Sea-level pressure variability around Antarctica since A.D. 1750 inferred from subantarctic tree-ring records |
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Authors: | R Villalba E R Cook R D D’Arrigo G C Jacoby P D Jones M J Salinger J Palmer |
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Institution: | (1) Tree-Ring Laboratory, Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, USA, US;(2) Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK, GB;(3) National Institute of Water and Atmospheric Research, P O Box 109–695, New market, Auckland, New Zealand, NZ;(4) Department of Plant Science, Lincoln University, P O Box 84, Canterbury, New Zealand, NZ;(5) Departamento de Dendrocronologia e Historia Ambientol, IANIGLA, CONICET, C.C. 330, 5500 Mena, Argentina, AR |
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Abstract: | A tree-ring chronology network recently developed from the subantarctic forests provides an opportunity to study long-term
climatic variability at higher latitudes in the Southern Hemisphere. Fifty long (1911–1985), homogeneous records of monthly
mean sea-level pressure (MSLP) from the southern latitudes (15–65 °S) were intercorrelated on a seasonal basis to establish the most consistent, long-term Trans-Polar teleconnections during
this century. Variations in summer MSLP between the South America-Antarctic Peninsula and the New Zealand sectors of the Southern
Ocean are significantly correlated in a negative sense (r=−0.53, P<0.001). Climatically sensitive chronologies from Tierra del Fuego (54–55°) and New Zealand (39–47°) were used to develop verifiable reconstructions of summer (November to February) MSLP for both sectors of the Southern Ocean.
These reconstructions, which explain between 37 and 43% of the instrumentally recorded pressure variance, indicate that inverse
trends in MSLP from diametrically opposite sides of Antarctica have prevailed during the past two centuries. However, the
strength of this relationship varies over time. Differences in normalized MSLP between the New Zealand and the South America-Antarctic
Peninsula sectors were used to develop a Summer Trans-Polar Index (STPI), which represents an index of sea-level pressure
wavenumber one in the Southern Hemisphere higher latitudes. Tree-ring based reconstructions of STPI show significant differences
in large-scale atmospheric circulation between the nineteenth and the twentieth centuries. Predominantly-negative STPI values
during the nineteenth century are consistent with more cyclonic activity and lower summer temperatures in the New Zealand
sector during the 1800s. In contrast, cyclonic activity appears to have been stronger in the mid-twentieth than previously
for the South American sector of the Southern Ocean. Recent variations in MSLP in both regions are seen as part of the long-term
dynamics of the atmosphere connecting opposite sides of Antarctica. A detailed analysis of the MSLP and STPI reconstructions
in the time and frequency domains indicates that much of the interannual variability is principally confined to frequency
bands with a period around 3.3–3.6 y. Cross spectral analysis between the STPI reconstruction and the Southern Oscillation
Index suggests that teleconnections between the tropical ocean and extra-tropical MSLP variations may be influencing climate
fluctuations at southern latitudes.
Received: 18 December 1996/Accepted: 10 January 1997 |
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