Continuous monitoring of surface water vapour isotopic compositions at Neumayer Station III, East Antarctica

• Main Authors: Bagheri Dastgerdi, Saeid, Behrens, Melanie, Bonne, Jean-Louis, Hörhold, Maria, Lohmann, Gerrit, Schlosser, Elisabeth, Werner, Martin
• Format: Text
• Language: English
• Published: 2020
• Subjects: Austral; East Antarctica; Neumayer; Neumayer Station; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/tc-2020-302; https://tc.copernicus.org/preprints/tc-2020-302/

In this study, the first fully-continuous monitoring of water vapour isotopic composition at Neumayer Station III, Antarctica, during the two-year period from February 2017 to January 2019 is presented. Seasonal and synoptic-scale variations of both stable water isotopes H 2 18 O and HDO are reported, and their link to variations of key meteorological variables are analysed. Changes in local temperature and humidity are the main drivers for the variability of δ O 18 and δ D in vapour at Neumayer Station III, both on seasonal and shorter time scales. In contrast to the measured δ O 18 and δ D variations, no seasonal cycle in the Deuterium excess signal d–excess in vapour is detected. However, a rather high uncertainty of measured d–excess values especially in austral winter limits the confidence of this finding. Overall, the d–excess signal shows a stronger inverse correlation with humidity than with temperature, and this inverse correlation between d–excess and humidity is stronger for the cloudy-sky conditions than for clear-sky conditions during summertime. Back trajectory simulations performed with the FLEXPART model show that seasonal and synoptic variations of δ O 18 and δ D in vapour coincide with changes in the main sources of water vapour transported to Neumayer Station. In general, moisture transport pathways from the east lead to higher temperatures and more enriched δ O 18 values in vapour, while weather situations with southerly winds lead to lower temperatures and more depleted δ O 18 values. However, for several occasions, δ O 18 variations linked to wind direction changes were observed, which were not accompanied by a corresponding temperature change. Comparing isotopic compositions of water vapour at Neumayer Station III and snow samples taken in the vicinity of the station reveals almost identical slopes, both for the δ O 18 –δ D relation and for the temperature–δ O 18 relation.