Context
In a survey researchers from India’s National Centre for Polar and Ocean Research (NCPOR), have found that seasonal modifications in the Arctic sea ice is affecting the Indian monsoon.
Indian Summer Monsoon Rainfall
- The Indian summer monsoon rainfall (ISMR) over the Indian subcontinent, from July to September, is one of the most prominent monsoon systems within the world.
- In summer months, sunlight warms the Central Asian and Indian landmass more and quicker than the encompassing ocean.
- This creates a low strain band at the Tropic of Cancer known as the intertropical convergence zone (ITCZ).
- Trade winds blowing from the southeast are eventually deflected towards the Indian landmass because of the Coriolis force and the low pressure when they cross the equator.
- As they blow over the Arabian Sea, the winds select up moisture and deposit that as rain over India.
- Over the landmass, the southwest monsoon splits into two. The Arabian Sea arm brings rain to the west coast whilst the alternative arm travels to the Bay of Bengal and brings rain to India’s eastern and northeastern parts.
- The palms ultimately converge over Punjab and Himachal Pradesh because the Arabian Sea arm moves inward and the Bay of Bengal arm actions along the Himalaya.
Complexity of the Indian Summer Monsoon Rainfall
- For a long time, climate models have shown that the floor temperatures of the Indian, the Atlantic, and the Pacific Oceans have an effect on the ISMR.
- The circum-global teleconnection (CGT), a big-scale atmospheric wave flowing at the mid-latitudes, seemed to noticeably have an effect on the monsoon as well.
Influence of Arctic sea ice on the Indian monsoon
- The research reveals that much less sea ice in the primary Arctic leads to lower rain in western and peninsular India however more rain in crucial and northern India.
- On the other hand, lower sea ice ranges inside the upper latitudes, in particular inside the Barents-Kara Sea place encompassing the Hudson Bay, the Gulf of St. Lawrence and the Sea of Okhotsk, postpone the monsoon’s onset and render it more unpredictable.
Other atmospheric systems influencing pattern
- The scientists discovered that once sea ice stages within the Central Arctic increase, the warmth transferred from the ocean to the ecosystem triggers a cyclonic flow at slightly lower latitudes, like within the North Atlantic.
- This creates the Rossby waves, viz a fast-flowing flow of air, created via the earth’s rotation and differences in temperature and weather systems that flow west to east.
- It results in high stress over northwest India and low stress over the Mediterranean region.
- This in turn strengthens a slim, concentrated band of wind, referred to as the Asian jet circulation, over the Caspian Sea, inflicting the subtropical easterly jet, a jet flow blowing over the Indian subcontinent at some point of summer, to shift northward.
- It brings more rain over western and peninsular India.
- On the other hand, as sea ice ranges lower in the place, warmness rises from the Barents-Kara sea, developing an anticyclonic flow (calm, clean skies) over northwest Europe.
- This disturbs the top atmospheric location over subtropical Asia and India and promotes high rainfall over northeastern India while leaving vital and northwest areas of the country without a good deal.
Role played by climate change
- Climate change, by accelerating the reduction of Arctic sea ice, exacerbates the range and unpredictability of the ISMR.
- Lower Arctic sea ice can result in more frequent and high droughts in some regions at the same time as causing immoderate rainfall and flooding in others.
- Further the observation indicates the pressing need to enlarge research on climate changes and for scientists to prepare more accurate forecasts of the ever-converting monsoons.
Source: The Hindu