Rapid retreat of Thwaites Glacier in the pre-satellite era

Understanding the recent history of Thwaites Glacier, and the processes controlling its ongoing retreat, is key to projecting Antarctic contributions to future sea-level rise. Of particular concern is how the glacier grounding zone might evolve over coming decades where it is stabilized by sea-floor bathymetric highs. Here we use geophysical data from an autonomous underwater vehicle deployed at the Thwaites Glacier ice front, to document the ocean-floor imprint of past retreat from a sea-bed promontory. We show patterns of back-stepping sedimentary ridges formed daily by a mechanism of tidal lifting and settling at the grounding line at a time when Thwaites Glacier was more advanced than it is today. Over a duration of 5.5 months, Thwaites grounding zone retreated at a rate of >2.1 km per year—twice the rate observed by satellite at the fastest retreating part of the grounding zone between 2011 and 2019. Our results suggest that sustained pulses of rapid retreat have occurred at Thwaites Glacier in the past two centuries. Similar rapid retreat pulses are likely to occur in the near future when the grounding zone migrates back off stabilizing high points on the sea floor

Swirls and scoops: Ice base melt revealed by multibeam imagery of an Antarctic ice shelf

Knowledge gaps about how the ocean melts Antarctica’s ice shelves, borne from a lack of observations, lead to large uncertainties in sea level predictions. Using high-resolution maps of the underside of Dotson Ice Shelf, West Antarctica, we reveal the imprint that ice shelf basal melting leaves on the ice. Convection and intermittent warm water intrusions form widespread terraced features through slow melting in quiescent areas, while shear-driven turbulence rapidly melts smooth, eroded topographies in outflow areas, as well as enigmatic teardrop-shaped indentations that result from boundary-layer flow rotation. Full-thickness ice fractures, with bases modified by basal melting and convective processes, are observed throughout the area. This new wealth of processes, all active under a single ice shelf, must be considered to accurately predict future Antarctic ice shelf melt

Service Learning as an Alternative Academic Trend in U. S. Higher Education from the late-1960s to the mid-1980s: A Case Study from Michigan State University

The article sheds light on the way in which alternative academic trends that originated alongside student protests in the late-1960s and early-1970s influenced higher education in the U. S. It focuses on a case study from Michigan State University (MSU), analysing the initiation and implementation process of service learning, an alternative trend in education that combined community service with academic education, from the late-1960s to the mid-1980s. It examines the roles different stakeholders at the local level (i. e., students, faculty, and administrators) as well as others on the national level (i. e., politicians and education commissioners) played in influencing that process. The case of service learning at MSU exemplifies that an alternative trend, one introduced from the bottom up, could become a standard academic practice, yet one that was not implemented without numerous adjustments and compromises. This article will demonstrate the pedagogical method’s execution and how its educational goals changed according to common standards in higher education that were usually established from the top down

Controlling the nutrient profile of fruits and vegetables during prolonged storage prior to processing

The seasonal nature of fruit and vegetable crops requires either that supply is maintained over a wide geographical distribution range or that produce can be stored relatively long term. We have shown that relatively long term storage of fruit and vegetables can be undertaken with little deterioration in texture and without compromising microbiological safety. Associated experiments, to test produce from different geographical locations have also been undertaken. The availability of fruits and vegetables for processing offers the opportunity to develop novel products, with improved quality and stability for transport and shelf-life. The effect of transport and storage on nutrient profile was studied in carrots, broccoli and tomatoes. Phytochemicals assayed include carotene, lycopene, folate, and ascorbic acid. The plant cell wall composition, free sugars and fibre content have also been determined. In carrot (mg/g dry weight), -carotene was ?0.7mg; ascorbic acid ?0.3mg, sugars ?500mg, and dietary fibre ?300mg. In broccoli, corresponding nutrients were: ascorbic acid up to 8.6mg, folate ?0.005mg, sugars ?250mg, and dietary fibre ?400mg. In tomato, corresponding nutrients were: lycopene ?0,8mg, ascorbic acid ?2.5 mg, sugars ?480mg, and dietary fibre ?400mg. The storage conditions chosen were temperatures of 2-4\ub0C and relative humidity between 70 and 99%, depending on the raw materials. During storage, little change was found in sample compositions post harvest. Fully ripe tomatoes had lost some lycopene but vitamin C in broccoli increased during storage. Although total dietary fibre content did not change during storage there was a noted modification to constituent pectic polysaccharides; shown as a loss of pectic arabinan andgalactan in carrot. The results show that carefully controlled storage conditions were appropriate for the purpose of maintenance or enhancement of nutritional and textural properties. However, shelf life of produce may be compromised by transport conditions. It is therefore recommended to keep transport time short and to ensure that optimum storage conditions can be maintained during transport. Preliminary results indicate that transport rather than storage conditions are the major problem in maintaining product nutrient profile and microbiological quality prior to processing

Powerful ways of (not) knowing New Urban Tourism conflicts. Thin problematisation as limitation for tourism governance in Berlin

