Basal roughness of the Institute and Möller Ice Streams, West Antarctica: Process determination and landscape interpretation

We present a detailed analysis of bed roughness beneath Institute and Möller Ice Streams, west Antarctica, using radio-echo sounding data (RES) acquired in the austral summer of 2010/11. We assess roughness using a two-parameter approach and also assess the directionality of roughness relative to present-day ice flow. Our work highlights the wealth of additional information that resides in analyses of bed roughness. Employing these multiple approaches we show that spatially variable roughness patterns are partly a consequence of the ability of flowing ice not only to smooth the bed but also to redistribute and remove sediments, and to do this along-flow. Accordingly, we identify some fast-flow tributaries underlain by topography that has been streamlined and other tributaries that are underlain by sediments. We also identify locations that are currently protected from erosion, but where more ancient erosion may once have occurred. We conclude that detailed roughness analysis is a useful tool for landscape interpretation; and we suggest that the roughness of an ice-sheet’s bed should be viewed as the consequence not only of ancient marine sedimentation, but also as a product of more contemporary erosion and redistribution of sediments, as well as bedrock-smoothing that is ongoing because of continuing dynamic activity. In this way, basal roughness has the potential to evolve continually with ice sheet form and flow, and should not be viewed simply as a snapshot of either present-day or palaeo-basal conditions

PRISMA-S: an extension to the PRISMA Statement for Reporting Literature Searches in Systematic Reviews

Background: Literature searches underlie the foundations of systematic reviews and related review types. Yet, the literature searching component of systematic reviews and related review types is often poorly reported. Guidance for literature search reporting has been diverse, and, in many cases, does not offer enough detail to authors who need more specific information about reporting search methods and information sources in a clear, reproducible way. This document presents the PRISMA-S (Preferred Reporting Items for Systematic reviews and Meta-Analyses literature search extension) checklist, and explanation and elaboration. Methods: The checklist was developed using a 3-stage Delphi survey process, followed by a consensus conference and public review process. Results: The final checklist includes 16 reporting items, each of which is detailed with exemplar reporting and rationale. Conclusions: The intent of PRISMA-S is to complement the PRISMA Statement and its extensions by providing a checklist that could be used by interdisciplinary authors, editors, and peer reviewers to verify that each component of a search is completely reported and therefore reproducible.Melissa L. Rethlefsen, Shona Kirtley, Siw Waffenschmidt, Ana Patricia Ayala, David Moher, Matthew J. Page, Jonathan B. Koffel, and PRISMA-S Grou

Esca-Studies of the Structure and Composition of the Passive Film Formed On Stainless-Steels by Various Immersion Temperatures in 0.1 M Nacl Solution

This paper deals with the structure and composition of the passive film formed on the surface of two commercial stainless steels during immersion in 0.1 M NaCl for 0.5 h at 25, 60, and 90°C. The data shows that the passive films formed at 60 and 90°C by short-time solution exposure are very similar to these formed at 25°C, and are consistent with the three-factor model described previously: a hydrated layer in contact with the solution, an oxide layer consisting of iron and chromium oxides having maxima at depths of 3 and 10 Å, respectively, and a metallic layer enriched in nickel. There is a smooth transition between the layers, with the thickness of the outer two layers being about 15 Å

Paleoclimate, Paleoclimate history of the Arctic

Although the Arctic occupies less than 5% of the Earth's surface, it includes some of the strongest positive feedbacks in the climate system. Reconstructing the climate history of the Quaternary requires a suite of climate proxies that can be placed in a secure time frame. Most Arctic proxies reflect past summer temperatures, although a subset is sensitive to winter temperatures and/or precipitation. During the Quaternary, the Arctic has experienced a greater change in temperature, vegetation, and ocean surface characteristics than has any other Northern Hemisphere latitudinal band. Arctic temperature amplification is a consequence of several strong positive feedbacks. They include the fast feedbacks of snow and ice albedo, sea-ice insulation, vegetation, and permafrost, as well as a suite of slower responding feedbacks operating on glacial–interglacial timescales tied to the growth and decay of aerially extensive, thick continental ice sheets. Large changes in Arctic temperatures impact regions outside the Arctic through their proximal influence on the planetary energy balance and circulation of the Northern Hemisphere atmosphere and ocean, and with potential global impacts through changes in sea level, the release of greenhouse gases, and impacts on the ocean's meridional overturning circulation. Quantitative paleoclimate reconstructions for specific cold and warm times during the Quaternary suggest that Arctic temperature changes have been 3 to 4 times the corresponding hemispheric or globally averaged changes. This article provides a brief overview of climate changes leading up to the last ice age, then overviews the changes in Arctic climate during the Quaternary

Corrosion of Stainless-Steels in Chloride Solution - An Xps Investigation of Passive Films

Five commercial steels ranging from the martensitic stainless steel containing 12% chromium to the superferrite containing 29% chromium, 4% molybdenum, and 2% nickel have been studied by XPS. In addition, a pure iron-chromium alloy containing 7% chromium has been investigated. Armco iron and pure chromium (99.99%) were included as references. The formation of the passive films (or corrosion) occurred in deoxygenated 0.1 M NaCl solution (pH=5.6), from which the samples were transferred directly to the XPS chamber under controlled atmosphere (Ar). Concentration profiles (at.-%) of the alloy constituents in their oxidized and metallic states have been determined separately from the measured XPS depth profiles. For c≳= 12% chromium the passive films have the following structure: there is a depletion of Cr in the inner region, followed by an enrichment (concentration maximum) in the central region of the films. The height of this maximum increases, and its position shifts towards the surface with increasing chromium content in the alloy. The outermost monolayers are rich in water and hydroxyl groups. Various significant properties of the films change drastically at the critical chromium concentration of about 12%. This behaviour is rather independent of the other components (Mo, Ni, Cu) present in the alloys and is discussed in terms of a phase transition in the films which is controlled by the chromium concentration