Coastal hydrogeology plays a fundamental role in shaping biogeochemical processes at the land-ocean interface and the seafloor, influencing carbon dynamics and climate mitigation strategies. One carbon dioxide removal (CDR) approach is coastal enhanced weathering through olivine dissolution. Olivine weathering in coastal zones, where freshwater and saltwater converge, may accelerate dissolution due to enhanced geochemical gradients, dynamic groundwater flow, and temperature variations. Sea surface temperature (SST) is a critical factor in mineral dissolution rates, yet its role in coastal sediment weathering processes remains underexplored. Additionally, most prior studies focus on olivine dissolution in the water column, whereas this study explores weathering after the mineral powder settles on the seafloor. To address this, we employ a 2D reactive transport modeling approach of the coastal aquifer using FEFLOW coupled with piChem to investigate how submarine groundwater discharge (SGD), porewater flow, sediment permeability, tidal pumping, and SST control olivine weathering rates in coastal sediments. The results confirm that warmer SST enhances weathering efficiency, making temperature a key driver of olivine dissolution. High permeability and high tidal pumping further amplifies dissolution rates by facilitating reactive transport, while slow groundwater flow within sediments limits dissolution compared to the water column due to localized saturation effects. These findings emphasize that seafloor permeability, temperature, and tidal dynamics are key hydrogeological controls on olivine dissolution in coastal environments. Accounting for the interplay between slow groundwater flow and enhanced reactive transport mechanisms is essential for optimizing coastal enhanced weathering as a viable CDR strategy.