Researcher Tiina Jaaskelainen takes a picture of an iceberg floating in Baffin Bay in the Canadian Arctic Archipelago while aboard the Finnish icebreaker MSV Nordica, Tuesday, July 25, 2017. Experts can tell from the shape of an iceberg how much of it is likely to be hidden under the waterline. Small icebergs the size of a person are called growlers. Medium bergs can be as big as a large ferry, while a very large berg is the size of several skyscrapers. AP/David Goldman

The suns sets against an iceberg floating in the Nuup Kangerlua Fjord near Nuuk in southwestern Greenland, Tuesday, Aug. 1, 2017. Greenland's glaciers have been melting and retreating at an accelerated pace in recent years due to warmer temperatures. If all of that ice melts, sea levels will rise by several meters, though there will be regional differences. AP/David Goldman

The sun sets through a hole melted in an iceberg floating in the Nuup Kangerlua Fjord near Nuuk in southwestern Greenland, Tuesday, Aug. 1, 2017. Icebergs aren't sea ice, despite being best known for floating about the ocean. They are actually chunks of glaciers that have broken off at the water's edge. AP/David Goldman

An iceberg floats past Bylot Island in the Canadian Arctic Archipelago, Monday, July 24, 2017. Icebergs aren't sea ice, despite being best known for floating about the ocean. They are actually chunks of glaciers that have broken off at the water's edge. Since glaciers are made from freshwater and compacted over dozens if not hundreds of years, icebergs are naturally among the hardest types of ice a ship might encounter. AP/David Goldman

The suns sets as an iceberg floats in the Nuup Kangerlua Fjord near Nuuk in southwestern Greenland, Tuesday, Aug. 1, 2017. Greenland's glaciers have been melting and retreating at an accelerated pace in recent years due to warmer temperatures. If all of that ice melts, sea levels will rise by several meters, though there will be regional differences. AP/David Goldman

An iceberg floats past the Finnish icebreaker MSV Nordica as it sails the Davis Strait toward Greenland, Thursday, July 27, 2017. Since glaciers are made from freshwater and compacted over dozens if not hundreds of years, icebergs are naturally among the hardest types of ice a ship might encounter. AP/David Goldman