Surface energy balance analysis reveals causes of Greenland’s abnormal warming

Global warming, caused by human activities, has led to rising average temperatures worldwide. However, Greenland is warming at an even faster rate than the rest of the world, which has accelerated the melting of the ice sheet. This intensified warming in northern regions, known as Arctic amplification, has the potential to significantly raise sea levels, posing a threat to coastal areas and ecosystems worldwide. Understanding the factors driving this phenomenon is essential to predicting future climate impacts.

Studies have already attributed Arctic amplification to local climate feedback processes, heat release from the Arctic Ocean, and energy transport from the south. Summer sea ice melt further amplifies warming trends through a process known as surface albedo feedback, where less ice leads to less sunlight reflected back into space.

In addition, the Greenland Blocking Index, a climate mode indicating the strength of high-pressure blocking conditions over Greenland, has been linked to temperature trends in the region. However, past studies have focused primarily on general warming trends, often neglecting the specific causes of year-to-year extreme temperature events and relying primarily on energy balance models.

To fill these gaps, a team of Korean researchers, led by Professor Kyung-Ja Ha of the Department of Climate System at Pusan ​​National University, including Manuel Tobias Blau, also of Pusan ​​National University, and Dr. Eui-Seok Chung of the Division of Atmospheric Sciences at the Korea Polar Research Institute, studied anomalous warming trends in Greenland from 1979 to 2021.

“In this study, we focused on annual perturbations in the surface energy balance to explain Greenland’s extreme temperature,” says Professor Ha. Their study was published in the journal Earth & Environment Communications July 28, 2024.

The researchers used a surface energy budget framework, which separates contributions from radiative and nonradiative sources, to analyze the temperature anomalies over Greenland. Their results revealed that increased clear-sky longwave downwelling radiation (heat radiated from the atmosphere to the surface on clear days) and the resulting surface albedo feedback were the dominant drivers of Greenland’s surface warming.

The researchers also studied the mechanism of this increase in solar radiation and found that the increase in atmospheric temperature was the main factor. Specifically, during warm years, the combination of increased surface temperatures and tropospheric warming led to turbulent heat exchange between the atmosphere and the surface.

This process also promoted the transport of moisture from the south towards Greenland and contributed to the formation of a high-pressure system resembling a blocking anticyclone, which trapped and maintained warm conditions. This dynamic led to intense ice melt, creating a feedback loop that further amplified the warming effects. In addition, different modes of natural climate variability, particularly those related to the blocking index, can amplify or moderate these warming trends, leading to extreme temperature events.

“The results suggest that natural variability plays an important role in explaining the atmospheric anomalies that lead to extreme summers in Greenland,” says Professor Ha. “Given climate change, extreme summer temperatures in Greenland will further accelerate the melting of the ice sheet, leading to rapid sea level rise.”

By shedding light on the factors driving extreme summer temperatures in Greenland, this study provides crucial information that could help project future development of the Greenland ice sheet and inform strategies to prevent further degradation.