Calving rates at tidewater glaciers vary strongly with ocean temperature

TerraSAR-X data were provided by DLR (project OCE1503), and funded by the Conoco Phillips-Lundin Northern Area Program through the CRIOS project (Calving Rates and Impact on Sea level). A.L. and S.B. are affiliated to the Climate Change Consortium of Wales (C3W). Mooring work is supported by the UK Natural Environment Research Council (Oceans 2025 and Northern Sea Program) and the Research Council of Norway (projects Cleopatra: 178766, Cleopatra II: 216537, and Circa: 214271/F20). Contribution by F.C. was undertaken through the Scottish Alliance for Geoscience Environment and Society (SAGES).Rates of ice mass loss at the calving margins of tidewater glaciers (frontal ablation rates) are a key uncertainty in sea level rise projections. Measurements are difficult because mass lost is replaced by ice flow at variable rates, and frontal ablation incorporates sub-aerial calving, and submarine melt and calving. Here we derive frontal ablation rates for three dynamically contrasting glaciers in Svalbard from an unusually dense series of satellite images. We combine ocean data, ice-front position and terminus velocity to investigate controls on frontal ablation. We find that frontal ablation is not dependent on ice dynamics, nor reduced by glacier surface freeze-up, but varies strongly with sub-surface water temperature. We conclude that calving proceeds by melt undercutting and ice-front collapse, a process that may dominate frontal ablation where submarine melt can outpace ice flow. Our findings illustrate the potential for deriving simple models of tidewater glacier response to oceanographic forcing.Publisher PDFPeer reviewe

Systems Analysis of complex glaciological processes and application to calving of Amery Ice Shelf, East Antarctica

Calving is a complex process subject to several cooperating atmospheric, oceanographic and glaciological forcings that vary in space and time, and whose relative effects are challenging to separate. Statistical ‘Systems Analysis’ is commonly used in engineering and economics to extricate complex ‘force–response’ relationships. Here we apply Systems Analysis to the Amery rift system, East Antarctica. We develop a scalable ‘System Model’ driven by a coarsely-sampled dataset characteristic of glaciological observations in remote locations, and validate it using rift lengths observed in 2000–06 and 2012. In this initial demonstration, we forecast a detachment date of ∼2019 ± 5 years for the large tabular iceberg colloquially known as the ‘Loose Tooth’, for which relative humidity surprisingly emerges as the best statistical predictor. RACMO2 climate modelling reveals that relative humidity correlates best with surface albedo and snowmelt, both of which are intimately linked to firn compaction and ice shelf temperature and flow. We postulate that relative humidity can therefore serve as a proxy for internal stress, a known key control of ‘Loose Tooth’ calving. Although no physical causality is implied in Systems Analysis, postulates such as this can aid in setting priorities in studies of complex glaciological processes

Extrusion induced low-order starch matrices: enzymic hydrolysis and structure

Waxy, normal and highwaymen maize starches were extruded with water as sole plasticizer to achieve low-order starch matrices. Of the three starches, we found that only high-amylose extrudate showed lower digestion rate/extent than starches cooked in excess water. The ordered structure of high-amylose starches in cooked and extruded forms was similar, as judged by NMR, XRD and DSC techniques, but enzyme resistance was much greater for extruded forms. Size exclusion chromatography suggested that longer chains were involved in enzyme resistance. We propose that the local molecular density of packing of amylose chains can control the digestion kinetics rather than just crystallinity, with the principle being that density sufficient to either prevent/limit binding and/or slow down catalysis can be achieved by dense amorphous packing

Do oxytocin neurones affect feeding?

From Wiley via Jisc Publications RouterHistory: received 2021-06-02, rev-recd 2021-07-30, accepted 2021-08-19, pub-electronic 2021-09-08Article version: VoRPublication status: PublishedFunder: Medical Research Council; Id: http://dx.doi.org/10.13039/501100000265; Grant(s): MR/P024017/1Abstract: There has been a long history of research on the effects of oxytocin on feeding behaviour. The classic‐held view is that the neurohormone is anorexigenic at least in rodents, although the data for humans are not so clear cut. Likewise, a physiological role for oxytocin is disputed. Thus, although pharmacological, anatomical and physiological data suggest oxytocin may have a function in satiety signalling, this view is not supported by the latest research using the genetic recording and manipulation of oxytocin neurones. Here, we avoid a discussion of the pharmacological effects of oxytocin and examine evidence, from both sides of the argument, concerning whether the endogenous oxytocin system has a role in the regulation of normal feeding

Seminar sejarah nasional v subtema sejarah kesenian

Buku ini berisi tulisan-tulisan dari Seminar sejarah nasional v dengan subtema sejarah kesenian

Creative aspiration and the betrayal of promise? The experience of new creative workers

