HR: 11:35h
AN: PP12A-06    [Abstracts]
TI: Quasi-periodic Climate Teleconnections via the North Atlantic Oscillation: A New Perspective From Tree Rings
AU: * Meyers, S R
EM: stephen.meyers@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave., New Haven, CT 06511 United States
AU: Pagani, M
EM: mark.pagani@yale.edu
AF: Yale University, Department of Geology and Geophysics, 210 Whitney Ave., New Haven, CT 06511 United States
AB: Internal modes of climate variability such as the North Atlantic Oscillation (NAO) and the El Nino-Southern Oscillation (ENSO) significantly contribute to regional weather patterns on an inter-annual basis. Changes in the behavior of these modes over decadal and/or centennial timescales may represent an important driver of past climate events and future climate change. Importantly, if the internal modes express band-limited (periodic to quasi-periodic) variability, they provide a useful template for climate forecasting. Unfortunately, our ability to directly quantify the periodic/quasi-periodic nature of climate response to the internal modes is constrained by the limited temporal extent of instrumental records. In this study we present a novel approach toward recognition of band-limited climatic effects of the NAO in proxy records that span the past 400 years. The spatial climatic response of the NAO between northern and southern Europe provides a framework for detecting the influence of the NAO in proxy climate records. Specifically, if the NAO-forced climate signal is present it should be strongly correlated and anti-phased between the northern and southern regions of western Europe. To prospect for the NAO signal in paleoclimate data we employ independent networks of tree ring width series from Scandinavia and the Mediterranean. These locations were selected because modern instrumental records of the NAO and precipitation are significantly correlated in these regions, and tree ring width sensitivity to climate variability is maximized. The tree-ring width data from western Europe reveals a distinct 25-year quasi-periodic synchronization of climate change between Scandinavia and the Mediterranean during the 17th-20th centuries. Based on the dipole character of this signal, we propose that it is representative of climate forcing via the NAO. On this timescale of climate variability, dry/cold climate events in northern Europe are closely tied to wet events in southern Europe, and vice versa. Further, the 25-year quasi-period is modulated by a 200 year cycle, with the most pronounced climate cycles in Europe during the early 19th century and the weakest cycles during the late 17th century-early 18th century. The interval of weakest 25-year cycle expression (centered on 1700 AD) occurs within the Little Ice Age during the Maunder Minimum, and is coincident with a maximum in cosmogenic Delta 14C. These results, in conjunction with the 208-year and 23-26 year cycles observed in the cosmogenic Delta 14C record, suggest that the NAO embodies a mechanism for amplifying climate response to minor changes in solar irradiance.
DE: 3344 Paleoclimatology
DE: 3354 Precipitation (1854)
DE: 4215 Climate and interannual variability (3309)
DE: 4221 Dendrochronology
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting