Simulating Coastal Wetland Processes in the E3SM Land Model
Image source: Benjamin Sulman, Oak Ridge National Laboratory
Coastal wetland carbon cycling and greenhouse gas production are strongly dependent on salinity and tidal influences. This study used a new model framework to simulate a network of biogeochemical reactions, including sulfur, carbon, and iron cycles, along with dynamic tidal hydrology and salt marsh vegetation directly within the land surface model component of the Energy Exascale Earth System Model.
Wetlands are hot spots of carbon storage and biogeochemical cycling due to salinity and tidal fluctuations, but current land models use simple decomposition frameworks that cannot directly resolve these biogeochemical influences. The new model framework presented here allows complex biogeochemical reaction networks and their responses to tidal influences to be simulated directly in a full-featured land model, allowing more accurate process-based simulations of coastal wetland carbon cycling and greenhouse gas production.
Current land surface models, including the Energy Exascale Earth System Model (E3SM) Land Model (ELM), lack process-based representation of the elemental interactions that drive wetland biogeochemistry. Here, we directly linked ELM to a flexible chemical reaction simulator, connecting organic matter decomposition with elemental cycles involving sulfur, iron, oxygen, and methane. We then simulated the impacts of tide-driven water level and salinity fluctuations on organic matter decomposition and greenhouse gas production in saline and freshwater tidal wetlands in Massachusetts, USA. The model predicted much lower methane emissions from saltwater-affected wetlands, which compared well to field measurements from coastal wetland sites. This model improves process-based simulations of carbon cycling and greenhouse gas production in wetland ecosystems, and the new capability of coupling complex reaction networks directly into a land surface model opens a broad range of possibilities for simulating subsurface biogeochemical interactions.