scholarly journals Water isotopic signature of surface snow metamorphism in Antarctica

2021 ◽  
Author(s):  
M. Casado ◽  
A. Landais ◽  
G. Picard ◽  
L. Arnaud ◽  
G. Dreossi ◽  
...  
Keyword(s):  
Isotopic Signature ◽  
Surface Snow ◽  
Snow Metamorphism

scholarly journals Exploring the role of snow metamorphism on the isotopic composition of the surface snow at EastGRIP

2021 ◽  
Author(s):  
Romilly Harris Stuart ◽  
Anne-Katrine Faber ◽  
Sonja Wahl ◽  
Maria Hörhold ◽  
Sepp Kipfstuhl ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Pore Space ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Water Isotopes ◽  
Climate Signal ◽  
Depositional Processes ◽  
Decay Model ◽  
Surface Snow ◽  
Snow Metamorphism

Abstract. Stable water isotopes from polar ice cores are invaluable high-resolution climate proxy records. Recent studies have aimed to improve knowledge of how the climate signal is stored in the water isotope record by addressing the influence of post-depositional processes on the surface snow isotopic composition. In this study, the relationship between changes in surface snow microstructure after precipitation/deposition events and water isotopes is explored using measurements of snow specific surface area (SSA). Continuous daily SSA measurements from the East Greenland Ice Core Project site (EastGRIP) situated in the accumulation zone of the Greenland Ice Sheet during the summer seasons of 2017, 2018 and 2019 are used to develop an empirical decay model to describe events of rapid decrease in SSA, driven predominantly by vapour diffusion in the pore space and atmospheric vapour exchange. The SSA decay model is described by the exponential equation SSA(t) = (SSA0 −26.8) e−0.54t + 26.8. The model performance is optimal for daily mean values of surface temperature in the range 0 °C to −25 °C and wind speed < 6 m s−1. The findings from the SSA analysis are used to explore the influence of surface snow metamorphism on altering the isotopic composition of surface snow. It is found that rapid SSA decay events correspond to decreases in d-excess over a 2-day period in 72 % of the samples. Detailed studies using Empirical Orthogonal Function (EOF) analysis revealed a coherence between the dominant mode of variance of SSA and d-excess during periods of low spatial variability of surface snow over the sampling transect, suggesting that processes driving change in SSA also influence d-excess. Our findings highlight the need for future studies to decouple the processes driving surface snow metamorphism in order to quantify the fractionation effect of individual processes on the snow isotopic composition.

Using triple water isotopes signatures of surface snow to gauge metamorphism in Antarctica

2020 ◽  
Author(s):  
Mathieu Casado ◽  
Amaelle Landais ◽  
Ghislain Picard ◽  
Laurent Arnaud ◽  
Giuliano Dreossi ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Ice Core ◽  
Chemical Properties ◽  
Ice Cores ◽  
Blowing Snow ◽  
Climate Reconstructions ◽  
Climatic Signal ◽  
Surface Snow ◽  
Snow Metamorphism ◽  
Deposition Processes

&lt;p&gt;Water isotopic composition is a key proxy for past climate reconstructions using deep ice cores from Antarctica. As precipitation forms, the local temperature is imprinted in the snowfalls &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O. However, this climatic signal can be erased after snow deposition when snow is exposed to the atmosphere for a long time in regions with extremely low accumulation. Understanding this effect is crucial for the interpretation of ice core records from the extremely dry East Antarctic Plateau, where post-deposition processes such as blowing snow or metamorphism affect the physical and chemical properties of snow during the long periods of snow exposure to the atmosphere. Despite the importance of these processes for the reliable reconstruction of temperature from water isotopic composition in ice cores, the tools required to quantify their impacts are still missing. Here, we present a first year-long comparison between (a) time series of surface snow isotopic composition including d-excess and &lt;sup&gt;17&lt;/sup&gt;O-excess at Dome C and (b) satellite observations providing information on snow grain size, a marker of surface metamorphism. Long summer periods without precipitation tend to produce a surface snow metamorphism signature erasing the climatic signal in the surface snow &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O. Using a simple model, we demonstrate that d-excess and &lt;sup&gt;17&lt;/sup&gt;O-excess allow the identification of the latent fluxes induced by metamorphism, and their impact on surface snow isotopic composition. In turn, their measurements can help improve climate reconstructions based on &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O records ice by removing the influence of snow metamorphism.&lt;/p&gt;

