As climate warming is reaching further into the Antarctic continent, the Antarctic system is facing a regime shift with serious and global consequences (Abram 2025). This regime shift will entail changes to atmospheric and oceanic circulation patterns, reduced and more variable sea ice extent, pronounced melt events potentially leading to ice shelf destabilization, and a reordering of the local and ice-sheet-wide mass balance components. We currently use General Circulation Models (GCM) to study the consequences of this regime shift on the water cycle dynamics in Antarctica and the future contribution of Antarctic sea level rise, but validation and improvement of these models rely on pan-Antarctic, synchronous observations (Werner 2025, Bong 2026). This working group aims to address the need for a coordinated stable water isotope observational network within the Antarctic hydrological cycle. This work is necessary to trace the origins and transport pathways of moisture reaching both the Antarctic coast and the interior, and the subsequent differentiation into various (sub-) compartments of the current hydrological cycle (Casado 2026, Dutrievoz 2026). Stable water isotope measurements provide a powerful tracer of diabatic processes, linking key local physical processes and the large-scale atmospheric circulation (Sodemann et al. 2021, Dee 2023, Bailey 2025). By predictable isotope dynamics they further help to constrain the differentiation and mixing of water cycle compartments (Thurnherr 2021, Gao et al 2024). Thus, stable water isotopes can be used to identify water cycle pathways, constrain local mass balance components, improve process understanding and identify model biases. To leverage stable water isotopes as tracers of the water cycle, synchronous, high-quality and standardized modern-day in situ observations are imperative (Bailey 2023, Lauwers 2025). Our use of “modern-day” includes any studies on the water cycle that measure processes relevant to the InSync period.
Such tracer observations will be valuable to answer cross-theme (Theme I, II, III, VI, VII) and cross-disciplinary (atmospheric, cryospheric, oceanic) research questions and thus provide a truly collaborative network within the Antarctica InSync initiative. By focusing on the modern-day water cycle connection, we naturally bridge across multiple themes. Stable water isotopes directly support Theme I’s focus on Southern Ocean freshwater fluxes, Theme II’s investigation of sea ice decline and its impact on moisture sources, and Theme
VII’s study of climate variability, extremes and tipping points affecting the hydrological cycle. Theme VI further benefits from isotope-enabled constraints on cloud microphysics and precipitation formation. Overall, this working group is needed to ensure more impactful science throughout the InSync years in the lead up to the International Polar Year (IPY).
The working group targets observations based on state-of-the-art instrumentation for the identification of the isotopic composition of different components of the water cycle in Antarctica, such as water vapour, precipitation, fresh and saltwater bodies, surface snow and sea ice.
The approach followed by this working group is to define universally agreed precision and accuracy standards and reporting norms. Further, working group members agree to share their data following FAIR (Findable, Accessible, Interoperable, and Reusable) principles and adhere to the ACDD (Attribute Convention for Data Discovery) standards for metadata. The datasets shall be made publicly available on open data servers upon publication.
Our links to other initiatives is currently dependent on our members’ involvement and we currently have connections to the SCAR Antarctica InSync Action Group (this initiative will be listed here: https://scar.org/science/excom/insync). In addition, Alexander Haumann (AWI) has organized a O18 lab intercomparison on water samples, with which this working group will be in close collaboration.
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The call for participation was distributed on various email lists (5+) before the WG application submission to the InSync Leader board. The application is reviewed by all participants who have had the opportunity to contribute to defining the scope and objective of the working group. Afterwards, we foresee a regular online meeting quarter-yearly for general updates, exchanges and the identification of specific topic-focused meetings with sub-groups of the WG. One of these meetings will be held each year in person at the SCAR open science conference. We plan to organise a workshop and seminar for ECRs who are involved in the InSync process. This will be advertised through APECS in 2026/2027. We also plan to organise a data workshop for our members which will include the following: quality control and quality assessments, data publication format discussions following available guidelines, and the use of DataServers for “secure” data sharing.
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Members of our core team have already registered for multiple InSync WGs, for example the WG Mass Balance (Sonja Wahl and Amy Macfarlane), and WG Extreme Events (Sonja Wahl) this will allow a seamless cross over between the groups work as feedback and ideas can be continuously exchanged.
