Floating art iceberg on the waterfront in Oslofjord, Oslo, Scandinavia, Europe

Kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

Kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

National Geographic photographer Joel Sartore and his wife Kathy kayaking with a leopard seal near Danco Island, Antarctica

Natural history staff from the Lindblad Expedition ship National Geographic Endeavour doing various things in and around the Antarctic Peninsula

Aerial view, atolls on Baldeneysee lake, art event for the RUHR.2010, islands in the Baldeneysee lake, Schachtzeichen RUHR.2010 art installation, Essen, Ruhrgebiet region, North Rhine-Westphalia, Germany, Europe

An iceberg with a deep crevasse or fissure, and the contours of melting ice, in Antarctica, Antarctica

Gentoo penguin on an iceberg, Antarctica, Antarctica

Icebergs and ice formations in the Antarctic. A large fissure or hole in the centre of a block of ice, with smooth sides, Antarctica

A shard of aufeis reaches toward the arctic sky, Arctic National Wildlife Refuge, Brooks Range, Alaska, USA

Gentoo penguins, Antarctica

A waterfall is created by a melting iceberg, Svalbard, Norway, Svalbard, Norway

Icicles hanging from an iceberg, Antarctica