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Only a few localised ice streams drain most of the ice from the Greenland Ice Sheet. Thus, understanding ice stream behaviour and its temporal variability is crucially important to predict future sea-level change. The interior trunk of the 700 km-long North-East Greenland Ice Stream (NEGIS) is remarkable due to the lack of any clear bedrock channel to explain its presence. Here, we present a 3-dimensional analysis of the folding and advection of its stratigraphic horizons, which shows that the localised flow and shear margins in the upper NEGIS were fully developed only ca 2000 years ago. Our results contradict the assumption that the ice stream has been stable throughout the Holocene in its current form and show that upper NEGIS-type development of ice streaming, with distinct shear margins and no bed topography relationship, can be established on time scales of hundreds of years, which is a major challenge for realistic mass-balance and sea-level rise projections.

We present laboratory experiments on the growth of a tubular ice structure surrounding a plume of cold brine that descends under gravity into water with a higher freezing point. Brinicles are geological analogues of these structures found under sea ice in the polar regions on Earth. Brinicles are hypothesized to exist in the oceans of other celestial bodies, and being environments rich in minerals, serve a potentially analogous role as an ecosystem on icy-ocean worlds to that of submarine hydrothermal vents on Earth.

We present laboratory experiments on the growth of a tubular ice structure surrounding a plume of cold brine that descends under gravity into water with a higher freezing point. Brinicles are geological analogues of these structures found under sea ice in the polar regions on Earth. Brinicles are hypothesized to exist in the oceans of other celestial bodies, and being environments rich in minerals, serve a potentially analogous role as an ecosystem on icy-ocean worlds to that of submarine hydrothermal vents on Earth.

A better understanding of ice flow and deformation is needed to improve the projections of future sea level rise. Especially ice streams, the main contributors to solid ice discharge, still require more observational data to be represented sufficiently in computer models. The East Greenland Ice-core Project (EastGRIP) thus successfully drilled the first continuous deep ice core from an ice stream, the Northeast Greenland Ice Stream (NEGIS) while serving as a hub for geophysical measurements. A major unknown is the ice microstructure, i.e. the size and orientation of ice crystals (CPO) and its interplay with chemical impurities. Impurities are a climate proxy but are also assumed to impact microstructural processes, such as deformation and grain growth, and it is thus crucial to investigate where impurities are located in the microstructure. By combining microstructural (fabric analyser, microstructure-mapping, large area scanning macroscope) and impurity (Raman spectroscopy, inductively coupled plasma mass spectrometry 2D imaging) methods, we here present a systematic overview of the evolution of the microstructure and of the location of impurities throughout the EastGRIP ice core. Solid impurities, such as dust, are preferably located in the grain interior, while soluble impurities are mainly in the grain boundaries. This shows that microstructure should be considered when using impurities as a climate proxy due to the large spatial variability on the (sub-) millimetre scale. The analysed microstructure in the EastGRIP ice core further assists in reconstructing the original orientation of the ice core via visual stratigraphy, delivering the ground-truthing for an improved method of interfering horizontal fabric with co-polarised phase-sensitive radar and gaining new insights into the spatial variability of anisotropy and ice viscosity within NEGIS. Combining microstructural data with numerical modelling enables new insights into the processes underlying CPO formati

The supplementary material deposited in this dataset are movies at real time describing the crystal growth of ice brinicles in different experimental conditions simulating the natural forms found in Arctic and Antarctic oceans and other planets.