Previous studies have linked Arctic Amplification to local climate feedbacks, heat release from the Arctic Ocean, and energy transport from southern regions. The melting of sea ice in summer further intensifies warming through surface albedo feedback, where reduced ice leads to less sunlight being reflected back into space. Additionally, the Greenland blocking index - a measure of high-pressure systems over Greenland - has been associated with regional temperature trends. However, these studies have generally focused on long-term warming trends, often neglecting the specific causes of extreme temperature events and relying mainly on energy balance models.

To fill these gaps, a research team from Korea, led by Professor Kyung-Ja Ha from the Department of Climate System at Pusan National University, including Manuel Tobias Blau, also from Pusan National University, and Dr. Eui-Seok Chung from the Division of Atmospheric Sciences at Korea Polar Research Institute, analyzed the abnormal warming trends in Greenland from 1979 to 2021. "In this study, we focused on the year-to-year perturbations of the surface energy budget to explain Greenland's extreme temperature," explains Prof. Ha. Their research was published in the journal 'Communications Earth and Environment' on July 28, 2024.

The team used a surface energy budget framework, which separates radiative and non-radiative contributions, to examine temperature anomalies over Greenland. Their findings showed that increases in clear-sky downwelling longwave radiation - the heat emitted by the atmosphere to the surface on clear-sky days - along with surface albedo feedback, were the main contributors to Greenland's surface warming.

The researchers also explored the cause of the increase in clear-sky radiation and identified rising atmospheric temperatures as the key factor. Specifically, in warmer years, the combination of higher surface temperatures and tropospheric warming led to increased heat exchange between the atmosphere and the surface. This process also enhanced moisture transport from southern regions to Greenland and contributed to the formation of a high-pressure system, similar to a blocking anticyclone, which trapped and sustained warm conditions. These dynamics led to intense ice melting, creating a feedback loop that further amplified the warming effects. Additionally, different modes of natural climate variability, particularly those related to the blocking index, can either amplify or moderate these warming trends, resulting in extreme temperature events.

"The results suggest a significant impact of natural variability in explaining the atmospheric anomalies leading to extreme summers over Greenland," says Prof. Ha. She further emphasized, "Considering climate change, the extreme summer temperature over Greenland will further accelerate the ice sheet melting, leading to a rapid sea level rise."

This study provides important insights into the causes of Greenland's extreme summer temperatures, which could help in forecasting the future behavior of the Greenland ice sheet and developing strategies to mitigate further ice loss.

Research Report:Extreme summer temperature anomalies over Greenland largely result from clear-sky radiation and circulation anomalies

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