Freezing/thawing index variations over the circum-Arctic from 1901 to 2015 and the permafrost extent

Yaya Shi; Fujun Niu; Zhanju Lin; Jing Luo

doi:10.1016/j.scitotenv.2019.01.121

Freezing/thawing index variations over the circum-Arctic from 1901 to 2015 and the permafrost extent

Sci Total Environ. 2019 Apr 10:660:1294-1305. doi: 10.1016/j.scitotenv.2019.01.121. Epub 2019 Jan 14.

Authors

Yaya Shi¹, Fujun Niu², Zhanju Lin³, Jing Luo⁴

Affiliations

¹ State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: shiyaya@lzb.ac.cn.
² State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China; South China Institute of Geotechnical Engineering, School of Civil Engineering and Transportation, South China University of Technology, Guangzhou 510006, China. Electronic address: niufujun@lzb.ac.cn.
³ State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China. Electronic address: zhanjulin@lzb.ac.cn.
⁴ State Key Laboratory of Frozen Soil Engineering, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.

PMID: 30743924
DOI: 10.1016/j.scitotenv.2019.01.121

Abstract

Due to sparse data and discontinuous time observations in the circum-Arctic region, freezing index and thawing index, as useful indicators, are widely used in permafrost distribution, climate changes and cold-region engineering analysis. However, previous researches on freezing/thawing index over this region were estimated based on mean monthly air temperature. In this paper, we analyzed the spatial and temporal variations of the freezing/thawing index over the circum-Arctic from 1901 to 2015 based on the daily datasets, besides monthly datasets. The results showed that freezing index had a downward changing trend and thawing index had an upward trend during 1901-2015. More important, the change trend in freezing/thawing index after 1988 was more significant than before. Furthermore, different freezing/thawing index based on daily datasets and the monthly datasets were assessed and compared according to daily data from 17 meteorological stations, comprehensive relative errors evaluation implied that freezing/thawing based on daily datasets was more accurate generally, although both of other datasets were available in calculating the freezing/thawing index. As the daily datasets are better in calculating annual freezing/thawing index, therefore, the permafrost extent was estimated by a climate-based predictive model combined with snow depth data from Canadian Meteorological Centre (CMC). Finally, considering that the published permafrost map of the circum-Arctic only shows the past permafrost distribution, but it cannot reflect the permafrost distribution after 2000 under the climate warming. Hence, we simulated the current (mean from 2000 to 2015) permafrost area which is 19.96 × 10⁶ km², and the results showed some discrepancies between published and simulated permafrost extent mainly located in isolated permafrost regions.

Keywords: Circum-Arctic; Freezing/thawing index; M-K test method; Permafrost extent.