Abstract:An intermediate-depth (1751 m) ice core was drilled at the South Pole between 2014 and 2016 using the newly designed US Intermediate Depth Drill. The South Pole ice core is the highest-resolution interior East Antarctic ice core record that extends into the glacial period. The methods used at the South Pole to handle and log the drilled ice, the procedures used to safely retrograde the ice back to the National Science Foundation Ice Core Facility (NSF-ICF), and the methods used to process and sample the ice at… Show more
“…We obtained an ice core at 89.99°S, 98.16°W, approximately 2 km from the geographic South Pole, during the 2014-2015 and 2015-2016 austral summers (Johnson et al, 2020;Souney et al, 2020). The core, "SPC14", was drilled to a depth of 1751 m, equivalent to an age of approximately 54 ka.…”
The δD and δ18O values of water are key measurements in polar ice-core research, owing to their strong and well-understood relationship with local temperature. Deuterium excess, d, the deviation from the average linear relationship between δD and δ18O, is also commonly used to provide information about the oceanic moisture sources where polar precipitation originates. Measurements of δ17O and “17O excess” (Δ17O) are also of interest because of their potential to provide information complementary to d. Such measurements are challenging because of the greater precision required, particularly for Δ17O. Here, high-precision measurements are reported for δ17O, δ18O, and δD on a new ice core from the South Pole, using a continuous-flow measurement system coupled to two cavity ring-down laser spectroscopy instruments. Replicate measurements show that at 0.5 cm resolution, external precision is ∼0.2‰ for δ17O and δ18O, and ∼1‰ for δD. For Δ17O, achieving external precision of <0.01‰ requires depth averages of ∼50 cm. The resulting ∼54,000-year record of the complete oxygen and hydrogen isotope ratios from the South Pole ice core is discussed. The time series of Δ17O variations from the South Pole shows significant millennial-scale variability, and is correlated with the logarithmic formulation of deuterium excess (dln), but not the traditional linear formulation (d).
“…We obtained an ice core at 89.99°S, 98.16°W, approximately 2 km from the geographic South Pole, during the 2014-2015 and 2015-2016 austral summers (Johnson et al, 2020;Souney et al, 2020). The core, "SPC14", was drilled to a depth of 1751 m, equivalent to an age of approximately 54 ka.…”
The δD and δ18O values of water are key measurements in polar ice-core research, owing to their strong and well-understood relationship with local temperature. Deuterium excess, d, the deviation from the average linear relationship between δD and δ18O, is also commonly used to provide information about the oceanic moisture sources where polar precipitation originates. Measurements of δ17O and “17O excess” (Δ17O) are also of interest because of their potential to provide information complementary to d. Such measurements are challenging because of the greater precision required, particularly for Δ17O. Here, high-precision measurements are reported for δ17O, δ18O, and δD on a new ice core from the South Pole, using a continuous-flow measurement system coupled to two cavity ring-down laser spectroscopy instruments. Replicate measurements show that at 0.5 cm resolution, external precision is ∼0.2‰ for δ17O and δ18O, and ∼1‰ for δD. For Δ17O, achieving external precision of <0.01‰ requires depth averages of ∼50 cm. The resulting ∼54,000-year record of the complete oxygen and hydrogen isotope ratios from the South Pole ice core is discussed. The time series of Δ17O variations from the South Pole shows significant millennial-scale variability, and is correlated with the logarithmic formulation of deuterium excess (dln), but not the traditional linear formulation (d).
“…The aluminum rail assemblies were fully adjustable so they could be aligned to each other to minimize stress on the core as it was pushed out of the core barrel and onto the core tray, dried, logged, cut into 1 m lengths, and packed. Further details about the core processing line are described in Souney and others (2020). Site construction, including all snow excavation and drill assembly, was completed over a period of 12 days by the 11 member SPICEcore team along with additional support, as needed, by equipment operators, carpenters, and electricians provided by ASC.…”
Section: Drill Setupmentioning
confidence: 99%
“…9). Details about how the ice cores were handled, logged, and packed are described in Souney and others (2020). Fig.…”
Section: Drill Operationsmentioning
confidence: 99%
“…In the following sections, we discuss the setup, operation, and performance of the IDD system for the SPICEcore project. Details of how the ice cores were handled, logged and retrograded back to the USA are described in Souney and others (2020).…”
Over the course of the 2014/15 and 2015/16 austral summer seasons, the South Pole Ice Core project recovered a 1751 m deep ice core at the South Pole. This core provided a high-resolution record of paleoclimate conditions in East Antarctica during the Holocene and late Pleistocene. The drilling and core processing were completed using the new US Intermediate Depth Drill system, which was designed and built by the US Ice Drilling Program at the University of Wisconsin–Madison. In this paper, we present and discuss the setup, operation, and performance of the drill system.
“…To monitor the change of ice sheet mass, ice mass loss can be estimated by the change of under-ice structures [3][4][5][6][7][8]. Glaciologists, at first, could only drill ice cores [9][10][11] to determine the structure of sub-surface ice, while researchers now use ground-penetrating radar (GPR) [12,13] flying over ice sheets to collect under-ice structural data over a large range [14][15][16].…”
Analyzing the surface and bedrock locations in radar imagery enables the computation of ice sheet thickness, which is important for the study of ice sheets, their volume and how they may contribute to global climate change. However, the traditional handcrafted methods cannot quickly provide quantitative, objective and reliable extraction of information from radargrams. Most traditional handcrafted methods, designed to detect ice-surface and ice-bed layers from ice sheet radargrams, require complex human involvement and are difficult to apply to large datasets, while deep learning methods can obtain better results in a generalized way. In this study, an end-to-end multi-scale attention network (MsANet) is proposed to realize the estimation and reconstruction of layers in sequences of ice sheet radar tomographic images. First, we use an improved 3D convolutional network, C3D-M, whose first full connection layer is replaced by a convolution unit to better maintain the spatial relativity of ice layer features, as the backbone. Then, an adjustable multi-scale module uses different scale filters to learn scale information to enhance the feature extraction capabilities of the network. Finally, an attention module extended to 3D space removes a redundant bottleneck unit to better fuse and refine ice layer features. Radar sequential images collected by the Center of Remote Sensing of Ice Sheets in 2014 are used as training and testing data. Compared with state-of-the-art deep learning methods, the MsANet shows a 10% reduction (2.14 pixels) on the measurement of average mean absolute column-wise error for detecting the ice-surface and ice-bottom layers, runs faster and uses approximately 12 million fewer parameters.
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