Chinese researchers have produced a new generation of permafrost map of the northern hemisphere with a one-kilometer resolution for the period of 2000-2016, according to a recent research article published in the journal Earth System Science Data.

The map, integrating large amounts of field data and multisource satellite data and using statistical learning modelling with an ensemble strategy, is considered to be more accurate than previous maps.

It shows that the area of permafrost in the northern hemisphere is about 14.77 million square kilometers, excluding glaciers and bodies of water.

Ran Youhua, a researcher from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences, said that the distribution of annual mean ground temperature in the northern hemisphere had an obvious latitudinal gradient, from the extremely cold permafrost in the High Arctic to the warm permafrost in alpine and high-plateau regions at low latitudes, such as the Qinghai-Tibet Plateau and Mongolian Plateau.

The average annual ground temperature of the permafrost in the third Pole is about minus 1.56 degrees Celsius, while the temperature of the Arctic permafrost is about minus 4.70 degrees Celsius.

Both the annual mean ground temperature and active layer thickness, the two most important indexes of permafrost thermal state, are shown.

The map has been made available online for free download, supporting project planning and research on disasters, carbon cycles, water cycles and ecosystems in cold regions. (Xinhua)