text: The silicic acid leakage hypothesis (SALH) is a suggested mechanism that aims to explain the atmospheric CO variations between glacial and interglacial periods. This hypothesis proposes that during glacial periods, as a result of enhanced dust deposition in the southern ocean, diatoms consume less Si relative to nitrogen. The decrease in the Si:N uptake ratios leads to Si excess in the southern ocean, which leaks to lower latitudes of the ocean that are dominated by coccolithophores. As the Si concentrations rise, the diatom population may outcompete the coccolithophores, reducing the CaCO precipitation and altering ocean alkalinity and the carbonate pump. These changes would induce a new ocean-atmosphere steady state with lower atmospheric CO concentrations, consistent with the draw down of CO observed in the last glacial period. The δSi and δN isotopic values archived in the southern ocean diatom sediments has been used to examine this hypothesis, as the dynamics of Si and N supply and utilization during the last deglaciation could be interpreted from this record. In alignment with the silicic acid leakage hypothesis, these isotopic archives suggest that Si utilization in the southern ocean increased during the deglaciation.