As humanity grapples with the escalating crisis of climate change, understanding and mitigating the fluxes of carbon dioxide (CO2) is imperative. A lesser-known yet significant aspect of this crisis lies in the role of the vast expanses of marine sediments which encompass two-thirds of the Earth’s surface. A key component of these sediments is calcium carbonate (CaCO3), a family of minerals that makes up the shells and skeletons of marine organisms. CO2 emissions lead to ocean acidification, triggering CaCO3dissolution, which in turn neutralizes CO2, acting as a crucial CO2 sink over millennial timescales. However, the mechanisms and rate of this dissolution remain unknown due to the challenges posed by the deep ocean’s high pressures and the elusive bacterial communities mediating the dissolution process. Proposed here is an ambitious five-year research initiative aimed at understanding deep-sea CaCO3 dissolution, thereby paving the way towards a more thorough understanding and potential mitigation of climate change impacts. By focusing on the abyssal and hadal realms, this groundbreaking research seeks to unveil the nature and rate of CaCO3 dissolution through high pressure reactors. These reactors, which simulate the pressure and temperature of deep-sea environments, present a robust alternative to in-field studies. With the integration of cutting-edge sensors and the use of advanced CaCO3 imaging techniques, we will generate precise and continuous data on the unfolding biogeochemical processes. By housing bacterial cultures within the reactors, alongside natural CaCO3 grains, this project will delve into the mechanisms driving dissolution. The insights will be instrumental in refining a global biogeochemical model, thereby promoting a deeper comprehension of the ocean’s role in carbon sequestration and propelling forward the global efforts towards effective climate change mitigation.