Building the Holocene clinothem in the Gulf of Papua: An ocean circulation study

This paper investigates the role that tidal and wind-driven flows and buoyant river plumes play in the development of the Holocene clinothem in the Gulf of Papua. Time series data from bottom tripods and a mooring were obtained at four locations near the mouth of the Fly River during portions of 2003 and 2004. Flows in the Gulf of Papua during calendar year 2003 were hindcast every 3 h using the Navy Coastal Ocean Model (NCOM) with boundary conditions from the Navy Atmospheric Prediction System, the east Asian seas implementation of NCOM, and the OTIS Tidal Inversion System. Results show that tidal flows on the modern clinoform are strong and are landward and seaward directed. Peak spring tidal velocities can provide the shear stresses necessary to keep sediment up to sand size in motion as the wind-driven and baroclinic currents distribute it from the river mouths across and along the shelf in two circulation states. During the monsoon season, the clinoform topset is swept by a seaward surface flow and landward bottom flow, reflecting river plumes and coastal upwelling. Seaward, this structure evolves into a SW directed surface current over the clinothem foreset with accompanying landward directed near-bed currents that trend obliquely up the foreset to the WSW over much of the clinothem. During the trade wind season, the inner and outer topset are swept by NE directed, contour-parallel surface currents, underneath which lie obliquely landward near-bed currents. These modeled flows and complex gyres in shallow water coupled with wave- and current-supported gravity flows or river floods can explain the form, internal clinoform shapes, and mineralogy of the modern Gulf of Papua clinothem

Molecular and morphometric variation in European populations of the articulate brachiopod <i>Terebeatulina retusa</i>

Molecular and morphometric variation within and between population samples of the articulate brachiopod &lt;i&gt;Terebratulina&lt;/i&gt; spp., collected in 1985-1987 from a Norwegian fjord, sea lochs and costal sites in western Scotland, the southern English Channel (Brittany) and the western Mediterranean, were measured by the analysis of variation in the lengths of mitochondrial DNA (mtDNA) fragments produced by digestion with nine restriction endonucleases and by multivariate statistical analysis of six selected morphometric parameters. Nucleotide difference within each population sample was high. Nucleotide difference between population samples from the Scottish sites, both those that are tidally contiguous and those that appear to be geographically isolated, were not significantly different from zero. Nucleotide differences between the populations samples from Norway, Brittany, Scotland and the western Mediterranean were also very low. Morphometric analysis confirmed the absence of substantial differentiation

Intense hurricane activity over the past 1500 years at South Andros Island, the Bahamas

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in E. J., Donnelly, J. P., van Hengstum, P. J., Wiman, C., Sullivan, R. M., Winkler, T. S., d'Entremont, N. E., Toomey, M., & Albury, N. Intense hurricane activity over the past 1500 years at South Andros Island, the Bahamas. Paleoceanography and Paleoclimatology, 34(11), (2019): 1761-1783, doi:10.1029/2019PA003665.Hurricanes cause substantial loss of life and resources in coastal areas. Unfortunately, historical hurricane records are too short and incomplete to capture hurricane‐climate interactions on multi‐decadal and longer timescales. Coarse‐grained, hurricane‐induced deposits preserved in blue holes in the Caribbean can provide records of past hurricane activity extending back thousands of years. Here we present a high resolution record of intense hurricane events over the past 1500 years from a blue hole on South Andros Island on the Great Bahama Bank. This record is corroborated by shorter reconstructions from cores collected at two nearby blue holes. The record contains coarse‐grained event deposits attributable to known historical hurricane strikes within age uncertainties. Over the past 1500 years, South Andros shows evidence of four active periods of hurricane activity. None of these active intervals occurred in the past 163 years. We suggest that Intertropical Convergence Zone position modulates hurricane activity on the island based on a correlation with Cariaco Basin titanium concentrations. An anomalous gap in activity on South Andros Island in the early 13th century corresponds to a period of increased volcanism. The patterns of hurricane activity reconstructed from South Andros Island closely match those from the northeastern Gulf of Mexico but are anti‐phased with records from New England. We suggest that either changes in local environmental conditions (e.g., SSTs) or a northeastward shift in storm tracks can account for the increased activity in the western North Atlantic when the Gulf of Mexico and southeastern Caribbean are less active.This work was funded by the National Science Foundation Graduate Research Fellowship (to E.J.W.), National Science Foundation grant OCE‐1356708 (to J.P.D. and P.J.vH.), the Dalio Explore Foundation and the USGS Land Change Science Program (M.R.T.). We are grateful to members of WHOI Coastal Systems Group, in particular Stephanie Madsen, for their help in the processing core samples. We thank two anonymous reviewers, Matthew Lachniet, Marci Robinson (USGS) and Miriam Jones (USGS) for their helpful feedback on earlier versions of this manuscript. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The data are available on the National Climatic Data Center (http://www.ncdc.noaa.gov/dataaccess/paleoclimatology‐data) and WHOI Coastal Systems Group (https://web.whoi.edu/coastal‐group/) websites

