Moisture origin as a driver of temporal variabilities of the water vapour isotopic composition in the Lena River Delta, Siberia

• Main Authors: Bonne, Jean-Louis, Meyer, Hanno, Behrens, Melanie, Boike, Julia, Kipfstuhl, Sepp, Rabe, Benjamin, Schmidt, Toni, Schönicke, Lutz, Steen-Larsen, Hans Christian, Werner, Martin
• Format: Text
• Language: English
• Published: 2020
• Subjects: Arctic; Climate change; lena delta; lena river; Siberia
• Online Access: https://doi.org/10.5194/acp-2019-942; https://www.atmos-chem-phys-discuss.net/acp-2019-942/

In the context of the Arctic amplification of climate change affecting the regional atmospheric hydrological cycle, it is crucial to characterize the present-day’s moisture sources of the Arctic. The isotopic composition is an important tool to enhance our understanding of the drivers of the hydrological cycle, due to the different molecular characteristics of water stable isotopes during phase change. This study introduces two years of continuous in situ water vapour and precipitation isotopic observations conducted since July 2015 in the east-Siberian Lena delta, at the research station on the Samoylov Island. The vapour isotopic signals are dominated by variations at the seasonal and synoptic time scales. Diurnal variations of the vapour isotopic signals are masked by synoptic variations, indicating low variations of the amplitude of local sources at the diurnal scale in winter, summer and autumn. Low amplitude diurnal variations in spring may indicate exchange of moisture between the atmosphere and the snow-covered surface. Moisture sources diagnostics based on semi-Lagrangian backward trajectories reveal that different air mass origins have contrasted contributions to the moisture budget of the Lena delta region. At the seasonal scale, the distance from the net moisture sources to the arrival site strongly varies. During the coldest months, no contribution from local secondary evaporation is observed. Variations of the vapour isotopic composition during the cold season on synoptic time scale are strongly related to moisture source regions and variations in the atmospheric transport: warm and isotopically-enriched moist air is linked with fast transport from the Atlantic sector; while dry and cold air with isotopically-depleted moisture is generally associated to air masses moving slowly over northern Eurasia.