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The National Science Foundation Ice Core Facility (NSF-ICF, fka NICL) is in the process of building a new facility including freezer and scientist support space. The facility is being designed to minimize environmental impacts while maximizing ice core curation and science support. In preparation for the new facility, we are updating research equipment and integrating ice core data collection and processing by assigning International Generic Sample Numbers (IGSN) to advance the “FAIR”ness and establish clear provenance of samples, fostering the next generation of linked research data products. The NSF-ICF team, in collaboration with the US ice core science community, has established a metadata schema for the assignment of IGSNs to ice cores and samples. In addition, in close coordination with the US ice core community, we are adding equipment modules that expand traditional sets of physical property, visual stratigraphy, and electrical conductance ice core measurements. One such module is an ice core hyperspectral imaging (HSI) system. Adapted for the cold laboratory settings, the SPECIM SisuSCS HSI system can collect up to 224 bands using a continuous line-scanning mode in the visible and near-infrared (VNIR) 400-1000 nm spectral region. A modular system design allows expansion of spectral properties in the future. The second module is an updated multitrack electrical conductance system. These new data will guide real time optimization of sampling for planned analyses during ice core processing, especially for ice with deformed or highly compressed layering. The aim is to facilitate the collection of robust, long-term, and FAIR data archives for every future ice core section processed at NSF-ICF. The NSF-ICF is fully funded by the National Science Foundation and operated by the U.S. Geological Survey. 

Geology and bed topography influence how ice sheets respond to climate change. Despite the West Antarctic Ice Sheet’s capacity to retreat and advance quickly over its over-deepened interior, little is known about the subglacial landscape of the East Antarctic elevated interior that probably seeded West Antarctic ice streams and glaciers. At Hercules Dome, we use three-dimensional swath radar technology to image the upstream origin of large subglacial basins that drain ice from the Antarctic interior into West Antarctic ice streams. Radar imaging reveals an ancient, alpine landscape with hanging tributary valleys and large U-shaped valleys. On the valley floors, we image subglacial landforms that are typically associated with temperate basal conditions and fast ice flow. Formation mechanisms for these subglacial landforms are fundamentally inconsistent with the currently slowly flowing ice. Regional aerogravity shows that these valleys feed into larger subglacial basins that host thick sediment columns. Past tectonism probably created these basins and promoted ice flow from Hercules Dome into the Ross and Filchner–Ronne sectors. This suggests that the landscape at Hercules Dome was shaped by fast-flowing ice in the past when the area may have served as or been proximal to a nucleation centre for the West Antarctic Ice Sheet.

 

Hercules Dome, Antarctica, has long been identified as a prospective deep ice core site due to the undisturbed internal layering, climatic setting and potential to obtain proxy records from the Last Interglacial (LIG) period when the West Antarctic ice sheet may have collapsed. We performed a geophysical survey using multiple ice-penetrating radar systems to identify potential locations for a deep ice core at Hercules Dome. The surface topography, as revealed with recent satellite observations, is more complex than previously recognized. The most prominent dome, which we term ‘West Dome’, is the most promising region for a deep ice core for the following reasons: (1) bed-conformal radar reflections indicate minimal layer disturbance and extend to within tens of meters of the ice bottom; (2) the bed is likely frozen, as evidenced by both the shape of the measured vertical ice velocity profiles beneath the divide and modeled ice temperature using three remotely sensed estimates of geothermal flux and (3) models of layer thinning have 132 ka old ice at 45–90 m above the bed with an annual layer thickness of ~1 mm, satisfying the resolution and preservation needed for detailed analysis of the LIG period. 

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 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. 

A large volcanic sulfate increase observed in ice core records around 1450 C.E. has been attributed in previous studies to a volcanic eruption from the submarine Kuwae caldera in Vanuatu. Both EPMA–WDS (electron microprobe analysis using a wavelength dispersive spectrometer) and SEM–EDS (scanning electron microscopy analysis using an energy dispersive spectrometer) analyses of five microscopic volcanic ash (cryptotephra) particles extracted from the ice interval associated with a rise in sulfate ca. 1458 C.E. in the South Pole ice core (SPICEcore) indicate that the tephra deposits are chemically distinct from those erupted from the Kuwae caldera. Recognizing that the sulfate peak is not associated with the Kuwae volcano, and likely not a large stratospheric tropical eruption, requires revision of the stratospheric sulfate injection mass that is used for parameterization of paleoclimate models. Future work is needed to confirm that a volcanic eruption from Mt. Reclus is one of the possible sources of the 1458 C.E. sulfate anomaly in Antarctic ice cores.

 

The geothermal flux is an important boundary condition for ice‐sheet models because it influences whether the ice is melting at the bed and able to slide. Point measurements and remotely sensed estimates vary widely for the Ross Ice Sheet. A basal temperature measurement at Roosevelt Island reveals a geothermal flux of 84 ± 13 mW/m². The presence of Raymond Arches, which form only at ice divides that are frozen at the bed, allows inferences of the maximum geothermal flux at two coastal domes along the Siple Coast: Engelhardt Ridge, 85 ± 11 mW/m²and Shabtaie Ridge, 75 ± 10 mW/m². These measurements indicate heat flows similar to measurements at Siple Dome and the Whillans grounding zone and to the continental crust average. The high values measured at Subglacial Lake Whillans and estimated from satellite observations of Curie depths are not widespread.

 

Subglacial lakes require a thawed bed either now or in the past; thus, their presence and stability have implications for current and past basal conditions, ice dynamics, and climate. Here, we present the most extensive geophysical exploration to date of a subglacial lake near the geographic South Pole, including radar‐imaged stratigraphy, surface velocities, and englacial vertical velocities. We use a 1.5‐dimensional temperature model, optimized with our geophysical data set and nearby temperature measurements, to estimate past basal‐melt rates. The ice geometry, reflected bed‐echo power, surface and vertical velocities, and temperature model indicate that the ice‐bed interface is regionally thawed, contradicting prior studies. Together with an earlier active‐source seismic study, which showed a 32‐m deep lake underlain by 150 m of sediment, our results suggest that the lake has been thermodynamically stable through at least the last 120,000 years and possibly much longer, making it a promising prospective site for sediment coring.

 

A comprehensive record (WHV2020) of explosive volcanic eruptions in the last 11,000 years is reconstructed from the West Antarctica Ice Sheet Divide deep ice core (WDC). The chronological list of 426 large volcanic eruptions in the Southern Hemisphere and the low latitudes during the Holocene are of the highest quality of all volcanic records from ice cores, owing to the high‐resolution chemical measurement of the ice core and the exceptionally accurate WDC timescale. No apparent trend is found in the frequency (number of eruptions per millennium) of volcanic eruptions, and the number of eruptions in the most recent millennium (1,000–2,000 CE) is only slightly higher than the average in the last 11 millennia. The atmospheric aerosol mass loading of climate‐impacting sulfur, estimated from measured volcanic sulfate deposition, is dominated by explosive eruptions with extraordinarily high sulfur mass loading. Signals of three major volcanic eruptions are detected in the second half of the 17th century (1700–1600) BCE when the Thera volcano in the eastern Mediterranean was suspected to have erupted; the fact that these signals are synchronous with three volcanic eruptions detected in Greenland ice cores suggests that these are likely eruptions in the low latitudes and none should be attributed exclusively to Thera. A number of eruptions with very high sulfur mass loading took place shortly before and during an early Holocene climatic episode, the so‐called 8.2 ka event, and are speculated to have contributed to the initiation and magnitude of the cold event.