## 2 Materials and Methods
### In Situ Data  
The SeaExplorer sea glider obtained through the Oceanography Malta Research Group at the University of Malta (Figure 2) facilitated the acquisition of real-time, in situ measurements for SSS and SST. By leveraging changes in buoyancy to glide horizontally and vertically through the water column, it reached depths of up to 700 m, consistently gathering salinity and temperature data, which was transmitted back to the researcher upon surfacing. The sea glider was employed in two separate missions within the Mediterranean Sea area. The initial mission, launched in the southern vicinity of the Maltese Island near Filfla, extended for a duration of 38 days, commencing on 30 July 2021 and concluding on 6 September 2021. Its trajectory encompassed a journey towards Northern Tunisia before returning to Malta. Conversely, the subsequent mission commenced in the Gozo Channel, situated in the northern region of Maltese Island, lasting for a period of 29 days, running from 9 November 2021 to 8 December 2021. Its course was oriented towards southern Tunisia before returning to Malta. As this research focused exclusively on the sea surface data gathered by the sea glider, in situ data underwent a cleansing process, with any data collected below the initial 5 m depth level being excluded. The missions and satellite data employed in this study are depicted in Figure 3. This data was utilised to generate predictions for SSS and SST for the years 2022 and 2023.  
Figure 1: A cartographic representation of the Mediterranean Sea delineating the position of the Maltese Islands with a star symbol (Latitude: 35.99\({}^{\circ}\) N, Longitude: 14.31\({}^{\circ}\) E).  
Regarding the 2024 SSS and SST measurements, in situ salinity and temperature data were acquired using an ARGO float equipped with a CTD instrument (Figure 2), deployed north of Gozo on 22 June 2024 (Website containing the information of the Argo float used: [[https://fleetmonitoring.euro-argo.eu/float/7901135](https://fleetmonitoring.euro-argo.eu/float/7901135)]([https://fleetmonitoring.euro-argo.eu/float/7901135](https://fleetmonitoring.euro-argo.eu/float/7901135)), accessed on 15 June 2024). The float primarily spends its time drifting with deep ocean currents and subsequently collects a series of measurements while moving through the water column. Upon reaching the surface, the float determines its location, typically via GPS, and then transmits its collected data through a satellite. Consequently, similar to the sea glider, the dataset from the float required cleaning by excluding measurements taken below the sea surface threshold,  
Figure 3: Satellite and in situ data used for the training and testing stages of SSS and SST for 2022 and 2023.  
Figure 2: (a) Sea Explorer sea glider and (b) ARGO Float. Reproduced from (a) [[https://www.alseamar-alecn.com](https://www.alseamar-alecn.com)]([https://www.alseamar-alecn.com](https://www.alseamar-alecn.com)), accessed on 17 May 2024 (b) [[https://www.teledynemarine.com](https://www.teledynemarine.com)]([https://www.teledynemarine.com](https://www.teledynemarine.com)), accessed on 17 May 2024.  
retaining only the SSS and SST measurements. The data points collected by the ARGO float are illustrated in Figure 4.