[1] Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up-glacier dip, and an outer element that lacks a consistent foliation and has a down-glacier, slope-parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co-isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.

One feature of high-latitude areas is the formation of ice clusters attached to the beds of rivers, lakes and the sea. This anchor ice, as it is widely known, plays an important role in mobilizing bed sediments, as well as ecological roles as a food source, habitat and potentially fatal environment. Much work has been devoted to fluvial anchor ice in the Northern Hemisphere, yet comparatively little work has described anchor ice in polar marine environments, despite its description by Antarctic expedition scientists over a century ago. In this paper, we review the current understanding of anchor ice formation in polar marine environments. Supercooled water is a necessity for anchor ice to form and frazil adhesion is the most likely common mechanism for initial anchor ice growth. Strong biological zonation has led some authors to suggest that anchor ice does not form to depths of greater than 33 m, yet in Antarctica there appear to be no physical reasons for such a limit given the production of supercooled water to substantial depths associated with ice shelves. Future work should focus on the potential extent of anchor ice production and identify the key oceanographic, glaciological and meteorological conditions conducive to its formation.

A combination of ground-penetrating radar surveys, physical sedimentology and ice composition measurements has been used to characterize ice and sediment accreted to the southern margin of the McMurdo Ice Shelf, Antarctica. The radar data and surface observations show that the ice-shelf margin consists of strongly layered debris-rich ice that contains marine sediment and fossils. A modified Rayleigh-based distillation system has been used to model the isotopic fractionation from sea water to ice in a closed system. The model of ice formation is consistent with formation during almost complete freezing of a sea-water reservoir. By contrast, ice on the upstream side of the grounding line has formed during the early stages of freezing in which a small fraction of the sea-water reservoir has frozen. The model results and the presence of delicate, well-preserved marine fossils are interpreted as evidence of anchor ice formation on the seabed, and rafting of glaciomarine sediment into the bottom of the ice shelf. We argue that repeated accretion of sea water and marine sediment has produced a stacked sequence of ice and glaciomarine debris that forms shore-parallel ice-cored moraines.

Informal community‐based supply, characterised by abstractions from surface water and shallow wells, is the main water supply source in the urban areas of developing nations. Formal sector supply has failed to extend their services to many urban areas yet the formal sector continues to view these community‐based practices as small‐scale, traditional and ‘backward’, and ones that must be eradicated from urban areas. While the formal sector continues to idealise the notion of the ‘modern infrastructure ideal’, based solely upon the expansion of piping networks, this paper argues against this ideal, instead presenting an opportunity for ‘institutional bricolage’ between the formal sector and the techniques that have arisen as a part of informal community‐based water supply in developing nations. Based on interview and questionnaire data, this paper uses the city of Ndola, Zambia to demonstrate the resilience that has arisen within communities as a response to the failure of the formal sector, and hence the value of informal supply systems in the future water provisioning policies for developing cities. Informal supply is abundant in Ndola and local communities have taken their pre‐existing rural customs and adapted these to provide water in the urban context; so that hand dug shallow wells now dominate supply. These practices have been successful in providing daily water, however, challenges remain, for example ensuring safe water quality with appropriate well protection. Herein lies the opportunity for the formal sector to become involved in informal community‐based supply; instead of aiming to marginalise the residents of informal areas out of urban centres, the formal sector should adopt and better support the techniques used in informal areas, for example, through well protection education and provision of resources, to help in achieving the MDG for safe water.

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