Earth's climate is approaching dangerous tipping points. Among these, the collapse of the Greenland Ice Sheet (GIS) and North Atlantic Subpolar Gyre (NA/SPG) pose considerable threats to European climate. Accelerated ice melt and expected changes in ocean-atmosphere-ice interactions will modify (1) stratification, (2) deep water formation, (3) air-sea fluxes, (4) ocean and atmospheric circulation, and (5) precipitation patterns over the NA. Despite an urgent need for an early warning system, major gaps between ocean observations and the data required to constrain predictive models exist, limiting any confidence in future climate projections. Present-day observations simply do not sample the rapidly evolving processes at kilometre and sub-kilometre scales in complex environments such as the marginal ice zone. Hence, different observations are needed to quantify the role of these processes in horizontal and vertical exchanges of freshwater, heat, and momentum between the GIS and SPG.

AEROSTATS (Aerial Experimental Remote sensing of Ocean Salinity, heaT, Advection, and Thermohaline Shifts) is a UK-led, international project aimed at demonstrating a new approach to sustained, low-cost, low-carbon monitoring of freshwater exchanges. AEROSTATS focuses on innovative airborne platforms for remote, high-resolution imaging of (i) total surface current vectors, (ii) ocean surface winds, (iii) sea surface salinity, (iv) ocean colour, and (v) sea surface temperature at 1-10 km and sub-daily scales. Funded by the UK to conduct high-risk, high-reward science, AEROSTATS will collect and fuse data from novel instruments, in situ surface and subsurface platforms, space-borne sensors, and high-resolution reanalyses and models to improve present-day understanding and representation of these fine-scale processes. A core component of the project is a 2028 field demonstration of these systems across multiple seasons in this unforgiving environment. By combining multi-platform observations with reanalyses and models, and using digital tools such as machine learning and digital twins to detect changes in freshwater exchanges, AEROSTATS will serve as a key component of an early warning system for these tipping points. Such a system could form the basis of a long-term partnership between Greenland and European stakeholders, delivering a sustained observations of critical components of the climate system.