Journal Article

Permafrost Thermal Responses to Asymmetrical Climate Changes: An Integrated Perspective

Wang, Kang, Clow, Gary D., Zhang, Tingjun

2023

Overview

An integrated perspective of permafrost dynamics is a key bridge between permafrost and global socioeconomic assessments. This study investigated the air temperature changes (1976–2020) among permafrost zones in the Northern Hemisphere and their potential impacts on permafrost. We found that continuous permafrost zones experienced faster warming than other regions. The freezing index declined 724°C‐day while the thawing index increased only 166°C‐day over continuous permafrost zones. This may explain why the temperature of cold permafrost increased rapidly but the active layer thickness changed only slightly. Assuming permafrost carbon emissions arise only from thaw processes may miss a significant source of the emissions. An often‐neglected factor is that cold‐season snow amplifies permafrost warming caused by summertime air temperature changes. Due to seasonal effects, using mean‐annual air temperature to depict permafrost evolution under integrated assessment frameworks may lead to significant errors. Plain Language Summary Permafrost dynamics remains a core aspect of what people are concerned about. Some researchers are making efforts to couple permafrost to socioeconomic processes. Challenges include mismatched spatiotemporal scales and developing mathematical descriptions that are not too complex. To address these challenges, we attempt to capture the fundamental features of permafrost dynamics from an integral perspective in this study. We found that permafrost temperature changes during 1976–2020 were largely controlled by rapid changes in the air temperature during the cold seasons. We also realized that similar warming magnitudes during cold season and warm season may play an equivalent role in permafrost temperature evolution because seasonal snow cover can amplify the warming that occurred during the previous summer. The asymmetrical responses of cold and warm permafrost are critical for assessing permafrost carbon cycles and feedbacks. This is particularly true for cold continuous permafrost because about half of permafrost carbon is stored in the upper 1 m of soils and the carbon density in continuous permafrost is generally higher than other permafrost zones. Key Points Rapid changes in cold permafrost during 1976–2020 may be explained by a strong air temperature increase during the cold season Unchanging snow cover is still able to enhance the effect of climate warming on permafrost The asymmetric seasonal responses in cold and warm permafrost are critical for assessing permafrost carbon cycles and feedbacks

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Active layer / Air temperature / Annual temperatures / Carbon / Carbon emissions / Climate change / Continuous bridges / Datasets / Emissions / Freezing / Heat / Northern Hemisphere / Permafrost / Precipitation / Regions / Temperature / Temperature changes / Thawing / Thickness / Trends