The 'snowball Earth' hypothesis posits the occurrence of a sequence of glaciations in the Earth's history sufficiently deep that photosynthetic activity was essentially arrested. Because the time interval during which these events are believed to have occurred immediately preceded the Cambrian explosion of life, the issue as to whether such snowball states actually developed has important implications for our understanding of evolutionary biology. Here we couple an explicit model of the Neoproterozoic carbon cycle to a model of the physical climate system. We show that the drawdown of atmospheric oxygen into the ocean, as surface temperatures decline, operates so as to increase the rate of remineralization of a massive pool of dissolved organic carbon. This leads directly to an increase of atmospheric carbon dioxide, enhanced greenhouse warming of the surface of the Earth, and the prevention of a snowball state.

We have observed that the second-harmonic signal generated from oxidized Si(001) varies on a time scale of several seconds in experiments involving a fundamental beam of lambda = 770 nm, 110-fs pulses at 76 MHz. We suggest that the temporal behavior arises from absorption of weak (<100-fW average power) third-harmonic light generated in air or in the sample, inducing charge transfer across the Si-SiO(2) interface and trapping in the oxide layer. Detrapping has been determined to take several minutes.

Taken together, these findings indicate that in beta cells the deacetylase SIRT1 regulates the expression of specific mitochondria-related genes that control metabolic coupling, and that a decrease in beta cell Sirt1 expression impairs glucose sensing and insulin secretion.

Surface liquid water is essential for standard planetary habitability. Calculations of atmospheric circulation on tidally locked planets around M stars suggest that this peculiar orbital configuration lends itself to the trapping of large amounts of water in kilometers-thick ice on the night side, potentially removing all liquid water from the day side where photosynthesis is possible. We study this problem using a global climate model including coupled atmosphere, ocean, land, and sea-ice components as well as a continental ice sheet model driven by the climate model output. For a waterworld we find that surface winds transport sea ice toward the day side and the ocean carries heat toward the night side. As a result, night-side sea ice remains O(10 m) thick and night-side water trapping is insignificant. If a planet has large continents on its night side, they can grow ice sheets O(1000 m) thick if the geothermal heat flux is similar to Earth's or smaller. Planets with a water complement similar to Earth's would therefore experience a large decrease in sea level when plate tectonics drives their continents onto the night side, but would not experience complete day-side dessication. Only planets with a geothermal heat flux lower than Earth's, much of their surface covered by continents, and a surface water reservoir O(10%) of Earth's would be susceptible to complete water trapping.

[1] We examine the general conditions that must be satisfied by the configuration of the continents in order that steady state solutions for Neoproterozoic climate exist that are characterized by heavy continental glaciation but for which a substantial area of open water in the equatorial region persists. Such solutions have previously been termed "soft snowball" or "slush ball" to distinguish them from the "hard snowball" solutions that some have suggested be required to fit the observational constraints. It is found that three conditions are critical in this regard: (1) the continental area in high latitudes should be large enough that a massive ice sheet may develop even when pCO 2 is relatively high, an ice sheet complex that is subsequently capable of flowing to lower latitude. (2) The continental fragments in low latitude must be connected (or separated only by continental shelves above which water depths are small) to a significant degree with those at higher latitudes. (3) A relatively simple supercontinental outline favors the formation of the "soft snowball" state. Although the latter requirement is important, we have nevertheless found that soft snowball solutions are realized for the realistic Sturtian continental configuration of Li et al. (2008) that existed at ∼720 Ma. However, in order for these states to exist, the positions of the individual continental fragments must be slightly adjusted so as to improve their connectivity. These adjustments are consistent with the error bars on the paleomagnetic inferences of paleolatitude and the even less well constrained paleolongitude. We also demonstrate that "soft snowball" solutions do not exist in models devoid of active continental ice sheets capable of flowing over the landscape. These results for Sturtian conditions extend our previously published results for the Marinoan period during which the supercontinent was centered upon much higher latitudes.

