4 . A huge section of the Milne Ice Shelf, located on Ellesmere Island in the northern Canada, collapsed into the Arctic Ocean, according to the Canadian Ice Service. This created an “ice island” which is about 30 square miles in size. As a comparison, Manhattan Island is about 23 square miles.

“Entire cities are that size. These are big pieces of ice,” Luke Copland, a glaciologist at the University of Ottawa who was part of the research team studying the ice shelf, told Reuters. “This was the largest remaining intact (完整的) ice shelf, and it’s collapsed, basically. ”

The Canadian Ice Service said on Twitter that “above-normal air temperatures, offshore winds and open water in front of the ice shelf are all part of the recipe for the ice shelf to break up.” A huge section of the Milne Ice Shelf has collapsed into the Arctic Ocean, producing a 30-square-mile ice island.

The ice shelf has now been reduced in area by about 43%. An ice shelf is a thick slab of ice, attached to a coastline and extending out over the ocean, according to the National Snow and Ice Data Center. “Some shelves have existed for thousands of years,” the center said.

So what’s going on up there? Though the planet is warming worldwide due to climate change, the Arctic has been warming at a rate twice that of the rest of the world. This summer has been particularly warm: Arctic sea ice melted to its lowest July level on record and in June, a town in Siberia soared (急升) to 100.4 degrees Fahrenheit, believed to be a record high for the Arctic.

“When I first visited those ice caps, they seemed like such a permanent fixture of the landscape,” Mark Serreze, director of the NSIDC and geographer at the University of Colorado, Boulder, said in a statement. “To watch them die in less than 40 years just blows me away.”