Observed decrease in soil and atmosphere temperature coupling in recent decades over northern Eurasia

• Published in: Geophysical Research Letters
• Main Authors: Chen, Liangzhi, Aalto, Juha, Luoto, Miska
• Other Authors: Department of Geosciences and Geography, BioGeoClimate Modelling Lab, Helsinki Institute of Sustainability Science (HELSUS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2021
• Subjects: 1171 Geosciences; permafrost
• Online Access: http://hdl.handle.net/10138/329015

Coupling of soil-air temperature is fundamentally relevant to various biophysical and biogeochemical functions near the land surface. However, coupling at an interannual scale is less addressed than at finer timescales, such as diurnal and seasonal scales. Here, we show that interannual variability of soil-air temperature coupling decreased significantly during 1984-2013 across 196 stations in northern Eurasia. Coupling at a depth of 0.2 m remained significant in only 53% of stations during 1999-2013, while it was significant in 80% of stations during 1984-1998. Decreased coupling is mainly attributable to air temperature change in the snow-free season and snow cover retreat. Moreover, change in the extreme snow cover frequency also contributes to the decline, while other climate extremes are less influential. The findings can help us to understand long-term land-climate thermal interactions and to evaluate soil temperature profiles simulated by land surface models. Plain Language Summary The near-surface air temperature closely relates to soil temperature, and the strength of this relationship may be altered by the presence of other environmental elements such as snow cover, soil moisture, and vegetation. In this study, by using paired observations at 196 stations collected from 1984 to 2013 over northern Eurasia, we show that coupling of soil-air temperature was not constant and decreased over time. In the European part of the study region, the coupling consistently decreased; however, there was no clear pattern over the permafrost area. We found that this decline may relate to the increase in air temperature during the snow-free season and snow cover retreat over the period. The decreased coupling was also affected by extreme snow cover frequency. Moreover, we found that the decrease in coupling may accelerate if warming continues in the future. Under a changing climate, the compound impacts of multiple environmental changes on the interannual variability of coupling remain uncertain. The results can advance ...