Casado, M., Leroy-Dos Santos, C., Fourré, E., Favier, V., Agosta, C., Arnaud, L., Prié, F., Akers, P. D., Janssen, L., Kittel, C., Savarino, J., and Landais, A.. (2022). Water vapor isotopic signature along the EAIIST traverse.
Abstract: Stable Water Isotopes Are A Tracer Of Hydrological Processes And A Paleoclimate Proxy From Ice Core Records. The Interpretation Of The Latter Relies On Fractionation Processes Throughout The Hydrological Cycle, From The Evaporation Over The Ocean, During Each Precipitation Event, And During Post-deposition Processes, In Particular Due To The Exchanges Between The Snow And The Moisture In The Atmosphere. Thanks To New Developments In Infrared Spectroscopy, It Is Now Possible To Monitor Not Only The Snow Isotopic Composition But Also The Vapour Continuously, And Thus Document Exchanges Between The Snow And The Vapour. On The East Antarctic Plateau, Records Of Water Vapour Isotopic Composition In Kohnen And Dome C During Summer Have Revealed Significant Diurnal Variability Which Can Be Used To Address The Exchange Between Surface Snow And Atmospheric Water Vapour As Well As The Stability Of The Atmospheric Boundary Layer. in This Study, We Present The First Vapour Monitoring On A Transect Across East Antarctica For A Period Of 3 Months From November 2019 To February 2020 During The Eaiist Traverse, Covering More Than 3600 Km. In Parallel, We Also Monitored The Vapour Isotopic Composition At Two Stations: Dumont D’urville (Ddu), The Starting Point, And Dome C, Half Way Through. Efforts On The Calibration On Each Monitoring Station, As Well As Cross-calibration Of The Different Instruments Offer A Unique Opportunity To Compare Both The Spatial And Temporal (Diurnal Variability Or At The Scale Of Several Days) Gradients Of Humidity, Temperature And Water Vapour Isotopic Composition In East Antarctica During The Summer Season. with The Use Of The Modele Atmospherique Régional (Mar), We Compare The Variability Measured In Water Vapour Isotopic Composition, Temperature And Humidity With The Different Systems (Fixed Or Mobile Location). Although Further Comparisons With The Surface Snow Isotopic Composition Are Required To Quantify The Impact Of The Snow-atmosphere Exchanges On The Local Surface Mass Balance, These Three Simultaneous Measurements Of The Vapour Isotopic Composition Show The Potential Of Using Water Stables Isotopes To Evaluate Hydrological Processes In East Antarctica.
Programme: 1205
|
Dedieu, J.-P., A. Wendleder, B. Cerino, J. Boike, E. Bernard, J.-C. Gallet, and H.-W. Jacobi. (2021). Snow change detection from polarimetric SAR time-series at X-band (Svalbard, Norway), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-149..
Abstract: Due to recent climate change conditions, i.e. increasing temperatures and changing precipitation patterns, arctic snow cover dynamics exhibit strong changes in terms of extent and duration. Arctic amplification processes and impacts are well documented expected to strengthen in coming decades. In this context, innovative observation methods are helpful for a better comprehension of the spatial variability of snow properties relevant for climate research and hydrological applications. Microwave remote sensing provides exceptional spatial and temporal performance in terms of all-weather application and target penetration. Time-series of Synthetic Active Radar images (SAR) are becoming more accessible at different frequencies and polarimetry has demonstrated a significant advantage for detecting changes in different media. Concerning arctic snow monitoring, SAR sensors can offer continuous time-series during the polar night and with cloud cover, providing a consequent advantage in regard of optical sensors. The aim of this study is dedicated to the spatial/temporal variability of snow in the Ny-Ålesund area on the Br∅gger peninsula, Svalbard (N 78°55’ / E 11° 55’). The TerraSAR-X satellite (DLR, Germany) operated at X-band (3.1 cm, 9.6 GHz) with dual co-pol mode (HH/VV) at 5-m spatial resolution, and with high incidence angles (36° to 39°) poviding a better snow penetration and reducing topographic constraints. A dataset of 92 images (ascending and descending) is available since 2017, together with a high resolution DEM (NPI 5-m) and consistent in-situ measurements of meteorological data and snow profiles including glaciers sites. Polarimetric processing is based on the Kennaugh matrix decomposition, copolar phase coherence (CCOH) and copolar phase difference (CPD). The Kennaugh matrix elements K0, K3, K4, and K7 are, respectively, the total intensity, phase ratio, intensity ratio, and shift between HH and VV phase center. Their interpretation allows analysing the structure of the snowpack linked to the near real time of in-situ measurements (snow profiles). The X-band signal is strongly influenced by the snow stratigraphy: internal ice layers reduce or block the penetration of the signal into the snow pack. The best R2 correlation performances between estimated and measured snow heights are ranging from 0.50 to 0.70 for dry snow conditions. Therefore, the use of the X-band for regular snow height estimations remains limited under these conditions. Conversely, this study shows the benefit of TerraSAR-X thanks to the Kennaugh matrix elements analysis. A focus is set on the Copolar Phase Difference (CPD, Leinss 2016) between VV and HH polarization: Φ CPD = Φ VV – Φ HH. Our results indicate that the CPD values are related to the snow metamorphism: positive values correspond to dry snow (horizontal structures), negative values indicate recrystallization processes (vertical structures). Backscattering evolution in time offer a good proxy for meteorological events detection, impacting on snow metamorphism. Fresh snowfalls or melting processes can then be retrieved at the regional scale and linked to air temperature or precipitation measurements at local scale. Polarimetric SAR time series is therefore of interest to complement satellite-based precipitation measurements in the Arctic.
