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

Saeid Bagheri Dastgerdi,Elisabeth Schlosser,Gerrit Lohmann,Martin Werner,Maria Hörhold,Melanie Behrens,Jean-Louis Bonne

doi:10.5194/tc-15-4745-2021

Abstract

Abstract. In this study, the first fully continuous monitoring of water vapour isotopic composition at Neumayer Station III, Antarctica, during the 2-year period from February 2017 to January 2019 is presented. Seasonal and synoptic-scale variations in both stable water isotopes H218O and HDO are reported, and their links to variations in key meteorological variables are analysed. In addition, the diurnal cycle of isotope variations during the summer months (December and January 2017/18 and 2018/19) has been examined. Changes in local temperature and specific humidity are the main drivers for the variability in δ18O and δD in vapour at Neumayer Station III, on both seasonal and shorter timescales. In contrast to the measured δ18O and δD variations, no seasonal cycle in the Deuterium excess signal (d) in vapour is detected. However, a rather high uncertainty in measured d values especially in austral winter limits the confidence of this finding. Overall, the d signal shows a stronger inverse correlation with specific humidity than with temperature, and this inverse correlation between d and specific 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 in δ18O and δD in vapour coincide with changes in the main sources of water vapour transported to Neumayer Station III. In general, moisture transport pathways from the east lead to higher temperatures and more enriched δ18O values in vapour, while weather situations with southerly winds lead to lower temperatures and more depleted δ18O values. However, on several occasions, δ18O 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 δ18O–δD relation and for the temperature–δ18O relation.

Highlights

During the last few decades, Antarctic ice cores have been proven to be one of the most important climate archives
Meteorological data are weather station data measured at a distance of 50 m from the main station building at a height of 2 m, and the isotope values have been measured with the Picarro instrument, sampling air from the station roof at a height of 24 m
Water vapour isotope data are missing for some days because of maintenance or repair of the instrument, measuring humidity response functions, or due to the removal of data outliers related to instable measurements of the Picarro instrument

Summary

Introduction

During the last few decades, Antarctic ice cores have been proven to be one of the most important climate archives. They have enabled a detailed climate reconstruction on glacial–interglacial timescales over the last 800 000 years (EPICA Members, 2004; Jouzel et al, 2007) and are the only climate archive which allows direct measurements of past greenhouse gas changes (Petit et al, 1999; Siegenthaler et al, 2005; Loulergue et al, 2008; Lüthi et al, 2008). Recent Antarctic ice core records allow studying the phasing of climate changes and the linkage between northern and southern polar regions in an unprecedented way (WAIS Divide Project Members, 2015).

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