The Ross Sea, home to Antarctica’s largest ice shelf, is missing a basic accounting of where its freshwater comes from and how it changes over time. That gap matters because freshwater—whether from melting glaciers, sea ice, or rain—alters the density of seawater, which in turn drives ocean currents that move heat around the planet. Without a reliable freshwater budget, climate models cannot accurately predict how the Southern Ocean will respond to warming. FRESH will build the first observation-based, time-varying freshwater budget for the Ross Sea by combining decades of physical, chemical, and dynamical seawater measurements with new data from a UK-Italy-New Zealand partnership. If successful, the project will settle a key question: whether glacial meltwater dominates the Ross Sea’s freshwater balance over decades, while sea ice controls it year-to-year. This is fundamental science—it will not directly change a product or policy tomorrow. But a clearer picture of how Antarctica’s freshwater moves and mixes is essential for improving the ocean models that underpin global climate projections, sea-level forecasts, and the management of polar marine ecosystems.
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Antarctica's freshwater influences local and global ocean dynamics, by affecting water density and the distribution of heat. However, because of Antarctica's remote location and multiple freshwater sources, the balance between freshwater and salt - the freshwater budget - remains poorly understood. FRESH (The Origins, Characteristics, and Processes of Antarctic FRESHwater) aims to address this knowledge gap by creating the first observation-based, time-varying freshwater budget in the Ross Sea. The Ross Sea features the largest Antarctic ice shelf and has been shown to significantly contribute to local and global ocean dynamics. Here, the freshwater budget is influenced by glacial meltwater, ocean advection, sea ice, and precipitation. Limited observational evidence suggests that glacial meltwater dominates the Ross Sea's freshwater budget on decadal scales, with sea ice playing a role on annual scales. By tracking water masses and their freshwater sources, quantifying the magnitude and variability of freshwater components, and comparing historical measurements, FRESH will test this hypothesis. Specifically, our project will combine physical, chemical, and dynamical seawater measurements collected since the 1970s, new observations of extreme and ambient water mass properties, and innovative techniques to measure ocean transport and diagnose freshwater sources. Led by an early career scientist at the University of Southampton, our team will leverage a new partnership between the United Kingdom, Italy, and New Zealand to achieve a new understanding of the Antarctica's freshwater budget.
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