During the age of industrial whaling, humans killed more than 1.5 million great whales in the Southern Ocean — half of the global population. Even 40 years after the end of whaling, the effects of this slaughter continue to shape the productivity of the region, with cascading effects that devastate these ecosystems — and the global ocean and climate system at large. But even as we face the catastrophic impacts of climate change, we now have the knowledge and ability to act, and if we do, we can use the time we still have to create a better future for whales, the ocean, and ourselves.

Antarctica’s Southern Ocean is a lifeline for all the world’s oceans — the mixing zone where cold and warm waters meet, where winds and sea ice stir up the deep ocean and propel the circulation of heat and nutrients across the planet. Plunge into the depths of Antarctica’s waters and explore how the powerful overturning of the Southern Ocean removes carbon from the atmosphere, fuels marine food chains, and drives our global climate.

Antarctica’s magnificence has been millions of years in the making. In this episode, we take you back more than 30 million years, when the Antarctic Circumpolar Current first began and Australia and Antarctica separated to form the distinct continents we know today. Dive into the history of remarkable Antarctic fish, the climate pressures that shaped their evolution, the new environmental pressures that are shaping their future — and explore how climate science can inform more sustainable fisheries management throughout the Southern Ocean.

Warming waters. Stronger storms. Diminishing sea ice. The gentoo penguin — less than a meter tall and recognizable by its red-orange beak and white feathers banded across its head — is in a uniquely vulnerable position. The world’s fastest swimming bird is one of the few penguin species that doesn’t migrate seasonally to feed, breed, and nest. Gentoo and other penguins across Antarctica are now being born out of season, into unfamiliar elements such as freezing rain. But the remarkable adaptability of the gentoo has been a sign of hope, with population sizes exploding since the 1990s as the seabirds move their colonies inland. In this series finale, you'll explore some of the most remote reaches of the Antarctic Peninsula with series director John Weller. Along the way, he’ll guide us through the challenges facing the continent, the penguins and other creatures that call it home, and you'll learn why — no matter the circumstances — hope matters.