A52D-07 Climate and land use impacts on soil hydrogen sink in the 21st century

As hydrogen (H₂) emerges as a cornerstone of low-carbon energy transitions, its indirect climate impacts—remain underexplored. Soil is responsible for >60% of atmospheric H₂ removal. Therefore, the strength and respond to global environmental change of soil H₂ sink are important uncertainties. We investigate how future changes in climate and land use may affect the terrestrial sink of atmospheric H₂ by implementing a new soil H₂ deposition scheme in the Community Terrestrial Systems Model (CTSM), which includes the effects of soil temperature, moisture, texture and active organic matter content. Our scheme shows improved accuracy in matching observed H₂ deposition velocity over previous studies, with more consistent performance over different climate zones. The newly developed model is applied to simulate the range of H₂ deposition velocity under a business-as-usual climate scenario (6.0 W m^-2 at 2100) with difference assumptions of climate sensitivity and patterns of temperature/precipitation changes. We found that global soil H₂ deposition velocity is likely to increase by 5 – 10% at the end of the century relative to 2020, especially under warmer and drier conditions, driven mainly by reduced snow cover over the high latitudes. However, regional decreases in soil sink capacity also emerge, highlighting spatial heterogeneity and uncertainty. We also find the lack of observations over regions where soil H₂ sinks are expected to undergo substantial changes in the coming century (e.g. snow-covered regions in high latitudes in northern Hemisphere). Our work refines the estimates of the strength of global soil H₂ sinks, which can be readily applied to refine the estimates of the global warming potential of H₂ and highlight key processes and regions where future observation and modelling effort should focus on.