Current dynamics, drivers, and vertical thermal structure around Sir Bu Nair Island (Arabian/Persian Gulf)
- 1New York University Abu Dhabi (Abu Dhabi, United Arab Emirates)
- 2Universidade Federal de Alagoas (Maceió, Brazil)
Abstract
Sir Bu Nair Island (SBN) in the central Arabian Gulf is one of the last locations in the UAE's Gulf waters to retain extensive and well-developed coral reefs, whereas many nearshore environments have experienced severe degradation following recurrent marine heatwaves. Although tides, winds, and subtidal circulation are thought to influence reef-level thermal conditions at SBN, the local physical processes governing circulation and temperature variability have not previously been resolved from in situ observations. Here, we analysed a 17 month record (May 2021–October 2022) of currents, sea level, and temperature from bottom-mounted ADCPs and multi-depth temperature moorings, complemented by wind reanalysis and long-term regional satellite and model products. Currents at SBN were strongly anisotropic and aligned along a dominant principal axis, reflecting topographic steering around the island. Currents were substantially stronger and more directionally organized at the northwest site than at the southern site, demonstrating pronounced spatial variability around the island. Tidal forcing dominated current variability, explaining up to ∼80 % of the along-axis variance at the northwest site but substantially less in the cross-axis direction and at the southern site. Wind–current coupling was strongest at subtidal timescales, with rapid (0–2 h) responses consistent with local barotropic adjustment to wind forcing. Summer temperatures exceeded 35 °C, and vertical temperature differences of 2–4 °C developed during late spring and summer before undergoing rapid transitions toward thermal homogeneity. The diurnal band accounted for much of the variability in vertical temperature structure, with additional variability at synoptic (2–4 d) timescales associated with wind, sea level, and currents. Long-term regional analyses showed that the exceptionally warm conditions observed in 2021 extended across the southeastern Gulf, whereas regional current speeds remained within historical variability. Together, the observations indicated that changes in vertical thermal structure were associated with interacting tidal, atmospheric, and lower-frequency circulation processes rather than a single mechanism. These findings provide the first integrated observational description of circulation and thermal structure at SBN and highlight how regional forcing and local topographic modification combine to produce spatially and temporally heterogeneous conditions around an isolated reef system in the central Gulf.
Versions
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BibTeX
@article{cavalcante2026current,
title = {{Current dynamics, drivers, and vertical thermal structure around Sir Bu Nair Island (Arabian/Persian Gulf)}},
author = {Geórgenes H. Cavalcante and Filipe Vieira and Rita Bento and Aaron Bartholomew and John A. Burt},
journal = {Ocean Science},
year = {2026},
month = oct,
doi = {10.5194/os-22-3165-2026},
url = {https://os.copernicus.org/articles/22/3165/2026/},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Current dynamics, drivers, and vertical thermal structure around Sir Bu Nair Island (Arabian/Persian Gulf)
AU - Geórgenes H. Cavalcante
AU - Filipe Vieira
AU - Rita Bento
AU - Aaron Bartholomew
AU - John A. Burt
PY - 2026
DA - 2026/10/14
JO - Ocean Science
DO - 10.5194/os-22-3165-2026
UR - https://os.copernicus.org/articles/22/3165/2026/
AB - Sir Bu Nair Island (SBN) in the central Arabian Gulf is one of the last locations in the UAE's Gulf waters to retain extensive and well-developed coral reefs, whereas many nearshore environments have experienced severe degradation following recurrent marine heatwaves. Although tides, winds, and subtidal circulation are thought to influence reef-level thermal conditions at SBN, the local physical processes governing circulation and temperature variability have not previously been resolved from in situ observations. Here, we analysed a 17 month record (May 2021–October 2022) of currents, sea level, and temperature from bottom-mounted ADCPs and multi-depth temperature moorings, complemented by wind reanalysis and long-term regional satellite and model products. Currents at SBN were strongly anisotropic and aligned along a dominant principal axis, reflecting topographic steering around the island. Currents were substantially stronger and more directionally organized at the northwest site than at the southern site, demonstrating pronounced spatial variability around the island. Tidal forcing dominated current variability, explaining up to ∼80 % of the along-axis variance at the northwest site but substantially less in the cross-axis direction and at the southern site. Wind–current coupling was strongest at subtidal timescales, with rapid (0–2 h) responses consistent with local barotropic adjustment to wind forcing. Summer temperatures exceeded 35 °C, and vertical temperature differences of 2–4 °C developed during late spring and summer before undergoing rapid transitions toward thermal homogeneity. The diurnal band accounted for much of the variability in vertical temperature structure, with additional variability at synoptic (2–4 d) timescales associated with wind, sea level, and currents. Long-term regional analyses showed that the exceptionally warm conditions observed in 2021 extended across the southeastern Gulf, whereas regional current speeds remained within historical variability. Together, the observations indicated that changes in vertical thermal structure were associated with interacting tidal, atmospheric, and lower-frequency circulation processes rather than a single mechanism. These findings provide the first integrated observational description of circulation and thermal structure at SBN and highlight how regional forcing and local topographic modification combine to produce spatially and temporally heterogeneous conditions around an isolated reef system in the central Gulf.
SN - 1812-0792
ER -