Only a very small portion of Earth’s water isn’t in the ocean — about two percent can be accounted for as frozen glaciers and ice caps, and less than one percent is freshwater. Meanwhile, the ocean covers more than 70 percent of Earth’s surface, but much of it remains inadequately studied or monitored. The ocean is deeply connected to processes, including regulating Earth’s climate, supporting marine ecosystems, and providing resources people depend on, like food, energy, and even medicine! 

Ocean monitoring is essential for identifying changes and understanding how ocean conditions shift over time. Strong monitoring coverage is consistent and long-term, extends beyond the ocean surface, and measures key physical, biological, and chemical parameters. It is most effective when conducted through a standardized framework like the Global Ocean Observing System (GOOS), a coordinated, international program that brings together governments, agencies, and research institutions to systematically observe the world’s oceans. This information helps scientists better understand ocean change, predict climate and weather patterns, and inform decisions related to conservation and resource management. 

Physical vs. chemical vs. biological parameters. Physical (temperature, salinity, currents), chemical (oxygen, pH, nutrients, carbon), and biological (species, plankton, biomass) parameters are the core measurements scientists use to understand ocean conditions.

Despite the perception that the ocean may be well-monitored, through buoys, satellites, and Argo floats, global ocean observation remains uneven, selective, and largely disconnected. Many programs operate in isolation, collecting valuable data that never gets integrated into the broader scientific record. Bridging the gaps between collection systems would allow for more comprehensive datasets, stronger cross-regional comparisons, and accelerated scientific development in our understanding of ocean change.

Case Study 1: Biological Monitoring Gap 

GOOS actually organizes Essential Ocean Variables (EOVs) into three groups:
Physical – sea surface temperature, salinity, sea level, currents, sea ice
Biogeochemical – oxygen, nutrients, inorganic carbon, nitrous oxide, transient tracers
Biological/Ecosystem – phytoplankton, zooplankton, fish abundance, marine turtles, seabirds, marine mammals

EOVs were developed under GOOS as a set of key measurements that scientists have agreed are the most important for understanding how the ocean is changing. The GOOS EOV framework is best for defining and establishing international standards because variables like dissolved oxygen, nutrients, and ocean carbon don’t fit neatly into either physical or biological. The EOVs, as defined by GOOS, are an important tool for standardizing ocean measurements across regions and maintain the complexity needed to understand ocean change at a global scale.

Image courtesy of Global Ocean Observing System (GOOS).

Of the three most common parameter groups, physical parameters are the most consistent and extensively monitored, followed by biogeochemical, with biological/ecosystem parameters having the least global coverage. 

A 2021 global audit revealed that the coverage of biological EOVs is incomplete and unevenly distributed, with the 203 active long-term observing programs that responded to the survey covering only 7% of the entire ocean surface (Satterthwaite et al., 2021). Coverage is most sparse across the open ocean and along coastlines in South America, Eastern Europe, Asia, Oceania, and Africa. These under-monitored regions often overlap with areas of high marine biodiversity and significant human activity. The resulting data gaps hinder efforts to address pollution, biodiversity decline, and ecosystem degradation in our oceans.

Image courtesy of The Global Ocean Observing System.

The 40-year failure of the annual upwelling that occurs in the Gulf of Panama highlights the need for monitoring to better detect long-term or seasonal changes. Every year, Panama’s Pacific coast depends on powerful seasonal winds that drive cold, nutrient-rich waters to the surface. This process is important for sustaining fisheries and protecting coral reefs. In 2025, for the first time in at least four decades, the expected seasonal drop in temperature and surge in productivity did not occur. The ocean eventually cooled, six weeks later than usual, lasting only 12 days instead of the normal two months. Scientists suspect that a significant reduction in wind patterns, linked to broader climate disruptions, was the cause of this unprecedented event.


Map of the Gulf of Panama showing high chlorophyll concentrations in February 2024 (left) compared to extremely low chlorophyll concentrations in February 2025 (right). Image courtesy of Aaron O’Dea.

These consequences were immediately observed. Without the expected annual upwelling of cold, nutrient-rich water, phytoplankton blooms that feed the marine food web were suppressed, and fisheries productivity declined. Coral reefs also lost their yearly thermal buffer, leaving them exposed to heat stress. In the ocean, our poor understanding of how biodiversity is distributed limits its management and protection. This event was documented because the monitoring infrastructure was in place. In less-monitored regions, a failure of the same magnitude could pass entirely unrecorded. This is why biological monitoring matters so much. While physical and chemical measures describe the environment, biological data describe the response to that environment. For example, a temperature reading tells you the water is warmer than usual. Meanwhile, a biological measurement, like a shift in phytoplankton species presence, tells you that the ecosystem is being harmed by that warmth.

Case Study 2: The Deep Ocean Blind Spot 

The deep sea is defined by the Intergovernmental Panel on Climate Change (IPCC) as the region below 200 m (0.2 km) depth. It is the largest habitat on Earth by both volume and area, covering about 66% of the planet’s surface and accounting for roughly 95% of its habitable volume. As illustrated in the Deep Ocean Observing Strategy (DOOS), monitoring relies on a combination of platforms including fixed sites/moorings, research cruises, satellites, and instruments on the seafloor. Autonomous systems like Argo and Deep Argo floats collect data as they move through the water, often reaching depths of 2,000 (2 km) or more. While these technologies have greatly improved our ability to observe the ocean, they are unevenly distributed, and large parts of the deep ocean are still barely monitored.