News
Reconstructing past deep-water circulations of Indian Ocean
Global overturning circulation — the equatorward transport of cold, deep waters and the poleward transport of warm, near-surface waters — controls ocean heat distribution and atmospheric carbon dioxide levels, thus playing a critical role in global climate, says a report published by The Hindu yesterday.
It said: Studies have indicated that tectonically driven changes in the ocean gateways such as the closure of the Central American Seaway, a body of water that once separated North America from South America, since the late Miocene period, had a dramatic impact on the circulation.
It is thought that tectonic changes might have led to the formation of two separate water bodies — northern component water in the North Atlantic and Antarctic Bottom Water (AABW) in the Southern Ocean. Consequently, it is also hypothesised that there would have been large-scale changes in the Deep Water Circulation (DWC) in the oceans across the world, thus impacting global climate through ocean-atmosphere carbon dioxide and heat exchanges.
But these formulations have remained untested due to lack of adequate data. Some records that are available are from near the deep-water formation regions mostly from the Pacific and the Atlantic Oceans. Hence, they might not necessarily reflect the impact and change in deep water circulation.
Now, the Indian Ocean does not have any major deep-water formations of its own. It acts only as a host for NCW and AABW. Further, the northern parts of the Indian Ocean are located at one of the terminal ends of the GOC, far away from the deep-water formation regions and oceanic seaways. These specific features could make the northern Indian Ocean an ideal basin to do this.
Few studies have been carried out in the Indian Ocean to reconstruct past deep water circulations based on iron-manganese crust records and authigenic neodymium isotope composition of sediment cores. But iron-manganese crusts are situated at deeper depths and are bathed only by AABW, making it suitable only for the reconstruction of the history of AABW, and authigenic neodymium isotope records are available only from the Bay of Bengal region. But they too cannot help as the Himalayan rivers that empty into the Bay also bring in substantial amounts of Neodymium particulates.
A new study by a team of researchers from the Goa-based National Centre for Polar and Ocean Research and the School of Earth, Ocean and Atmospheric Sciences in Goa University has now sorted out the issue.
The scientists have generated an authigenic neodymium isotope record from the Arabian Sea and reconstructed the DWC record of the Indian Ocean for the period from 11.3 million years ago (Miocene era) to 1.98 million years ago (Pleistocene era).
“The record shows a clear shift from the Pacific water dominated deep circulation system before about nine million years ago, to the onset of a modern-like deep water circulation system in the Indian Ocean comprising of Antarctic bottom water and northern component water during the Miocene-Pliocene transition (about six million years ago). Our finding suggests a widespread impact of the late Miocene Central American Seaway closure on the evolution of ocean deep water circulation and validates the so-called Panama Closure Hypothesis,” says Dr. Waliur Rahaman from the National Centre for Polar and Ocean Research (NCPOR) and one of the corresponding authors.
The two months long expedition was carried out on-board drilling vessel R/V JOIDES Resolution from March 31 to May 31, 2015.
Commenting on the findings, Dr. Sambuddha Misra, Associate Professor, Centre for Earth Sciences, Indian Institute of Science, who was not part of the research work, says the study is highly significant since it provides unequivocal evidence in support of the theory that the closing of the gap between North and South America had led to the evolution of the modern form of GOC. The work is also commendable as it involved extremely difficult measurements, he adds.
Marking the completion of two years of the ‘Vision’ Programme, students from Pinnawala Central College and Matale Siri Seevali College were given an opportunity on Thursday (24) to visit the Presidential Secretariat.
The ‘Vision’ Programme was launched for schoolchildren jointly by the Presidential Secretariat, the Ministry of Education and the Department of Communication of the Parliament of Sri Lanka.
Following a visit to the former Parliament building at the Presidential Secretariat, the students were also briefed on the history of Parliament.
The role of the President’s Fund and its importance to schoolchildren were explained by Senior Additional Secretary to the President Roshan Gamage.
The ‘Vision’ commemorative book, featuring the two-year journey of the ‘Vision’ Programme and its special activities, was also presented to the participating schools.
As part of the programme, valuable plants were also presented to the schools as a symbolic gesture underscoring the importance of environmental conservation.
Director General of Public Relations Dharmasiri Gamage, the Director and Assistant Director of the Tri-Services Security Coordination Unit, the principals and teaching staff of Pinnawala Central College and Matale Siri Seevali College, and students were among those present on the occasion.
President’s Media Division (PMD)
Opposition and SJB Leader Sajith Premadasa yesterday vowed that an SJB government would repeal the 22nd Amendment (22A) to the Constitution.Premadasa made the pledge while addressing thousands of SJB supporters who gathered near Parliament to protest against 22A.
Addressing the rally at Polduwa Junction, Battaramulla, Premadasa said the proposed constitutional amendment would undermine democracy and judicial independence and enable the concentration of political power in the Executive.
“Even if they pass it, under an SJB government we will scrap it,” Premadasa told the gathering, claiming that 22A was aimed at paving the way for a one-party state and placing the State under the control of a single political party.
Braving the rain, Premadasa said they had gathered there peacefully and had no intention of resorting to violence.
“We have gathered here to protect democracy,” he said, challenging the government to hold Provincial Council elections if it was confident of facing the people.
Premadasa said the SJB was prepared to work with any democratic and clean political force committed to the country’s progress and public welfare, amid ongoing discussions on cooperation among Opposition parties, including the United National Party.
Premadasa also accused groups aligned with the government of attempting to discourage people from attending the protest through statements and other measures.
SJB General Secretary Ranjith Madduma Bandara said the protest had been organised against the proposed amendment, which the party had opposed on the grounds that it could pave the way for authoritarianism.
The demonstration began around 9 a.m. at Polduwa Junction and coincided with Parliament taking up the proposed 22nd Amendment for debate. Proceedings on the Bill are scheduled to continue today (25).
The Supreme Court has determined that the proposed amendment does not require approval at a referendum and could be passed with a special majority in Parliament.
Meanwhile, traffic congestion was reported on roads surrounding Parliament and Polduwa Junction following the demonstration.
Security was also tightened in and around the Parliamentary complex, with a heavy police presence observed at Polduwa Junction and near the main entrance to Parliament.
Two retired female Navy petty officers were ordered to be remanded until October 5 over their alleged involvement in the abduction and disappearance of two women in Trincomalee during the war.
Trincomalee Chief Magistrate M.S.M. Samsudeen yesterday ordered that the two suspects be remanded and directed that they be produced for an identification parade on October 5.
The suspects, residents of Chilaw and Haputale, were arrested after appearing before the CID in connection with another court case. They were subsequently produced before the Trincomalee Magistrate’s Court.
The court was informed that the investigation concerned the alleged abduction of Sasikumar Thenmoli and Mary Delsia, residents of Paalaiyootru, Trincomalee, on or around May 13, 2008.
The CID told court that information uncovered during its investigations indicated that the two women had allegedly been detained at an underground location known as the “Gun Site” at the Trincomalee Naval Base while the two suspects were serving in the Navy. The women were subsequently reported missing.
Further investigations into the alleged abduction and disappearance of the two women are continuing.
‘Vision’ Programme Marks Two Years
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