A high-pressure system developing over the northern Atlantic Ocean could significantly impact weather patterns in the United States this winter. Known as “Greenland blocking,” this phenomenon can increase the likelihood of storms and other extreme weather events in the Northeast. Here’s what you need to know about this unique weather pattern and its potential effects.
What is Greenland Blocking?
Greenland blocking occurs when a region of high atmospheric pressure forms near Greenland. This pressure acts as a barrier, disrupting the usual west-to-east movement of weather systems such as fronts and storms.
Connection to the North Atlantic Oscillation
This weather pattern is associated with the negative phase of the North Atlantic Oscillation (NAO), a system that monitors circulation in the North Atlantic. A negative NAO often aligns with the formation of Greenland blocking, leading to significant weather changes.
Impact on U.S. Weather
Greenland blocking alters U.S. weather by forcing the polar jet stream into a sharp southward plunge over the eastern United States. This shift can bring cold Canadian air into the region and set the stage for East Coast snowstorms.
Snowstorms and Coastal Impacts
When the jet stream aligns with the Eastern Seaboard, it can steer low-pressure systems up the coast. These systems often bring snow, rain, wind, and coastal flooding. If the jet stream tilts westward, storms are more likely to affect the northeastern U.S. and eastern Canada directly.
Greenland’s Annual Ice Loss
Beyond weather, Greenland itself is experiencing significant ice loss. The 2023-24 year marked the 28th consecutive year of net ice loss, with 80 billion tonnes of ice calving off the ice sheet.
Seasonal Snowfall and Melting
Greenland’s annual surface mass budget (SMB) measures snowfall accumulation versus ice loss. The 2023-24 SMB ended slightly above the 1981-2010 average, thanks to strong snowfall events, although the ice sheet still experienced a net loss.
Blocking Patterns and Global Weather
Blocking patterns like those over Greenland have wide-ranging effects. While Greenland experienced cooler conditions, Svalbard and parts of Europe saw record heat and glacier loss. This illustrates how blocking can create weather extremes across different regions.
The Role of the Jet Stream
The jet stream’s omega-like shape during blocking events highlights its influence. High-pressure ridges over North America and Europe trap heat, while low-pressure troughs over Greenland bring cooler, wetter conditions.
Greenland Blocking and its Role in Climate Variability
Greenland blocking not only influences short-term weather patterns but also plays a role in long-term climate variability. By disrupting typical weather flows, it can lead to prolonged periods of extreme weather, such as extended cold snaps or unseasonably warm conditions. These disruptions are closely monitored by meteorologists, as they can have cascading effects on agriculture, energy demand, and transportation systems in affected regions.
Implications for Global Weather Trends
The ripple effects of Greenland blocking extend beyond the Atlantic region. For example, changes in the jet stream can amplify weather extremes in Europe and Asia while indirectly impacting monsoon systems and precipitation patterns globally. As scientists continue to study these phenomena, understanding Greenland blocking is becoming increasingly important for predicting and mitigating the impacts of climate change on weather systems worldwide.
Looking Ahead
Unlike El Niño, Greenland blocking patterns operate on shorter timescales, making it difficult to predict how often they will occur this winter. However, their potential to disrupt weather patterns and exacerbate extreme conditions remains significant.
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References:
https://www.carbonbrief.org/guest-post-how-the-greenland-ice-sheet-fared-in-2024/
https://weather.com/science/weather-explainers/news/2024-11-12-greenland-block-new-england-north-atlantic-oscillation
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