Continued decline of global soil moisture content, with obvious soil stratification and regional difference

Soil is an important component connecting atmosphere and vegetation, and is an important 'regulator' of slope hydrological process. Global warming accelerates the global water cycle, and Soil Moisture Content (SMC) will change, but this change is not yet clear. Here, we study the global trend of SMC at different depths over the past 70 years and the next 70 years, based on the GLDAS-NOAH025 dataset and precipitation and temperature data from 15 CMIP6 models. We found that compared with the long-term average of 70 years, the global 0-200 cm SMC is decreasing at a rate of 1.284 kg/m(2) per year from 2000 to 2020, and the area showing a significant decreasing trend accounts for 31.67 % of the global. Over the past decade, 0-200 cm SMC reduction rate (2.251 kg/m(2)) doubled. Global warming and precipitation reduction are the main reasons for the attenuation of SMC at different depths in the global from 2000 to 2020. Under the SSP126, SSP245, SSP370 and SSP585 scenarios, the global 0-200 cm SMC will continue to decay in the future, and the area showing a significant reduction trend accounts for 22.73-49.71% of the global, but the stratified soil and regional differences are obvious. The attenuation of SMC will further aggravate the global water cycle and enhance the variability of extreme meteorological disasters. We will face more severe soil drought problems.

Automated summary

Soil is a crucial mediator between the atmosphere and vegetation, serving as a regulator of slope hydrological processes. The impact of global warming on Soil Moisture Content (SMC) remains unclear. This study examines the global trend of SMC at various depths over the past 70 years and projected trends for the next 70 years using the GLDAS-NOAH025 dataset and CMIP6 models. Findings indicate a significant decrease of 0-200 cm SMC at a rate of 1.284 kg/m² per year from 2000 to 2020, with 31.67% of the global area showing a significant decreasing trend. Global warming and reduced precipitation contribute to the attenuation of SMC. Future scenarios predict further SMC decay, exacerbating global water cycle and extreme meteorological disasters, leading to more severe soil drought challenges.