CR 29:73-84 (2005)  -  doi:10.3354/cr029073

Sea-level pressure composite mapping in dendroclimatology: advocacy and an Agathis australis (kauri) case study

Anthony Fowler*

School of Geography and Environmental Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand

ABSTRACT: A typical starting point in dendroclimatological research is to statistically relate tree-ring growth indices to local or regional climate variables (response function analysis). This sometimes leads to identification of links between tree growth and (often oscillatory) perturbations in atmospheric circulation, such as the El Niño–Southern Oscillation (ENSO) phenomenon. This approach relies on the researcher linking the (hopefully known) local-scale climate impacts of an oscillatory phenomenon with the response function results. A supplementary approach, advocated here, is to directly investigate relationships between tree growth and atmospheric circulation using composite mapping techniques. This paper demonstrates composite mapping, using the United Kingdom Meteorological Office gridded global monthly mean sea-level pressure (MSLP) data set and Agathis australis (kauri) tree rings. The results show that composite mapping is a powerful tool for tree-ring research, capable of identifying atmospheric circulation characteristics associated with wide and narrow tree rings, and helping to determine the potential of tree rings for reconstructing atmospheric circulation features. Results for kauri indicate that MSLP anomaly patterns associated with wide (narrow) tree rings have strong similarities to anomaly patterns associated with El Niño (La Niña) events. Relationships are strongest for wide tree rings and for the western pole of the Southern Oscillation. The results indicate that kauri is a strong ENSO proxy, with reconstruction potential strongest for the 6 mo from September to February.

KEY WORDS: Sea-level pressure · Composite mapping · Dendroclimatology · Kauri · Agathis australis

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