Radiative and dynamic contributions to the observed temperature trends in the Arctic winter atmosphere

The Arctic has been experiencing unprecedented changes in recent years due to anthropogenic greenhouse gas emissions leading to what is known as Arctic amplification, whereby the Arctic is warming faster than any other area of the planet. While the majority of research has focused on the near-surface level heating and radiative forcing, one under-explored area of research is the change in temperature and heating rates throughout the stratosphere and upper troposphere, particularly during the winter months (December–February). For instance, reanalysis data has revealed that the Arctic middle-lower stratosphere has been warming at a rate of approximately 0.5 K/decade over the 1980–2019 period in contrast to the prevailing cooling trends in the other regions of the stratosphere. To understand what is driving these non-negligible temperature trends, this work investigates the underlying dynamical and radiative heating rates over the same 40-year period. It is found that dynamics is the main driver of the stratospheric temperature change in the Arctic, with the middle-lower stratospheric warming being largely explained by trends in adiabatic motion. In comparison, besides the dynamical effects, the tropospheric warming trend is also driven radiatively by surface warming and thermodynamically by latent heating. Lastly, it is found that the stratospheric warming trend mainly occurs in the years with sudden stratospheric warming events, highlighting the influence of these events in driving the stratospheric temperature trends.