Using a coupled-oscillator model of speech rhythm to estimate rhythmic variability in two Brazilian Portuguese varieties (CE and SP)

This paper presents preliminary results of a semi-automatic methodology to extract three parameters of a dynamic model of speech rhythm. The model attempts to analyze the production of rhythm as a system of coupled oscillators which represent syllabicity and phrase stress as levels of temporal organization. The estimated parameters are the syllabic oscillator entrainment rate (alpha), the syllabic oscillator decay rate (beta), and the coupling strength between the oscillators (w0). The methodology involves finding the <alpha, beta, w0> combination that minimizes the distance between natural duration contours and simulated contours generated using several combinations of the parameters. The distance between natural and model-generated contours was measured in two ways by comparing: (1) plain or overt syllable to syllable duration and (2) relative change along both contours.We applied this methodology to read speech produced by five speakers of the state of Ceará (CE) and eight speakers of the state of São Paulo (SP). Mean w0 and alpha values are compatible with the view that Brazilian Portuguese is a mixed-rhythm language. Results from two bayesian hierarchical regression models do not suggest a difference between SP and CE speakers, but indicate a difference between the two methods, with the relative change method generating lower alpha values and higher w0 values, and the reverse for the plain duration method.

The MIS 11 – MIS 1 analogy, southern European vegetation, atmospheric methane and the "early anthropogenic hypothesis"

Marine Isotope Stage (MIS) 11 has been considered a potential analogue for the Holocene and its future evolution. However, a dichotomy has emerged over the precise chronological alignment of the two intervals, with one solution favouring a synchronization of the precession signal and another of the obliquity signal. The two schemes lead to different implications over the natural length of the current interglacial and the underlying causes of the evolution of greenhouse gas concentrations. Here, the close coupling observed between changes in southern European tree populations and atmospheric methane concentrations in previous interglacials is used to evaluate the natural vs. anthropogenic contribution to Holocene methane emissions and assess the two alignment schemes. Comparison of the vegetation trends in MIS 1 and MIS 11 favours a precessional alignment, which would suggest that the Holocene is nearing the end of its natural course. This, combined with the divergence between methane concentrations and temperate tree populations after 5 kyr BP, provides some support for the notion that the Holocene methane trend may be anomalous compared to previous interglacials. In contrast, comparison of MIS 1 with MIS 19, which may represent a closer astronomical analogue than MIS 11, leads to substantially different conclusions on the projected natural duration of the current interglacial and the extent of the anthropogenic contribution to the Holocene methane budget. As answers vary with the choice of analogue, resolution of these issues using past interglacials remains elusive.

The MIS 11 – MIS 1 analogy, southern European vegetation, atmospheric methane and the "early anthropogenic hypothesis"

Marine Isotope Stage (MIS) 11 has been considered a potential analogue for the Holocene and its future evolution. However, a dichotomy has emerged over the precise chronological alignment of the two intervals, with one solution favouring a synchronization of the precession signal and another of the obliquity signal. The two schemes lead to different implications over the natural length of the current interglacial and the underlying causes of the evolution of greenhouse gas concentrations. Here the strong coherence observed between changes in temperate tree populations in southern Europe and atmospheric methane concentrations is used to evaluate the two alignment schemes. Comparison of the vegetation trends in MIS 1 and MIS 11 favours a precessional alignment, which would suggest that the Holocene is nearing the end of its natural course. It also provides some support for the notion that the Holocene methane trend may be anomalous compared to previous interglacials. In contrast, comparison of MIS 1 with MIS 19, which may represent a closer astronomical analogue than MIS 11, leads to substantially different conclusions on the projected natural duration of the current interglacial and the extent of the anthropogenic contribution to the Holocene methane budget. As answers vary with the choice of analogue, resolution of these issues using past interglacials remains elusive.