Researchers Reveal Mechanism Triggering Arctic Daily Warming
Prof. REN Baohua and his team from the School of Earth and Space Sciences, the University of Science and Technology of China (USTC), uncovered the connection between Arctic daily warming and the equator region as well as Atlantic storms. The series of studies have been published in npj Climate and Atmospheric Science, Environmental Research Letters, and Advances in Atmospheric Sciences.
As one of the coldest places where the average winter temperature is -30℃, the Arctic temperature has reached the melting point several times, for instance, in late December 2015 and 2022. Those Artic daily warming events have drawn growing interest.
Currently, most researchers focus on the long-term growth of the Arctic temperature but pay little attention to Arctic daily warming events. In the series of studies, the research team investigated the influence of the North Atlantic Oscillation (NAO), the El Niño-Southern Oscillation (ENSO), and the Central Pacific El Niño-Southern Oscillation (CP ENSO) on the Arctic daily warming occurrence.
The researchers investigated the impact of the NAO on the Arctic winter daily warming events induced by Atlantic storms, known as the Atlantic pattern-Arctic Rapid Tropospheric Daily Warming (Atlantic-RTDW) event.
They discovered that the relationship between the NAO and the Atlantic-RTDW-event frequency has weakened since the mid-1980s, which was attributed to a stronger Atlantic Storm Track (AST) activity intensity. During this period, the strong AST induced an enhanced NAO-related cyclone via transient eddy-mean flow interactions, resulting in the disappearance of southerly and northerly wind anomalies over the NA.
The geopotential height and horizontal 500-hPa wind speed composite anomalies for the two periods in the positive NAO years (Image by Prof. REN’s team)
Furthermore, the researchers found that ENSO has urged a stronger Rossby wave due to its heightened intensity since the late 1970s, allowing El Niño to deepen the Aleutian Low, thus decreasing (increasing) Arctic daily warming events. This model offered a potential link between the equator and the Arctic which can assist in the prediction of extreme Arctic daily warming events. With global warming, this potential relation may be strengthened.
Interdecadal change of the sea surface temperature, Rossby wave, and winter geophysical fields related to ENSO (Image from Prof. REN’s team)
Nevertheless, after the mid-1980s, the planetary wave associated with CP ENSO could not propagate upwards into the stratosphere, cutting the teleconnection between CP ENSO and Iceland Low. As a result, CP ENSO’s influence on the occurrence frequency of A-RTDW events was weakened.
Atmospheric conditions associated with the CP ENSO (Image from Prof. REN’s team)
The findings provided a new perspective on the weather and climate changes in the Arctic. Those studies can help strengthen the prediction of Arctic daily warming events.