Researchers at The Shirshov Institute used Argo’s extensive temperature and salinity records to identify the Atlantic Equatorial Water (AEW), a previously unrecognized water mass in the equatorial Atlantic thermocline. The AEW lies roughly along the equator and separates northern and southern Atlantic waters down to the upper 2,000 meters. Finding the AEW fills a gap in the global pattern of equatorial water masses and improves understanding of how oceans store and transport heat, salt and dissolved gases.
Hidden 'Blob' of Equatorial Water Discovered in the Atlantic — What It Means for Global Oceans
Scientists Finally Found a Missing Blob of WaterOlena Malik - Getty Images
Scientists have identified a previously overlooked mass of water in the equatorial Atlantic that helps separate northern and southern Atlantic waters and clarifies a long-standing gap in our understanding of global ocean structure.
Researchers at The Shirshov Institute of Oceanology in Moscow detected the Atlantic Equatorial Water (AEW) by reanalyzing large, high-quality temperature and salinity datasets collected by the international Argo program. The findings were published in Geophysical Research Letters.
How the Discovery Was Made
Launched in 1998, Argo operates a global array of drifting robotic profilers that repeatedly sample the ocean from the surface to mid-depths. Using Argo’s extensive records, Viktor Zhurbas and colleagues constructed a detailed volumetric temperature–salinity diagram of the upper 2,000 meters of the Atlantic Ocean. That analysis revealed a distinct water mass within the main thermocline — the transition layer between warm surface waters and cooler deep waters — that had previously gone unrecognized.
What the AEW Is and Where It Lies
The Atlantic Equatorial Water (AEW) is a coherent water mass that lies roughly along the equator in the Atlantic and acts as a boundary between northern and southern oceanic regimes. Similar equatorial layers had long been mapped in the Pacific and Indian Oceans, and the AEW fills an expected spot in the global pattern of equatorial water masses.
Why This Matters
Water masses like the AEW serve as reservoirs of heat, salt and dissolved gases, and they play a crucial role in how the ocean stores and redistributes climate signals. Identifying the AEW improves scientists’ ability to track how heat, oxygen and nutrients move through the ocean — processes that influence regional climates, marine ecosystems and global circulation patterns.
“Re-examination of water masses using previously unavailable high-quality large-volume Argo data allowed us to distinguish a formerly unnoticed water mass in the main thermocline of the Equatorial Atlantic,” the authors write.
The discovery highlights how expanded observational networks such as Argo enable detection of subtle but climatically important features of ocean structure, helping to better connect ocean observations with models of global climate dynamics.
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