Context: 

• The 2023 winter season in Antarctica ended with a historic low in sea ice coverage, coinciding with the early emergence of the ozone hole over the continent. 

More about the news: 

• Melting of Sea ice: Antarctica, whose temperature can go as low as -98°C, sees the melting of the sea ice cover every summer season between December and February before returning to its original state during the winters.
  •  Data from NASA Earth Observatory in the US revealed that the sea ice extent in July had reached lowest at approximately 13.5 million square kilometers since 1978. 
  • By August, an area of sea ice equivalent in size to Greenland had failed to regenerate.
• Five-sigma event: Scientists have described this as a five-sigma event, implying that, without climate changes, such a minimal sea ice cover would typically occur once in 7.5 million years. 
• Changes in the polar vortex(PV) location: PV is a region of low pressure and cold air that encircles both Earth’s poles.
  • It has shifted to allow for a greater southward flow over the Antarctic sea ice. As a result, more sea ice is being pushed towards the southern reaches of the continent.
  • PV speeds up the mechanism by which the Ozone Depleting Substances (ODS)present in the stratosphere destroy ozone.

Shrinking sea ice: 

• Antarctic sea ice is marked by reduced overall sea ice extent and shorter durations of sea ice presence reflecting impact of climate change and anthropogenic greenhouse gas emissions.
• As reported by NASA Earth Observatory, record-low extents in Antarctica sea ice was observed in 2017, 2022, and now in 2023.

Challenges with melting of sea ice:

• Rise in extreme events: Increasing temperatures is leading to a recurring series of extreme events impacting its atmosphere, ocean, cryosphere, and biosphere.
  • Heatwave: In March 2022, east Antarctica experienced an unprecedented heatwave with temperature reaching 38.5°C and subsequent melting event. 
    • This extreme heat event was linked to an atmospheric river that transported warm and moisture-laden air from Australia deep into the heart of the continent.
    • In February 2020, Antarctica’s mainland recorded its highest temperature of 18.3°C at the Esperanza station. 
  • Cyclonic events: These were witnessed on account of calving of an iceberg on the Brunt Ice Shelf.

• Impact on marine ecosystem:

• • Absorption capacity of oceans: The reduction in sea ice leads to greater absorption of the sun’s energy by the oceans, accelerating the melting of sea ice, creating a self-reinforcing feedback loop.
  • Impact on Antarctic bottom water: It plays a vital role in regulating the ocean’s capacity to store heat and capture carbon.
  • Reduced production of Antarctic bottom water:  It results in reduced production of Antarctic bottom water, a critical component of the meridional overturning circulation.
  • As per the study published in the journal Nature Climate Change,  the bottom waters in the Weddell Sea in Antarctica have shrunk by 20 per cent over the past 30 years, while shallower waters warmed at a rate five times higher than the rest of the global ocean.
• Impact on atmospheric determinants: 
  • Gaseous exchange: Disruption of the sea ice melt and growth cycle impacts the exchange of gasses and other materials between the ocean and atmosphere. 
    • For instance, ocean water absorbs more carbon dioxide than sea ice, which stores the compound in the form of a salty brine solution.
  • Impact on cloud formation: Aerosol production gets affected by the low sea ice cover, leading to less cloud cover over the Southern Ocean.
    • This leads to more striking of the sun’s energy to the Earth and further warming.
• Impact on Antarctic biosphere: 
  • Impact on local ecology: As per a research paper published in Nature Communications Earth and Environment, out of five emperor penguin colonies studied in Antarctica, four showed complete failure of breeding in the season.
    • Between 2018 and 2022, approximately 42 percent of emperor penguin colonies experienced total or partial breeding failure due to fast ice breakup in at least one year. 
  • Impact on primary producers: Krill, zooplankton and phytoplankton get affected by low sea ice extent having a knock-on effect on other organisms dependent on them.

Expansion of Ozone hole in Antarctica: The ozone hole formation over Antarctica starts at the end of September, reaches its peak size in October, and then gradually closes in November or December. 

• However, this year, the ozone hole began forming in August, raising concerns about the potential for a larger-than-average hole.

• On September 1, the ozone hole over Antarctica measured 19.67 million square kilometers, as reported on NASA’s ozone hole webpage.

Reason behind early eruption of Antarctic ozone hole: 

• Volcanic eruption: It can be attributed to the eruption of the Hunga-Tonga volcano in January 2022.
  • The volcanic eruption released water vapor estimated at around 50 million tonnes into the stratosphere which eventually reached the Antarctic stratosphere.
• Polar stratospheric clouds(PSC): The increased water vapor in the stratosphere promoted the formation of PSC where chlorofluorocarbons can react and accelerate ozone depletion.
  • The presence of water vapor contributes to cooling the Antarctic stratosphere, enhancing the formation of these PSCs resulting in a stronger polar vortex.

Success of Montreal Protocol in recovery of ozone hole:

• Recovery of ozone hole:  It has been gradually recovering since the 1987 Montreal Protocol led to the phasing out of ODS like chlorofluorocarbons.
  • In October 2022, the World Meteorological Organization predicted that the entire world, except for the poles, would recover from the ozone hole by 2040.
  •  Full recovery at the poles is expected by 2066.
• Despite the ongoing recovery, the past three years have seen the presence of robust and enduring Antarctic stratospheric polar vortices, with ozone holes that have been among the largest and most persistent on record.

Way Forward: 

• Reducing emissions from feedstocks: Feedstocks refers to substances that undergo a chemical transformation during the process of making other chemicals. 
  • The production, use and disposal of feedstocks results in harmful emissions, but ODS and HFC production for feedstock use is exempt from Montreal Protocol controls. 
  • It is therefore imperative that Parties agree measures to reduce industrial emissions from the production and use of feedstocks.
• Global framework for destroying ODS and HFCs banks:  The stores of ODS and HFCs contained in existing equipment (fridges, air-conditioning units, etc) are known as banks.
  • Currently, banks are releasing about 150 million tonnes of CO2-equivalent emissions every year. 
  • Emissions from banks of ozone-destroying CFCs alone could potentially delay Antarctic ozone hole recovery by about six years.
• Strengthening MRV+E: Monitoring, reporting, verification and enforcement (MRV+E) are at the core of Montreal Protocol’s success.
  • CFC-11 is being illegally produced and used in eastern China (potentially delaying polar ozone recovery by up to three years).
• Curbing N2O emissions:In the past four decades, anthropogenic (human-caused) N2O emissions have increased by 30 per cent. These undermine both the recovery of the ozone layer, and global efforts to limit warming. 
• Attaining paris agreement goals: Achieving the 1.5-degree Celsius target outlined in the Paris climate agreement would lead to a reduction in melting of Antarctic ice.
• Global agreement: The effectiveness of the Montreal Protocol provides a lesson for establishing a worldwide treaty framework for addressing concerns related to climate change.

News Source: DTE

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