The Diminishing Antarctic Currents

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The Diminishing Antarctic Currents

By Laura McGovern Olszewski


The cycle of warming-melting-dilution-slowing-warming must be corrected as quickly as possible or the livelihood of every living being on Earth is at stake. It is no longer just about future generations; it is about every generation.


n the ongoing war to combat global warming, it is imperative that we understand how the ocean traps and locks carbon from the atmosphere, so scientists are constantly studying this phenomenon. Our oceans absorb 90 per cent of the heat produced by fossil fuels as well as nearly half of the additional carbon dioxide (CO2). The Southern Ocean alone is responsible for 75% of that absorption, so anything affecting that region will lead to greater consequences.      

This brings us to the infamous Drake passage. Ocean lovers are quite familiar with the formidable reputation of the Drake Passage. Anyone who has read of the Drake Passage and those fortunate enough to have crossed it knows this 1,000-kilometre-wide passage can fluctuate between calm waters and raging waves reaching up to 9-12 metres. On its roughest days, it is affectionately nicknamed the “Drake Shake.” As the water currents coming from the north collide with the colder waters flowing in from the Southern Ocean, it can be quite a spectacle. But if you are a passenger on a boat on a particularly rough day, you might spend most of the time praying for it to be over.

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Recently, scientists have discovered that when the Drake Passage is in a particularly brutal mood, it has a unique superpower. While it is estimated that typically only five per cent or less of most ocean’s waters typically interact with the atmosphere, the Drake Passage is a champion of carbon absorption. It turns out this thrashing mixture of currents between South America and the South Shetland Islands, where the Atlantic and Pacific meet, is also responsible for trapping massive amounts of carbon. Of course, we also have our friends, the phytoplankton, to thank for helping with this. After they absorb carbon dioxide from the atmosphere through photosynthesis, they are swept down to a much greater depth in the high energy swirling Drake waters than anywhere else in the world, releasing their carbon dioxide where it is consequently trapped more easily. 

Beyond this, the churning water also sinks cold, oxygen-filled water (to the tune of 250 trillion tons annually) to the bottom of the ocean and transports nutrients back to the surface. These nutrients are critical to phytoplankton and krill and continue up the food chain supporting the survival of fish, marine mammals and birds.  

The circulation then spreads eastward in a circular pattern driven by winds and is referred to as the Antarctic Circumpolar Current (ACC). While it is true that most land masses are not directly affected by the ACC, this singular global current directly impacts the southern portions of the Atlantic, Pacific and Indian oceans, ultimately affecting all life in one way or another.  

The ACC flows at a speed of about 0.2 knots to 2 knots, with an average of 1 knot.  Considered to be the strongest ocean current in the world, it is not impeded by any landmass and forms a huge circular-shaped current. Frequently referred to as the “ocean’s conveyor belt” understandably, the slightest changes in the ACC will be felt globally.

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Climate change desperately needs these currents to fight the ever-losing battle of increasing global sea temperatures. Regrettably, these superhero currents are showing signs of slowing due to the freshwater runoff of Antarctic ice.  This freshwater decreases the salinity and consequently, the density of the ocean, slowing down the circulation.  The diluted water does not sink as quickly or as well as the water with a higher concentration of salt. The consequences of this could be catastrophic and irreversible for the climate and would include:

  • A cycle of warming water-melting ice-saline dilution-current slowing-warming
  • Increased greenhouse gases.
  • Increased and accelerated global warming.
  • Opening of cold-water pathways for additional warmer water.
  • Changes in tropical weather and rainfall band shifts to locations over 900 km north.
  • Accelerated ice melting in Antarctic and Arctic zones.
  • Consequential collapse of food chains.

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Projections of scientists are that in the next 30 years, the Antarctic current overturning is going to decrease by 40 per cent due to melting ice. The resulting ocean temperature increase will prevent phytoplankton survival and cascade down the food chain. This cycle of warming-melting-dilution-slowing-warming must be corrected as quickly as possible or the livelihood of every living being is at stake. It is no longer just about future generations; it is about every generation. The time is now.

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