ASIATODAY.ID, JAKARTA – An extraordinary ocean phenomenon occurred in the waters of the Mulut Kumbang Strait, Alor Kecil, East Nusa Tenggara. Within less than an hour, the tropical sea temperature suddenly dropped from an average of 28°C to as low as 12°C.
This extreme occurrence, known as an Extreme Upwelling Event (EUE), marks the first recorded case in the world, drawing the attention of oceanography experts from Indonesia—particularly researchers from Diponegoro University and the National Research and Innovation Agency (BRIN), along with several international partners.
According to Achmad Sahri, Senior Researcher at BRIN’s Center for Marine Biosystem Research, an EUE is a sudden and massive upwelling of very cold, deep-sea water to the surface.
“Normally, temperature drops caused by upwelling in tropical waters are only around two degrees Celsius, but in Alor we recorded a ten-degree plunge in less than an hour,” said Sahri on Friday, October 31, 2025.
Meanwhile, Prof. Anindya Wirasatriya, Head of the Oceanography Department at Diponegoro University and lead researcher of the study, provided detailed insight into how the event unfolded.
“This occurred simultaneously with a spring tide, which triggered vertical water movement at a velocity of around 0.012 meters per second. Along with the temperature drop, seawater salinity also increased from 30 PSU to 36 PSU, indicating that the upwelled water originated from deeper layers, where the temperature is lower and salinity is higher,” Anindya explained.
The EUE lasted between one and four days and could occur twice daily, following the semi-diurnal tidal cycle. This makes it a rare but critical phenomenon to understand due to its significant impact on local marine ecosystems.
Researchers noted that the Mulut Kumbang Strait EUE is the first and only event of its kind globally, as no similar occurrences have been reported in other tropical waters. The drastic temperature shift reflects unique local oceanographic and topographic processes unseen in other regions, making this event a globally rare and scientifically significant phenomenon.
“This is a unique case because it has never been reported in other tropical seas. It means the local dynamics and topography of the Mulut Kumbang Strait are special and trigger this rare event,” Anindya added.
He further explained that the EUE was triggered by complex interactions between tidal currents, deep-sea circulation, and steep underwater topography.
“During high tide, cold deep-sea water is pushed northward through an underwater channel, while the warm Indonesian Throughflow (ITF) moves southward. The collision of these opposing currents generates strong turbulence that forces the cold water to the surface,” said Anindya.
The phenomenon only occurs between August and November, suggesting a strong influence of the annual monsoon system on current and temperature dynamics. The combination of tidal forces, deep-sea flow, steep seabed structure, and monsoonal effects makes the Mulut Kumbang Strait an ideal site for such rare oceanographic occurrences.
The EUE has direct effects on marine life. The extreme temperature drop caused tropical fish to experience thermal shock, leaving many stunned and easily caught by local residents.
“The event also attracted dolphins and other marine mammals that took advantage of the situation to hunt the disoriented fish,” Sahri noted.
Beyond its ecological impact, the EUE in Alor holds significant economic and tourism potential. This rare natural event could be developed into a scientific ecotourism attraction, allowing visitors to witness a remarkable ocean phenomenon sustainably.
“People can watch dolphins directly from the shore without using boats, minimizing disturbance to marine life,” added Sahri.
BRIN plays a leading role in studying the behavioral and ecological aspects of marine mammals during the event. The research involves collaboration with Diponegoro University, Tribuana University Kalabahi, Sriwijaya University, Konservasi Indonesia, and international partners such as University of Maryland (USA), Tohoku University (Japan), University of Tsukuba (Japan), and Srinakharinwirot University (Thailand).
“We aim to understand how extreme ocean dynamics affect dolphin behavior and ecosystem responses in the region,” Sahri explained.
Through institutional cooperation with the Alor Regency and East Nusa Tenggara Marine and Fisheries Offices, researchers hope that findings from this EUE study will contribute not only to global oceanography but also to sustainable marine resource management and ecotourism development in Alor and surrounding regions.
“This phenomenon reminds us how dynamic Indonesia’s seas are. Beneath their beauty lies a complex natural system still full of mysteries waiting to be uncovered,” Sahri concluded. (AT Network)
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