El Nino may be drying out the southern hemisphere — here’s how that affects the whole planet

Subject : Geography

Section: Physical geography

Context:

A new study has shown that the southern hemisphere has been drying out more than the northern hemisphere over the past two decades (2001-2020).

Key findings of the study:

The principal cause is the weather phenomenon known as El Nino, which occurs every few years when ocean water in the eastern Pacific is warmer than usual.
Even though the southern hemisphere has only a quarter of the global land area (excluding Antarctica), it appears to have a substantially greater effect on global water availability than the northern hemisphere.
- Water availability is the net difference between the amount of water supplied to the landscape, in the form of rainfall on land, and the water removed to the atmosphere by general evaporation or by plants through their leaves.
Regions facing a decrease in water availability: South America, most of Africa, and central and northwestern Australia.
The water availability in the northern hemisphere is more or less balanced due to extensive human influences such as irrigation, dams and food production.

Impact of drying of Southern continents:

South America includes the Amazon rainforest, which is a key regulator for the climate, as well as a globally important habitat for species and home to many Indigenous communities.
Drying of the rainforest would reduce vegetation, increase the risk of fire, potential to release billions of tons of carbon currently locked into forest vegetation and soils.
South America is a major agricultural exporter of soybeans, sugar, meat, coffee, cassava, and fruits for the global market. Changes in water availability will increase stress on food systems globally.
Change in vegetation patterns. Climate vulnerability to coastal populations.

El-Nino phenomenon:

El Niño means Little Boy or Christ Child in Spanish.
It is a weather phenomenon that describes the anomalous warming of surface waters in the eastern tropical Pacific Ocean. It happens more often than La Nina.
During an El Nino year, air pressure falls across broad regions of the central Pacific and along the South American coast.
In the western Pacific, a weak high replaces the regular low-pressure system.
Weak Walker Cell trade winds are diminished as a result of this shift in pressure pattern. Walker Cell can even be reversed at times.
This decrease permits the equatorial countercurrent (current through the doldrums) to amass warm ocean water along the Peruvian and Ecuadorian coasts.
The concentration of warm water causes the thermocline in the eastern Pacific Ocean to descend, cutting off the upwelling of cold deep ocean water near Peru’s coast.
El Nino weather patterns bring dryness to the western Pacific, rain to South America’s equatorial coast, and convective storms and hurricanes to the central Pacific.

Source of this article: Down to earth