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explored in Chapter 6 ), precipitation, not only over the Atlantic side of
the Arctic strongly influenced by the Icelandic Low, but extending across
large areas of the northern high latitudes. As explored in Chapter 7 , The
NAO and AO also have pronounced influences on the sea ice circulation,
sea concentration, and extent. Recently, some attention has been paid
to the Arctic Dipole Anomaly (DA), with centers of action over the
northern Beaufort Sea and the Kara Sea, associated with an anomalous
wind pattern that strongly affects sea ice conditions. Other patterns with
prominent expression in the Arctic include the Pacific North American
(PNA) teleconnection and the Pacific Decadal Oscillation (PDO), the
latter strongly influencing the climate of Alaska.
4.1
Historical Perspective
The major “centers of action” in the Northern Hemisphere circulation - the Azores
and Pacific highs, the subpolar Icelandic and Aleutian lows, and the Siberian High -
had been identified in the 1880s by Teisserene de Bort. By 1920, the Bergen School
of Meteorology (founded by Professor Vilhelm Bjerknes and colleagues in 1917) had
developed pioneering ideas on the characteristics of extratropical cyclones. The
nature of the general circulation of the atmosphere was interpreted in terms of a
three-cell model by Bjerknes, Carl Rossby, and others. This model includes ther-
mally direct Hadley cells in low latitudes, thermally indirect Ferrell cells in middle
latitudes, and thermally direct cells in high latitudes, separated by the subtropical
and polar front jet streams. Inroads were being made on the nature of climate var-
iability. In 1932, Sir Gilbert Walker and E.W. Bliss ( 1932 ) published a landmark
paper demonstrating that the North Atlantic Oscillation, reflecting covariability in
the strengths of the Icelandic Low and Azores High, is a key atmospheric telecon-
nection (large-scale model of atmospheric variability) in the Northern Hemisphere,
with impacts on the climates of northeastern North America and northern Europe.
However, a clear understanding of the Arctic circulation lagged behind. The
earliest views of the Arctic's atmospheric circulation can be attributed to H. von
Helmholtz ( 1888 ), who argued that the Arctic was dominated by a more-or-less per-
manent anticyclone beneath a tropospheric vortex, a view that prevailed well into
the twentieth century. His basic thinking was developed by W. Hobbs ( 1910 , 1926 )
in his glacial anticyclone theory and further elaborated in a later paper (Hobbs,
1945 ) that focused on the perceived existence of a “Greenland glacial anticy-
clone” - a persistent anticyclone over the Greenland ice sheet having strong impacts
on middle latitude weather. From today's perspective, Hobbs' papers provide for an
amusing read.
Given the dearth of observations, misconception regarding the circulation north
of the subpolar centers of action is not surprising. It was not until the 1940s and
early 1950s that data were sufficient to make more definitive conclusions. Sea level
pressure (SLP) analyses in the U.S. Historical Weather Map Series produced during
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