Eastern Atlantic pattern

Eastern Atlantic pattern
Name	Eastern Atlantic pattern
Type	atmospheric teleconnection
Region	North Atlantic, Europe, North Africa
Period	interannual to decadal
Related	North Atlantic Oscillation, Arctic Oscillation, Scandinavian pattern

Eastern Atlantic pattern is a principal mode of variability in the North Atlantic sector that organizes storm tracks, pressure anomalies, and surface climate across Europe, North Africa, and the North Atlantic Ocean. It modulates precipitation, temperature, and wind regimes through shifts in the mid-latitude jet and interactions with other teleconnections such as the North Atlantic Oscillation, Arctic Oscillation, and the Scandinavian Pattern. Research on the pattern draws on observational networks, reanalysis products, and climate model experiments developed by groups at institutions like the Met Office, the National Oceanic and Atmospheric Administration, and the European Centre for Medium-Range Weather Forecasts.

Definition and characteristics

The Eastern Atlantic pattern is defined as a leading empirical orthogonal function or rotated principal component of sea level pressure, geopotential height, or 500 hPa anomalies centered east of the Greenland-Iceland-Norway corridor, with centers of action often near the Bay of Biscay, the Azores High periphery, and western Russia. It is characterized by zonally asymmetrical pressure anomalies that shift the North Atlantic storm track and modify the position of the mid-latitude jet stream that connects to regions such as the British Isles, Iberian Peninsula, France, Germany, and Scandinavia. Index definitions commonly use standardized principal component time series, rotated empirical orthogonal functions, or projection onto observed loading patterns used by laboratories such as NOAA/ESRL and the Met Office Hadley Centre.

Mechanism and atmospheric dynamics

Dynamically, the pattern arises from interactions among baroclinic eddies, upper-level wave trains, and transient synoptic systems, influenced by sea surface temperature gradients in the North Atlantic Drift and the Gulf Stream region. Rossby wave propagation from forcing centers near the Mediterranean Sea, the Bering Sea, or the North Pacific can project onto the pattern via waveguide effects along the subtropical and polar jets, similar to mechanisms studied for the Pacific-North American pattern and the East Atlantic–West Russia pattern. Blocking episodes near the Azores or the Icelandic Low alter eddy-mean flow feedbacks that sustain the anomaly structure, as described in work by researchers at Imperial College London, University of Reading, and the Max Planck Institute for Meteorology.

Climatic and weather impacts

Positive and negative phases of the pattern modulate regional extremes: for instance, anomalies influence winter temperature anomalies across Spain, Portugal, Italy, and the Balkans, and precipitation regimes across the Benelux, the Alps, and northwest Africa. It affects storm frequency and intensity impacting shipping lanes around Biscay and infrastructure in port cities like Lisbon, Bordeaux, and Bergen. The pattern also alters cold-air outbreaks affecting aviation hubs such as Heathrow, Charles de Gaulle Airport, and Schiphol, and contributes to seasonal flood risk in river basins including the Thames, the Seine, and the Po River. Impacts on renewable energy production have been documented for offshore wind farms off Scotland and solar arrays in Andalusia.

Seasonal and regional variability

The Eastern Atlantic pattern exhibits strongest expression during boreal winter and autumn when the meridional temperature gradient and jet strength are maximized, with weaker but important manifestations in spring linked to Eurasian snow cover anomalies including events over Siberia and the Ural Mountains. Spatial sensitivity varies: anomalies project differently toward southern Europe and the Mediterranean Basin versus northern Europe and the Barents Sea. Interannual variability is modulated by tropical forcings such as major El Niño–Southern Oscillation events, Indian Ocean dipole phases documented by researchers at CSIRO and Scripps Institution of Oceanography, and decadal shifts tied to the Atlantic Multidecadal Variability described by teams at NOAA Geophysical Fluid Dynamics Laboratory.

Teleconnections and interactions

The Eastern Atlantic pattern interacts with other teleconnections including the North Atlantic Oscillation, the Arctic Oscillation, the Scandinavian Pattern, the East Atlantic–West Russia pattern, and Eurasian blocking regimes studied by scientists at University of Oxford and ETH Zurich. Cross-basin coupling arises via the stratosphere; sudden stratospheric warming events tracked by the British Antarctic Survey and the National Center for Atmospheric Research can modulate the pattern through downward coupling that alters tropospheric circulation. Tropical-extratropical pathways involving the Walker Circulation, Madden–Julian Oscillation, and convective anomalies over the Maritime Continent have also been implicated in generating precursors.

Observation and indices

Indices for the pattern are constructed from gridded datasets like ERA5, NCEP/NCAR Reanalysis, JRA-55, and observational compilations by the Hadley Centre. Operational monitoring appears in bulletins from the European Centre for Medium-Range Weather Forecasts and climate diagnostics by NOAA Climate Prediction Center. Paleoclimate proxies from tree rings, ice cores, and lake sediments provide longer-term context used by teams at Lamont–Doherty Earth Observatory and the University of Bern.

Historical variability and trends

Analyses of the instrumental era reveal multidecadal modulation of the pattern associated with phases of the Atlantic Multidecadal Oscillation and anthropogenic influences assessed in reports by the Intergovernmental Panel on Climate Change and studies from Woods Hole Oceanographic Institution and the National Center for Atmospheric Research. Climate model ensembles from the Coupled Model Intercomparison Project indicate changes in pattern frequency and amplitude under greenhouse gas forcing, with regional consequences examined by research groups at ETH Zurich, MPI, and the Met Office Hadley Centre.

Category:Atmospheric teleconnections