SGER: Solar Influence on High-frequency Climate Variability--Possible Links to the Atlantic Multidecadal Oscillation and Hurricane Activity

University Of South Florida, Tampa FL

Investigators

Abstract

This award funds research, under the auspices of the Small Grants for Exploratory Research (SGER) program, to test the hypothesis that the Atlantic Multidecadal Oscillation (AMO) is related to an 80-year cycle in energy output from the sun (i.e. the Gleissberg cycle). The AMO is characterized by statistically significant variability in North Atlantic Ocean sea-surface temperature. As reported by several researchers, analyses of global instrumental records, proxy climate records of the last 400 years, and model output have identified a 60 year to 80 year oscillation in climate signals. Although the AMO is most strongly expressed in the North Atlantic Basin, the influence of the AMO extends to areas adjacent to the North Atlantic. The AMO correlates with rainfall variations in the Mississippi River Basin, African drought frequency, and winter temperatures in Europe. The AMO also appears to influence the frequency of hurricanes in the North Atlantic Basin. The mechanism behind how the AMO is forced is currently unknown, but most researchers infer that the AMO represents an internal oscillation of the atmosphere-ocean system. Specifically, the researchers will analyze the frequency of existing highly resolved climate proxy records adjacent to the North Atlantic Basin to determine if AMO-like variability occurs over the late Holocene (~last 2,000 years). Identifying the presence of AMO-like oscillations for the last few thousand years will help evaluate whether these oscillations are a persistent feature of late Holocene climate. In addition, the researchers will analyze existing highly resolved late Holocene climate proxy records from area distal to the North Atlantic Basin for the presence of AMO-like oscillations. The researchers are motivated by the hypothesis that if the AMO is an internal oscillation of the atmosphere-ocean system focused in the North Atlantic Basin, then the occurrence of AMO-like oscillations in records far from the North Atlantic Basin should be subdued or absent. In contrast, if the AMO is forced by variations in solar output, the researchers speculate that AMO-like oscillations should be a persistent global signal and be present in climate proxy records from a wide geographic area. The proposed research seems to fit well into the high risk and exploratory nature of the SGER program. The proposed research is quite unique and timely. The 2005 hurricane season was unusually active, as evidenced by written records, and some key research questions have emerged that involve exploring paleoclimate archives for evidence of large-scale climate oscillations and identifying possible physical forcing mechanisms. Such research may yield a significant scientific payoff in terms of a more complete understanding of Earths climate.