Equatorial Pacific Subsurface Temperature
Depth–longitude cross-sections along the equator from the TAO/TRITON moored-buoy array. The subsurface warm reservoir along the thermocline often leads the surface ENSO signal.
Equatorial Pacific Subsurface Temperature
Depth–longitude cross-section along the equator (0°N) from the TAO/TRITON moored-buoy array: temperature (top) and its anomaly versus the 1991–2020 average (bottom), 5-day smoothed. The thermocline (here the 26°C and 28°C isotherms) tilts upward toward the east, and subsurface anomalies along it often lead the surface ENSO signal.
Subsurface Temperature: Climate Trend Removed
The same equatorial cross-section, comparing the anomaly versus the 1991–2020 average (top) with the same anomaly after the secular climate trend is removed (bottom). The trend is a per-depth, per-longitude linear fit over the 1991–2020 TAO record, so de-trending strips the slowly-evolving background and isolates the ENSO signal. The panels differ where the background trend lives, notably subsurface warming in the far west and cooling along the eastern thermocline.
Tropical Pacific Surface Currents
Daily surface-current fields over the last month for the equatorial Pacific (15°S–15°N, 130°E–80°W) from the Copernicus Marine 1/12° ocean model: speed shaded (blue slow to red fast) with streamlines tracing the flow. The westward South Equatorial Current straddles the equator, the eastward North Equatorial Counter Current sits near 5–10°N, and Tropical Instability Wave eddies ripple along the cold tongue.
Equatorial Zonal Current & the Undercurrent
Depth–longitude slice along the equator (1.5°S–1.5°N), 160°E–90°W, from the Copernicus Marine 1/12° global ocean model: zonal current (shaded, eastward in red) with the 20°C isotherm (the thermocline) in black. It resolves the Equatorial Undercurrent, the eastward subsurface jet at about 50–200 m, the surface-westward South Equatorial Current, and the east–west thermocline tilt. The loop is pinned to start 1 March 2026 and grows daily, so downwelling Kelvin waves (a deepening of the 20°C isotherm with an eastward current pulse) can be followed across the basin.
Equatorial Surface Current: Strip / Hovmöller
Longitude × time strip of the daily surface zonal current averaged 2°S–2°N, 150°E–90°W (same Copernicus Marine model). Red is eastward, blue is westward. The equatorial surface normally flows westward (the trade-driven South Equatorial Current); as El Niño matures, downwelling Kelvin waves drive eastward surges into the east Pacific. Newest day at the bottom.
