A negative Pacific volume slope contrast persisted across 21 temperature thresholds in 1980-2024 fits

We tested whether a reported Pacific warm water volume slope contrast depends on a temperature threshold exactly at zero. We used frozen NOAA GODAS and ERSSTv5 monthly data. Six-month volume change was fitted with starting volume, month and time controls at 21 fixed Nino 3.4 thresholds from -0.50 to +0.50 C. Across 534 starts in 1980-2024, upper minus lower temperature slopes ranged from -1.237 to -1.161 in units of 10^14 cubic metres per degree C. A conditional 95% three-year block band over the grid stayed below zero; its highest upper limit was -0.312. Five-year blocks and recent-history controls also gave negative bands over their grids. The contrast thus did not require the exact zero threshold in these fits. This is a sensitivity test on the same revised data as prior work, not independent confirmation. It does not establish a physical break, causal heat loss, or forecast skill. Few climate cycles, fixed model terms and conditional block uncertainty limit the result.

ENSO · warm water volume · threshold sensitivity · simultaneous band · GODAS · recharge