INDIAN OCEAN DIPOLE - GEOGRAPHY
News: Indian
Ocean Dipole: What is it, how it can limit El Nino effects
What's in the news?
● With
the El Nino phenomenon almost certain to affect the Indian monsoon this year,
high hopes are pinned on the development of a positive Indian Ocean Dipole
(IOD) and its ability to counterbalance the El Nino effect.
Key takeaways:
● It
is also a much weaker system than El Nino, and thus has relatively limited
impacts.
Indian Ocean Dipole:
● IOD
(sometimes referred to as the Indian
Nino) is a similar phenomenon to the El Nino, playing out in the relatively smaller area of the Indian Ocean
between the Indonesian and Malaysian coastline in the east and the African
coastline near Somalia in the west (also referred in means of Arabian Sea
and Bay of Bengal too).
● One
side of the ocean, along the equator, gets warmer than the other. IOD is said
to be positive when the western side
of the Indian Ocean, near the Somali coast, becomes warmer than the eastern
Indian Ocean. It is negative when
the western Indian Ocean is cooler.
● A
positive IOD event is often seen
developing at times of an El Nino, while a negative
IOD is sometimes associated with La Nina.
Impacts of Positive and Negative IOD:
● Positive IOD does have
the potential to offset the impacts of El Nino
to a small measure in neighbouring areas.
● A
positive IOD helps rainfall along
the African coastline and also over the Indian sub-continent while suppressing
rainfall over Indonesia, southeast Asia and Australia.
● The
impacts are opposite during a negative
IOD event. In this, there is a lesser rainfall over the African coastline
and greater rainfall over Indonesia, southeast Asia and Australia.
Impacts of IOD on Indian Ecosystem:
● The
India Meteorological Department (IMD) has also reported an 80% chance of a
positive IOD during the June-August 2023 season. The development of a positive
IOD would have implications for weather patterns in the Indian Ocean region.
1. Rainfall Distribution:
● IOD
significantly influences rainfall patterns in the Indian Ocean region.
● During
a positive IOD, there is increased
convection and rainfall along the African coastline and over the Indian subcontinent.
● Conversely,
a negative IOD leads to suppressed
rainfall in these regions.
2. Drought and Floods:
● Positive IOD
events can bring above-average rainfall to the affected regions, which can
alleviate drought conditions and replenish water resources.
● However,
this increased rainfall can also result in flooding and water-related disasters
in certain areas.
3. Agricultural Productivity:
● IOD
has implications for agriculture as it affects the availability and
distribution of rainfall.
● Positive IOD
events can enhance agricultural productivity in the affected regions, while negative IOD events may lead to reduced
crop yields and agricultural challenges.
4. Fisheries:
● IOD
impacts the productivity of marine ecosystems.
● During
positive IOD, increased upwelling of
nutrient-rich waters occurs, which promotes higher fish stocks and benefits
fisheries.
● In
contrast, negative IOD can disrupt
the marine food chain and impact fish populations.
5. Coral Bleaching:
● IOD
influences sea surface temperatures, and prolonged positive IOD events can contribute to increased sea surface
temperatures in the affected regions. This can lead to coral bleaching,
negatively impacting coral reefs and marine biodiversity.
6. Indian Monsoon:
● IOD
can influence the strength and distribution of the Indian monsoon rainfall.
● Positive IOD
events are generally associated with enhanced monsoon rainfall over the Indian
subcontinent, while negative IOD
events can lead to reduced monsoon rainfall.
7. Weather Extremes:
● IOD
can contribute to the occurrence of extreme weather events such as heatwaves,
storms, and tropical cyclones in the Indian Ocean region.
8. Economic and Social Impacts:
● The
impacts of IOD on rainfall, agriculture, fisheries, and other sectors have
direct economic and social implications.
● These
impacts can affect livelihoods, water
availability, food security, and overall economic development in the
affected regions.
Thus,
an IOD can either aggravate or weaken
the impact of El Nino on Indian monsoon. If there is a positive IOD, it can
bring good rains to India despite an El Nino year. Similarly, a negative IOD
and El Nino had cooperatively produced deficient rainfall.