The massive iceberg A23a did not collide violently with the remote wildlife-rich island of South Georgia.

Instead, it was approaching the small British overseas territory at a glacial pace of 1 kilometer per hour.

However, given the size of this megaberg, which spans 40 miles across and weighs around five times more than Mount Everest, its grounding on the rocky shelf surrounding the island was significant.

What impact will it have on wildlife?

The potential effect of a trillion tonnes of ice melting close to one of the world’s most critical wildlife sanctuaries is uncertain. This event could potentially impede many of South Georgia’s millions of penguins from reaching food sources and has already disrupted navigation around the area.

How has it been around for so long?

Such massive icebergs are not common. Gigantic chunks of ice constantly break off from Antarctica’s ice shelves but most fracture into fragments immediately after they start floating in the warmer ocean surrounding the continent.

But A23a has endured for a long time.

It was initially formed after calving off from the Ronne-Filchner ice shelf – a massive floating ice platform in Antarctica’s Weddell Sea – all the way back in 1986.

It even carried a former Soviet research station, Druzhnaya I, that had been established on its edge.

For twenty years, the iceberg barely moved, then in 2020, it started drifting slowly northwards, entering a collision course with the mountainous wildlife-dense island of South Georgia – 1,000 miles away from its starting point.

It remained in the Southern Ocean for six months last year, revolving within an ocean current before finally breaking free in the New Year, heading towards the island of South Georgia at a speed of around 30 kilometers a day. “Pretty swift for an iceberg,” remarks Andrew Meijers, an oceanographer at the British Antarctic Survey in Cambridge.

An imminent concern is whether it will shrink or not.

The waters surrounding South Georgia are comparatively warmer than the iceberg’s Antarctic origins, thus, the iceberg is expected to get slimmer, more brittle, and crumble relatively quickly.

The potential impacts are likely to be localized, but not negligible, especially to the millions of penguins or seals residing in South Georgia.

Given a trillion tonnes of fresh water, floating atop denser sea water, this might push marine animals’ food deeper underwater.

Alternatively, if the iceberg is carrying a significant amount of mud and sediment, it could enrich the water with nutrients, providing additional sustenance for marine life.

What are the consequences?

A23a is emblematic of a far more worldwide and significantly more consequential trend: the fast thawing of ice in Antarctica.

The continent is losing approximately 150 billion tonnes of water as ice annually, with half carried away as icebergs and the remainder from ice melting directly off the continent itself.

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As the world’s largest reservoir of fresh water, this is leading to a steady rise in sea level – anticipated to be around 60cm by 2100 – due to Antarctic melting alone.

A more critical concern is the effect of all that fresh water on the Antarctic Circumpolar Current – a slow circulation of ocean water functioning as our planet’s cooling mechanism.

Warm air from the rest of the world heats the surface waters, currents then bring this warmer water down, replacing it with cooler water from the ocean depths.
“It does all of the heavy lifting in terms of trapping heat from global warming,” explains Dr. Meijers.

Microscopic plants – phytoplankton – in the region also absorb the most planet-warming carbon dioxide, which, like the warmer water, is carried deep into the ocean and stored there.

A study suggests fresh water from melting icebergs and the Antarctic continent is already slowing down this circumpolar current and could reduce its speed by 20% by 2050.