An Interdecadal Change in the Influence of the NAO on Atlantic-Induced Arctic Daily Warming around the Mid-1980s

After approaching 0°C owing to an Atlantic storm at the end of 2015, the Arctic temperature approached freezing again in 2022, indicating that Arctic daily warming events remain a concern. The NCEP/NCAR Reanalysis dataset was used to investigate the influence 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. Atlantic-RTDW events are triggered by Atlantic storms that transport warm and humid air masses moving into the Arctic. Furthermore, an interdecadal change in the influence of NAO on Atlantic-RTDW-event frequency was observed around the mid-1980s. Specifically, before the mid-1980s (pre-transition period), 500-hPa southerly (northerly) wind anomalies occupied the North Atlantic (NA) in the positive (negative) phase of NAO, which increased (decreased) the Atlantic-RTDW events occurrence by steering Atlantic storms into (away from) the Arctic; thus, the NAO could potentially influence the Atlantic-RTDW-event frequency. However, the relationship between the NAO and the Atlantic-RTDW-event frequency has weakened since the mid-1980s (post-transition period). In the post-transition period, such 500-hPa southerly (northerly) wind anomalies over the NA hardly existed in the positive (negative) phase of NAO, which was attributed to a stronger Atlantic Storm Track (AST) activity intensity than that in the pre-transition period. 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.