Governance habits of (not) knowing tourism conflicts predetermine options to act upon conflict-laden New Urban Tourism. Using Berlin as a case, the power of rendering tourism conflicts doable is empirically reconstructed in terms of various ‘thin problematisations’ mobilised by destination governance actors. In order to align doable problems and viable solutions—so the argument goes—Berlin’s municipal tourism governance builds on different knowledge formats (statistics, media statements, myths, concept work). The chapter argues that maintaining ‘thin problematisations’ of tourism conflicts limits a more far-reaching understanding and governance of (possibly unsolvable) contradictions of New Urban Tourism. Nevertheless, it is assumed that the complexity of New Urban Tourism inevitably needs to be reduced in order to be known and governed. Instead of relapsing into simplifications regarding (new urban) tourism conflicts, a further discussion of academic and more practice-related ways of knowing tourism problems is needed. To jointly venture into research co-operations with epistemic partners from tourism research and urban practice might help to gradually establish a more complex understanding of tourism frictions

Applicability of in vitro models in prediciting the in vivo bioavailability of lycopene and beta-carotene from differently processed soups

Presently, there is no clear consensus on the best approach to estimate carotenoid bioavailability. The best alternative would be to use human studies, but they are labour-intensive and expensive and can only be used to investigate a lim-ited number of samples. Hence, a number of in vitro models have been developed to study pre-absorptive processes and factors affecting bioavailability. The question is, however, how well the results obtained by the various methods correlate to each other and to the in vivo situation. In the present paper, we have compared in vivo data from two human studies on differently processed soups containing carrots, tomato and broccoli, with results obtained by in vitro characterisation of the same soups. In vitro bioaccessibility was estimated by a static in vitro digestion investigating matrix release and micellarization of carotenoids and by uptake studies in a human intestinal cell line (Caco-2). In vivo data was obtained from clinical studies measuring total plasma carotenoid concentrations in human subjects after 4 weeks daily consumption of the soups. Comparison of the in vitro and in vivo results indicate that the combination of a two-step in vitro digestion and Caco-2 cells seems to be a useful tool for estimation of β-carotene bioaccessibility and screening of factors governing the release of β-carotene from this type of food. For lycopene the in vitro and in vivo results were less consistent, suggesting that reliable prediction of lycopene bioavailability might be more problematic

Applicability of in vitro models in prediciting the in vivo bioavailability of lycopene and beta-carotene from differently processed soups

Presently, there is no clear consensus on the best approach to estimate carotenoid bioavailability. The best alternative would be to use human studies, but they are labour-intensive and expensive and can only be used to investigate a lim-ited number of samples. Hence, a number of in vitro models have been developed to study pre-absorptive processes and factors affecting bioavailability. The question is, however, how well the results obtained by the various methods correlate to each other and to the in vivo situation. In the present paper, we have compared in vivo data from two human studies on differently processed soups containing carrots, tomato and broccoli, with results obtained by in vitro characterisation of the same soups. In vitro bioaccessibility was estimated by a static in vitro digestion investigating matrix release and micellarization of carotenoids and by uptake studies in a human intestinal cell line (Caco-2). In vivo data was obtained from clinical studies measuring total plasma carotenoid concentrations in human subjects after 4 weeks daily consumption of the soups. Comparison of the in vitro and in vivo results indicate that the combination of a two-step in vitro digestion and Caco-2 cells seems to be a useful tool for estimation of β-carotene bioaccessibility and screening of factors governing the release of β-carotene from this type of food. For lycopene the in vitro and in vivo results were less consistent, suggesting that reliable prediction of lycopene bioavailability might be more problematic

Warm water flow and mixing beneath Thwaites Glacier ice shelf, West Antarctica

The fate of the West Antarctic Ice Sheet is the largest remaining uncertainty in predicting sea-level rise through the next century, and its most vulnerable and rapidly changing outlet is Thwaites Glacier . Because the seabed slope under the glacier is retrograde (downhill inland), ice discharge from Thwaites Glacier is potentially unstable to melting of the underside of its floating ice shelf and grounding line retreat, both of which are enhanced by warm ocean water circulating underneath the ice shelf. Recent observations show surprising spatial variations in melt rates, indicating significant knowledge gaps in our understanding of the processes at the base of the ice shelf. Here we present the first direct observations of ocean temperature, salinity, and oxygen underneath Thwaites ice shelf collected by an autonomous underwater vehicle, a Kongsberg Hugin AUV. These observations show that while the western part of Thwaites has outflow of meltwater-enriched circumpolar deep water found in the main trough leading to Thwaites, the deep water (> 1000 m) underneath the central part of the ice shelf is in connection with Pine Island Bay - a previously unknown westward branch of warm deep water flow. Mid-depth water (700 - 1000 m) enters the cavity from both sides of a buttressing point and large spatial gradients of salinity and temperature indicate that this is a region of active mixing processes. The observations challenge conceptual models of ice-ocean interactions at glacier grounding zones and identify a main buttressing point as a vulnerable region of change currently under attack by warm water inflow from all sides: a scenario that may lead to ungrounding and retreat more quickly than previously expected