At the end of 2016, scientists detected a crack in the Larsen C ice shelf on the Antarctic Peninsula, which led to the detachment of iceberg A-68 in July 2017.
This iceberg, with more than double the size of Luxembourg and 235 meters thick, embarked on a 3 and a half year odyssey to a remote island in the Southern Ocean.
Journey and Transformation
Initially trapped in the sea ice, A-68 started moving north in 2018, driven by currents and winds. During Christmas 2020, its journey went viral on social media.
As it progressed, ecologists feared it would impact South Georgia Island, threatening local species, but the iceberg broke apart and gradually melted, releasing thousands of millions of tons of fresh water into the ocean.
Impact on the Marine Ecosystem
The detachment of A-68 exposed the seabed, transforming the habitat and creating unique conditions for marine life.
During its transient life, A-68 acted as a frozen lifeboat for various species. Scientists have tracked its impact, revealing how giant icebergs influence the surrounding ocean.
Melting and Disintegration
As A-68a drifted into warmer waters, it fractured into smaller pieces and melted. Satellites detected layers of fresh water extending over 1,000 km from the iceberg.
Melting fresh water is less dense than saltwater, creating a revealing surface layer.
In April 2021, A-68a concluded its journey as a mass of melted ice, having transformed the marine habitat around it and sustained an ecosystem of life during its existence.
In the boreal summer of 2020, iceberg A-68a, detached from the Larsen C ice shelf, posed a serious threat to the ecosystem of South Georgia Island. This ecosystem is incredibly rich and dynamic due to nutrients from glaciers and terrestrial runoff.
Risks for the Ecosystem
A-68a was large enough to erode the seabed, destroy ecosystems, and alter the chemical composition of seawater with its mass of fresh water.
Additionally, it could have prevented animals in reproductive stages from accessing the sea to feed their young, reducing the levels of colony survival.
Expedition and Iceberg Collapse
In December 2020, A-68a began to disintegrate, shedding pieces and showing numerous cracks. A corner of the iceberg wedged into the continental shelf near the island, eroding the seabed.
A study found that powerful ocean currents caused a second break. Researchers deployed robotic gliders and measured water conditions and marine life as the iceberg collapsed.
Melting and Ecosystem Effects
The iceberg rapidly melted in the warmer waters of the northern Scotia Sea, thinning at a rate of 7 meters per month.
At its peak, it poured 1.5 billion tons of fresh water into the ocean each day. This melting increased nutrient levels in the water, promoting algae growth and attracting zooplankton and possibly humpback whales.
Contribution to Marine Carbon
The weight of A-68a’s fresh water pushed down water layers and food particles, increasing the amount of carbon buried in the bottom of the Southern Ocean. This could reduce greenhouse gas concentrations in the atmosphere, a phenomenon not observed before.
Iceberg A-68, detached from the Larsen C ice shelf, exemplifies the effects of climate change in Antarctica. The melting of large ice sheets releases huge amounts of fresh water into the ocean, altering currents.
Impact of Freshwater Discharges
While an individual iceberg may not make a big difference, the trapped water in Antarctic ice will eventually end up in the ocean, complicating processes around the Antarctic coast.
To better understand these effects, larger-scale studies are being planned. Since the detachment of A-68, other giant icebergs like A-74 and A-76 have emerged.
Consequences for Antarctic Wildlife
Iceberg detachments can have drastic consequences for wildlife. For example, in 2024, iceberg A-83 blocked access to the sea for an Emperor penguin colony in Halley Bay.
As climate change continues to thaw Antarctica, the likelihood of more icebergs entering the Iceberg Alley will increase. Understanding these phenomena is crucial to anticipate and mitigate their impacts.
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