Arctic ice on the verge of another all-time low   This animation is comprised of Envisat ASAR mosaics of the Arctic Ocean and highlights the changes in sea ice between June and mid-August 2008. The dark grey colour represents ice-free areas while blue represents areas covered with sea ice. The Arctic is one of the most inaccessible regions on Earth, so obtaining measurements of sea ice was difficult before the advent of satellites.   Envisat ASAR mosaic from mid-August 2008 showing an almost ice-free Northwest Passage. The direct route through the Northwest Passage is highlighted in the picture by an orange line. The orange dotted line shows the indirect route, called the Amundsen Northwest Passage, which has been passable for almost a month.   The German research vessel Polarstern off the coast of Greenland at the beginning of August 2008 before going on to journey through the Northwest Passage.   ESA’s Envisat ASAR data mosaic showing sea-ice coverage as of mid-August 2008. The red line indicates the all-time minimum Arctic sea-ice coverage in September 2007. The Arctic is one of the most inaccessible regions on Earth, so obtaining measurements of sea ice was difficult before the advent of satellites.   Envisat's ASAR image acquired on 25 August 2008 highlighting the open Parry Channel - part of the direct route through the Northwest Passage. Release date: 3 December 2009