Icebergs: the Hidden Face of Ice Giants

Continental glaciers are formed in polar or mountainous regions. Snow accumulates on land in mountain valleys. It is gradually compressed and is eventually transformed into ice to form a very wide glacier.

By the time the glacier reaches the coast, it may range in height from several tens to several hundreds of meters. Here we see the terminus of the Perito Moreno glacier in Patagonia, Argentina, which is 60 meters high.

Being subject to different pressures such as currents, tides, waves, and its own weight, the terminus of the glacier fractures and eventually releases blocks of ice. It is through this phenomenon, known as calving, that icebergs are born.

In some cases, a large drifting iceberg may undergo calving after colliding with a glacier terminus. For example, iceberg B9B collided with the Mertz glacier in the Antarctic in 2010. This image, taken in 2016, shows that it is continuing to fragment.

An iceberg’s journey may end when it runs aground on the ocean floor. Icebergs may occasionally be captured by the polar pack ice, as we see here in the Antarctic. Pack ice is made up of frozen sea water, unlike icebergs, which consist of frozen freshwater.

Throughout the life of an iceberg, its shape is continually being modified by waves and tides. It undergoes numerous transformations and turnarounds. Here we see a wedge iceberg in the southern Drake Passage in the Antarctic Ocean.

Tabular iceberg in the Antarctic. The area of these immense plateaus may be up to several hundred or even several thousand square kilometers. They originate in glaciers travelling down a wide and gently sloping valley.

Arched iceberg (Antarctic).

Dry-dock or eroded iceberg (Antarctic).

Pinnacle iceberg (Antarctic).

Below the water, the continuous pressure of currents striking the iceberg and swirling free may occasionally sculpt small hollows – or dimples – on its surface.

Icebergs provide a safe haven for certain species, such as the Adélie penguins seen here in the Antarctic, since they carry large amounts of nutrients, particularly iron and algae.

Some surprising discoveries can be made, such as this sea worm. Some of these annelid worms measure tens of centimeters in length.

If you want to know how old an iceberg is, remember that the bluer it is, the older it is. The ice contained in a young iceberg is white because it is well aerated (it contains large numbers of air bubbles). However, over time, the ice gradually becomes denser, and the compressed air bubbles give it a blueish tint.