How and why do Greenland blocking patterns vary significantly between different summer months?

Journal article

Greenland atmospheric blocking, a persistent anticyclonic pattern, strongly influences local and regional weather and climate. It is known to significantly exacerbate Greenland ice sheet melt and mass loss in summer as well as influence atmospheric conditions over the North Atlantic. Greenland blocking has been observed to increase in intensity since the summer of 2000s, but this trend has partly reversed after 2012. This decadal variability is highly correlated with the negative phase of the North Atlantic Oscillation (NAO), the dominant pattern of climate variability in the North Atlantic. However, summer NAO shows different temporal variation in June in comparison with later summer months, i.e. July and August. In this study, we analyse the individual summer months in turn to evaluate differences between their respective spatial patterns of Greenland blocking events. We use different approaches including a self-organising map to evaluate individual blocking days, and an event-based analysis to assess the development of blocking events over the course of 7 d. The results show that spatial patterns of Greenland blocking are similar between July and August but are distinctly different in June. In particular, Greenland blocking in June is strongly related to cyclonic wave breaking over the eastern Atlantic. Our analysis using wave activity flux of the zonally varying mean flow reveals a distinct pattern of wave energy and pseudo-momentum associated with cyclonic wave breaking prior to Greenland blocking high anomalies in June, in contrast to the other two summer months. This might partially explain the difference in the spatial patterns and evolution of blocking in June compared with July and August.

Authors: Luu, LN; Hanna, E; Woollings, T; Fettweis, X; Screen, JA

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: IOP Publishing
• Journal: Environmental Research: Climate
• Volume: 5
• Issue: 3
• Pages: 035017
• Article number: 035017
• Publication date: 2026-06-22
• Acceptance date: 2026-05-22
• DOI: 10.1088/2752-5295/ae71fc
• EISSN: 2752-5295
• ISSN: 2752-5295
• Language: English
• Keywords: atmospheric blocking; self organising map; wave propagation; atmospheric dynamics; greenland blocking