Time To Read
Date Last Modified
Place 05 · The Southern Ocean · Wrap-up
The Bottom of the World
Antarctica has been run by a treaty instead of a country for more than 60 years, and the question now is whether the rules can keep up with the fishing fleets, the tourists and the melting ice.
About 20 minutes · 1 video · a full practice review of the whole Southern Ocean
Look back
Seven chapters ago you did not know this
You can now
Freeze the sea
Seawater freezes at about −1.8 °C and pushes most of its salt out as brine. White ice reflects up to 90% of sunlight; open water only about 6%.
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Sort the water
Cold, salty water is dense water. Antarctic Bottom Water, made on the Weddell and Ross Sea shelves, sinks to the bottom and spreads north for centuries.
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Follow the ring
With no land in the way, the westerlies drive the Antarctic Circumpolar Current all the way around the planet: about 173 Sv through Drake Passage.
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Build a wave
Wind speed, duration and fetch make waves, and storms sort them into swell. The Southern Ocean’s endless fetch builds seas like the 23.8 m wave of 2018.
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Fill the sink
Cold water holds more gas. About 40% of the human-made CO2 in the ocean went in through the Southern Ocean, and it is making the water more acidic.
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Shorten the chain
Diatoms, krill, whale: with only three links, far more of the Sun’s energy reaches the top, as long as there is enough iron, sea ice and krill.
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Float or ground
Melting floating ice barely changes sea level; ice on land raises it. Antarctica holds about 58 m of it, and Thwaites Glacier alone 65 cm.
Photos: Cara Denison, CHRISTIAN PFEIFER, Rachel Claire, Blue Record, Diana ✨, Jeffry Surianto, ArcticDesire.com Polarreisen / Pexels
One more thing
Who decides the Southern Ocean’s future?
United Nations — 1959 Antarctic Treaty: The Most Peaceful Place on Earth. Two and a half minutes on how twelve countries, in the middle of the Cold War, agreed to keep a whole continent for peace and science.
The Southern Ocean by the numbers
- 1959 — Antarctic Treaty signed by 12 countries; 58 countries are Parties today
- 1.55 million km² — Ross Sea Marine Protected Area, created in 2016; about 1.12 million km² of it is closed to commercial fishing
- 620,000 t — krill catch trigger level, reached in 2025 and again in 2026, closing the fishery early both times
- 118,491 — visitors to Antarctica in the 2024–25 season, according to the tour operators’ association IAATO
Nobody owns Antarctica outright. The Antarctic Treaty, signed in 1959 by the 12 countries doing science there and in force since 1961, keeps everything south of 60°S for peaceful purposes and science, and a 1991 protocol added strict environmental rules, including a ban on mining. The ocean’s living things are managed by CCAMLR, set up in 1982, which sets krill catch limits and in 2016 created the Ross Sea Marine Protected Area, 1.55 million km², most of it closed to commercial fishing. The pressure is rising: in 2025, and again in August 2026, the krill fleet hit its 620,000-tonne trigger level and the fishery closed early; CCAMLR’s members have not agreed on a single new marine protected area since 2016; and more than 118,000 people visited Antarctica in the 2024–25 season.
Figures: Antarctic Treaty Secretariat, CCAMLR and IAATO.
Two pictures to leave with
Who visits the ice now, and what the next place is full of
Put it all together
Southern Ocean Review
Seven chapters, one ocean. This review walks the whole place, from the first frazil crystal to the ice on land, with a few questions that tie chapters together. Retry as often as you like. If one trips you up, the feedback names the chapter to revisit, and every chapter has its own eight-question practice set at the bottom of the page.
Practice
Southern Ocean Review: the whole place
Twenty questions covering all seven chapters and this page. Aim for a clean run, then you are ready to head north again.
Where we go next
Next stop: The North Pacific Garbage Patch
The currents you just followed around Antarctica have cousins in every ocean basin: giant loops of water called gyres. In the middle of the North Pacific’s gyre, the circling currents gather up what the rest of us throw away. Place 06 goes to the North Pacific Garbage Patch, and it needs everything this course has taught you so far: currents, density, sunlight, food chains and the chemistry of the sea.
Photo credits (Pexels): Gu Bra, Cara Denison, CHRISTIAN PFEIFER, Rachel Claire, Blue Record, Diana ✨, Jeffry Surianto, ArcticDesire.com Polarreisen, Jan Tang, Çağrı KANMAZ.