Geochemical investigations at Tsanfleuron Glacier, Switzerland

Subg1acially precipitated calcites, formed since 1860, are exposed by the retreating of the Tsanfleuron glacier in the Swiss Alps. They have been sampled together with different types of ice and water, for their isotopic composition. The isotopic study suggests that the initial water, from which calcium carbonate is precipitated by partial freezing, is produced by melting of the basal ice layer, not of glacier ice. Because of the wide range of isotopic composition of basal ice, some doubts are expressed on the possibility given by such subglacially precipitated calcites to determine the isotopic composition of Pleistocene ice sheets and to correct the paleotemperature scale

Low salinity frazil ice generation at the base of a small antarctic ice shelf

Chemical, isotopic and crystallographic characteristics of marine ice formed at the base of the Hells Gate Ice Shelf, Terra Nova Bay, allow a better understanding of the dynamics of marine ice accretion under small ice shelves. The observed properties of the different types of frazil ice found in the area immediately behind the ice shelf front, result from a progressive evolution of the individual ftazil ice crystals initially accreted at the base of the ice-shelf. Basal melting caused by the descending plumes of water masses at a temperature above their local freezing point, initiates partial melting of the frazil ice crystals. This dilutes the interstitial water and initiates chemical sorting effects as diffusion proceeds from the normal sea water in the free water column to the diluted interstitial water in the loose frazil layer. Different environmental conditions will result in contrasting properties. Where the subglacial interface is sculptured with domes or inverted channels, it will favour the accumulation of thick units of frazil ice, in a calm environment, that will be further protected from convection mixing over long time periods. This will result in the formation of orbicular frazil showing c-axes at random, strong dilution and important sorting effects. On the contrary, where no channel or dome exist, or where those are already filled with frazil, rectangular or wave-like banded frazil will form with properties showing interfacial streaming effects induced by water currents. Strong c-axes concentration at a single maximum, less dilution and weaker chemical sorting effects are then observed. These findings provide a tentative explanation for the apparent contradiction between the very low salinity levels detected in marine ice at the base of ice shelves and the comparatively minor salinity fluctuations in sea water profiles near ice shelves. © 1993, Antarctic Science Ltd. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

On the signature of melting and freezing processes affecting large marine ice masses at Hell's Gate Ice Shelf (Victoria Land Antarctica)

info:eu-repo/semantics/nonPublishe

Preliminary results from shallow cores and from one 45.m deep marine ice core at Hells gate Ice Shelf, Victoria Land, Antarctica

info:eu-repo/semantics/nonPublishe

Preliminary results from 60 shallow cores and from one 45-m deep marine ice core at Hells gate Ice Shelf, Victoria Land, Antarctica

info:eu-repo/semantics/publishe

New insights in marine ice transfer along the bottom of ice shelves

info:eu-repo/semantics/publishe

Ice composition evidence of marine ice transfer along the bottom of a small Antarctic ice shelf

The existence of marine ice transfer along the underside of the Hell's Gate Ice Shelf (Victoria Land), is indicated by an isotopic and chemical study of ice cores. Because of top surface ablation, the marine ice formed at the ice shelf-ocean interface, ultimately appears at shelf surface. A succession of congelation, platelet and frazil ice is shown to occur. Two different freezing zones separated by a melting zone exist; the parent water for the frazil ice is meltwater from congelation ice which appears in the upstream zone. -from AuthorsSCOPUS: NotDefined.jFLWNAinfo:eu-repo/semantics/publishe