Recently, Scientists have discovered a new tipping point toward “runaway melting” of Antarctic ice sheets, caused by warm ocean water intruding between the ice and the land it sits on
- As ocean temperatures rise due to human-caused global warming, Antarctic ice sheets are melting, threatening a rise in global sea levels and putting coastal communities at risk.
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- Vicious Cycle: Warming ocean temperatures could also lead to a “runaway” feedback effect that allows warm seawater to push further inland, leading to more melting and faster sea level rise.
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Tipping points
- According to IPCC, tipping points are ‘critical thresholds in a system that, when exceeded, can lead to a significant change in the state of the system, often with an understanding that the change is irreversible.
Runaway melting
- Increases in ocean temperature can lead to a tipping point being passed, beyond which ocean water intrudes in an unbounded manner beneath the ice sheet, via a process of runaway melting.
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Intrusions of Warm Seawater Beneath The Ice
- Causative Reason: Such intrusions occur due to the difference in density between the fresh water flowing out from beneath the ice sheet and the relatively warm ocean water where the ice meets the seafloor – an area known as the grounding line.
- It occurs beneath hundreds of metres of ice, but simulations suggest the warm water could extend inland for kilometres in some places.
- “Runaway” positive feedback effect: When ocean water reaches a certain temperature threshold, it melts ice at the grounding line faster than can be replaced by the flowing ice.
- As this cavity grows, more seawater can flow beneath the ice sheet and intrude further inland in what amounts to a “runaway” positive feedback effect.
Impact of Antarctic Ice Melting
- Sea Level Rise: Melting Antarctic glaciers contribute significantly to global sea level rise, affecting coastal regions worldwide.
- For example: The Thwaites Glacier in West Antarctica alone could raise sea levels by over 3 meters if it collapses completely.
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Thwaites Glacier – Doomsday Glacier
- It is 120 km wide at its broadest, fast-moving, and melting fast over the years.
- Because of its size (1.9 lakh square km), it contains enough water to raise the world sea level by more than half a metre.
- Along with the Pine Island Glacier, it has been described as part of the “weak underbelly” of the West Antarctic Ice Sheet, because of its apparent vulnerability to significant retreat.
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- Thermohaline Circulation: Freshwater from melting glaciers can disrupt thermohaline circulation, impacting global climate systems, including the El Niño and La Niña phenomena.
- For example: Changes in the Southern Ocean’s salinity have been linked to altered El Niño patterns.
- Sudden Stratospheric Warming (SSW): Melting glaciers can lead to SSW in Antarctica, affecting weather patterns in the Southern Hemisphere, such as increased wildfire incidence in Australia.
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- For example: The 2019-2020 Australian bushfires were partly attributed to Antarctic SSW events.
- Albedo Effect: Reduced ice cover decreases the Earth’s albedo effect, leading to higher temperatures and accelerated melting.
- For instance: The Antarctic Peninsula has seen significant ice loss, contributing to reduced albedo.
- Biodiversity Impact: Loss of ice affects marine ecosystems, disrupting the habitat of species such as krill, which are crucial for the Antarctic food web.
- For example: Declines in krill populations have been observed, impacting penguins and other marine species.
- Ocean Acidification: Increased melting leads to more freshwater entering the oceans, which can alter pH levels and contribute to ocean acidification.
- For example: The Southern Ocean is experiencing faster rates of acidification, impacting marine life.
June 28, 2024