S U M M A R YWe determine Euler vectors for 12 plates, including the Philippine Sea plate (PH), relative to the fixed Pacific plate (PA) by inverting the earthquake slip vectors along the boundaries of the Philippine Sea plate, GPS observed velocities, and 1122 data from the NUVEL-1 and the NUVEL-1A global plate motion model, respectively. This analysis thus also yields Euler vectors for the Philippine Sea plate relative to adjacent plates. Our results are consistent with observed data and can satisfy the geological and geophysical constraints along the Caroline (CR)-PH and PA-CR boundaries. The results also give insight into internal deformation of the Philippine Sea plate. The area enclosed by the Ryukyu Trench-Nankai Trough, Izu-Bonin Trench and GPS stations S102, S063 and Okino Torishima moves uniformly as a rigid plate, but the areas near the Philippine Trench, Mariana Trough and Yap-Palau Trench have obvious deformation.

Abstract. We identify the "hard snowball" bifurcation point at which total sea-ice cover of the oceans is expected by employing the comprehensive coupled climate model CCSM3 (Community Climate System Model version 3) for two realistic Neoproterozoic continental configurations, namely a low-latitude configuration appropriate for the 720 Ma Sturtian glaciation and a higher southern latitude configuration reconstructed for 570 Ma but which has often been employed in the past to study the later 635 Ma Marinoan glaciation. Contrary to previous suggestions, we find that for the same total solar insolation (TSI) and atmospheric CO 2 concentration (pCO 2 ), the 570 Ma continental configuration is characterized by colder climate than the 720 Ma continental configuration and enters the hard snowball state more easily on account of the following three factors: the higher effective albedo of the snow-covered land compared to that of sea ice, the more negative net cloud forcing near the ice front in the Northern Hemisphere (NH), and, more importantly, the more efficient sea-ice transport towards the Equator in the NH due to the absence of blockage by continents. Beside the paleogeography, we also find the optical depth of aerosol to have a significant influence on this important bifurcation point. When the high value (recommended by CCSM3 but demonstrated to be a significant overestimate) is employed, the critical values of pCO 2 , beyond which a hard snowball will be realized, are between 80 and 90 ppmv (sea-ice fraction 55 %) and between 140 and 150 ppmv (sea-ice fraction 50 %) for the Sturtian and Marinoan continental configurations, respectively. However, if a lower value is employed that enables the model to approximately reproduce the present-day climate, then the critical values of pCO 2 become 50-60 ppmv (sea-ice fraction 57 %) and 100-110 ppmv (sea-ice fraction 48 %) for the two continental configurations, respectively. All of these values are higher than previously obtained for the present-day geography (17-35 ppmv) using the same model, primarily due to the absence of vegetation, which increases the surface albedo, but are much lower than that obtained previously for the Marinoan continental configuration using the ECHAM5/MPI-OM model in its standard configuration (∼ 500 ppmv). However, when the sea-ice albedo in that model was reduced from 0.75 to a more appropriate value of 0.45, the critical pCO 2 becomes ∼ 204 ppmv, closer to the values obtained here. Our results are similar to those obtained with the present-day geography (70-100 ppmv) when the most recent version of the NCAR model, CCSM4, was employed.

The thermal structures of lithosphere in North China(105°E – 124°E, 30°N – 41°N) were calculated using two kinds of average heat flow on 1° × 1° Latitude‐Longitude grid combining with four heat production models which were obtained from observed heat production and from the inversion of Curie depth distribution. By comparison and analysing the thermal structures obtained from different models, the most reasonable model was obtained. The temperature at Moho‐discontinuity is about from 450°C to 750°C. The thickness of thermal lithophere is from 60km to 180km. It is found that big fault systems are related to thiner part of the lithosphere and the earthquakes of MS >6.5 occurred near the area of thiner part of the lithosphere and the area in which the temperature of the Moho‐discontinuity is higher.