thermal image of the iceberg sitting in the Amundsen Sea on June 3, 2014.
The iceberg is visible as a purple tinted, roughly rectangular object near the center of the image. This image was acquired from Band 31 on the MODIS instrument. Band 31 is an emissive band, which means it measures energy emitted from the Earth’s surface, rather than reflected light. Temperature affects the amount of energy emitted from the Earth or ice, so Band 31 can detect differences in surface temperature. This is especially useful in the winter months in Antarctica, when light dims and the bands measuring light reflectance have difficulty capturing true-color images. This thermal image successfully shows the iceberg and separates it from liquid water, sea ice, other icebergs, land ice and clouds.
In this image, the darkest colors, beginning with deep, dark purple, are coldest while warmer temperatures are increasingly light. Freshwater ice, such as Iceberg B31, other icebergs and land ice appear bright purple. Thin sea ice that has just started to form is colder and appears darker purple. Clouds are lighter purple to pinkish.
On June 6, the U.S. National Snow and Ice Data Center estimated B31’s location at 72°37’S and 109°04’W, only 35.4 mi () away from its location reported on May 2 (72°30’ S and 107°22’ W). The iceberg remains nearly the same size at the day it calved from the glacier.