This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: High on the Qinghai-Xizang Plateau, the ground stays frozen, with only the top few meters melting each summer. Although the region is warming about twice as fast as the global average, a new study finds that more than a third of its permafrost, mainly in the central plateau, has gained ice since 2000.
Stronger westerly winds bring more rain and snow, which seeps into the ground in summer and freezes again in winter. The work was led by Li Dongfeng at Peking University's College of Environmental Sciences and Engineering, with colleagues from the Alfred Wegener Institute in Germany, Nanjing Normal University and the Chinese Academy of Sciences, among others. It was published in Science Advances.
Roads, buildings and bridges on the plateau rest on frozen ground, and the plateau feeds rivers that supply water to about 2 billion people downstream. Most permafrost research asks how much warming will melt the ice. Far less is known about what happens when rainfall changes.
This study begins to fill that gap and shows that ground ice can continue to grow even in a warmer climate. Ice buried underground is hard to measure, so the team turned to boreholes—narrow holes drilled into the permafrost. In the field, they compared pairs of nearby holes, one drilled before 2000 and one after.
The newer hole generally held more ice, mostly near the bottom of the layer that melts each summer. The likely reason is water: Weather data show that yearly rain and snow in the westerly-influenced interior plateau rose by 60% after 2000. In summer, the extra water seeps into the bottom of the active layer and refreezes in the perennially subzero environment, adding to the existing ground ice over time and driving the anomalous ice increase.
To test this, the team ran a computer model of heat and water in the soil. In the simulation, when rain and snow were kept at constant levels while warming continued, the ice gains turned into losses; when temperature was held steady and rain dialed up, the ice grew. So, the conclusion was that a rapid increase in precipitation may outweigh temperature in driving ground ice evolution.
Extract — continue reading at the source.
