未来青藏高原东北部季节冻土变化趋势OA

Based on 22 bias-corrected and downscaled high-resolution simulations from NEX-GDDP-CMIP6,this study projects changes in the annual maximum freezing depth,freezing start date,thawing end date,and areal extent of seasonally frozen ground over the northeastern Qinghai-Xizang Plateau under SSP1-2.6,SSP2-4.5,and SSP5-8.5 scenarios for the mid-21st century(2025-2060)and late-21st century(2061-2100).The results show that,across all three scenarios,the annual maximum freezing depth is projected to decrease significantly by 9.8-14.9 cm during the mid-21st century relative to the historical reference period.Concurrently,the freezing start date is projected to delay at a rate of 1-3 days per decade,while the thawing end date to advance at a rate of 2-4 days per decade,with the advance occurring nearly twice as rapidly as the delay.The shortening of the frozen pe-riod becomes more pronounced under higher emission scenarios.Under SSP1-2.6 scenario,changes in seasonal-ly frozen ground remain relatively stable in the late 21st century.Under SSP2-4.5 scenario,the rates of change in maximum freezing depth and freeze-thaw timing resemble those projected for the mid-21st century under SSP1-2.6.Under SSP5-8.5 scenario,the maximum freezing depth continues to decrease substantially,accompanied by a significant shortening of the frozen period.Across different ecological functional zones,the annual maximum freezing depth of seasonally frozen ground decreases most rapidly in the eastern agricultural area during the mid-and late-21st century under SSP1-2.6 and SSP2-4.5 scenarios,whereas the Three River Source Region experi-ences the fastest rate of decline under SSP5-8.5.Moreover,the frozen peiod shortens most significantly in the Three River Source region across all scenarios.The area of seasonally frozen ground is projected to expand by 14.4×104-19.8×104 km2 in the mid-21st century across all scenarios relative to the historical reference period.This expansion continues into the late-21st century,with further increases of 2.2×104 km2,8.6×104 km2,and 12.4×104 km2 under SSP1-2.6,SSP2-4.5,SSP5-8.5,respectively.Overall,seasonally frozen ground in the north-eastern Qinghai-Xizang Plateau will be profoundly affected by future climate change,with the most pronounced reductions in maximum freezing depth and frozen period duration under SSP5-8.5 alongside accelerated perma-frost-to-seasonally-frozen-ground conversion,and energy conservation and emission reduction measures can ef-fectively mitigate this degradation trend.