The promise of ‘doing what you love’ continues to attract new aspirants to creative work, yet most creative industries are so characterised by low investment, shifting foci and ongoing technological innovation that all promises must be unreliable. Some would-be creative workers negotiate their own pathways from the outset, ‘following their dream’ as they attempt to convert personal enthusiasms and amateur activities into income-earning careers. Others look to the proliferation of available training and education options, including higher education courses, as possible pathways into creative work. This chapter reviews recent research from the USA, Australia and the UK on the effectiveness – or otherwise – of higher education as preparation for a creative career. The chapter discusses the obstacles that many creative workers, including graduates, encounter on their creative pathways, for instance, as a result of informal work practices and self-employment. The chapter also looks at sources of advantage and disadvantage, such as those associated with particular geographic locations or personal identities. The chapter concludes by introducing the subsequent chapters in the collection. These critically explore the experience of new creative workers in a wide range of national contexts including Australia, Belgium, China, Ireland, Italy, Finland, the Netherlands, Russia and the United Kingdom

Melt-under-cutting and buoyancy-driven calving from tidewater glaciers: new insights from discrete element and continuum model simulations

This work was funded by the ConocoPhillips Northern Area Program (CRIOS: Calving Rates and Impact on Sea Level) and the Nordic Research Council (SVALI: Stability and Variation of Arctic Land Ice and eSTICC: eScience Tools for Investigating Climate Change in northern high latitudes).The simple calving laws currently used in ice sheet models do not adequately reflect the complexity and diversity of calving processes. To be effective, calving laws must be grounded in a sound understanding of how calving actually works. Here, we develop a new strategy for formulating calving laws, using a) the Helsinki Discrete Element Model (HiDEM) to explicitly model fracture and calving processes, and b) the continuum model Elmer/Ice to identify critical stress states associated with HiDEM calving events. A range of observed calving processes emerges spontaneously from HiDEM in response to variations in ice-front buoyancy and the size of subaqueous undercuts. Calving driven by buoyancy and melt undercutting is under-predicted by existing calving laws, but we show that the location and magnitude of HiDEM calving events can be predicted in Elmer/Ice from characteristic stress patterns. Our results open the way to developing calving laws that properly reflect the diversity of calving processes, and provide a framework for a unified theory of the calving process continuum.Publisher PDFPeer reviewe

The structural and dynamic responses of Stange Ice Shelf to recent environmental change

Stange Ice Shelf is the most south-westerly ice shelf on the Antarctic Peninsula, a region where positive trends in atmospheric and oceanic temperatures have been recently documented. In this paper, we use a range of remotely sensed datasets to evaluate the structural and dynamic responses of Stange Ice Shelf to these environmental changes. Ice shelf extent and surface structures were examined at regular intervals from optical and radar satellite imagery between 1973 and 2011. Surface speeds were estimated in 1989, 2004 and 2010 by tracking surface features in successive satellite images. Surface elevation change was estimated using radar altimetry data acquired between 1992 and 2008 by the European Remote Sensing Satellite (ERS) -1, -2 and Envisat. The mean number of surface melt days was estimated using the intensity of backscatter from Envisat’s Advanced Synthetic Aperture Radar instrument between 2006 and 2012. These results show significant shear fracturing in the southern portion of the ice shelf linked to enhanced flow speed as a consequence of measured thinning. However, we conclude that, despite the observed changes, Stange Ice Shelf is currently stable

A matter of divergence: Tracking recent warming at hemispheric scales using tree ring data

No current tree ring (TR) based reconstruction of extratropical Northern Hemisphere (ENH) temperatures that extends into the 1990s captures the full range of late 20th century warming observed in the instrumental record. Over recent decades, a divergence between cooler reconstructed and warmer instrumental large-scale temperatures is observed. We hypothesize that this problem is partly related to the fact that some of the constituent chronologies used for previous reconstructions show divergence against local temperatures in the recent period. In this study, we compiled TR data and published local/regional reconstructions that show no divergence against local temperatures. These data have not been included in other large-scale temperature reconstructions. Utilizing this data set, we developed a new, completely independent reconstruction of ENH annual temperatures (1750–2000). This record is not meant to replace existing reconstructions but allows some degree of independent validation of these earlier studies as well as demonstrating that TR data can better model recent warming at large scales when careful selection of constituent chronologies is made at the local scale. Although the new series tracks the increase in ENH annual temperatures over the last few decades better than any existing reconstruction, it still slightly under predicts values in the post-1988 period. We finally discuss possible reasons why it is so difficult to model post-mid-1980s warming, provide some possible alternative approaches with regards to the instrumental target and detail several recommendations that should be followed in future large-scale reconstruction attempts that may result in more robust temperature estimates