Victoria Mode in North Pacific Linked to Expanding Aridity in Northern India

A study published by researchers from the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) in the journal MAUSAM highlights how an oceanic cycle called the Victoria Mode (VM) influences long-term climate shifts and rainfall reduction across northern India. Examining 30-year climatological windows between 1951 and 2020 on 0.25-degree gridded squares, the researchers observed a marked eastward migration of semi-arid climate zones over the Indo-Gangetic plains.

Observed Climatic Shifts Across Regions

The study highlights notable variations in regional climate profiles across India:

• North-West India: The hot, semi-arid steppe zone expanded from 25.7% of the area during 1951–1980 to 33.1% during 1991–2020, while the milder temperate zone declined from 25.8% to 18.7%. The eastern limit of the steppe zone moved from western Uttar Pradesh towards the eastern parts of the state.
• Eastern and North-Eastern India: Regions such as Bihar, Gangetic West Bengal, and eastern Uttar Pradesh experienced declining moisture influx. In the north-east, the tropical savannah zone dropped from 18.4% to 11.8%, while temperate classifications increased from 74.8% to 82.5%.
• Peninsular India: In contrast, the semi-arid steppe zone contracted from 30.3% to 16.4%, while tropical savannah expanded from 61.6% to 75.7%, with tropical monsoon zones growing along coastal Karnataka, Konkan, Goa, Kerala, and Mahe.

Oceanic Teleconnections: Victoria Mode vs ENSO and PDO

The Victoria Mode represents a recurring sea-surface temperature pattern of warm and cool waters in the North Pacific, structurally independent of the Pacific Decadal Oscillation (PDO). The negative phase of the VM has been associated with weakening moisture transport towards northern India. While the Indian monsoon is widely known to be vulnerable to El Niño events and phases of the PDO, understanding additional North Pacific oceanic cycles such as the VM is critical for evaluating long-term risks to food security, agrarian livelihoods, and regional displacement caused by shifting aridity boundaries.