The Moderate Resolution Imaging Spectroradiometer (MODIS) is keeping a watchful eye on Iceberg B31, despite the darkness of winter in the Antarctic. The giant iceberg calved from the Pine Island Glacier in November, 2013 and continues to slowly drift into Amundsen Sea, despite being surrounded by a freezing ocean.
This thermal image was captured by Band 31 on the MODIS aboard NASA’s Aqua satellite on June 24, 2014. 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. The darkest colors, deep, dark purple, represents the coldest temperatures 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 light purple to pinkish.
On July 4, the U.S. National Snow and Ice Data Center estimated B31’s location at 72°29’S and 109°32’W, roughly 13 miles away from its location reported on June 6 (72°37’ S and 109°04’ W). The iceberg remains nearly the same size at the day it calved from the glacier.