Sea surface salinity (SSS) is a key variable for ocean–atmosphere interactions and the water cycle. Due to its climatic importance, increasing efforts have been made for its global in situ observation, and dedicated satellite missions have been launched more recently to allow homogeneous coverage at higher resolution. Cross-shore SSS gradients can bear the signature of different coastal processes such as river plumes, upwelling or boundary currents, as we illustrate in a few regions. However, satellites performances are questionable in coastal regions. Here, we assess the skill of four gridded products derived from the Soil Moisture Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) satellites and the GLORYS global model reanalysis at capturing cross-shore SSS gradients in coastal bands up to 300 km wide. These products are compared with thermosalinography (TSG) measurements, which provide continuous data from the open ocean to the coast along ship tracks. The comparison shows various skills from one product to the other, decreasing as the coast gets closer. The bias in reproducing coastal SSS gradients is unrelated to how the SSS biases evolve with the distance to the coast. Despite limited skill, satellite products generally agree better with collocated TSG data than a global reanalysis and show a large range of coastal SSS gradients with different signs. Moreover, satellites reveal a global dominance of coastal freshening, primarily related to river runoff over shelves. This work shows a great potential of SSS remote sensing to monitor coastal processes, which would, however, require a jump in the resolution of future SSS satellite missions to be fully exploited.

The region located in the far northeast of the Gulf of Guinea (NEGG), eastern tropical Atlantic, remains poorly documented due to a lack of available in situ ocean data. Heavy rainfall and intense ...

This study examined the carbon cycling dynamics in the tropical Atlantic Ocean from 1985 to 2023, focusing on factors influencing the surface partial pressure of CO₂ (pCO₂), freshwater input, total alkalinity (ALK), total dissolved carbon (TCO₂), and pH levels. The time series data revealed significant trends, with average pCO₂ concentrations rising from approximately 350 μatm in the early 1990s to over 400 μatm by 2023. The TCO₂ levels increased from about 2000 μmol/kg to 2200 μmol/kg, while ALK rose from approximately 2300 μmol/kg to 2500 μmol/kg. This increase highlights the ocean’s role as a carbon sink, particularly in areas with high biological productivity and upwelling where TCO₂ also rose. This study employed Empirical Orthogonal Functions (EOFs) to identify variability modes and understand spatial patterns of pCO₂. Freshwater dynamics significantly affect TCO₂ concentrations, particularly in coastal regions, where pH can shift from 8.2 to 7.9, exacerbating acidification. Rising sea surface temperatures have been linked to elevated pCO₂ values. These findings support the need for ongoing monitoring and effective management strategies to mitigate the impacts of climate change and ensure the sustainability of marine resources. This study documented the long-term trends in tropical Atlantic CO₂ parameters linked to the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO).

Sea level rise (SLR) is a global concern in the era of climate change, prompting the exploration of interventions such as solar radiation modification through stratospheric aerosol injection (SAI). This intervention could affect the physical system in various ways. The present study analyzes the global and regional impacts of SAI using ARISE-SAI-1.5 (SAI-1.5) simulations with the Community Earth System Model 2. We calculated the regional thermosteric sea level under different scenarios. After validating our methodology for sea level components over the period 1995–2014, we determined changes in sea level variables under both SAI-1.5 and the underlying Shared Socioeconomic Pathway 2–4.5 (SSP2-4.5) relative to the reference period (1995–2014). In contrast to sea surface temperature, which under this SAI strategy should be maintained near 1.5 °C above preindustrial values, global SLR would continue increasing under SAI-1.5. However, SAI would significantly impact thermal expansion in SSP2-4.5 simulations, reducing the global long-term sea level trend from 3.7 ± 0.03 mm yr ⁻¹ for SSP2-4.5–1.9 ± 0.04 mm yr ⁻¹ for SAI-1.5, a 49% reduction. The associated ocean heat content is reduced from (2.0 ± 0.3) × 10 ²² J yr ⁻¹ under SSP2-4.5 to (1.17 ± 0.30) × 10 ²² J yr ⁻¹ under SAI, a 42% reduction. Additionally, SAI would impact the regional and global ocean by reducing the SLR rate. These findings underscore the potential of SAI as a climate intervention strategy with significant implications for sea level change.