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| Titel |
Volcanic forcing of the North Atlantic Oscillation over the last 2,000 years |
| VerfasserIn |
Sebastian F. M. Breitenbach, Harriet E. Ridley, Franziska A. Lechleitner, Yemane Asmerom, Kira Rehfeld, Keith M. Prufer, Douglas J. Kennett, Valorie V. Aquino, Victor Polyak, Bedartha Goswami, Norbert Marwan, Gerald H. Haug  , James U. L. Baldini |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106862
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| Publikation (Nr.) |
 EGU/EGU2015-6541.pdf |
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| Zusammenfassung |
| The North Atlantic Oscillation (NAO) is a principal mode of atmospheric circulation in the
North Atlantic realm (Hurrell et al. 2003) and influences rainfall distribution over Europe,
North Africa and North America. Although observational data inform us on multi-annual
variability of the NAO, long and detailed paleoclimate datasets are required to understand the
mechanisms and full range of its variability and the spatial extent of its influence.
Chronologies of available proxy-based NAO reconstructions are often interdependent and
cover only the last ~1,100 years, while longer records are characterized by low sampling
resolution and chronological constraints. This complicates the reconstruction of regional
responses to NAO changes.
We present data from a 2,000 year long sub-annual carbon isotope record from speleothem
YOK-I from Yok Balum Cave, Belize, Central America. YOK-I has been extensively dated
using U-series (Kennett et al. 2012). Monitoring shows that stalagmite δ13C in Yok Balum
cave is governed by infiltration changes associated with tropical wet season rainfall. Higher
(lower) δ13C values reflect drier (wetter) conditions related to Intertropical Convergence
Zone position and trade winds intensity.
Comparison with NAO reconstructions (Proctor et al. 2000, Trouet et al. 2009, Wassenburg et
al. 2013) reveals that YOK-I δ13C sensitively records NAO-related rainfall dynamics over
Belize. The Median Absolute Deviation (MAD) of δ13C extends NAO reconstructions to the
last 2,000 years and indicates that high latitude volcanic aerosols force negative NAO
phases.
We infer that volcanic aerosols modify inter-hemispheric temperature contrasts at
multi-annual scale, resulting in meridional relocation of the ITCZ and the Bermuda-Azores
High, altering NAO and tropical rainfall patterns. Decade-long dry periods in the 11th and the
late 18th century relate to major high northern latitude eruptions and exemplify the climatic
response to volcanic forcing by reorganization of atmospheric circulation over the North
Atlantic.
References
Hurrell et al. (2003) An Overview of the North Atlantic Oscillation. Geophys. Monogr.
134
Kennett & Breitenbach et al. (2012) Development and Disintegration of Maya Political
Systems in Response to Climate Change. Science 338, 788-791
Proctor et al. (2000) A thousand year speleothem proxy record of North Atlantic climate from
Scotland. Clim. Dyn. 16, 815-820
Trouet et al. (2009) Persistent Positive North Atlantic Oscillation Mode Dominated the
Medieval Climate Anomaly. Science 324, 78-80
Wassenburg et al. (2013) Moroccan speleothem and tree ring records suggest a variable
positive state of the North Atlantic Oscillation during the Medieval Warm Period. Earth
Planet. Sci. Lett. 375, 291-302 |
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