Spatial–Temporal Characteristics of Freezing/Thawing Index and Permafrost Distribution in Heilongjiang Province, China

Under the trend of climate warming, high-latitude permafrost in Heilongjiang Province is becoming seriously degraded. The question how to quantitatively analyze spatial and temporal trends multi-year has become fundamental for current research. In this study, variations annual mean air temperature (MAAT), ground (MAGST) freezing/thawing index based on surface data from 34 meteorological stations 1971–2019, as well variation characteristics distribution, were analyzed freezing model. results showed that both MAAT MAGST tended decrease with increase altitude latitude. For interannual variation, warming rates be consistent across Province, −8.64 5.60 °C −6.52 7.58 °C, respectively. From (AFI) (GFI) declined at −5.07 °C·d·a−1 −5.04 °C·d·a−1, respectively, whereas thawing (ATI) (GTI) elevated 7.63 11.89 distribution multiyear AFI, ATI, GFI GTI exhibited a latitudinal trend, effect northern mountainous areas was greater than Permafrost primarily discovered Daxing’an Xiaoxing’an Mountains north, sporadically central regions. southern boundary shifted nearly 2° north 1970 2010s, while stable 51° N. total area narrowed 1.11 × 105 km2 1970s 6.53 104 2010s. study take critical significance analysis perennial degradation high latitudes whole northeastern China, mapping large using This provides reference natural cold resource development, ecological protection, change engineering construction maintenance areas.