Climate model and proxy data constraints on ocean warming across the Paleocene-Eocene Thermal Maximum

Constraining the greenhouse gas forcing, climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community. Here we provide a new compilation and synthesis of the available marine proxy temperature data across the largest of these hyperthermals, the Paleocene-Eocene Thermal Maximum (PETM). This includes the application of consistent temperature calibrations to all data, including the most recent set of calibrations for archaeal lipid-derived palaeothermometry. This compilation provides the basis for an informed discussion of the likely range of PETM warming, the biases present in the existing record and an initial assessment of the geographical pattern of PETM ocean warming. To aid interpretation of the geographic variability of the proxy-derived estimates of PETM warming, we present a comparison of this data with the patterns of warming produced by high pCO2 simulations of Eocene climates using the Hadley Centre atmosphere-ocean general circulation model (AOGCM) HadCM3L. On the basis of this comparison and taking into account the patterns of intermediate-water warming we estimate that the global mean surface temperature anomaly for the PETM is within the range of 4 to 5°C

Calcareous nannofossil assemblages of the Late Cretaceous Fiqa Formation, north Oman

This study presents the first detailed calcareous nannofossil assemblage data from the Late Cretaceous succession of the subsurface Aruma Basin, north Oman. The taxonomic description and documentation of assemblage composition are based on extensive quantitative analysis of ditch cuttings and side-wall samples from eight hydrocarbon exploration wells across north Oman. The samples studied from those wells cover the Coniacian to earliest Maastrichtian deep marine shales and marls of the subsurface Fiqa Formation. These fine-grained siliciclastic deposits often yield moderately to well-preserved nannofossil assemblages, especially in the Campanian intervals. Consequently, diverse assemblages have been recorded from the Fiqa Formation, with a total diversity of ∼200 species, including two new species, Staurolithites ormae sp. nov. and Chiastozygus fahudensis sp. nov., which are illustrated and described. Extensive imaging of this diversity is provided here, as are stratigraphic distributions of the main components from a key reference well in north Oman, W-4. Poorly described groups such as Staurolithites are closely investigated and their utility for stratigraphic applications is highlighted. Relative abundances of nannofossil taxa with strong palaeoenvironmental preferences have revealed new insights into the palaeo-productivity of the basin. High-fertility species like Discorhabdus ignotus, Biscutum constans and Zeugrhabdotus erectus show substantial variations in abundance throughout the Fiqa Formation, reflecting long-term shifts in the productivity conditions of the basin. This is supported by abundance patterns of Watznaueria barnesiae and Micula staurophora that show a broadly inverse correlation with the high-fertility species. The Fiqa Formation represents a key regional seal unit for the Cretaceous hydrocarbon reservoirs of Oman, as well as being a productive unit elsewhere in the Arabian Peninsula. Beyond the Aruma Basin of Oman, this study will provide a key reference point for future biostratigraphic or palaeoenvironmental analyses of the Late Cretaceous calcareous nannofossil assemblages across the Middle East and other southern Tethyan areas.</p

Evidence that smooth pursuit velocity, not eye position, modulates alpha and beta oscillations in human middle temporal cortex

Suppression of 5–25 Hz oscillations have been observed in MT1 during pursuit eye move- ments, suggesting oscillations that play a role in oculomotor control and/or the integration of extrareti- nal signals during pursuit. The amplitude of these rhythms appears to covary with head-centered eye position, but an alternative is that they depend on a velocity signal that lags the movement of the eyes. To investigate, we explored how alpha and beta amplitude changes related to ongoing eye move- ment depended on pursuit at different eccentricities. The results revealed largely identical patterns of modulation in the alpha and beta amplitude, irrespective of the eccentricity at which the pursuit eye movement was performed. The signals we measured therefore do not depend on head-centered posi- tion. A second experiment was designed to investigate whether the alpha and beta oscillations depended on the direction of pursuit, as opposed to just speed. We found no evidence that alpha or beta oscillations depended on direction, but there was a significant effect of eye speed on the magni- tude of the beta suppression. This suggests distinct functional roles for alpha and beta suppression in pursuit behavior

Bispectrum of the Sunyaev-Zel'dovich Effect

We perform a detailed study of the bispectrum of the Sunyaev-Zel'dovich effect. Using an analytical model for the pressure profiles of the intracluster medium, we demonstrate the SZ bispectrum to be a sensitive probe of the amplitude of the matter power spectrum parameter sigma_8. We find that the bispectrum amplitude scales as B_SZ ~ sigma_8^{11-12}, compared to that of the power spectrum, which scales as A_tSZ ~ sigma_8^{7-9}. We show that the SZ bispectrum is principally sourced by massive clusters at redshifts around z~0.4, which have been well-studied observationally. This is in contrast to the SZ power spectrum, which receives a significant contribution from less-well understood low-mass and high-redshift groups and clusters. Therefore, the amplitude of the bispectrum at l~3000 is less sensitive to astrophysical uncertainties than the SZ power spectrum. We show that current high resolution CMB experiments should be able to detect the SZ bispectrum amplitude with high significance, in part due to the low contamination from extra-galactic foregrounds. A combination of the SZ bispectrum and the power spectrum can sharpen the measurements of thermal and kinetic SZ components and help distinguish cosmological and astrophysical information from high-resolution CMB maps.Comment: 12 pages, 8 figures, published in The Astrophysical Journa