SST dynamics at different scales: evaluating the oceanographic model resolution skill to represent SST processes in the Southern Ocean

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Skakala, J, Smyth, TJ, Torres, R, Buckingham, CE, Brearley, A, Hyder, P, Coward, AC
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU 2019
• Subjects: Curl; Southern Ocean
• Online Access: http://plymsea.ac.uk/id/eprint/8169/; http://plymsea.ac.uk/id/eprint/8169/13/Skakala_et_al-2019-Journal_of_Geophysical_Research__Oceans.pdf; https://doi.org/10.1029/2018JC014791

In this study we demonstrate the many strengths of scale analysis: we use it to evaluate the Nucleus for European Modelling of the Ocean (NEMO) model skill in representing sea surface temperature (SST) in the Southern Ocean (SO) by comparing three model resolutions: 1/12°, 1/4° and 1°. We show that whilst 4‐5 times resolution scale is sufficient for each model resolution to reproduce the magnitude of satellite Earth Observation (EO) SST spatial variability to within ±10%, the representation of ∼ 100 km SST variability patterns is substantially (e.g ∼50% at 750 km) improved by increasing model resolution from 1° to 1/12°. We also analysed the dominant scales of the SST model input drivers (short‐wave radiation, air‐sea heat fluxes, wind stress components, wind stress curl, bathymetry) variability with the purpose of determining the optimal SST model input driver resolution. The SST magnitude of variability is shown to scale with two power law regimes separated by a scaling break at ∼200 km scale. The analysis of the spatial and temporal scales of dominant SST driver impact helps to interpret this scaling break as a separation between two different dynamical regimes: the (relatively) fast SST dynamics below ∼200 km governed by eddies, fronts, Ekman upwelling and air‐sea heat exchange, whilst above ∼200 km the SST variability is dominated by long‐term (seasonal and supra‐seasonal) modes and the SST geography.