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Reconstructing past deep-water circulations of Indian Ocean

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The global conveyor belt, shown in part here, circulates cool subsurface water and warm surface water throughout the world. The Atlantic Meridional Overturning Circulation is part of this complex system of global ocean currents.

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.



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Sun directly overhead Neriyakulam, Punewa, Kebithigollewa, Pankulam and Sinhapura at about 12.10 noon today (31)

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The sun is going to be directly over the latitudes of Sri Lanka from  28th of August to 07th of September due to its apparent southward relative motion.

The nearest places of Sri Lanka over which the sun is overhead today (31) are Neriyakulam, Punewa, Kebithigollewa, Pankulam and Sinhapura about 12.10 noon.

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BASL takes exception to Justice Ganepola being denied a place in SC

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… highlights injustice caused to Justice R. Gurusinghe

The Bar Association of Sri Lanka (BASL) has alleged that due to the failure on the part of President Anura Kumara Dissanayake to fill the existing vacancies in the Supreme Court, a Senior Justice of the Court of Appeal, Justice Dhammika Ganepola, retired at the age of 63 without being considered for, or granted, a promotion to the Supreme Court, to which he was well entitled. The BASL pointed out at the time of Ganepola’s retirement there were four vacancies in the Supreme Court.

In a letter dated 17 August, 2026, addressed to President Dissanayake, the BASL declared that the failure to promote and recognise Ganepola’s distinguished judicial service, resulting in his retirement at the age of 63, is indeed a loss to the Judiciary.

A top BASL spokesman told The Island yesterday (30) that the Bar Council, over the weekend, had decided to release the hitherto confidential letter.

The official said that they also wanted to remind the President of his assurance given to BASL, on 12 August, 2026, that vacancies in the Supreme Court and Court of Appeal would be filled as soon as possible, within a month.

The following is the text of the BASL letter, signed by  Rajeev Amarasuriya, President, BASL, and its Secretary Nalin De Silva: “We write further to our letters dated 29th December 2025 and 30th June 2026 in relation to the above, to which we have not received any response.

We also refer to our meeting with Your Excellency on 12th August. As discussed during the meeting, there have been vacancies in the Supreme Court since May 2025, and the number of vacancies has now increased to four (04). There are also four (04) vacancies in the Court of Appeal. These are all matters we have already written to Your Excellency about.

Your Excellency informed the BASL Delegation when we met that you would be taking steps to make recommendations to fill these vacancies as soon as possible, within a month.

We write to reiterate the importance of giving due consideration to the criteria set out in our aforesaid letter dated 29th December 2025. We also wish to emphasise that, in making judicial appointments and promotions, seniority should be given due priority, in keeping with longstanding practice, until such time there are objective and defensible guidelines governing the assessment of merit.

The only justifiable departure to this criterion would be where there exists a specific and recognized demerit in respect of the particular Judge concerned or such other known compelling circumstances that are objectively identifiable such as where a Judge has previously been overlooked for promotion unfairly or conversely, where a Judge has been unfairly previously granted promotions above others.

This approach will safeguard both the integrity of the Judiciary and the trust reposed in it by the public.

Further, while there has been considerable discussion and representation by the Government regarding the importance of retaining experienced judges, as reminded to Your Excellency at our said meeting that, only a few months ago on 8th May 2026, a Senior Justice of the Court of Appeal, Justice Dhammika Ganepola, retired at the age of 63 without being considered for, or granted, a promotion to the Supreme Court, to which he was well entitled, and in which there were four vacancies at the time.

The failure to promote and recognise his distinguished judicial service, resulting in his retirement at the age of 63, is indeed a loss to the Judiciary.

We also drew Your Excellency’s attention at the said meeting to the fact that the Senior-most Justice of the Court of Appeal, Justice R. Gurusinghe, who joined the Judicial Service in 1996, who also Acted in the Office of President of the Court of Appeal (appointed by Your Excellency) on 11th May 2026, is due to retire at the end of this month. In fact, we learnt through the Media that Her Ladyship then Chief Justice Justice Murdu Fernando, PC, had previously in July 2025 recommended to Your Excellency the promotion of Justice R. Gurusinghe to the Supreme Court, but the same is pending from that time.

 He too is well deserving of promotion to the Supreme Court and has already been recommended by the former Chief Justice, and his case must also receive due and urgent consideration before his impending retirement.

We hope that Your Excellency will take due note of and give due regard to the concerns of the Bar, as well as to the established principles, practices and conventions governing judicial appointments, when taking steps to fill these vacancies.

On this, Your Excellency is already open to the accusation that these vacancies have been kept open, to fill with favourites of the Government which is yet another serious indictment on the independence of the judiciary which accusation would be confirmed if recommendations are made outside established practice.

Moreover, the BASL expresses grave concern that withholding promotions of Judicial Officers for extended periods of time places undue pressure on Judicial Officers in the discharge of their duties and constitutes both directly and indirectly, interference with the independence of the Judiciary, in addition to the strain obviously caused to the dispensation of justice in other Courts and the stifling and delay of career progression of Judges legitimately entitled to promotions.

We do hope that Your Excellency would take due note and cognizance of the foregoing when effecting these judicial promotions which have been long overdue and which have already adversely impacted the efficiency and effectiveness of the administration of justice.”

The BASL has copied the letter to Prime Minister Dr. Harini Amarasuriya, Speaker Dr. Jagath Wickremaratne, Opposition Leader Sajith Premadasa and all members of the Constitutional Council.

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Sajith challenges govt. to hold PC polls

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Sajith

Opposition Leader Sajith Premadasa on Saturday (29) challenged the government to hold the long-delayed Provincial Council elections, saying the polls would provide an opportunity to gauge the level of public support enjoyed by the administration.

Addressing a farmers’ meeting in Tissamaharama, Hambantota, Premadasa also criticised the latest Rs. 17 per kilogram increase in wheat flour prices, warning that it would push up the prices of bread, bakery products and other flour-based food items and place further pressure on households already struggling with the rising cost of living.

He said Sri Lanka ranked 120th among 130 countries in an international comparison of minimum wages, arguing that wages remained inadequate to meet the escalating cost of living.

Premadasa also questioned official assessments of living standards, asking whether a person could survive for an entire month on Rs. 17,315, a figure he attributed to the Department of Census and Statistics.

He claimed that between 30 and 40 percent of the population was living in poverty and called for a clear programme to help affected families improve their economic conditions.

Turning to the proposed 22nd Amendment to the Constitution, which seeks to increase the retirement age of superior court judges, the Opposition Leader accused the government of attempting to undermine judicial independence and interfere with democratic institutions.

He also criticised the government’s handling of poverty, employment, agriculture, healthcare and investment, saying more effective measures were needed to provide relief to people facing economic hardships.Premadasa called for stronger policies to attract foreign direct investment and urged the government to formulate a national strategy for developing the tourism industry.

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