Dynamics of global wetlands by TOPMODEL

Dynamics of global wetlands are closely linked to biodiversity conservation, hydrology, and greenhouse gas emissions. However, long-term time series of global wetland products are still lacking. Using a TOPMODEL-based diagnostic model, we produced an ensemble of 28 gridded maps of monthly global/regional wetland extent products at 0.25° × 0.25° spatial resolution based on four observation-based wetland products and seven reanalysis soil moisture datasets for the period 1980–2020. The parameters of the model are calibrated on grid-scale against four observation-based wetland products. Overall, our products can capture the spatial distributions, seasonal cycles, and interannual variabilities of observed wetland extent well, and also show a good agreement with satellite-based terrestrial water storage estimates. The resulting mean annual maximum global wetland area fluctuates within a range of 3.3–5.6 Mkm2. The long temporal coverage beyond the era of satellite datasets, the global coverage and the opportunity to provide real-time update from ongoing SM data make these products helpful for various applications such as analyzing the wetland-related methane emission.