The Bay of Bengal is the largest basin in the world. It has been called the Bay of Bengal after the evolution of Bengal delta. The bay is included within Andaman & Nicobar Islands, Palk Straits, Gulf of Mottama, Gulf of Manar, Andaman sea & some part of the Malacca strait. Simply the bay is considered as a stretch of sea from the Indian ocean to the pacific but in actual sense, it is the heart of global history. Because, it is the area of competition between 7 countries as well as: India, China, Bangladesh, Nepal, Myanmar, Srilanka & Thailand for collecting the marine resources. From the view of pre-history, it has been keeping a significant role both in economic & ecological values.
Location & Boundary:
The Bay of Bengal is located in South Asia & South-East Asia region. It is a northern extension of the Indian Ocean positioned between India & Srilanka in the West, Bangladesh to the North, Myanmar in the southern part & Northern part of the Andaman –Nicobar islands to the East.
The bay is bordered in the East by the western coast of Myanmar including the Gulf of Motlama & western coast of the Isthmus of Kra including Phuket of Thailand or the Andaman Sea. The northeastern coast of India’s entire south coast of Bangladesh & northern coast of Mayanmar makes its border to the north.
The Bay Of Bengal is adorned with many features. Those features are as follows :
- Basin Areas: Bangladesh, India, Indonesia, Malaysia, Myanmar, Thailand & Srilanka.
- Surface area: ( 2.2 million km2) precisely 2172000 km2
- Average depth: 2600 meters
- Maximum depth: 4694 meters
5.Major Flora: Seagrass, Marine Algae, Navicula, Chorella, Azolae, etc
6.Major Funnas: Coral Reef, Tropical Dolphin, Sharks, Olivine Ridley Sea Turtle, Gave fish(Tuna, Marlins), Irrawaddy Dolphin
7.Major Rivers: Kaveri, Krishna, Godawari, Ganges, Brahmaputra, Irrawaddy
8.Primary Inflow: Indian Ocean
The topography of Bay Of Bengal:
The surface topography of the Bay Of Bengal is mainly determined by the U shaped basin with its south opening to the Indian ocean. But in the central part of the bay, it is extremely simple. The head of the bay from the Ganges-Deltic region is comparatively flat & narrow type & cut only by the submarine canyon. In fact, in many places, submerged valleys dissect with some plain type topographical features.
The surface temperature is not the same everywhere in the bay. Near the offshore areas, the uniform temperature is can be seen but temperature gradually changes towards the north. The mean annual temperature of the surface water of BoB is about 28° C.The maximum temperature is observed on May 30°c & the minimum temperature 25° c in January- February.
From the open part of the Bay surface salinity varies from 32% to 34.5% ppt & in the coastal regions salinity varies from 10% to 25 %. But in the river mouth, the salinity decreases to 5% or even less. Salinity may decrease to 1% during the summer season & increase to 15% to 20% in winter season along the Ganges-Brahmaputra deltic coast salinity increment is seen from the coast towards the open part of the bay.
The density distribution is directly related to salinity. As density changes proportionately with the unit change of salinity. For example, at the head of the BoB where lower salinity shows relatively low density & its variation exists as an extensive pattern throughout the year. On the contrary, density is relatively high in the southern portion of the area where salinity is high. Generally, surface density values vary from 21.75 in February to greater than 22.0 in August.
In the Bay Of Bengal, the semi-diurnal tide type is mainly seen where 2 high tides & 2 low tides periodically occur existing as a period of 24 hours & 52 minutes. Due to the influence of bottom relief & the configuration of the coast, the high tide occurs & it is prominent in shallow water or in the bay. Actually, the tides develop in the mouth of the rivers like Hoogly & Meghna.
In the Bay, currents are not constant & determined by the strength & duration of the wind. Surface current circulation is generally clockwise from January to July & counter-clockwise from August to December. One of the most important issues of Bay Of Bengal that both Upwelling & Sinking exits on the eastern coast. Upwelling is a continuous process wherein the sub-surface water moves towards the surface & reversely the surface water moves downward causing sinking. Currents continuing from the northeast direction generally persist longer time & flows at greater speed due to the stronger southeast monsoon.
Waves are not followed as constant & regular patterns in the BoB( Bay Of Bengal). It is changed due to wind direction & spatial variations. In the deeper part of the bay, the waves are seen to be more destructive & conversely less destructive at the shallow portion of the bay. In general, mainly 3 types of ocean waves can be seen in the Bay Of Bengal such as:
3.Shallow internal waves.
Standing waves by the name refer waves moving from forward to backward without changing its exact position. Internal waves refer only to the vertical oscillations in the sea. Shallow internal waves are the vertical oscillation also but it occurs within a short period of time.
Sediments in the BoB are dominated by terrigenous deposits from the rivers, derived mainly from the Indian continents & Himalayas. Calcareous clays, organic matter & Oozes are found near the Andaman & Nicobar Island & atop the Ninetyeast ridge. The large volume of continental sediments is being discharged by Ganges & Brahmaputra river into the BoB & the finer sediment particle reaches even 7° latitude. The sediment deposition is exceptionally thick( about 21 km) at the apex of the Bengal fan’s offshore region & sediment thickness gradually decreases about 8 to 2 km in the central & southern parts.
Climate & Natural Calamities in the Bay Of Bengal:
The climate of the BoB is mainly determined by the Monsoons. From November to April a continental high-pressure system produces northeast winds (the northeast monsoon) in the northern part & characterized by the winter season. During June to September (monsoon summer)the rain-bearing southeast monsoon prevails, as intense heat produces a low –pressure system over the continent and subsequent airflow from the ocean ( BoB Britania).
The Tropical storms, Cyclone, Tornado, Tsunami, Coastal Erosion, Salinity intrusions are the more common natural calamities which occur frequently in the Bay Of Bengal. Environmental pollution is another concerned problem.
Importance Of Bay Of Bay Bengal For Bangladesh:
Bangladesh is located on the northwestern part of the Bay Of Bengal, as a result, it has a very important strategic value for security, politics & economic perspectives. Bangladesh is a prominent member country of BIMSTEC (The Bay Of Bengal Initiative For Multi-sectoral, Technical & Economic Co-operation) wherein 7 South Asian countries can easily operate trade & economic activities. Bangladesh can easily access one or two deep seaports for opening trade facilities with India, Nepal, Bhutan, China, and for herself also. Due to being a 1st line littoral state of the Indian ocean, Bangladesh has a great opportunity for accessing as a good source of marine resources from the BoB. The Exclusive Economic Zone(EEZ)of Bangladesh lies from the baseline to 200 nautical miles seaward. A total of 442 marine & 76 species fish are collected every year from the sea areas of the bay. BoB plays a vital role in Bangladesh to exchange foreign economics. At present, “Blue economy” is the main concerned issue for Bangladesh for supplying marine resources gathered from the access boundary of BoB.
The Bay of Bengal is not only a bay but also a great reservoir of marine resources & bio-diversities. It provides a new hope & sprit for Bangladesh. It has the possibility of emerging a conflict in which the “Water War” can be brought about among the Seven countries in the future. So it is the time to develop a complex inter-related network of the Ramsar Site including its coastal areas in which network may help to improve a common strategy for the proper management & conservation of its resources. All people should be aware of for conserving the marine resources in a sustainable way & make the bay a friendly based eco-system bio-diversities for ensuring a better life in the future.
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Md Omar Faruk
Department of Coastal Studies & Disaster Management,
University Of Barishal, Bangladesh