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Author: search.filters.author.Ansari, KutubuddinSubject: search.filters.subject.El Niño–Southern Oscillation (ENSO)

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    Item type:Publication,
    How the Impact of ENSO Events on the Indonesian Throughflow and Interannual Variability of Circulation in the Halmahera Sea
    (2026-09-01)
    Lubis, Muhammad Zainuddin
    ;
    Dwinovantyo, Angga
    ;
    Batara, B.
    ;
    Kausarian, Husnul
    ;
    Hidayat, Syarief
    This study investigates the influence of El Niño–Southern Oscillation (ENSO) on the Indonesian Throughflow (ITF) in the Halmahera Sea (HS) during 2013–2023. Although ITF variability has been widely studied, the response of the HS to different ENSO phases remains insufficiently understood. Using a validated CROCO model, we quantified changes in HS throughflow and associated oceanographic conditions under El Niño and La Niña events. EOF analysis of sea surface height (SSH), meridional velocity, and salinity revealed dominant modes explaining more than 50% of the total variance and exhibiting clear ENSO-related variability. During El Niño events, ITF transport weakened substantially, with volume transport becoming less negative from − 4.0 ± 2.0 Sv to − 1.5 ± 1.5 Sv in the upper layer (0–100 m) and from − 5.0 ± 2.5 Sv to − 2.0 ± 2.0 Sv in the intermediate layer (0–400 m). These conditions were associated with a shallower thermocline, lower sea surface temperatures (25.5–26.0°C), and reduced surface salinity (34.74 PSU). In contrast, La Niña events strengthened the ITF, with transport reaching −7.0 ± 1.5 Sv in the upper layer and −7.0 ± 2.0 Sv in the intermediate layer, accompanied by a deeper thermocline and higher SSTs (29.8–30.42°C). The results suggest that ENSO-related variability in the HS is associated with coupled changes in thermocline structure, SSH gradients, and salinity, highlighting the importance of the HS in regulating ITF transport variability.
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    Decadal and seasonal oceanographic trends influenced by climate changes in the Gulf of Thailand
    (2025-06-01)
    Lubis, Muhammad Zainuddin
    ;
    Ghazali, Muhammad
    ;
    Simanjuntak, Andrean V.H.
    ;
    Riama, Nelly F.
    ;
    Pasma, Gumilang R.
    Our study investigates the decadal and seasonal variability of sea surface height (SSH) and sea surface temperature (SST) in the Gulf of Thailand (GoT) using data from CMEMS from 1993 to 2021. We employed statistical analyses utilizing GLM and GAM to assess the variables comprehensively. The reveals a significant upward trend in SSH, increasing from ∼0.79 m in 1993–1998 to ∼0.89 m in 2017–2021, highlighting the impacts of climate change. SST analysis revealed fluctuations, with a maximum reaching ∼30.6 °C in 2019–2020, correlating with climatic events such as El Niño. Our study results at station 1 (near Bangkok) showed that the average SSH in 1998 during strong El Niño years was equal to 0.82 m, while the maximum SST was equal to 29.89 °C. Seasonal patterns indicated SSH peaks in DJF and SON at ∼0.92 m, while SST peaked in spring MAM and summer JJA at ∼30.7 °C. Volume transport analysis showed significant variability, with 0.3634 Sv (0–55 m) at longitude 99°E-107° E and latitude 6° N, indicating complex circulation patterns influenced by bathymetry and wind. Time series analysis revealed an average SSH increase of 0.0038 m/year, with a high pseudo-R-squared of 0.99. Our findings underscore the critical influence of climate variability on oceanographic conditions in the GoT, emphasizing the need for ongoing monitoring to address the implications of rising sea levels and temperature fluctuations. In conjunction with increased SSH, the rising SST heightens the risk of flooding in low-lying areas, exacerbating vulnerabilities for local populations and necessitating adaptive management strategies to mitigate these impacts.