Core handling, transportation and processing for the South Pole ice core (SPICEcore) project

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 the NSF-ICF are described. The South Pole ice core exhibited minimal brittle ice, which was likely due to site characteristics and, to a lesser extent, to drill technology and core handling procedures

Reconstruction of Antarctic accumulation from 1801-2000 CE

<p>An annually resolved reconstruction of gridded snow accumulation anomalies over Antarctica, from 1801-2000 CE. </p><p>Reconstructions are generated using the Last Millennium Reanalysis data assimilation framework (Hakim et al., 2016; Tardif et al., 2019), a comprehensive ice core proxy database, and a multi-model ensemble of climate simulations. </p><p>We incorporate a database of water isotope (Stenni et al., 2017) and accumulation (Thomas et al., 2017) ice core records from the Pages 2k consortium, in addition to individual records from the South Pole ice core (Kahle et al., 2021), Derwael Ice Rise (Philippe et al., 2016), and the PIG2010, DIV2010, and THW2010 sites (Criscitiello et al., 2013). </p><p>The multi-model ensemble is constructed using nine CMIP5 Last Millennium Simulations: CCSM4 (Gent et al., 2011), iCESM (Brady et al., 2019), BCC-CSM1.1 (Wu et al., 2014), CSIRO Mk3L (Phipps et al., 2012), FGOALS-s2 (Bao et al., 2013), GISS-E2-R (Schmidt et al., 2014), HadCM3 (Collins et al., 2001), IPSL-CM5A-LR (Dufresne et al., 2013), and MPI-ESM (Gutjahr et al., 2019). </p&gt

Glacier Status and Contribution to Streamflow in the Olympic Mountains, USA

The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km² and their combined area is 30.2 ± 0.95km². Only four glaciers are \u3e1km² and 120 of the others are -¹ (1900–80) to 0.54 km² a-¹ (1980–2009). Thinning rates on four of the largest glaciers averaged nearly 1ma-¹ from 1987 to 2010, resulting in estimated volume losses of 17–24%. Combined glacial snow, firn and ice melt in the Hoh watershed is in the range 63–79 ± 7 × 106m3, or 9–15% of total May–September streamflow. In the critical August–September period, the glacial fraction of total basin runoff increases to 18–30%, with one-third of the water directly from glacial ice (i.e. not snow and firn). Glaciers in the Elwha basin produce 12–15 ± 1.3 × 106m3 (2.5–4.0%), while those in the Dungeness basin contribute 2.5–3.1 ± 0.28 × 106m3 (3.0–3.8%)

Physical properties of the WAIS Divide ice core

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

Antarctic surface temperature and elevation during the Last Glacial Maximum

Water-stable isotopes in polar ice cores are a widely used temperature proxy in paleoclimate reconstruction, yet calibration remains challenging in East Antarctica. Here, we reconstruct the magnitude and spatial pattern of Last Glacial Maximum surface cooling in Antarctica using borehole thermometry and firn properties in seven ice cores. West Antarctic sites cooled ~10°C relative to the preindustrial period. East Antarctic sites show a range from ~4° to ~7°C cooling, which is consistent with the results of global climate models when the effects of topographic changes indicated with ice core air-content data are included, but less than those indicated with the use of water-stable isotopes calibrated against modern spatial gradients. An altered Antarctic temperature inversion during the glacial reconciles our estimates with water-isotope observations. © 2021 American Association for the Advancement of Science. All rights reserved