Absence of internal multidecadal and interdecadal oscillations in climate model simulations

For several decades the existence of interdecadal and multidecadal internal climate oscillations has been asserted by numerous studies based on analyses of historical observations, paleoclimatic data and climate model simulations. Here we use a combination of observational data and state-of-the-art forced and control climate model simulations to demonstrate the absence of consistent evidence for decadal or longer-term internal oscillatory signals that are distinguishable from climatic noise. Only variability in the interannual range associated with the El Niño/Southern Oscillation is found to be distinguishable from the noise background. A distinct (40–50 year timescale) spectral peak that appears in global surface temperature observations appears to reflect the response of the climate system to both anthropogenic and natural forcing rather than any intrinsic internal oscillation. These findings have implications both for the validity of previous studies attributing certain long-term climate trends to internal low-frequency climate cycles and for the prospect of decadal climate predictability.

Excitation and Dynamics of Domain Walls in Three-Layer Ferromagnetic Structure with Different Parameters of the Magnetic Anisotropy and Exchange

The dynamics of domain walls (DW) in three-layered ferromagnetic was studied. The minimum velocity required for a DW to pass through the spatial modulation region was calculated. The excitation of DW internal oscillation modes and localized magnetic inhomogeneity of breather type was analyzed.

Losing the beat: deficits in temporal coordination

Tapping or clapping to an auditory beat, an easy task for most individuals, reveals precise temporal synchronization with auditory patterns such as music, even in the presence of temporal fluctuations. Most models of beat-tracking rely on the theoretical concept of pulse: a perceived regular beat generated by an internal oscillation that forms the foundation of entrainment abilities. Although tapping to the beat is a natural sensorimotor activity for most individuals, not everyone can track an auditory beat. Recently, the case of Mathieu was documented (Phillips-Silver et al. 2011 Neuropsychologia 49 , 961–969. ( doi:10.1016/j.neuropsychologia.2011.02.002 )). Mathieu presented himself as having difficulty following a beat and exhibited synchronization failures. We examined beat-tracking in normal control participants, Mathieu, and a second beat-deaf individual, who tapped with an auditory metronome in which unpredictable perturbations were introduced to disrupt entrainment. Both beat-deaf cases exhibited failures in error correction in response to the perturbation task while exhibiting normal spontaneous motor tempi (in the absence of an auditory stimulus), supporting a deficit specific to perception–action coupling. A damped harmonic oscillator model was applied to the temporal adaptation responses; the model's parameters of relaxation time and endogenous frequency accounted for differences between the beat-deaf cases as well as the control group individuals.

Mid-Holocene emergence of a low-frequency millennial oscillation in western Mediterranean climate: Implications for past dynamics of the North Atlantic atmospheric westerlies

The nature and tempo of Holocene climate variability is examined in the record of forest vegetation from western Mediterranean marine core MD95-2043. Episodes of forest decline occurred at 10.1, 9.2, 8.3, 7.4, 5.4–4.5 and 3.7–2.9 cal. ka BP, and between 1.9 cal. ka BP and the top of the record (1.3 cal. ka BP). Wavelet analysis confirms a ~900 yr periodicity prior to and during the early Holocene and the dominance of a ~1750 yr periodicity after 6 cal. ka BP. The ~900 yr periodicity has counterparts in numerous North Atlantic and Northern Hemisphere palaeoclimate records, and in solar irradiance proxies (Δ14C and 10Be), and may relate to a Sun–climate connection during the early Holocene. Comparisons between the MD95-2043 forest record and strategically located records from Morocco, Iceland, Norway and Israel suggest that the ~1750 yr mid- to late-Holocene oscillation reflects shifts between a prevailing strong and weak state of the zonal flow, with impacts similar to the positive and negative modes of the present-day North Atlantic Oscillation (NAO). The mid- to late-Holocene millennial oscillation in zonal flow appears closely coupled to North Atlantic surface ocean circulation dynamics, and may have been driven by an internal oscillation in deep-water convection strength. The findings suggest that the mid-Holocene transition in western Mediterranean climate was accompanied by a shift in the fundamental tempo of millennial-scale variability, reflecting contrasting sensitivity of the North Atlantic climate system to different forcing factors (solar versus oceanic) under deglacial and fully interglacial conditions.