Seasonal_Interannual_Variability_Summer_Thermocline_Balearic_Sea_2022‑2026

Vertical thermal stratification governs upper-ocean heat storage, regulates nutrient supply to the euphotic zone, and modulates marine heatwave (MHW) development. Most long‑term thermocline investigations for the Mediterranean Sea are built upon basin‑wide merged Argo float datasets. Relatively few studies focus on continuous local time‑series derived from an individual float, particularly for the Balearic Sea. This study employs five consecutive years of vertical temperature profiles (2022‑2026) from a single Argo buoy at 40.89°N, 2.76°E. Using a custom gradient‑threshold workflow implemented in Python 3.14, four thermocline‑associated metrics are extracted from 80 summer observations: upper‑boundary depth, lower‑boundary depth, layer thickness, and maximum vertical temperature gradient. The results show distinct intra‑seasonal variability. Between July and September, the thermocline upper boundary deepens, accompanied by increasing vertical temperature gradients. Summer 2023 exhibits a notable anomaly: a thicker and deeper thermocline, consistent with the severe marine heatwave documented across the western Mediterranean that year. For comparison, March 2022 winter profiles display nearly homogeneous water temperature with no discernible thermocline, in sharp contrast to highly stratified summer conditions. This work shows that time‑series records from one individual Argo buoy are capable of capturing local inter‑annual stratification anomalies. It further provides a fully reproducible quantitative workflow implemented in Python. Two main limitations should be noted: concurrent salinity measurements are absent, and September observations are missing within the 2026 summer dataset.