Impact of Arctic Sea Ice Changes on Indian Monsoon Patterns

Impact of Arctic Sea Ice Changes on Indian Monsoon Patterns

Sub :Geo

Sec: Climatology

Why This is in the News

Recent research highlights a critical link between declining Arctic Sea ice and the increasingly unpredictable patterns of the Indian monsoon. The findings have significant implications for climate science and weather forecasting, particularly in light of recent severe weather events in India.

Influence of Arctic Sea Ice on the Monsoon

A study published in Remote Sensing of Environment in June utilized data from 1980 to 2020 and climate models (CMIP5 and CMIP6) to explore the impact of Arctic sea ice changes on the Indian monsoon.

Key Observations:

• Reduced Sea Ice in Central Arctic: Leads to decreased rainfall in western and peninsular India, but increased rainfall in central and northern India.
• Reduced Sea Ice in Barents-Kara Sea Region: Results in a delayed and more unpredictable monsoon onset.
• Accelerated Ice Loss: Climate change accelerates the reduction of Arctic Sea ice, which exacerbates variability and unpredictability in the ISMR.

Atmospheric Mechanisms

• Cyclonic Circulation and Rossby Waves: Reduced Sea ice in the central Arctic enhances cyclonic circulation at lower latitudes, impacting Rossby waves. These waves affect high and low-pressure systems, shifting the Asian jet stream and altering rainfall patterns.
• Barents-Kara Sea Influence: Lower Sea ice levels create high pressure over southwest China, affecting atmospheric stability over the Indian subcontinent and leading to increased rainfall in northeastern India while reducing rainfall in other regions.

About Monsoon:
Monsoons are periodic or seasonal winds that reverse direction with the changing seasons. These winds are a large-scale version of the land and sea breezes.

Duration and Intensity: The Indian Summer Monsoon Rainfall (ISMR) occurs from July to September, with peak rainfall in July and August.

Double System of Winds:

• Summer: Winds flow from the sea to the land (South-West Monsoon).
• Winter: Winds flow from land to sea (North-East Monsoon).

Global Occurrence: Monsoons are prominent in the Indian subcontinent, Southeast Asia, parts of Central Western Africa, and some other regions. However, they are most pronounced in the Indian subcontinent.

Indian Monsoon System: Monsoons in India are large-scale convection cells.

India experiences the South-West Monsoon in the summer and the North-East Monsoon in the winter.

South-West Monsoon brings heavy rainfall to most of India, while the North-East Monsoon brings rain primarily to the southeastern coast, including Tamil Nadu and Andhra Pradesh.

Formation of South-West Monsoon: Intense heating of the Tibetan Plateau during summer creates a low-pressure system.

Presence of a permanent high-pressure cell in the South Indian Ocean, northeast of Madagascar.

Onset Factors of South-West Monsoon:

• Heating of the Tibetan Plateau.
• Subtropical Jet Stream (STJ).
• Tropical Easterly Jet (African Easterly Jet).
• Inter-Tropical Convergence Zone (ITCZ).

Factors Affecting the Intensity of South-West Monsoon:

• Strength of low-pressure over Tibet and high-pressure over the southern Indian Ocean.
• Somali Jet (Findlater Jet): A strong air current from Somalia towards India.
• Somali Current: Ocean current that affects moisture movement.
• Indian Ocean Walker Cell: Large-scale atmospheric circulation.
• Indian Ocean Dipole: Temperature gradient in the Indian Ocean that affects monsoon variability.

Formation of North-East Monsoon:

• Formed due to high-pressure cells over the Tibetan Plateau and the Siberian Plateau in winter.
• The weakening of high-pressure cells over the Southern Indian Ocean.
• Southward shift of the ITCZ during the winter.

Circum-global teleconnection (CGT) refers to a large-scale atmospheric wave pattern that influences climate and weather patterns across the globe. It is a type of atmospheric wave that occurs primarily in the mid-latitudes, connecting distant regions through a series of high and low-pressure systems, much like how the atmosphere moves energy and moisture around the world.

Influence on the Indian Monsoon: The CGT plays a significant role in shaping the monsoon’s behavior. For example, when the CGT is strong, it can lead to enhanced monsoon activity, bringing more rainfall. Conversely, disruptions in the CGT can weaken monsoon currents, leading to droughts or irregular rainfall in the Indian subcontinent.

Rossby Waves: The meandering jet streams are called Rossby Waves.

Rossby waves are natural phenomenon in the atmosphere and oceans due to rotation of earth.

In planetary atmospheres, they are due to the variation in the Coriolis effect (When temperature contrast is low, speed of jet stream is low, and Coriolis force is weak leading to meandering) with latitude.

Rossby waves are formed when polar air moves toward the Equator while tropical air is moving poleward.

The existence of these waves explains the low-pressure cells (cyclones) and high-pressure cells (anticyclones).

Jet Stream: The Jet Stream is a geostrophic wind blowing horizontally through the upper layers of the troposphere, generally from west to east, at an altitude of 20,000 – 50,000 feet.

Jet Streams develop where air masses of differing temperatures meet. So, usually surface temperatures determine where t/he Jet Stream will form.

Greater the difference in temperature, faster is the wind velocity inside the jet stream.

Jet Streams extend from 20 degrees latitude to the poles in both hemispheres.

Arctic Sea

Location: Surrounds the Arctic region, bordering Canada, Russia, Greenland, Norway, and the U.S. (Alaska).

Key Seas: Includes Barents, Kara, Laptev, East Siberian, and Beaufort Seas.

Ice Coverage: Mostly covered by sea ice, with seasonal melting and freezing patterns.

Climate Change: Rapid warming has reduced ice, opening new shipping routes (e.g., Northern Sea Route) and access to resources.

Resources: Estimated 13% of the world’s undiscovered oil and 30% of natural gas reserves.

Arctic Council: Forum of 8 nations addressing Arctic governance, environment, and indigenous peoples’ issues.

Barents Sea

Location: The Barents Sea is part of the Arctic Ocean, located north of Norway and Russia.

Borders: It is bordered by the Norwegian Sea to the west and the Kara Sea to the east.

Strategic Importance: It is vital for Russia’s oil and gas exploration, particularly in the Arctic region, and houses significant petroleum reserves.

Kara Sea

Location: The Kara Sea lies to the east of the Barents Sea, between the Siberian coast of Russia and the Arctic Ocean.

Borders: It is enclosed by the Novaya Zemlya archipelago to the west and the Severnaya Zemlya archipelago to the east.

Natural Resources: Rich in oil and natural gas reserves, it is a key area for Russia’s Arctic energy projects, including the Vostochno-Prinovozemelsky oil fields.