Constraints on diffuse neutrino background from primordial black holes

We calculated the energy spectra and the fluxes of electron neutrino emitted in the process of evaporation of primordial black holes (PBHs) in the early universe. It was assumed that PBHs are formed by a blue power-law spectrum of primordial density fluctuations. We obtained the bounds on the spectral index of density fluctuations assuming validity of the standard picture of gravitational collapse and using the available data of several experiments with atmospheric and solar neutrinos. The comparison of our results with the previous constraints (which had been obtained using diffuse photon background data) shows that such bounds are quite sensitive to an assumed form of the initial PBH mass function.Comment: 18 pages,(with 7 figures

Ice wedges as archives of winter palaeoclimate: a review

Ice wedges are a characteristic feature of northern permafrost landscapes and grow mainly by snowmelt that refreezes in thermal contraction cracks that open in winter. In high latitudes the stable‐isotope composition of precipitation (δ18O and δD) is sensitive to air temperature. Hence, the integrated climate information of winter precipitation is transferred to individual ice veins and can be preserved over millennia, allowing ice wedges to be used to reconstruct past winter climate. Recent studies indicate a promising potential of ice‐wedge‐based paleoclimate reconstructions for more comprehensive reconstructions of Arctic past climate evolution. We briefly highlight the potential and review the current state of ice‐wedge paleoclimatology. Existing knowledge gaps and challenges are outlined and priorities for future ice‐wedge research are suggested. The major research topics are (1) frost cracking and infilling dynamics, (2) formation and preservation of the stable‐isotope information, (3) ice‐wedge dating, (4) age‐model development and (5) interpretation of stable‐isotope time series. Progress in each of these topics will help to exploit the paleoclimatic potential of ice wedges, particularly in view of their unique cold‐season information, which is not adequately covered by other terrestrial climate archives

Special Issue: Recent advances (2008 – 2015) in the study of ground ice and cryostratigraphy

Cryostratigraphy involves the description, interpretation and correlation of ground-ice 17 structures (cryostructures) and their relationship to the host deposits. Recent advances in the 18 study of ground ice and cryostratigraphy concern permafrost aggradation and degradation, 19 massive-ice formation and evaluation of ground-ice content. Field studies have increased our 20 knowledge of cryostructures and massive ground ice in epigenetic and syngenetic permafrost. 21 Epigenetic permafrost deposits are relatively ice-poor and composed primarily of pore-filled 22 cryostructures, apart from an ice-enriched upper section and intermediate layer. Syngenetic 23 permafrost deposits are commonly identified from cryostructures indicative of an aggrading 24 permafrost table and are characterized by a high ice content, ice-rich cryofacies, and nested 25 wedge ice. Degradation of ice-rich permafrost can be marked by thaw unconformities, 26 truncated buried ice wedges, ice-wedge pseudomorphs, and organic-rich ‘forest beds’. 27 Studies of massive ground ice have focused on wedge ice, thermokarst-cave ice, intrusive ice, 28 and buried ice. Significant advances have been made in methods for differentiating between 29 tabular massive ice bodies of glacier and intrasedimental origin. Recent studies have utilized 30 palynology, isotope geochemistry and hydrochemistry, in addition to sedimentary and 31 cryostratigraphic analyses. The application of remote sensing techniques and laboratory 32 methods such as CT scanning has improved estimations of the ice content of frozen 33 sediments

Snowball Earth climate dynamics and Cryogenian geology–geobiology

Geological evidence indicates that grounded ice sheets reached sea level at all latitudes during the long‐lived Sturtian (717–659 Ma) and Marinoan (ca 645–635 Ma) glaciations. Combined U-­‐Pb and Re-­‐Os geochronology suggests that the Sturtian glacial onset and both terminations were globally synchronous. Geochemical data imply that atmospheric pCO2 was 102x modern at the Marinoan termination, consistent with Snowball Earth hysteresis. Sturtian glaciation followed the breakup of a tropical supercontinent, and its onset coincided with the equatorial emplacement of a large igneous province. Modeling shows that the small thermal inertia of a globally frozen surface reverses the annual-mean Hadley circulation, resulting in equatorial net sublimation and net deposition elsewhere. Oceanic ice thickens, forming a sea glacier that flows gravitationally toward the equator, sustained by the hydrologic cycle and by basal freeze-on and melting. Tropical ice sheets flow faster as CO2 rises, but lose mass and become sensitive to orbital forcing. Dust accumulation in the equatorial zone engenders supraglacial oligotrophic meltwater ecosystems, favorable for cyanobacteria and many eukaryotes. Meltwater flushing through moulins enables organic burial and submarine deposition of subaerially-­‐erupted volcanic ash. The subglacial ocean is turbulent and well­‐mixed, in response to geothermal heating and conductive heat loss through the ice cover, increasing with latitude. Cap carbonates, unique to Snowball Earth terminations, are products of intense weathering and ocean stratification. Whole-­ocean warming and ice-sheet forebulge collapse allow marine coastal inundations to progress long after ice-sheet disappearance. The evolutionary legacy of Snowball Earth is perceptible in fossils and living organisms