Enhanced understanding of warming and humidifying on ground heat flux in the Tibetan Plateau Hinterland

The land surface layer is an important interface between the ground and atmosphere, and cross-surface ground heat flux (G₀) has a significant impact on land surface energy processes and associated cycles. Therefore, understanding dynamics in G₀ is critical for predicting climate changes and developing adaptation strategies. However, the harsh environment and geographic barriers of the Tibetan Plateau have led to a significant lack of observations and soil samples, ultimately limiting the accuracy and application of G₀ calculations. Here we investigated the changes in G₀ at the BJ station, a typical seasonally frozen ground region of the Tibetan Plateau, through soil sampling and long-term in-situ observations. We used the calorimetric method to minimize reliance on model assumptions, aiming to achieve consistent and broadly applicable results. During the freezing-to-thawing and thawing-to-freezing stages, daytime G₀ decreased while nighttime G₀ increased. Conversely, daytime G₀ increased while nighttime G₀ decreased in the completely thawed and completely frozen stages. In moist conditions, more energy was directed toward soil moisture evaporation and vegetation transpiration, whereas in dry conditions, net radiation primarily increased soil temperature, enhancing G₀. Our results revealed the dynamic changes in G₀ across different environmental conditions and their impact on land-atmosphere interactions, and that climate warming and humidifying will diminish the regulatory capacity of G₀. This study highlights the essential requirement for accurate G₀ to predict future climate changes accurately, emphasizing its importance for researchers focusing on land-atmosphere feedback mechanisms and climate modeling.