Adoption incentives and environmental policy timing under asymmetric information and strategic firm behaviour

We consider the incentives of a single firm to invest in a cleaner technology under emission quotas and emission taxation. We assume asymmetric information about the firm's cost of employing the new technology. Policy is set either before the firm invests (commitment) or after (time consistency). Contrary to conventional wisdom, we find that with commitment (time consistency), quotas give higher (lower) investment incentives than taxes. With quotas (taxes), commitment generally leads to higher (lower) welfare than time consistency. Under commitment with quadratic abatement costs and environmental damages, a modified Weitzman rule applies and quotas usually lead to higher welfare than taxes

How do MNC R&amp;D laboratory roles affect employee international assignments?

Research and development (R&#38;D) employees are important human resources for multinational corporations (MNCs) as they are the driving force behind the advancement of innovative ideas and products. International assignments of these employees can be a unique way to upgrade their expertise; allowing them to effectively recombine their unique human resources to progress existing knowledge and advance new ones. This study aims to investigate the effect of the roles of R&#38;D laboratories in which these employees work on the international assignments they undertake. We categorise R&#38;D laboratory roles into those of the support laboratory, the locally integrated laboratory and the internationally interdependent laboratory. Based on the theory of resource recombinations, we hypothesise that R&#38;D employees in support laboratories are not likely to assume international assignments, whereas those in locally integrated and internationally interdependent laboratories are likely to assume international assignments. The empirical evidence, which draws from research conducted on 559 professionals in 66 MNC subsidiaries based in Greece, provides support to our hypotheses. The resource recombinations theory that extends the resource based view can effectively illuminate the international assignment field. Also, research may provide more emphasis on the close work context of R&#38;D scientists rather than analyse their demographic characteristics, the latter being the focus of scholarly practice hitherto

Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon

It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event

Hubble Space Telescope observations of the Kepler-field cluster NGC 6819 - I. The bottom of the white dwarf cooling sequence

We use Hubble Space Telescope (HST) to reach the end of the white dwarf (WD) cooling sequence (CS) in the solar-metallicity open cluster NGC 6819. Our photometry and completeness tests show a sharp drop in the number of WDs along the CS at magnitudes fainter than mF606W = 26.050 ± 0.075. This implies an age of 2.25 ± 0.20 Gyr, consistent with the age of 2.25 ± 0.30 Gyr obtained from fits to the main-sequence turn-off. The use of different WD cooling models and initial–final-mass relations have a minor impact the WD age estimate, at the level of ∼0.1 Gyr. As an important by-product of this investigation we also release, in electronic format, both the catalogue of all the detected sources and the atlases of the region (in two filters). Indeed, this patch of sky studied by HST (of size ∼70 arcmin²) is entirely within the main Kepler-mission field, so the high-resolution images and deep catalogues will be particularly useful.JA and IRK acknowledge support from STScI grant GO-11688 and GO-12669. PB was supported in part by the NSERC Canada and by the Fund FRQ-NT (Québec)