An iceberg that is more than four times the size of Manhattan has broken free from Antarctica, the second massive piece of ice that has separated from the continent this year.

The new iceberg is not as large as the first one, but it is still a troubling sign for the future of our planet.

Massive Iceberg Breaks Free From Pine Island Glacier

Satellite images from Sept. 23 revealed a 100-square-mile iceberg breaking off from the Pine Island Glacier of Antarctica. The glacier is the fastest melting one in the continent and is responsible for 25 percent of the ice loss in Antarctica, equivalent to about 45 billion tons of ice annually.

The new iceberg, which is more than four times the size of Manhattan and first spotted in February this year, appears unstable, with smaller icebergs breaking off from it as it drifts out to sea.

The Pine Island Glacier, however, is drawing attention not just due the massive iceberg, but also because it is melting in a unique manner. While other parts of Antarctica are seeing breaks at the sides, the cracks of the Pine Island Glacier are found in the center and appear to be forming underneath the ice.

According to scientists, the unusual behavior may be due to ocean water that are warmer in temperature, which could also be the cause on why rifts are forming more often. If this continues, scientists believe that one possible result will be raised sea levels, with the entire main trunk of the Pine Island Glacier possibly breaking off in around 100 years.

Second Massive Iceberg Breaking Off From Antarctica

The Manhattan-sized iceberg is the second massive piece of ice that has broken free from Antarctica this year, following the Delaware-sized iceberg that was first spotted in January. The trillion-ton iceberg, which made up around 12 percent of the Larsen C ice shelf of Antarctica, finally broke off in July.

The first iceberg is many times bigger at about 2,300 square miles, making it one of the 10 largest icebergs ever recorded.

Scientists are divided over the reason why such a massive volume of ice broke free from Larsen C. There have been concerns that the incident was caused by rapid global warming, but scientists believe that it is too early and also too convenient to simply blame the Larsen C ice shelf break on climate change.

Calving is a natural process for iceberg, and researchers even said that melting icebergs can actually help slow down the negative effects of global warming, as it causes improved water nutrients that leads to plankton blooms.