Reconstructions of warm season AO SAT (top) and SLP index for AD 1650-1975. Click to enlarge.
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Tree-ring reconstructions of temperature and sea-level pressure variability
associated with the warm-season Arctic Oscillation since AD 1650
Geophysical Research Letters
Vol. 30, No. 11, 1549 (June 2003).
Rosanne D. D'Arrigo, Edward R. Cook, Gordon C. Jacoby
Lamont-Doherty Earth Observatory, Palisades, New York, USA.
Michael E. Mann
University of Virginia, Charlottesville, Virginia, USA.
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Arctic Oscillation (AO) changes are inferred from a treering
reconstruction of a warm-season temperature index. The
reconstruction covers AD1650-1975 and is based largely on
chronologies from circumpolar-Arctic and circum-North
Atlantic areas. It accounts for 48% of the variance in the
instrumental AO record from 1900 to 1975, verifies using
independent data, and exhibits its largest variance at low
frequencies. Positive levels during 20th century periods equal
or exceed values back to AD 1650. Trends (including lower
values during 'Little Ice Age' periods) resemble those of
Arctic temperature reconstructions, reflecting some data
overlap, but also the strong link between the AO and northern
temperatures. A reconstruction of an AO summer sea level
pressure index shows similar trends. Comparison of these
reconstructions with proxies of the North Atlantic Oscillation
(NAO) and other indices can help clarify relationships
between the AO and NAO, at least during the boreal warm
season.
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