Lakes In Himalayan Plateau Gradually Transitioning To Carbon Sinks From Sources: Study

Yearly carbon emissions from lakes in the Qingzang Plateau (QZP) or the Tibetan Plateau have declined with some lakes shifting from being carbon sources during 1970-2000 to becoming carbon sinks in the next two decades, new research has found.

Researchers said the trend of decreasing carbon emissions in QZP lakes over the past five decades suggested that these lakes could assume an increasingly significant role in both regional and global carbon cycles in the context of ongoing global climate change.

The Qingzang Plateau, known as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia and includes the Indian regions of Ladakh and Lahaul and Spiti.

While carbon sources release more carbon into the atmosphere than they absorb, carbon sinks absorb more carbon from the atmosphere than they release.

The researchers, including those from the Chinese Academy of Sciences, China, said their study offers insights into the timing and degree of shifting in the yearly carbon dioxide (CO2) exchange flux for lakes in the QZP region. Their findings are published in the journal Environmental Science and Ecotechnology.

The team found that between 1970 and 2000, the lake systems in the QZP had generally acted as carbon sources. However, from 2000 to 2020, some freshwater and saltwater lakes shifted from acting as carbon sources to small carbon sinks, with decreasing yearly CO2 exchange flux.

They also found that before 2000, the average temperature on the QZP from 1970 to 2000 was lower, aquatic plant and phytoplankton rates were relatively low, and the effect of respiration on carbon emissions was more pronounced.

After 2000, however, the average temperature on the QZP was seen to show a rising trend.

Further, the researchers found that the CO2 absorbed through photosynthesis exceeded the CO2 released through respiration, along with a reduction in the partial pressure of CO2 (pCO2) at the water-air interface and water bodies became increasingly less saturated. All of these conditions were conducive for CO2 entering water bodies, they said.

They found that in recent decades, the yearly solar radiation on the QZP has generally declined. This will weaken the circulation of warm and cold water in the water bodies, known to cause a significant outflow of CO2, and therefore reduce CO2 emissions, they said.

Phytoplankton and aquatic macrophytes, too, are sensitive to light and a slight reduction will slow respiration processes and gradually decrease CO2 emissions, they said.