Understanding the Cold Season Arctic Surface Warming Trend in Recent Decades

Whether sea-ice loss or lapse-rate feedback dominates the Arctic amplification (AA) remains an open question. Analysis of data sets based upon observations reveals a 1.11 K per decade surface warming trend in the Arctic (70 degrees-90 degrees N) during 1979-2020 cold season (October-February) that is five times higher than the corresponding global mean. Based on surface energy budget analysis, we show that the largest contribution (similar to 82%) to this cold season warming trend is attributed to changes in clear-sky downward longwave radiation. In contrast to that in Arctic summer and over tropics, a reduction in lower-tropospheric inversions plays a unique role in explaining the reduction of the downward longwave radiation associated with atmospheric nonuniform temperature and corresponding moisture changes. Our analyses also suggest that Arctic lower-tropospheric stability should be considered in conjunction with sea-ice decline during the preceding warm season to explain AA.

Automated summary

The Arctic amplification (AA) is still an open question whether sea-ice loss or lapse-rate feedback dominates. Analysis suggests that changes in clear-sky downward longwave radiation contribute the most to the surface warming trend during the cold season, while a reduction in lower-tropospheric inversions plays a unique role in the downward longwave radiation reduction.