The global ocean oxygen inventory (total amount of oxygen stored within the entire ocean volume) has declined by over two percent over the past six decades. Although changes in the dissolved oxygen inventory appear small, they have profound and long-lasting impacts on marine organism resilience. Ocean deoxygenation has altered the viability of marine ecosystems. The ability to sustain healthy marine life and ecosystems is dependent on species-specific vulnerability to deoxygenation. The sampling density in the deep ocean (below 2000m) is significantly lower than in the upper ocean, and this presents a major obstacle to accurately monitoring dissolved oxygen fluctuations in these depths. The dearth in global ocean oxygen makes it difficult to accurately understand and predict ocean deoxygenation. Increased dissolved oxygen sampling, particularly in the deep ocean, would be instrumental in providing much needed data for assimilation into numerical models, improving model predictions, and advancing our understanding of the mechanisms affecting oceanic dissolved oxygen variability. This award will fund the development of a new dissolved oxygen sensor for integration on Deep Argo floats, with multiple benefits. The new sensor will simplify usage and improve the quality and scientific value of dissolved oxygen measurements collected in the deep ocean. This technology will help to resolve top-to-bottom regional to global ocean oxygen fluctuations at subseasonal-to-decadal time scale