Stable water isotopes and accumulation rates in the Union Glacier region, Ellsworth Mountains, West Antarctica, over the last 35 years

Hoffmann, Kirstin; Fernandoy, Francisco; Meyer, Hanno; Thomas, Elizabeth R.; Aliaga, Marcelo; Tetzner, Dieter; Freitag, Johannes; Opel, Thomas; Arigony-Neto, Jorge; Göbel, Christian Florian; Jaña, Ricardo; Rodríguez-Oroz, Delia; Tuckwell, Rebecca; Ludlow, Emily; McConnell, Joseph R.; Schneider, Christoph

doi:10.5194/tc-14-881-2020

Cited by 19 publications

(14 citation statements)

References 108 publications

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“…C1) suggests that the isotope data could be explained by a simple twocomponent mixture of snow and seawater, with little variation in the isotope fractionation during freezing. Snow/firn from the Union Glacier region in the Weddell Sea sector has the respective endmember specifications (low δ 18 O of −30‰ to 35‰ clearly under the global meteoric water line (GMWL); Hoffmann et al, 2020).…”

Section: Ice Core Sampling and Analysismentioning

confidence: 99%

Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea

et al. 2021

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Abstract. Recent low summer sea ice extent in the Weddell Sea raises questions about the contributions of dynamic and thermodynamic atmospheric and oceanic energy fluxes. The roles of snow, superimposed ice, and snow ice are particularly intriguing, as they are sensitive indicators of changes in atmospheric forcing and as they could trigger snow–albedo feedbacks that could accelerate ice melt. Here we present snow depth data and ice core observations of superimposed ice and snow ice collected in the northwestern Weddell Sea in late austral summer 2019, supplemented by airborne ice thickness measurements. Texture, salinity, and oxygen isotope analyses showed mean thicknesses of superimposed and snow ice of 0.11±0.11 and 0.22±0.22 m, respectively, or 3 % to 54 % of total ice thickness. Mean snow depths ranged between 0.46±0.29 m in the south to 0.05±0.06 m in the north, with mean and modal total ice thicknesses of 4.12±1.87 to 1.62±1.05 m and 3.9 to 0.9 m, respectively. These snow and ice properties are similar to results from previous studies, suggesting that the ice's summer surface energy balance and related seasonal transition of snow properties have changed little in past decades. This is supported by our additional analyses of the summer energy balance using atmospheric reanalysis data and by melt onset observations from satellite scatterometry showing few recent changes.

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Section: Ice Core Sampling and Analysismentioning

confidence: 99%

Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea

et al. 2021

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“…Topographic data from the ICESat and ICESat-2 missions and the Reference Elevation Model of Antarctica (REMA), derived from very-high-resolution optical stereo images (Howat et al, 2019), are available as a reference for estimating the elevation bias in the InSAR DEMs. We use the ICESat and ICESat-2 data primarily for assessing the temporal stability of surface elevation.…”

Section: Topographic Data From Optical Satellite Sensorsmentioning

confidence: 99%

“…For spatially detailed comparisons of elevation we use the REMA DEM tile no. 32-19 with 8 m posting, covering Union Glacier (Howat et al, 2019). The dates of the image acquisitions for this tile range from January 2014 to December 2015.…”

Section: Topographic Data From Optical Satellite Sensorsmentioning

confidence: 99%

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Penetration of interferometric radar signals in Antarctic snow

et al. 2021

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Abstract. Synthetic aperture radar interferometry (InSAR) is an efficient technique for mapping the surface elevation and its temporal change over glaciers and ice sheets. However, due to the penetration of the SAR signal into snow and ice, the apparent elevation in uncorrected InSAR digital elevation models (DEMs) is displaced versus the actual surface. We studied relations between interferometric radar signals and physical snow properties and tested procedures for correcting the elevation bias. The work is based on satellite and in situ data over Union Glacier in the Ellsworth Mountains, West Antarctica, including interferometric data of the TanDEM-X mission, topographic data from optical satellite sensors and field measurements on snow structure, and stratigraphy undertaken in December 2016. The study area comprises ice-free surfaces, bare ice, dry snow and firn with a variety of structural features related to local differences in wind exposure and snow accumulation. Time series of laser measurements of NASA's Ice, Cloud and land Elevation Satellite (ICESat) and ICESat-2 show steady-state surface topography. For area-wide elevation reference we use the Reference Elevation Model of Antarctica (REMA). The different elevation data are vertically co-registered on a blue ice area that is not affected by radar signal penetration. Backscatter simulations with a multilayer radiative transfer model show large variations for scattering of individual snow layers, but the vertical backscatter distribution can be approximated by an exponential function representing uniform absorption and scattering properties. We obtain estimates of the elevation bias by inverting the interferometric volume correlation coefficient (coherence), applying a uniform volume model for describing the vertical loss function. Whereas the mean values of the computed elevation bias and the elevation difference between the TanDEM-X DEMs and the REMA show good agreement, a trend towards overestimation of penetration is evident for heavily wind-exposed areas with low accumulation and towards underestimation for areas with higher accumulation rates. In both cases deviations from the uniform volume structure are the main reason. In the first case the dense sequence of horizontal structures related to internal wind crust, ice layers and density stratification causes increased scattering in near-surface layers. In the second case the small grain size of the top snow layers causes a downward shift in the scattering phase centre.

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“…R crust and R Ca-Na sea water correspond to the mean ratios (w/w) in the earth crust (R crust = 1.78) and in bulk sea water (R Ca-Na sea water = 0.038), respectively [39]. The nssSO 4 2− and ssNa + were calculated to obtain the nssSO 4 2− :ssNa + ratio, which has been shown as a valuable tool to enhance austral summer peaks and winter troughs [40].…”

Section: Ice Core Discrete Chemistrymentioning

confidence: 99%

An Age Scale for the First Shallow (Sub-)Antarctic Ice Core from Young Island, Northwest Ross Sea

et al. 2021

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The climate of the sub-Antarctic is important in understanding the environmental conditions of Antarctica and the Southern Ocean. However, regional climate proxy records from this region are scarce. In this study, we present the stable water isotopes, major ion chemistry, and dust records from the first ice core from the (sub-)Antarctic Young Island. We present and discuss various dating approaches based on commonly used ice core proxies, such as stable water isotopes and seasonally deposited ions, together with site-specific characteristics such as melt layers. The dating approaches are compared with estimated precipitation rates from reanalysis data (ERA5) and volcanic cryptotephra shards likely presenting an absolute tie point from a 2001 CE eruption on neighboring Sturge Island. The resulting ice core age scale spans the period 2016 to 1995, with an uncertainty of ±2 years.

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Stable water isotopes and accumulation rates in the Union Glacier region, Ellsworth Mountains, West Antarctica, over the last 35 years

Abstract: Antarctica is well known to be highly susceptible to atmospheric and oceanic warming. However, due to the lack of long-term and in situ meteorological observations, little is known about the magnitude of the warming and the meteorological conditions in the intersection region between

Cited by 19 publications

References 108 publications

Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea

Recent observations of superimposed ice and snow ice on sea ice in the northwestern Weddell Sea

Penetration of interferometric radar signals in Antarctic snow

An Age Scale for the First Shallow (Sub-)Antarctic Ice Core from Young Island, Northwest Ross Sea

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