POST-GLACIAL ECOSYSTEMS AND CLIMATE CHANGE

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Context:

A study titled ‘The Development of Terrestrial Ecosystems Emerging After Glacier Retreat’, suggests that deglaciation may accelerate climate change by reducing surface reflectivity and releasing stored carbon but the post-glacial ecosystems could help slow it down.

What is a glacier?

• A glacier is an accumulation of ice and snow that slowly flows over land.
• At higher elevations, more snow typically falls than melts, adding to its mass.
• Eventually, the surplus of built-up ice begins to flow downhill.
• At lower elevations, there is usually a higher rate of melt or icebergs break off that removes ice mass.
• Alpine glaciers are frozen rivers of ice, slowly flowing under their own weight down mountainsides and into valleys.
• Glaciers also exist on the fringes of ice sheets.
• Ice sheets cover entire continents.
• During the Last Glacial Maximum, roughly 20,000 years ago, the Laurentide Ice Sheet covered much of North America, and its weight created basins that now hold the Great Lakes.
• Currently, there are only two ice sheets on Earth: the Antarctic and Greenland Ice Sheets.

Details about Ice sheet: https://www.iasgyan.in/daily-current-affairs/antarctic-ice-sheet#:~:text=What%20is%20Ice%20Sheet%3F,are%20sometimes%20called%20continental%20glaciers.

How do glaciers form?

• Accumulation: Glaciers begin to form when snow remains in the same area year round, where enough snow accumulates to transform into ice.
• Compression: Each year, new layers of snow bury and compress the previous layers. This compression forces the snow to recrystallize, initially forming grains similar to the size and shape of sugar grains.
• Grow: Gradually, the grains grow larger and the air pockets between the grains get smaller, causing the snow to slowly compact and increase in density.
• Firn formation: After about a year, the snow turns into firn—an intermediate state between snow and glacier ice.  At this point, it is about two-thirds as dense as water.
• Over time, larger ice crystals become so compressed that any air pockets between them are very tiny.
• In very old glacier ice, crystals can reach the size of an adult fist. For most glaciers, this process takes more than a hundred years.

Where are glaciers?

• The world's glaciers have an estimated total area of about 700,000 square kilometers (270,000 square miles).
• Most of the world’s glaciers are in Antarctica.
• Glaciers are mainly found near the poles, but glaciers exist on all the world’s continents except Australia.
• Although Australia has no glaciers, it is considered part of Oceania, where glaciers can be found in New Zealand and the large islands of Indonesia and Papua New Guinea.
• Most glaciers are found in regions of high snowfall in winter and low temperatures in summer.
• These conditions ensure that the snow that accumulates in the winter is not lost during the summer. Examples of such regions are Alaska, Patagonia, and the Himalayas.
• The Arctic islands of Canada get much less snowfall, but it is cold enough through the year that glaciers can form. 
• Closer to the equator, higher elevations are required for needed snowfall and lower temperatures. 

The Importance of Glacier

Reflecting

• As the largest ice mass on the planet, the Antarctic Ice Sheet plays a vital role in the overall energy balance of the earth. 
• The bright, white surface of the ice reflects up to 90% of the solar radiation that reaches it, helping to keep the planet cool.
• Ice has a higher ‘albedo’ (reflective capacity) than the ocean and land surfaces. 

Storing

• The Antarctic Ice Sheet contains around 70% of the freshwater on the planet. By storing it as ice, it helps to keep sea levels stable.
• By locking up all this water, the ice sheet plays an important role in setting sea levels around the planet. For over 10,000 years, sea levels have been relatively stable.
• During a warm period around 400,000 years ago, sea levels rose by over 20 feet (6 meters) due to melting Antarctic ice.

Regulating

Glaciers, in combination with the cold, dry atmosphere above and surrounds it, acts as a powerful global thermostat.

What is glacial retreat?

• Glacial retreat refers to the process of a glacier shrinking or receding in size over time.
• This occurs when the amount of ice melting or sublimating from the glacier exceeds the amount of new snow or ice accumulation.

Primary cause for retreat

One primary cause is rising global temperatures, which are largely attributed to human-caused greenhouse gas emissions.

Impact of  glacial retreat

• Availability of water: As the glacier melts, it can impact the availability of water in surrounding areas. This can lead to reduced water flow in rivers and streams, which can have negative effects on local ecosystems and the human communities that rely on them for drinking water and irrigation.
• Ecosystem: Glacial retreat can also alter local ecosystems, as the flora and fauna adapted to a colder, icier environment are displaced.
• Rising sea level: It contributes to rising sea levels. When glaciers melt, the water flows into the ocean and adds to the volume of water, causing sea levels to rise. This can have significant impacts on coastal communities and ecosystems around the world, as rising sea levels can lead to flooding, erosion, and the loss of critical habitats.
•  Natural disaster: It can increase the risk of natural disasters such as floods and landslides, as the melting ice can create unstable conditions in the surrounding landscape.

Key findings of the study

• The study suggests that deglaciation may accelerate climate change by reducing surface reflectivity and releasing stored carbon, but the post-glacial ecosystems could help slow it down.
• The study involved collecting more than 1,200 soil samples from nearly fifty glaciers worldwide, spanning diverse climates from tropical to subpolar regions.
• Samples from the Gangotri and Bara Shigri glaciers in the Indian Himalayas analysed to understand soil evolution, biodiversity, species arrival sequence and ecosystem development.
• After glacier retreat, microorganisms such as bacteria, protists and algae are the first to colonise the barren landscape, making minerals available for other species, within a decade, hardy plants like lichens, mosses and grass begin to establish, enriching the soil and paving the way for more complex plant life and larger animals.
• This Post-glacial ecosystems could help slow down climate change through carbon capture and storage through growing biogeochemical processes and biomass.

Importance of studying the development of terrestrial ecosystems after glacier retreat.

• As more areas become deglaciated, especially in the Himalayas and sub-polar regions, managing these new ecosystems will be vital.
• With proper management, these areas can develop rapidly, providing temporary habitats for species threatened by climate change.
• Though recently exposed, deglaciated terrains are crucial for biodiversity and could serve as refuges for cold-adapted species.
• Promoting wild herbivores could further enhance life in these regions and help mitigate climate change impacts.
• Particularly in the Himalayas these ecosystems regulate water availability, impacting rivers that support millions of people with drinking water, agriculture and hydropower.
• The biodiversity in these areas offers potential for medicinal and agricultural discoveries, while promoting eco-tourism to boost local economies.
• Protecting and studying these ecosystems can lead to valuable ecological benefits, including the discovery of new plants with potential for medicine and farming.

Must read articles

Antarctica Ice Sheet: https://www.iasgyan.in/daily-current-affairs/antarctic-ice-sheet#:~:text=What%20is%20Ice%20Sheet%3F,are%20sometimes%20called%20continental%20glaciers.

Green land: https://www.iasgyan.in/daily-current-affairs/green-land

Ancient landscape under Antarctic ice: https://www.iasgyan.in/daily-current-affairs/ancient-landscape-under-antarctic-ice

Source

https://nsidc.org/learn/parts-cryosphere/glaciers/why-glaciers-matter

https://www.watt-watchers.com/the-importance-of-glaciers/

https://www.climate.gov/news-features/understanding-climate/climate-change-mountain-glaciers

https://www.indiatimes.com/explainers/news/explained-what-is-glacial-retreat-and-how-does-it-impact-the-environment-595634.html