the Creative Commons Attribution 3.0 License. Climate of the Past Limitations of red noise in analysing Dansgaard-Oeschger events

• Main Authors: H. Braun, P. Ditlevsen, J. Kurths, M. Mudelsee, Correspondence To H. Braun
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2010
• Subjects: Dansgaard-Oeschger events; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.385.4342; http://www.pik-potsdam.de/members/kurths/publikationen/2009/clim-past-do-events-red_noise-braun/

Abstract. During the last glacial period, climate records from the North Atlantic region exhibit a pronounced spectral component corresponding to a period of about 1470 years, which has attracted much attention. This spectral peak is closely related to the recurrence pattern of Dansgaard-Oeschger (DO) events. In previous studies a red noise random process, more precisely a first-order autoregressive (AR1) process, was used to evaluate the statistical significance of this peak, with a reported significance of more than 99%. Here we use a simple mechanistic two-state model of DO events, which itself was derived from a much more sophisticated ocean-atmosphere model of intermediate complexity, to numerically evaluate the spectral properties of random (i.e., solely noise-driven) events. This way we find that the power spectral density of random DO events differs fundamentally from a simple red noise random process. These results question the applicability of linear spectral analysis for estimating the statistical significance of highly non-linear processes such as DO events. More precisely, to enhance our scientific understanding about the trigger of DO events, we must not consider simple “straw men ” as, for example, the AR1 random process, but rather test against realistic alternative descriptions.