[Folda] Reminder Friday seminar today at12:30 in 130: Dr. Mathieu Casado - 'Water stable isotopes in Antarctica: application as an atmospheric tracer and implications for paleoclimate reconstruction'

[Maren Kahl]

Dear all,

 

quick reminder that our final seminar talk will take place today at 12:30 in
Askja 130 with a presentation titled 'Water stable isotopes in Antarctica:
application as an atmospheric tracer and implications for paleoclimate
reconstruction' given by Dr. Mathieu Casado.

 

Abstract: The oldest ice core records are obtained from the East Antarctic
plateau. Water stable isotopes records are key for reconstructions of past
climatic conditions both over the ice sheet and at the evaporation source.
The accuracy of such climate reconstructions crucially depends on the
knowledge of all the processes affecting the water vapour, precipitation and
snow isotopic composition. Atmospheric fractionation processes are well
understood and can be integrated in Rayleigh distillation and complex
isotope enabled climate models. However, a comprehensive quantitative
understanding of processes potentially altering the snow isotopic
composition after the deposition is still missing, especially for exchanges
between vapour and snow. In low accumulation sites such as found on the East
Antarctic Plateau, these poorly constrained processes are especially likely
to play a significant role. This limits the interpretation of isotopic
composition from ice core records, specifically at short time scales. 

 

Here, we combine observations of isotopic composition in the vapour, the
precipitation, the surface snow and the buried snow from various sites of
the East Antarctic Plateau. At the seasonal scale, we highlight a
significant impact of metamorphism on surface snow isotopic signal compared
to the initial precipitation isotopic signal. In particular, in summer,
exchanges of water molecules between vapour and snow are driven by the
sublimation/condensation cycles at the diurnal scale. Using highly resolved
isotopic composition profiles from pits in five East Antarctic sites, we
identify a common 20 cm cycle which cannot be attributed to the seasonal
variability of precipitation. Altogether, the smaller range of isotopic
compositions observed in the buried and in the surface snow compared to the
precipitation, and also the reduced slope between surface snow isotopic
composition and temperature compared to precipitation, constitute evidences
of post-deposition processes affecting the variability of the isotopic
composition in the snow pack. To reproduce these processes in snow-models is
crucial to understand the link between snow isotopic composition and
climatic conditions and to improve the interpretation of isotopic
composition as a paleoclimate proxy.

 

 

 

Best regards,

Maria & Maren

 



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