This animation by NASA Goddard’s Scientific Visualization Studio shows the progression of the Arctic sea ice cover from its wintertime maximum extent, reached on Feb. 25, 2015, to its yearly minimum, reached on Sept. 11, 2015. Since the beginning of the satellite era, the Arctic sea ice cover has now experienced its lowest extent on record this winter and it’s fourth lowest extent this summer.

NASA, in conjunction with the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado at Boulder, recently released an analysis of their satellite data, and declared that the 2015 Arctic sea ice minimum extent is the fourth lowest on record. On Sept. 11, 2015, the ice covered 1.7 million square miles (4.41 million square kilometers), which, to put into perspective, is 699,000 square miles (1.81 million square km) less than the average minimum for all years between 1981 and 2010. In the photo below, you can see that difference between the 1981-2010 average superimposed as a gold line over this years minimum.

Arctic sea ice cover is made of frozen seawater that floats on top of the ocean. It helps regulate the planet’s temperature by reflecting solar energy back to space, and the sea ice cap naturally grows and shrinks with the seasons. Progressive thinning of its extend means more open ocean as the melt eats away at the ice pack.

Due to the effects of climate change, the Arctic sea ice has been in decline since roughly the 1970s, but recent research reveals the thinning is actually accelerating. According to a study published in March in the journal The Cryosphere, September sea ice thinned a whopping 85 percent (from 9.8 feet to 1.4 feet, or 3 to 0.43 m) between 1975 and 2012. We’ve seen the 10 lowest minimum extents in satellite history in the last 11 years.

The record holder for the lease Arctic sea ice hit back in 2012, when the ice covered a mere 1.32 million square miles (3.41 million square km), but even back then scientists understood that the low was driven partially by an August storm. Low sea-ice minimum extent has historically been at least in part exacerbated by meteorological factors, but what is most concerning about this years numbers is that this was not the case this year.

There is an obvious ongoing downward trend in ice coverage. And worse, sea ice is becoming less and less resilient.

“The sea-ice cap, which used to be a solid sheet of ice, now is fragmented into smaller floes that are more exposed to warm ocean waters,” said Walt Meier, a sea ice scientist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “In the past, Arctic sea ice was like a fortress. The ocean could only attack it from the sides. Now, it’s like the invaders have tunneled in from underneath and the ice pack melts from within.”

In June, Arctic ice was melting relatively slowly, but it sped up in July and continued through August. North of Alaska, an actual “hole” opened up in the ice pack covering the Beaufort and Chukchi seas, allowing the ocean to absorb even more heat leading to further melt.

Starting next week, NASA’s Operation IceBridge will be carrying out a series of flights over sea ice in the Arctic to validate satellite readings and provide insight into the impact of the recent melt on land and sea ice. Unfortunately, this continued degradation of the Arctic ice shown no sign of slowing.