Icelandic thermal brines with a mantle Sr isotopic signature

1981 ◽  
Vol 34 (4) ◽  
pp. 243-245 ◽  
Author(s):  
Norbert Clauer ◽  
Jon Olafsson
Keyword(s):  
Isotopic Signature

Methods for extraction of microorganism DNA from glacier surface snow

2012 ◽  
Vol 4 (6) ◽  
pp. 484
Author(s):  
Yan Pei-Ying ◽  
Hou Shu-Gui ◽  
Chen Tuo ◽  
Zhang Shu-Hong ◽  
Sun Wei-Jun
Keyword(s):  
Glacier Surface ◽  
Surface Snow

scholarly journals Geochemical Variation of Miocene Basalts within Shikoku Basin: Magma Source Compositions and Geodynamic Implications

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 25
Author(s):  
Shuang-Shuang Chen ◽  
Tong Hou ◽  
Jia-Qi Liu ◽  
Zhao-Chong Zhang
Keyword(s):  
Japan Sea ◽  
Isotopic Signature ◽  
Magma Source ◽  
Isotopic Compositions ◽  
Enriched Mantle ◽  
Shikoku Basin ◽  
Depleted Mantle ◽  
Parece Vela Basin ◽  
Back Arc ◽  
Ocean Ridge

Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we report mineral compositions, major, trace-element, and Sr-Nd-Pb isotopic compositions of bulk-rocks from Sites C0012 (>18.9 Ma) and 1173 (13–15 Ma) of the Shikoku Basin. Samples from Sites C0012 and 1173 are tholeiitic in composition and display relative depletion in light rare earth elements (REEs) and enrichment in heavy REEs, generally similar to normal mid-ocean ridge basalts (N-MORB). Specifically, Site C0012 samples display more pronounced positive anomalies in Rb, Ba, K, Pb and Sr, and negative anomalies in Th, U, Nb, and Ta, as well as negative Nb relative to La and Th. Site 1173 basalts have relatively uniform Sr-Nd-Pb isotopic compositions, close to the end member of depleted mantle, while Site C0012 samples show slightly enriched Sr-Nd-Pb isotopic signature, indicating a possible involvement of enriched mantle 1 (EM1) and EM2 sources, which could be attributed to the metasomatism of the fluids released from the dehydrated subduction slab, but with the little involvement of subducted slab-derived sedimentary component. Additionally, the Shikoku Basin record the formation of the back-arc basin was a mantle conversion process from an island arc to a typical MORB. The formation of the Shikoku Basin is different from that of the adjacent Japan Sea and Parece Vela Basin, mainly in terms of the metasomatized subduction-related components, the nature of mantle source, and partial melting processes.

scholarly journals The δ13C, δ18O and Δ47 records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

2021 ◽  
pp. 1-17
Author(s):  
Kazem Zamanian ◽  
Alex R. Lechler ◽  
Andrew J. Schauer ◽  
Yakov Kuzyakov ◽  
Katharine W. Huntington
Keyword(s):  
Land Snail ◽  
Isotopic Signature ◽  
Sediment Layer ◽  
Isotopic Signatures ◽  
Pedogenic Carbonates ◽  
Rhine Valley ◽  
Clumped Isotope ◽  
Time Specific ◽  
Sediment Layers ◽  
Paleoenvironmental Reconstructions

Abstract Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.

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