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Giant Waves, Monster Winds and Earth’s Strongest Current
The Southern Ocean: Overview
- The Southern Ocean is known for its wild and dynamic nature, characterised by some of the Earth’s strongest winds and largest waves.
- It is home to massive icebergs, some the size of cities, and the planet’s largest ocean current. Additionally, it features tiny turbulent flows that can fit inside a teacup.
- This ocean plays a crucial role in Earth’s natural systems.
- It forms the dense water that fills the world’s deep oceans, stores heat and carbon resulting from human-caused global warming, and regulates the heat flux to Antarctica’s ice sheet, which poses a significant risk for runaway global sea-level rise.
Masses of Ice at Risk:
- The Antarctic Ice Sheet, the largest ice mass on Earth, is equivalent to 58 metres of global sea level.
- It extends onto the Southern Ocean surface as giant ice shelves.
- Many of these ice shelves are being eroded from below by warmer ocean waters or are crumbling and breaking into icebergs at an accelerated rate.
- Beyond the ice shelves, millions of square kilometres of the Southern Ocean’s surface are covered by sea ice.
- Sea ice acts as a giant solar reflector, shielding the ice shelves from the powerful waves of the Southern Ocean.
- However, after decades of withstanding warming temperatures, the Southern Ocean’s sea ice has recently seen a dramatic decline, putting additional stress on both the ice shelves and the ice sheet.
Filling Earth’s Oceans:
- The formation of much of the sea ice occurs in small regions of open water known as “polynyas,” which are created by strong, cold winds blowing off Antarctica.
- These winds cool the ocean surface below the freezing point, causing ice to form and release salt into the ocean.
- This extra salt, combined with cooling effects from the atmosphere, makes the surface seawater denser.
- The dense water then sinks in turbulent plumes, resembling an upside-down volcano, and cascades through underwater canyons into the deep ocean while mixing with overlying waters.
- This dense water mass, formed in only a few relatively small regions of Antarctica, constitutes an extraordinary 40% of the global ocean volume.
- It is ultimately returned to the ocean surface by centimetre-scale turbulent eddies, similar to those seen when mixing milk into tea.
- In the deep ocean, this mixing is largely driven by ocean tides that interact with the rough seafloor and generate internal waves.
Climate System at Risk:
- The ocean water takes hundreds of years to cycle from the surface Southern Ocean to the deep and back.
- water returning to the surface today reflects cooler, pre-industrial climate conditions and has absorbed more carbon, which helps limit global warming.
- However, reductions in sea ice and ice shelves are weakening this crucial climate system. Warmer, less salty, and more buoyant water is less prone to sinking, which leads to decreased carbon storage and a warmer atmosphere in the future.
Knowledge Gaps and Research Needs:
- Measuring the Southern Ocean is challenging due to its remote location and harsh conditions, resulting in sparse data.
- Future research should focus on ocean temperatures, ice shelf melting, and dense water formation.
- More data is needed for monitoring climate changes and providing early warnings.
- Increased collaboration is essential for optimising resources and developing cost-effective observing systems.
Basic Facts About Southern Ocean Region:
- Location: The Southern Ocean encompasses the southernmost waters south of 60 degrees latitude. It encircles the Antarctic continent and includes parts of Australia, New Zealand, Argentina, and western Antarctica.
- Geological Formation: Formed about 30 million years ago when Antarctica and South America drifted apart, creating the Drake Passage.
- Depth: Typical depths range from 4,000 to 5,000 metres (13,100 to 16,400 feet). The deepest point is 7,235 metres (23,737 feet) in the South Sandwich Trench.
- Sea Temperature: Varies from about 10°C (50°F) in the northern regions to -2°C (28°F) in the southern areas.
- Ice Coverage: Warming of 2°C is predicted to reduce winter sea ice coverage by 10-15% and up to 30% in some key areas.
- Biodiversity:
- Birds: Around 100 million birds breed in Antarctica, with the continent’s 7 penguin species accounting for 90% of them.
- Youngest Ocean: The Southern Ocean is the youngest of the world’s oceans.
- Climate Impact: Its ice and temperature patterns significantly influence global climate and sea levels.
Defining Key Terms:
- Giant waves in the Southern Ocean, known as rogue waves, are exceptionally large and unpredictable, posing serious threats to ships and coastal infrastructure.
- Monster Winds: The Southern Ocean features some of the world’s strongest winds, often exceeding 60 knots (69 mph).
- The lack of landmasses allows these winds to flow unimpeded, generating large waves and influencing the ocean’s dynamic weather.
- These relentless winds create hazardous conditions for vessels and play a key role in ocean mixing and global climate patterns.
- Earth’s Strongest Current: The Antarctic Circumpolar Current (ACC) is the strongest ocean current on Earth, flowing continuously around Antarctica and connecting the Atlantic, Pacific, and Indian Oceans.
- Driven by the powerful winds of the Southern Ocean, the ACC regulates global ocean circulation and plays a key role in transporting heat and nutrients across vast distances.
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India’s Research Initiatives:
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