Evaluation of the GLORYS ocean model for environmental monitoring in the Agulhas Current System
Tarron Lamont*, Issufo Halo
Department of Forestry, Fisheries, and the Environment
Foretrust Building, Martin Hammerschlag Road, Foreshore Cape Town, Western Cape, South Africa Pincode: 8001 Mobile: 27822246239 E-mail: firstname.lastname@example.org
Limited societal drivers along South Africas southeast coast, inshore of the Agulhas Current system, have historically constrained in situ sampling in the region. Two recent hydrographic surveys conducted by the DFFE and ACEP Phakisa Ocean Cruises Initiative during the summer and autumn seasons of 2017 have provided the only high spatial resolution in situ observations across the entire shelf south of 30.5°S to date. While these surveys provided a good baseline description of the hydrographic variations and physical processes across the shelf, further opportunities for continued in situ sampling at similar spatial scales have been limited. Thus, we have evaluated output from the GLORYS (Global Ocean Reanalysis and Simulation) ocean model to determine its suitability for investigating oceanographic variability in shelf regions along the South African east coast. GLORYS accurately reflected most of the known large-scale seasonal changes in surface temperature and salinity, and the vertical hydrographic structure on the shelf agreed well with in situ observations. However, the model was unable to capture nearshore changes in salinity resulting from seasonally varying river outflows. In addition, the model was also very successful in capturing the dynamics associated with shorter-term mesoscale features. In particular, our study provides the first evidence that cyclonic eddies observed inshore of the Agulhas Current during the 2017 cruises were well resolved in the daily GLORYS output. Due to its relatively higher spatial resolution (~8km), the model highlights spatial variations associated with these eddies that could not be observed from coarser resolution satellite altimetry. In light of limited in situ data records, the GLORYS model is a useful tool to examine, understand, and monitor oceanographic variability and change in this region.