Atmospheric constraints on δ¹⁸O and d-excess in precipitation at the middle latitude in the southwestern Atlantic region

ABSTRACT

The mid-latitude coastal area at the western South-Atlantic out of the tropics is under the combined effect of different atmospheric circulation patterns at different temporal scales, which can be shown by the isotope composition of precipitation. This pattern effect is more changing and complex than that for the well-studied tropical areas, the isotope studies being an interesting proxy for identifying major processes. This study is focused on the isotope composition of precipitation at a mid-latitude zone, in the western South-Atlantic coastal area of Argentina. δ¹⁸O and d-excess were analysed in a data series of 14 years, obtained from the integration of three neighbouring rain collectors at 38°S. A seasonality is observed in both parameters, but with some differences in the extreme months. δ¹⁸O showed a seasonality according to the temperature effect, but with a displacement of high values to spring months. Significant linear links between δ¹⁸O and Southern Annular Mode (SAM) index and Southern Oscillation Index (SOI) were recognised for the summer and spring seasons, respectively.

KEYWORDS:

• Argentina
• Atlantic
• atmosphere
• hydrogen-2
• isotope hydrology
• oxygen-18
• precipitation
• seasonality
• water

Acknowledgments

It is important to recognise Mr. Miguel Cantón in San Manuel, and the officers of the Fisheries Station of Necochea, who have been collaborating on the rain samples collection since 15 years, in an absolutely ad honorem and responsible way. We acknowledge the Argentine National Weather Survey for providing the daily wind and precipitation data. PhD Melisa Albisetti (Iugo Pty Ltd., Australia) collaborated in the English revision of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The isotope data series included in this work has been obtained thanks to successive grants for research projects from the IAEA (CRP F33015 and CRP F31006), and the organisms for science development in Argentina: CONICET and ANPCyT.