sand spit movement

Sub Levels

sand spit movement

sand spit movement

Located on the Qinghai-Tibetan Plateau in western China, Qinghai Lake is a biodiversity outpost within the arid steppes and a sensitive indicator of climate change in the region. The lake’s fluctuating water levels act as a de facto gauge of climate change in this high-elevation basin.

Recent changes in lake levels are evident in this satellite image pair taken by Landsat 5’s Thematic Mapper (TM) and Landsat’s Operational Land Imager-2 (OLI-2) on July 29, 2010 (left). ). 9:00 on July 22, 2022 (right). The sand spit, which stretches for nearly 25 kilometers (15 miles), once cleared the surface and closed the lake within the lake. However, they were mostly submerged by 2022.

Researchers who measured the water level of Lake Qinghai reported that the water level steadily declined at an average rate of 8 centimeters (3 inches) per year from 1961 to 2004. ) per year until the end of the 2019 survey period.

According to the authors, the dramatic turnaround was consistent with trends of warming and wetness. Prior to 2004, lake levels were dropping, primarily due to reduced river runoff. The subsequent rise in lake level was caused by increased precipitation and stream runoff, and decreased evaporation. (There is no runoff from the lake.) Although the decrease in evaporation does not intuitively follow increases in temperature, the researchers found that temperatures were warmer in the winter months, when the lakes were covered with ice, than in the summer. Note that the rise was large. Summer has more precipitation, more cloudy days, and higher humidity, which reduces evaporation.

Spit evolution is one of the more dynamic effects of lake variability. Lower water levels exposed more lake bed sediment to the westerly winds, which swept sediment to the eastern shore of the lake. As sand dunes formed there, they divided Qinghai Lake into several sub-lakes. These include Shadao Lake (middle of upper left image) and Haiyan Bay (bottom right of wider view). These lakes appear isolated from Qinghai Lake in the 2010 imagery, but have been largely reorganized in 2022.

The importance of Qinghai Lake and its wetlands goes beyond its climatic signals. Many species are endemic to the plateau, and the critically endangered Przewalski gazelle lives only around Lake Qinghai. The ecosystem also plays an important role as a breeding and stopover site for many migratory waterbirds along the Central and East Asian flyways.

NASA Earth Observatory imagery by Alison Nussbaum, using Landsat data from the US Geological Survey. Story by Lindsey Dorman.

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