- Relatively new natural phenomenon identified in the Indian Ocean, which is influencing SL in various ways
As we know, the ocean covers 70% of the earth's surface. Importantly, oceans have become the heart of our planet, because they sustain marine habitats, give us oxygen, absorb 25% of the carbon dioxide, and use their vast network of flowing currents to control the temperature on a worldwide scale. However, at present, the entire world is experiencing the impacts of rising sea surface temperatures (SSTs) creating numerous negative impacts on the coastal states and the entire planet.
Moreover, Sri Lanka, as an island nation located in the middle of the Indian Ocean, has significant lands and experiences unique tropical weather patterns throughout the year. On the other hand, the western coast of the country is open to the Arabian Sea, while the eastern coast is open to the Bay of Bengal. Indeed, the latitudinal location, various modulations of the inter-tropical convergence zone (ITCZ), and monsoon weather phenomena are identified as prominent factors which are influencing the Sri Lankan climate. In particular, different ocean circulation patterns, currents, and gyres take place in two different ocean areas, affecting the country’s climate in several ways. Hence, an understanding of the natural phenomena taking place in the Indian Ocean is much required, since the country is located in the middle of it.
Importantly, it was believed that the impacts of the El Nino – southern oscillation (ENSO) and the Madden-Julian oscillation (MJO) are the two major natural phenomena influencing the Indian Ocean which is affecting the change climate pattern of Sri Lanka as well. However, recent studies have identified that the Indian Ocean dipole (IOD) is the most significant natural phenomenon occurring within the Indian Ocean, which has created direct and indirect impacts on climate changes for the Indian Ocean rim countries since the 1980s. Moreover, it has been identified that there are numerous direct and indirect influences by the IOD to Sri Lanka as well. Moreover, it has been examined that the citizens of Sri Lanka do not have much conversations on the phenomenon of the IOD, even though it creates tangible long-term and short-term impacts to the country.
What is the IOD?
In particular, a climatic event that takes place in the Indian Ocean is called the IOD. The differential in SSTs between the Indian Ocean's eastern and western portions is known as the IOD. Also, the temperature and weather patterns in the surrounding areas, which include portions of Australia, South-East Asia, and Africa, can be greatly impacted by the IOD. Furthermore, warmer-than-average SSTs to the western part of Indonesia, and colder-than-average SSTs off the east coast of Africa are the main drivers of the IOD's negative phase. This arrangement of SSTs supports regular circulation. On the other hand, warmer-than-usual SSTs off the African coast and colder-than-usual SSTs to the western part of Indonesia are the main drivers of the IOD's positive phase. Easterly winds build up throughout the equatorial Pacific, reversing the normal circulation caused by this arrangement of SSTs. Also, the IOD is intensifying locust swarms in Africa, and exacerbating Australian bushfires. The below figure expresses the phenomenon of the IOD.
Significance of the IOF for SL
More importantly, since Sri Lanka is located in the middle of the Indian Ocean, the country is very vulnerable to the various climate-related influences made by the IOD. In particular, positive and negative IOD significantly influences the rain pattern of Sri Lanka. Indeed, it has been identified that during the positive IOD, rainfall increases and that the negative IOD decreases the rainfall of the country. For instance, the wet zone of Sri Lanka experiences a significant rainfall increase during the positive IOD, which causes flash floods, damage to the agricultural sector, and property damage. Moreover, it is possible to distinguish between three different types of IOD events such as unseasonal, normal, and prolonged IOD events. For instance, they are defined as those that develop and mature primarily within the months of the June-August season and the September-November season.
With that, it has been identified that June to December in Sri Lanka is vulnerable to the impacts of the IOD. On the other hand, positive IOD increases the precipitation in the wet zone of the country, also covering the Western, Southern, Central, North-Central, and Sabaragamuwa Provinces, while negative IOD causes increased drought in the dry zone of the country. Indeed, the IOD hurts the agricultural sector of the country during the both Yala and Maha cultivation periods, since the IOD’s positive and negative phases occur from June to December. For instance, heavy rains and drought similarly affect the agricultural sector of the country, which challenge the national security of the country in terms of human, food, economic, and health-related security.
For instance, the IOD is driven by the differential SSTs occurring in the western and south-eastern Indian Ocean. Indeed, differential SSTs create several impacts on the easterly and westerly wind circulation and ocean circulation pattern within the Indian Ocean region (IOR). Importantly, the geographically centralised location of Sri Lanka within the Indian Ocean is directly impacted by the change in wind circulation and ocean circulation, creating unpredictable rainfall or drought.
Likewise, ocean circulation and wind circulation impact the coastal upwelling as well. Importantly, the southern coast of the country is significant, and is the primary location of upwelling taking place throughout both the monsoon seasons. Indeed, during the southwest monsoon, higher amounts of surface chlorophyll were noted. On the other hand, upwelling raises frigid waters rich in nutrients to the surface, promoting the growth of seaweed and phytoplankton blooms. Moreover, large populations of animals higher up the food chain, such as fish, marine mammals, and seabirds, rely on the phytoplankton blooms as their primary source of energy.
In particular, upwelling taking place during the positive IOD creates a good fishing ground for the fishermen. However, the absence of fishing grounds during the negative IOD creates impacts on national security in terms of food, health, economic and social security when considering the large fishing community of the country.
The way forward
In contrast, oceans are considered the heart of our planet for various reasons. In particular, being an island nation located in the middle of the Indian Ocean has a significant influence from the surrounding water body of the Indian Ocean. Importantly, recent studies have explored that the IOD is the most prominent natural phenomenon impacted by the IOR countries since the 1980s. Indeed, from June to December, positive and negative IODs are influencing the climate of the country. Moreover, positive IOD increases the rain, while negative IOD decreases the rain. Indeed, changes in rain patterns cause floods, drought, coastal upwelling, and many more issues. However, knowledge about IOD among Sri Lankan citizens was found to be very limited, even though IOD is the most influencing weather phenomenon occurring in the Indian Ocean for the country. Finally, it has been identified that the IOD can influence the national security of the country in terms of human, health, economic and food security. Hence, planning and starting to take quick action on high-availability disaster recovery, improved agricultural productivity, mitigation, tourism, global warming, and weather forecasting and modelling, are necessary to be monitored, studied, and paid attention to.
(The writer is a Commander who serves as a Military Research Officer (Navy) at the Institute of National Security Studies of Sri Lanka (INSS), under the Ministry of Defence. The opinions expressed are his own, and not necessarily reflective of the Institute or the Ministry)
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The views and opinions expressed in this article are those of the author, and do not necessarily reflect those of this publication