Warming trends of the Agulhas Current from 1982 to 2019.

This study was conducted in the Southern African region; the latitudinal and longitudinal extents of the study area are 15 degrees south - 45 degrees south and 0 degrees east- 45 degrees east respectively. 

The datasets used in this study include.

1.

A subset of the NOAA Optimum Interpolation SST (NOAA OI. v2 SST) version 2 daily average dataset (Reynolds et al. 2007) between 1982 and 2019 was used to conduct this study. Monthly fields are derived by averaging the 0.25o x 0.25o daily SST values over a month. The NOAA 0.25o x 0.25o daily OISST is a global grid-based product that combines data observations from ships, Argo floats, buoys, and high-resolution infrared satellite observations (9 km) from the AVHRR (advanced very high-resolution radiometer) sensor on NOAA (National Oceanic and Atmospheric Administration) satellites.

2. 

A subset of the global daily 0.25 degrees x 0.25 degrees gridded satellite altimetry data from 1993 to 2019. This dataset is only available from 1993 to the present date, hence its temporal scale is not the same as the SST dataset. The Copernicus Marine Environment Monitoring Service (CMEMS) distributes the altimetry product, which is available as a level 4 multi-mission product containing daily gridded Sea Surface Height (SSH), and its anomaly Sea Level Anomaly (SLA) and derived variables (Absolute and Anomalous geostrophic velocity: zonal and meridional components). CMEMS is a platform that provides systematic and regular data on the state of the physical ocean and regional seas. This product was produced by taking data from multiple altimetry missions and merging them with the same processing techniques, models, and geophysical corrections. During the merging of data from multiple altimetry missions, the OSTM and Jason-2 missions are used as a reference dataset, with accompanying data from Jason-3, Sentinel-3A, HY-2A, Saral/AltiKa, Cryosat-2, Jason-2, Jason-1, T/P, ENVISAT, GFO, and ERS1/2. An Optimum Interpolation is made by merging all the flying satellites to compute gridded Sea Level Anomalies (SLA) and Absolute Dynamic Topography (ADT). The geostrophic currents (geostrophic velocities anomalies and the absolute geostrophic velocities) are then derived from SLA and ADT, respectively.