Core handling and processing for the WAIS Divide ice-core project

Souney, Joseph M.; Twickler, Mark S.; Hargreaves, Geoffrey M.; Bencivengo, Brian M.; Kippenhan, Matthew J.; Johnson, Jay A.; Cravens, Eric D.; Neff, Peter D.; Nunn, Richard; Orsi, Anaïs; Popp, Trevor; Rhoades, John F.; Vaughn, Bruce H.; Voigt, D.; Wong, G. J.; Taylor, Kendrick C.

doi:10.3189/2014aog68a008

Cited by 23 publications

(29 citation statements)

References 17 publications

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“…This gas loss correction was not applied to the WD samples since the empirical gas loss relation was developed for bubbly ice and therefore is unlikely to apply to gas in a clathrate state as are all WD samples older than 10 ka. However, the WD samples exhibit much less gas loss in general due to very good temperature control during drilling, transport, and storage (Souney et al, 2014), such that the quality of the data is essentially the same as gas-loss-corrected Taylor Glacier data. For Taylor Glacier, a total of 725 samples from 352 separate locations or depths were analyzed mostly in duplicates.…”

Section: Study Area and Methodsmentioning

confidence: 99%

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

et al. 2017

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Abstract.Old ice for paleo-environmental studies, traditionally accessed through deep core drilling on domes and ridges on the large ice sheets, can also be retrieved at the surface from ice sheet margins and blue ice areas. The practically unlimited amount of ice available at these sites satisfies a need in the community for studies of trace components requiring large sample volumes. For margin sites to be useful as ancient ice archives, the ice stratigraphy needs to be understood and age models need to be established. We present measurements of trapped gases in ice from Taylor Glacier, Antarctica, to date the ice and assess the completeness of the stratigraphic section. Using δ 18 O of O 2 and methane concentrations, we unambiguously identify ice from the last glacial cycle, covering every climate interval from the early Holocene to the penultimate interglacial. A high-resolution transect reveals the last deglaciation and the Last Glacial Maximum (LGM) in detail. We observe large-scale deformation in the form of folding, but individual stratigraphic layers do not appear to have undergone irregular thinning. Rather, it appears that the entire LGM-deglaciation sequence has been transported from the interior of the ice sheet to the surface of Taylor Glacier relatively undisturbed. We present an age model that builds the foundation for gas studies on Taylor Glacier. A comparison with the Taylor Dome ice core confirms that the section we studied on Taylor Glacier is better suited for paleo-climate reconstructions of the LGM due to higher accumulation rates.

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Section: Study Area and Methodsmentioning

confidence: 99%

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

et al. 2017

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“…15). Precautions were taken at every step in coring and processing to minimize damage from brittle behavior (Souney and others, 2014). The brittle ice was confined to �650-1300 m depth (5.51-11.37 MPa bubble pressure, calculated from the overburden pressure and density data, assuming that bubble pressure had reached overburden pressure).…”

Section: Bubbles and Clathrates 61 Core Quality And Clathrate Obsermentioning

confidence: 99%

Physical properties of the WAIS Divide ice core

Fitzpatrick¹,

et al. 2014

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The WAIS (West Antarctic Ice Sheet) Divide deep ice core was recently completed to a total depth of 3405 m, ending 50 m above the bed. Investigation of the visual stratigraphy and grain characteristics indicates that the ice column at the drilling location is undisturbed by any large-scale overturning or discontinuity. The climate record developed from this core is therefore likely to be continuous and robust. Measured grain-growth rates, recrystallization characteristics, and grain-size response at climate transitions fit within current understanding. Significant impurity control on grain size is indicated from correlation analysis between impurity loading and grain size. Bubble-number densities and bubble sizes and shapes are presented through the full extent of the bubbly ice. Where bubble elongation is observed, the direction of elongation is preferentially parallel to the trace of the basal (0001) plane. Preferred crystallographic orientation of grains is present in the shallowest samples measured, and increases with depth, progressing to a vertical-girdle pattern that tightens to a vertical single-maximum fabric. This single-maximum fabric switches into multiple maxima as the grain size increases rapidly in the deepest, warmest ice. A strong dependence of the fabric on the impurity-mediated grain size is apparent in the deepest samples.

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“…the new SPICEcore from the South Pole), would improve characterization and help demonstrate that we are not observing some unknown peculiarity of our site, or some unknown artifact from the particular recovery and processing history of this core (Casey and others, 2014; Fegyveresi, 2015). We chose our sample depth to be great enough for notable deformation to have occurred but not so deep as to fall within the upper part of the ‘brittle ice’ zone (Souney and others, 2014), and to be above the depth of major grain subdivision or dominant nucleation of new grains (see above). We inspected the bubbles carefully in an attempt to avoid any possible effects of stress-relief cracks affecting bubble shape (see e.g.…”

Section: Discussionmentioning

confidence: 99%

Instruments and methods: a case study of ice core bubbles as strain indicators

et al. 2018

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Measurements of a sample from ~580 m depth in the WAIS Divide (WDC06A) ice core reveal that bubbles are preferentially elongated in the basal plane of their parent grain, as expected if bubble shape preserves the record of dominant basal glide. This suggests that a method using bubbles as strain gauges could provide insights to grain-scale ice deformation. We introduce a technique using fabric and image analyses of paired thin and thick sections. Comparison of the crystallographic orientations of 148 grains and the shape orientations of 2377 intragrain bubbles reveals a strongly preferred elongation of bubbles in the grain basal planes (R2 = 0.96). Elongation magnitudes are consistent with a balance between ice flow deformation and diffusive restoration, with larger bubbles more elongated. Assuming bubbles record ice strain, grains with greater resolved stress on their basal planes from the far-field ice flow stresses show greater deformation, but with large variability suggesting that heterogeneity of the local stress field causes deformation even in unfavorably oriented grains. A correlation is also observed among bubble elongation, grain size, and bubble size, explaining a small but significant fraction of the variance ( P< 0.05), with implications for controls on ice deformation, as discussed here.

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Core handling and processing for the WAIS Divide ice-core project

Cited by 23 publications

References 17 publications

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

Atmospheric gas records from Taylor Glacier, Antarctica, reveal ancient ice with ages spanning the entire last glacial cycle

Physical properties of the WAIS Divide ice core

Instruments and methods: a case study of ice core bubbles as strain indicators

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