Hybrid spectral downscaling and climate-driven variability of multimodal wave systems in the Gulf of Panama

The Gulf of Panama is a semi-enclosed tropical basin where coastal processes are driven by a multimodal wave climate with pronounced interannual-to-decadal variability (Vallarino-Castillo, 2026). Offshore wave conditions were characterized at three spectral locations near the Gulf entrance using GLOSWAC-5 spectral data (Portilla-Yandún and Bidlot, 2025), revealing dominant wave systems with distinct directional origins and seasonal variability. A persistent Southern Ocean swell dominates year-round from the south–southwest, while northerly wind-seas associated with the Panama Low-Level Jet prevail during the dry season (December–April). Their opposing directions lead to frequent crossing-sea conditions, particularly along the western Gulf entrance, where partial blocking by the Azuero Peninsula enhances directional spreading. In contrast, more exposed central-eastern locations exhibit consistently multimodal spectra, whereas sheltered eastern areas show reduced northerly wind-sea influence and narrower directional ranges. During the wet season (May–November), additional southerly swell components linked to subtropical trade winds and the Chocó Low-Level Jet reinforce low-frequency energy, while episodic North Pacific swell incursions further increase spectral complexity. Building on these offshore patterns, we analyze how wave systems transform as they propagate across the Gulf’s complex basin geometry.

To resolve coastal wave conditions efficiently, we applied a hybrid spectral downscaling framework across the Gulf. Remote swell was reconstructed using BinWaves (Cagigal et al., 2024), which disaggregates each offshore spectrum into frequency–direction bins and propagates them individually with SWAN, assuming linear wave superposition over the nearshore of the Gulf of Panama, such that nonlinear wave–wave interactions are neglected during propagation. Nearshore spectra are then reassembled using precomputed propagation coefficients that account for coastal geometry. Locally generated seas were reconstructed with HyXSeaSpec, which extracts dominant atmospheric modes via multivariate dimensionality reduction, projects SWAN spectra onto a reduced EOF/PCA space and learns the nonlinear mapping between atmospheric modes and spectral coefficients using radial basis functions (RBFs). During prediction, new wind fields are projected into the reduced space to recover full directional spectra through inverse transforms. The hybrid workflow generates a 3-hourly directional wave spectrum hindcast (1969–2023) that combines remote swell and locally generated wind-sea contributions throughout the basin.

The ongoing nearshore analysis uses the reconstructed spectra to identify dominant variability patterns and coherent wave regimes, assessing how energy is redistributed within the gulf and how nearshore conditions respond to seasonal and interannual atmospheric forcing.

References:

Vallarino-Castillo R, Antolínez JAA, Negro-Valdecantos V, Portilla-Yandún J (2026). “Beyond understanding the role of far-field climate in the Gulf of Panama coastal dynamics: an analysis of long-term and seasonal variability of wave systems”. Climate Dynamics. https://doi.org/10.1007/s00382-025-08007-w

Portilla-Yandún J, Bidlot J-R (2025). “A global ocean spectral wave climate based on ERA-5 data: GLOSWAC-5”. Journal of Geophysical Research: Oceans. https://doi.org/10.1029/2025JC022629

Cagigal, L., Méndez, F.J., Ricondo, A., Gutiérrez-Barceló, D. & Bosserelle, C. (2024). “BinWaves: An additive hybrid method to downscale directional wave spectra to near-shore areas” en Ocean Modelling. 84, 102346.