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The annual frequency of ground surface freeze–thaw (AFGSFT) is a crucial indicator of hydrological processes, climate change, and energy balance, as it directly measures the number of times the ground surface freezes and thaws within a year. Unlike other indicators, such as freezing depth and duration, AFGSFT is more closely related to ground surface water heat exchange. However, the mechanism behind the variability of the long-term AFGSFT time series in China remains largely unknown. Based on the observation data from 707 meteorological stations, the AFGSFT in China from 1960 to 2020 was analyzed. The analysis revealed a decreasing trend in AFGSFT from 1960 to 2020, with the highest value observed in the central Qinghai-Tibet Plateau, and the rate of change in AFGSFT increasing with elevation. Despite these changes, the spatial distribution of AFGSFT closely aligns with the two regions divided by the Hu Huanyong Line (Hu Line). Elevation was found to be the primary geographic factor explaining the spatial variation of AFGSFT, while the ground surface temperature was the main environmental factor. Using the autoregressive integrated moving average model (ARIMA), the study projected that the downward trend of AFGSFT will slow down in the next decade. The widespread climate warming was identified as the primary cause of AFGSFT changes, and this effect is expected to contribute significantly to the climate warming process in the future. [ABSTRACT FROM AUTHOR]

Paleoclimate reconstruction and aeolian deposits in China indicate a major environmental reorganization – the formation of a nonzonal monsoon-dominated climate pattern – in East Asia in the late Oligocene and the early Miocene. In contrast, a zonal planetary-wind-dominated climate pattern has prevailed during the Paleocene and Eocene. However, this classical paradigm describing the climate transition has been questioned by recent studies. Here, our study emphasizes the importance of considering orbital-scale climate oscillations to better understand and reassess the paradigm. By examining the halite and mudstone sequence in the Jianghan Basin and conducting numerical experiments using the Norwegian Earth System model, we propose the concept of a "green Yangtze" phenomenon, which utilizes orbital-scale climate oscillations to reconcile the wet and dry environmental indicators in Eastern China during the Paleogene. It is essential to differentiate the Paleogene climate, characterized by intense orbital-scale wet and arid oscillations, from the Neogene monsoon-dominated climate. The classic paradigm remains valuable in understanding the long-term mean environment, albeit without capturing the orbital-scale details. Future research should focus on uncovering orbital-scale variations to enhance our understanding of climate evolution and dynamics in East Asia during the Cenozoic. • The paradigm of Paleogene zonal and Neogene nonzonal climate patterns captures Cenozoic East Asian climate evolution. • Orbital-scale oscillations are crucial in differentiating the climate during the Paleogene and Neogene. • A green Yangtze phenomenon reconciles Paleogene wet and dry environmental indicators in Eastern China. [ABSTRACT FROM AUTHOR]

The latest Paleocene to early Eocene was an interval of globally warm climate. However, the driving mechanisms regulating climate across this interval remain unclear due to the paucity of well-dated and stratigraphically continuous records from terrestrial basins. In this study, we present a continuous ∼430-m lacustrine core record from the QY-1 borehole spanning the late Paleocene-Early Eocene in the Subei Basin, East China. This unique record can be used to better elucidate the response of terrestrial sedimentation to astronomically forced climate change. A 4.54 Myr long astronomical time scale spanning 57.1 to 52.56 Ma is constructed for the second member of the Funing Formation (E f 2) based on magnetostratigraphy and cyclostratigraphy. Low-latitude summer insolation via eccentricity modulation of precession controlled paleolake evolution in the basin during the studied interval. At the same time, we show that the climate system during this greenhouse state was sensitive enough to respond to the small changes in insolation associated with 200-kyr eccentricity cycles. Evidence from gamma ray data suggests that the climate in the Subei Basin changed from warm and humid to arid at ∼54.1 Ma. • Establish an ATS with magnetostratigraphy and cyclostratigraphy for E f 2 in Subei Basin, East China. • A record of astronomically forced climate changes in the late Paleocene to early Eocene terrestrial succession in the Subei Basin was conformed. • The climate system during this greenhouse state was sensitive enough to respond to the small changes in insolation associated with 200-kyr eccentricity cycles. [ABSTRACT FROM AUTHOR]