“It’s just the tip of the iceberg.” That’s what we say when there’s more to something—plenty more—than meets the eye.

Tabular icebergs like this one in the background typically have a length-to-height ratio of more than 5:1.

A melting iceberg in Scoresby Sund, Greenland.

Scientists studying this iceberg in Antarctica’s Weddell Sea found it supported a mini ecosystem extending about 2 and 1/4 miles (~3.7 km) around it.

Non-tabular icebergs come in many shapes, like this Pinnacle iceberg in Antarctica.

In fact, the phrase is scientifically accurate. An iceberg is a piece of freshwater ice that has broken off, or “calved,” from a glacier or ice shelf. Since the density of ice is just 90% that of seawater, only about a tenth of the total volume of an iceberg is above water. In short, what you see of an iceberg is generally only about a tenth of what’s there.

Icebergs range in size from as small as several feet across—also called “growlers” or “bergy bits”—to many miles across. The largest iceberg ever recorded broke off from the Ross Ice Shelf in Antarctica in 2000. At 183 miles (295 km) long and 23 miles (37 km) wide, it weighed roughly 3 billion tons.

Once at sea, icebergs are carried by winds and currents as they slowly melt. Melting icebergs make a fizzing sound as air trapped inside the ice is released, air that was originally compressed—along with mounting piles of snow—to form glacial ice.

As an iceberg melts, minerals from land trapped in the ice are also released, causing a small ecosystem to flourish in the iceberg’s vicinity. Fed by nutrients such as iron, communities of phytoplankton bloom. In turn, krill, fish, and seabirds arrive to feed on and around the iceberg.

This life-giving aspect of icebergs is eclipsed by their more deadly aspect; that is, their danger to maritime travel. After the deadly sinking of the Titanic in 1912, an organization called the International Ice Patrol was formed to monitor iceberg dangers near shipping lanes and major ports.

Will global warming put the International Ice Patrol out of business? Hardly. Calving of icebergs is actually increasing worldwide as warming temperatures cause ice shelves in the Arctic and Antarctic to break up and float away.

Kulusuk, Greenland.

Home to 57,000 people and 29,000 sled dogs, Greenland is the world’s largest island—a mountainous country the size of the American West situated between the Atlantic and Arctic oceans. Deceptively named, Greenland is largely covered by ice; humans and wildlife alike cling mainly to the ice-free shorelines of the sea and fjords.

Separated from North America by just 16 miles (26 kilometers) of water, Greenland first attracted human settlers from the Arctic roughly 4,500 years ago.

A traditional Inuit kayak frame at Ilulissat, Diskobay, West Greenland.

Waves of settlers from Norway and Denmark followed, though many perished in Greenland’s less-than-hospitable climes.

Today, Greenland is a self-governing province of Denmark, but the residents are still mostly (88 percent) Inuit. Danish and Greenlandic Inuit are the national languages, and most residents speak both. Inuit is the source of familiar borrowed words such as kayak and igloo.

No trees grow in Greenland, only short tundra plants that provide food for lemmings, Arctic Hare, caribou, and musk oxen. The rest of Greenland’s wildlife is carnivorous, including the gray wolf, Arctic Fox, short-tailed weasel, and polar bear.

A massive slab of ice—the Greenland Ice Sheet—covers over 80 percent of Greenland. Up to 2 miles (3 kilometers) thick, the ice sheet is heavy enough to have caused the underlying land to sag into a basin more than 1,000 feet (300 meters) below sea level.

The Greenland Ice Sheet from above.

The Greenland Ice Sheet is of enormous interest to climatologists. Ice cores drilled a little more than a mile (2 kilometers) down into the ice provide climate data stretching back more than 100,000 years into the past. But current research is equally concerned with the future of the Greenland Ice Sheet. Melting of the ice sheet has accelerated in recent years—the result of a global warming trend that has affected the Arctic especially—and researchers are scrambling to collect climate data that will help predict future melting. The fate of the Greenland’s ice sheet is no small matter: It holds 10 percent of the earth’s fresh water and, if melted completely, would raise the global sea level by 23 feet (7 meters).