Orbital signals in carbon isotopes: phase distortion as a signature of the carbon cycle

0480226 - GFÚ 2018 RIV US eng J - Článek v odborném periodiku
Laurin, Jiří - Růžek, Bohuslav - Giorgioni, M.
Orbital signals in carbon isotopes: phase distortion as a signature of the carbon cycle.
Paleoceanography. Roč. 32, č. 11 (2017), s. 1236-1255. ISSN 0883-8305
Grant CEP: GA ČR GA17-10982S
Institucionální podpora: RVO:67985530
Klíčová slova: Eocene thermal maximum * global warming events * Milankovitch cycles
Obor OECD: Geology
Impakt faktor: 2.718, rok: 2017

Isotopic mass balance models are employed here to study the response of carbon isotope composition (delta C-13) of the ocean-atmosphere system to amplitude-modulated perturbations on Milankovitch time scales. We identify a systematic phase distortion, which is inherent to a leakage of power from the carrier precessional signal to the modulating eccentricity terms in the global carbon cycle. The origin is partly analogous to the simple cumulative effect in sinusoidal signals, reflecting the residence time of carbon in the ocean-atmosphere reservoir. The details of origin and practical implications are, however, different. In amplitude-modulated signals, the deformation is manifested as a lag of the 405 kyr eccentricity cycle behind amplitude modulation (AM) of the short (similar to 100 kyr) eccentricity cycle. Importantly, the phase of AM remains stable during the carbon cycle transfer, thus providing a reference framework against which to evaluate distortion of the 405 kyr term. The phase relationships can help to (1) identify depositional and diagenetic signatures in delta C-13 and (2) interpret the pathways of astronomical signal through the climate system. The approach is illustrated by case studies of Albian and Oligocene records using a new computational tool EPNOSE (Evaluation of Phase in uNcertain and nOisy SEries). Analogous phase distortions occur in other components of the carbon cycle including atmospheric CO2 levels. Hence, to fully understand the causal relationships on astronomical time scales, paleoclimate models may need to incorporate realistic, amplitude-modulated insolation instead of monochromatic sinusoidal approximations. Finally, detection of the lagged delta C-13 response can help to reduce uncertainties in astrochronological age models that are tuned to the 405 kyr cycle.
Trvalý link: http://hdl.handle.net/11104/0276227