Programme: 1126
|
|
. (2021). 10 years of Polar Stratospheric Clouds lidar measurements at the French antarctic station Dumont d'Urville.
|
|
Vincent Lesur, Aude Chambodut. (2020). The French network of magnetic observatories.
|
|
. (2023). Diurnal variations in oxygen and nitrogen isotopes of atmospheric nitrogen dioxide and nitrate: implications for tracing NOx oxidation pathways and emission sources.
|
|
. (2023). Surface dynamics and history of the calving cycle of the Astrolabe glacier (Antarctica) derived from optical imagery.
|
|
. (2023). From atmospheric water isotopes measurement to firn core interpretation in Adelie Land: A case study for isotope-enabled atmospheric models in Antarctica.
|
. (2022). Sub-millennial climate variability from high resolution water isotopes in the EDC ice core.
Abstract: The EPICA Dome C (EDC) ice core provides the longest continuous climatic record covering the last 800 000 years (800 kyrs). Obtaining homogeneous high resolution measurements and accounting for diffusion provide a unique opportunity to study the evolution of decadal to millennial variability within the past glacial and interglacial periods. We present here a compilation of high resolution (11 cm) water isotopic records with 27 000 ?18O measurements and 7 920 ?D measurements (covering respectively 94 % and 27 % of the whole EDC record), including published and new measurements (2 900 for both ?18O and ?D) over the last 800 kyrs on the EDC ice core. We show that overlapping measurement series performed over multiple depth ranges over the past 20 years, using different analytical methods and in different laboratories, are consistent within analytical uncertainty, and therefore can be combined to provide a homogeneous data set. A frequency decomposition of the most complete ?18O record and a simple assessment of the possible influence of diffusion on the measured profile shows that the variability during glacial periods at multi-decadal to multi-centennial timescale is higher than variability of the interglacial periods. This analysis shows as well that during interglacial periods characterized by a temperature optimum at its beginning, the multi-centennial variability is the strongest over this temperature optimum.
Programme: 1110
|
|
. (2015). Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores
. Climate of the Past Discussions, 11(2), 1437–1477.
|
Fischer H, Severinghaus J, Brook E, Wolff E, Albert M, Alemany O, Arthern R, Bentley C, Blankenship D, Chappellaz J, Creyts T, Dahl-Jensen D, Dinn M, Frezzotti M, Fujita S, Gallee H, Hindmarsh R, Hudspeth D, Jugie G, Kawamura K, Lipenkov V, Miller H, Mulvaney R, Parrenin F, Pattyn F, Ritz C, Schwander J, Steinhage D, van Ommen T, Wilhelms F, . (2013). Where to find 1.5 million yr old ice for the IPICS “Oldest-Ice” ice core
. 1814-9324, 9(6), 2489–2505.
Abstract: The recovery of a 1.5 million yr long ice core from Antarctica represents a keystone of our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this progression. Here we tackle the question of where such ice may still be found in the Antarctic ice sheet. We can show that such old ice is most likely to exist in the plateau area of the East Antarctic ice sheet (EAIS) without stratigraphic disturbance and should be able to be recovered after careful pre-site selection studies. Based on a simple ice and heat flow model and glaciological observations, we conclude that positions in the vicinity of major domes and saddle position on the East Antarctic Plateau will most likely have such old ice in store and represent the best study areas for dedicated reconnaissance studies in the near future. In contrast to previous ice core drill site selections, however, we strongly suggest significantly reduced ice thickness to avoid bottom melting. For example for the geothermal heat flux and accumulation conditions at Dome C, an ice thickness lower than but close to about 2500 m would be required to find 1.5 Myr old ice (i.e., more than 700 m less than at the current EPICA Dome C drill site). Within this constraint, the resolution of an Oldest-Ice record and the distance of such old ice to the bedrock should be maximized to avoid ice flow disturbances for example, by finding locations with minimum geothermal heat flux. As the geothermal heat flux is largely unknown for the EAIS, this parameter has to be carefully determined beforehand. In addition, detailed bedrock topography and ice flow history has to be reconstructed for candidates of an Oldest-Ice ice coring site. Finally, we argue strongly for rapid access drilling before any full, deep ice coring activity commences to bring datable samples to the surface and to allow an age check of the oldest ice.
Programme: 902
|
