Critical dependence of global ocean heat monitoring on the ocean observing system

Ocean monitoring critically depends on the Global Ocean Observing System, which has provided upper-2,000-m temperatures with near-global coverage since around 2005 but is increasingly vulnerable to policy and economic pressures. Here we show that data reduction in the Global Ocean Observing System would substantially degrade its capability to monitor ocean heat content changes. We further highlight the shared responsibility of nations, through sustained international coordination and long-term national commitments, to maintain an adequate observing system.