Shrinking thermokarst lakes and ponds on the northeastern Qinghai‐Tibet plateau over the past three decades

Abstract

Identifying the changes in thermokarst lake dynamics has a significant contribution to landscape‐scale hydrology, ecology, and assessment of carbon budgets in permafrost regions. Changes in the number and areal extent of thermokarst lakes and ponds were quantified in a representative permafrost area (150 km2) in the south‐central Headwater Area of the Yellow River (HAYR). Water‐body inventories were generated from Landsat satellite imageries using the supervised Maximum Likelihood Classification method for three periods: 1986, 2000, and 2015. From 1986 to 2015, the number of water bodies larger than 0.36 ha decreased by 40% (461–277), while the total surface area decreased by 25% (542–406 ha). The ponds category (smaller than 1 ha) recorded the most substantial change, as their number decreased by 44% and their water‐surface area by 41%. Many lakes disintegrated, partially drained, and formed several remnant ponds, while the majority of the ponds did not drain completely, but shrank below 0.36 ha. These shrinking patterns are consistent with the warming climate in the HAYR, which suggests intense permafrost degradation. Future research will be focused on a better understanding of water–heat dynamics of thermokarst lakes and ponds in association with permafrost degradation at a landscape scale.