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THE CONTEXT: A recent study conducted by researchers from India’s National Centre for Polar and Ocean Research and South Korea’s Korea Polar Research Institute reveals the intricate influence of Arctic Sea ice decline on the Indian monsoon. By analyzing data from 1980 to 2020, the research highlights significant shifts in regional rainfall patterns, emphasizing the need to understand the broader implications of climate change.
ROSSBY WAVES: They are also known as planetary waves, are large-scale meanders in high-altitude winds that occur in rotating fluids, such as Earth’s atmosphere and oceans. These waves form due to the conservation of potential vorticity and are influenced by the Coriolis effect and pressure gradients. Rossby waves play a significant role in shaping weather patterns by influencing the position and strength of jet streams. They can cause large-scale weather phenomena, such as cyclones and anticyclones, and are responsible for day-to-day weather variations at mid-latitudes.
IMPACT OF ROSSBY WAVES ON INDIAN MONSOON:
- Atmospheric Circulation: These waves can alter the path and intensity of jet streams, including the Asian jet stream, which is crucial for the Indian monsoon.
- Monsoon Variability: The presence and phase of Rossby waves can significantly influence the variability of the Indian monsoon. For instance, during certain phases, these waves can enhance or suppress rainfall over the Indian subcontinent by altering the position of high and low-pressure systems.
- Teleconnections: Rossby waves can propagate from distant regions, such as the North Atlantic, and impact the Indian monsoon through teleconnections. These waves can carry atmospheric disturbances that influence weather patterns over India, leading to variations in monsoon onset and intensity.
- Influence on Rainfall Patterns: The spatial phase of Rossby waves can differ between wet and dry monsoon years, affecting the distribution of rainfall across India. This is linked to shifts in deep convection and heat sources in the Indian Ocean and adjoining regions.
Asian Jet Streams: Jet streams are fast-flowing, narrow air currents found in the upper atmosphere. The Asian jet streams include the Subtropical Jet Stream (STJ) and the Tropical Easterly Jet Stream (TEJ), both of which are crucial for the Indian monsoon. Jet streams are characterized by high-velocity winds, often reaching speeds of 400-500 km/h. They form due to significant thermal contrasts that create powerful pressure gradient forces.
IMPACT OF ASIAN JET STREAMS ON INDIAN MONSOON:
- Onset and Withdrawal of Monsoon: The northward movement of the Subtropical Jet Stream is a key indicator of the onset of the Indian monsoon. During summer, the STJ shifts northwards, allowing the monsoon winds to advance into the Indian subcontinent. Conversely, the southward retreat of the STJ signals the withdrawal of the monsoon.
- Influence on Rainfall Patterns: The Tropical Easterly Jet Stream, which forms over the Indian subcontinent during the summer, plays a crucial role in enhancing the southwest monsoon. It helps in the distribution of monsoon rains by influencing the flow of moist air from the Indian Ocean over the land.
- Seasonal Shifts: The STJ flows along the southern slopes of the Himalayas in winter and shifts northwards in summer, moving along the northern edge of the Tibetan Plateau. This seasonal migration is closely linked to the monsoon’s timing and intensity.
- Pressure Systems: The jet streams influence atmospheric pressure systems, which are critical for monsoon dynamics. For instance, the presence of high-pressure systems in the upper atmosphere can suppress monsoon activity, while low-pressure systems can enhance it.
KEY FINDINGS:
- Regional Rainfall Variations: Less sea ice in the central Arctic leads to lower rainfall in western and peninsular India, but more rain in central and northern India.
- Monsoon Onset: Lower sea ice levels in the Barents-Kara Sea region delay the monsoon’s onset and make it more unpredictable.
- Rossby Waves: Increased Sea ice in the Central Arctic enhances Rossby waves, affecting pressure systems over northwest India and the Mediterranean region.
- Jet Stream Shifts: Changes in sea ice levels influence the Asian jet stream, particularly the subtropical easterly jet, affecting atmospheric stability over India.
- Increased Variability: Climate change, by accelerating Arctic Sea ice reduction, exacerbates the variability and unpredictability of the Indian monsoon.
- Regional Weather Extremes: Lower Arctic Sea ice can lead to more frequent and severe droughts in some regions while causing excessive rainfall and flooding in others.
- Complex Interactions: The study highlights the intricate connections between Arctic Sea ice, global atmospheric circulation, and regional monsoon patterns.
THE WAY FORWARD:
- Enhanced Climate Research and Modeling: There is a need to expand research on climate dynamics, particularly focusing on the interactions between Arctic Sea ice and the Indian monsoon.
- Improved Weather Prediction Systems: Investing in advanced meteorological infrastructure, such as high-resolution regional climate models and automatic weather stations, can enhance the accuracy of monsoon predictions.
- Policy and Planning for Climate Adaptation: Formulating comprehensive climate adaptation policies at national and local levels is crucial. These should include strategies for water management, agriculture, and disaster preparedness to mitigate the impacts of erratic monsoon patterns.
- International Collaboration and Data Sharing: Collaborating with international research institutions and sharing data on climate models and observations can provide a broader understanding of global climate dynamics.
THE CONCLUSION:
This study emphasizes the critical role of Arctic Sea ice in shaping monsoon behavior, urging enhanced research and adaptive strategies to mitigate climate change impacts. Addressing these challenges is vital for ensuring resilience and sustainability in affected regions.
UPSC PAST YEAR QUESTION:
Q. How do the melting of the Arctic ice and glaciers of the Antarctic differently affect the weather patterns and human activities on the Earth? Explain 2021
MAINS PRACTICE QUESTION:
Q. Discuss the impact of declining Arctic Sea ice on the Indian Summer Monsoon Rainfall (ISMR). How do these changes influence regional rainfall patterns and what are the broader implications for India’s climate
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