London:
Researchers, including one of Indian origin, monitored 13,300 Arctic lakes using satellite imagery, and the results were quite worrisome. They found that the Arctic lakes that are wrapped with ice during winter season are melting away one day earlier each year.
Scientists from the University of Southampton in the UK revealed that the warming temperatures are leading to the breaking of ice earlier each spring, based on a 14-year period between 2000 and 2013.
They used information on how light is reflected off thelakes, as recorded by NASA's Moderate Resolution Imaging Spectrora diometer (MODIS) sensor, which collects a range of spectral and thermal data on a daily basis as it circles the globe on two satellites.
This study used the changes in reflectance to identify the freezing and thawing processes.
"Previous studies have looked into small numbers of lakesto show the impact of changes in temperature on the cyclicnature of lake-ice cover," said Jadu Dash, professor atUniversity of Southampton.
"However, ours is the first to use time-series of satellite data to monitor thousands of lakes in this way across the Arctic. It contributes to the growing range of observations showing the influence that warmer temperatures are having on the Arctic," said Dash.
Researchers discovered that all five study areas in the Arctic - Alaska, Northeast Siberia, Central Siberia, Northeast Canada and Northern Europe - showed significant trends of early ice break-up in the spring, but to varying degrees.
Central Siberia demonstrated the strongest trend, withice starting to break-up an average of 1.4 days earlier each year. Northern Europe showed the lowest change of ice break-upat 0.84 days earlier per year.
They found a strongrelationship between decreasing ice cover and an increasinglyearly spring temperature rise. Researchers also examined the timing of formation of icecover on the lakes in late autumn.
Although the use of satellite images was not possible dueto the short daylight period limiting valid satellite observation, observations on the ground suggest lake freezingis starting later - further shortening the ice period, although more work would be needed to confirm this.
"Our findings have several implications. Changing icecover affects the energy balance between the land andatmosphere," said Mary Edwards from the University ofSouthampton. "Less ice means a longer season for lake biology, which together with warmer temperatures will affect processes such as Carbon dioxide (CO2) and Methane (CH4) emissions," said Edwards.
"Furthermore, many people use ice-covered landscapes for winter transport, and so spring and autumn travel for commercial and subsistence activities is likely to be more andmore affected," added Edwards.
"This demonstrates the potential of routine satellite data for long term monitoring of physical changes on the Earth's surface," said Dash.
"In the future, the new Sentinel series of satellites from the European Space Agency provide potential opportunitiesto examine these changes in greater detail," Dash added. The study was published in the journal ScientificReports.
