On the relationship between Atmospheric Blocking and Arctic Amplification

Abstract

Atmospheric blocking is known to be one of the most important drivers of large-scale atmospheric variability at mid-high latitudes. Blocking events consist of a disruption and/or deceleration of the mean westerly circumpolar flow, and are generally associated with large-scale high-pressure patterns, which may be connected with the occurrence of climate extremes, such as heat waves and cold spells. Atmospheric dynamics in the Arctic region may be very important in shaping the spatial and temporal patterns of blocking at mid-high latitudes, and consequently the occurrence of associated climate extremes. In particular, Arctic Amplification (AA), namely the recent amplified warming in the Arctic region compared to lower latitudes, has recently been argued to have an impact on blocking patterns and behaviour at mid-high latitudes.The objective of this study is to investigate the most relevant mechanisms playing a role in the relationship between blocking and Arctic Amplification, by analysing the variability and frequency of the associated spatial patterns at various timescales using variables from the ERA5 reanalysis dataset for the time interval 1959-2022. Blocking events are detected based on geopotential height gradients between mid- and high-latitude regions, while Arctic Amplification is quantified as the difference of 1000hPa temperature between high and mid latitudes.The climatological number of events per year and their average lifetime, along with the long-term trends and their relationship with the AA are analysed. Furthermore, possible mechanisms linking blocking variability and the AA are explored through the analysis of the jetstream dynamics and teleconnection patterns in the Northern Hemisphere.