Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream

Gerber, Tamara Annina; Lilien, David A.; Rathmann, Nicholas; Franke, Steven; Young, Tun Jan; Valero-Delgado, Fernando; Ershadi, M. Reza; Drews, Reinhard; Zeising, Ole; Humbert, Angelika; Stoll, Nicolas; Weikusat, Ilka; Grinsted, Aslak; Hvidberg, Christine S.; Jansen, Daniela; Miller, Heinrich; Helm, Veit; Steinhage, Daniel; O’Neill, Charles; Paden, John; Gogineni, S.; Dahl‐Jensen, Dorthe; Eisen, Olaf

doi:10.1038/s41467-023-38139-8

Cited by 9 publications

(3 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…7) but shifted slightly upwards. This could be related to the different boundary conditions (temperature, elevation) at the drill sites, the impact of extensional deformation and high strain inside NEGIS and the hard shearing in flow direction (Westhoff et al, 2021;Stoll et al, 2021a;Gerber et al, 2023), and the strong dynamic recrystallisation observed at EGRIP (Stoll et al, ). However, the grain size evolution within both cores is still comparable, and the fast-flowing ice within NEGIS does not (yet) intensely affect the grain size in the upper 2121 m (∼ 80 % of ice sheet thickness).…”

Section: Grain Size Evolutionmentioning

confidence: 99%

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

et al. 2023

Self Cite

View full text Add to dashboard Cite

Abstract. Impurities in polar ice play a critical role in ice flow, deformation, and the integrity of the ice core record. Especially cloudy bands, visible layers with high impurity concentrations, are prominent features in ice from glacial periods. Their physical and chemical properties are poorly understood, highlighting the need to analyse them in more detail. We bridge the gap between decimetre and micrometre scales by combining the visual stratigraphy line scanner, fabric analyser, microstructure mapping, Raman spectroscopy, and laser ablation inductively coupled plasma mass spectrometry 2D impurity imaging. We classified approximately 1300 cloudy bands from glacial ice from the East Greenland Ice-core Project (EGRIP) ice core into seven different types. We determine the localisation and mineralogy of more than 1000 micro-inclusions at 13 depths. The majority of the minerals found are related to terrestrial dust, such as quartz, feldspar, mica, and hematite. We further found carbonaceous particles, dolomite, and gypsum in high abundance. Rutile, anatase, epidote, titanite, and grossular are infrequently observed. The 2D impurity imaging at 20 µm resolution revealed that cloudy bands are clearly distinguishable in the chemical data. Na, Mg, and Sr are mainly present at grain boundaries, whereas dust-related analytes, such as Al, Fe, and Ti, are located in the grain interior, forming clusters of insoluble impurities. We present novel vast micrometre-resolution insights into cloudy bands and describe the differences within and outside these bands. Combining the visual and chemical data results in new insights into the formation of different cloudy band types and could be the starting point for future in-depth studies on impurity signal integrity and internal deformation in deep polar ice cores.

show abstract

Section: Grain Size Evolutionmentioning

confidence: 99%

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

et al. 2023

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, the geometry of the ice stream, the position of its shear margins, and the origin of NEGIS itself are still not fully understood 21 , 49 – 54 . Progress in this field is expected from analyzing the EastGRIP ice core 55 , 56 , GPS measurements 46 , 57 , an extensive grid of RES profiles flown over NEGIS 58 , 59 , ground-based phase sensitive RES (pRES) measurements 60 , 61 , and modelling 62 – 64 .…”

Section: Methodsmentioning

confidence: 99%

Three-dimensional topology dataset of folded radar stratigraphy in northern Greenland

Franke,

Bons,

Streng

et al. 2023

Sci Data

Self Cite

View full text Add to dashboard Cite

We present a dataset of reconstructed three-dimensional (3D) englacial stratigraphic horizons in northern Greenland. The data cover four different regions representing key ice-dynamic settings in Greenland: (i) the onset of Petermann Glacier, (ii) a region upstream of the 79° North Glacier (Nioghalvfjerdsbræ), near the northern Greenland ice divide, (iii) the onset of the Northeast Greenland Ice Stream (NEGIS) and (iv) a 700 km wide region extending across the central ice divide over the entire northern part of central Greenland. In this paper, we promote the advantages of a 3D perspective of deformed englacial stratigraphy and explain how 3D horizons provide an improved basis for interpreting and reconstructing the ice-dynamic history. The 3D horizons are provided in various formats to allow a wide range of applications and reproducibility of results.

show abstract

“…In this work, we estimated the upstream ice deformation with a simple flow line model of ice dynamics combined with satellite data, in contrast to other work which couples fabric evolution to an ice-sheet simulation (Gerber et al, 2023). In particular, we have a vertically invariant deformation over the depth examined (although the deformation experienced by an ice parcel moving through the ice stream does of course change).…”

Section: Predicting Fabrics In Nature: Future Work In Ice and Other P...mentioning

confidence: 99%

Bridging the Gap Between Experimental and Natural Fabrics: Modeling Ice Stream Fabric Evolution and its Comparison With Ice‐Core Data

Richards,

Pegler,

Piazolo

et al. 2023

JGR Solid Earth

Self Cite

View full text Add to dashboard Cite

Fabrics, also known as textures or crystallographic preferred orientations, reveal information about the deformation history of the flow of polycrystalline materials, including glacial ice, olivine in the mantle, and feldspar and quartz in the crust. Ice fabrics can have an order‐of‐magnitude effect on the ease of flow in ice sheets. However, due to the choice of ice core drill site locations, the outputs of fabric models have mostly been compared to observations from the least dynamic regions of the ice sheet (ice divides). Recently, fabric data from an active ice stream have become available from ice cores drilled at the East Greenland Ice‐core Project (EGRIP). In this work, we present a novel approach that combines satellite‐derived velocity data with the fabric evolution model SpecCAF, a continuum model based on dominant dislocation creep. We directly compare model output to ice‐core observations from EGRIP, allowing us to examine the quantitative predictions of calibrated fabric models alongside those of active ice streams for the first time. As the model is calibrated against laboratory experiments, it provides a surrogate to compare the evolution of fabrics under laboratory and natural conditions. The predictions show good qualitative agreement with the observed fabric patterns and orientations, suggesting that a fabric between a girdle and horizontal maximum, orientated perpendicular to the flow direction, is the characteristic ice stream fabric. A discrepancy in fabric strength is attributed to the lower strain rates of ice sheets compared to laboratory experiments, revealing a significant strain‐rate dependence in the processes controlling fabric evolution.

show abstract

Crystal orientation fabric anisotropy causes directional hardening of the Northeast Greenland Ice Stream

Cited by 9 publications

References 77 publications

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

Chemical and visual characterisation of EGRIP glacial ice and cloudy bands within

Three-dimensional topology dataset of folded radar stratigraphy in northern Greenland

Bridging the Gap Between Experimental and Natural Fabrics: Modeling Ice Stream Fabric Evolution and its Comparison With Ice‐Core Data

Contact Info

Product

Resources

About