Researcher: Tingjun Zhang
Funding Source: NSF
Collaborators: Dr. K. Saito, Dr. Larry Hinzman, Dr. J. Walsh, Dr. N. Mölders
(IARC/UAF), Roger Barry, Oliver Frauenfeld, Kevin Schaefer, Mark Serreze (University of Colorado),
Daqing Yang (UAF), D. Gilichinsky (Russian Academy of Sciences), Qingbai Wu (Chinese Academy
of Sciences)
The primary goal of this project is to investigate seasonal, inter-annual, and inter-decadal changes in permafrost conditions and snow cover in the Arctic through data analysis and numerical modeling.
This work consists of three major parts: 1) Collect and rescue soil temperature, active layer, permafrost, and snow cover data from various sources. This work is mainly through NSF Fresh Water Initiative (FWI) project support and the NSIDC snow data rescue project. Soil temperature and permafrost data have been updated to 2000, while snow data from more than 5000 stations in regions north of 50°N have been updated to 2006. 2) Combine in situ snow depth data with satellite remote snow depth data through data assimilation, then re-grid into various resolutions for model calibration and validation. We also gridded soil temperature data over the Siberian Arctic into 25 km, 1° by 1° resolution and 2.8° by 2.8° resolution for model validation. 3) Detect changes in soil temperatures, active layer thickness, permafrost temperatures, and snow depth over the Arctic through data analysis and modeling.
We have collected soil temperature data from 420 stations over the Russian Arctic and active layer/permafrost temperature data from 39 stations up to 2000. Based on these data, we have derived soil monthly freeze/thaw depths, annual maximum freeze depth, and active layer depth since the mid 1950s. Soil temperature data have been re-gridded into a different resolution for model inputs and validation. We also collected snow depth and snow water equivalent data from more than 5000 stations in regions north of 50°N. For regional analysis, we assimilated in situ snow data with passive microwave satellite remote sensing data. Assimilated snow depth and snow water equivalent data from 1978–2003 were generated and used for model calibration and validation. In situ, gridded, and assimilated soil temperature and snow depth data are used for studies to detect seasonal and inter-annual climate changes in the Arctic and subarctic. The primary results show that over the period from the mid 1950s to 2000, soil temperatures up to 3.20 m from more than 400 stations have increased by more than 1.5°C, active layer thickness increased by 25 cm, the date of active layer freeze-up has been delayed by about a month, and permafrost temperatures have increased about 3.0°C. In many places, talik might have also developed. Increase in permafrost temperatures over the Russian Arctic are mainly caused by changes in snow conditions and air temperatures.
Data products and research results from this study have been used for synthesis studies of arctic science. Changes in soil seasonal freeze, active layer, permafrost temperatures, and talik development are key components of arctic change in recent decades. Results from these studies are also used for arctic hydrological cycle, ecosystem, and carbon exchange between the atmosphere and the land surface.