California upwelling winds did not continue their 1982-2008 rise in 2009-2025 (buoys, CUTI); Oregon-Washington upwelling rose; inland heat did not predict the change

Question: did upwelling-favourable alongshore wind in the California Current System (31-48 N, April-July) continue the increase that was reported for 1982-2008, and does inland heating (the Bakun mechanism) explain the change? Data: measured wind stress at 23 NDBC buoys (888 station-years, 1975-2025), the CUTI and BEUTI transport indices (1988-2025), the PFEL Bakun sea-level-pressure index (1967-2025) and CPC daily land Tmax. Method: trends with block-bootstrap intervals; an out-of-sample test that fits a line on 1982-2008 and predicts 2009-2025; latitude regression; daily lag and interannual regressions of stress on inland Tmax. The plan was written before the results. Results: at central California buoys (35.8-38.2 N) the 1982-2008 slopes were +8 to +16% per decade, but 2009-2025 means were 14-33% below the extrapolated trend. For CUTI 35-42 N the extrapolation predicted 2009-2025 worse than no change (skill -1.94, 95% interval -9.6 to -0.28); for 9 pooled California buoys skill was -0.31 (-6.4 to 0.44). The 2009-2025 forcing was only +0.22 to +0.28 SD above 1982-2008 (not clear). Off Oregon-Washington, CUTI 44-47 N rose by +0.92 SD (p 0.005) and the trend continued (skill +0.53), in the direction of projected poleward intensification. Inland Tmax warmed by +0.70 SD, but the interannual sensitivity of California buoy stress to inland Tmax was near zero (-2.5 to +4.4% per K, none clear); daily wind anomalies led inland heat, not the reverse. The Bakun index showed a larger rise (+22% per decade at 39 N) that drifted from the buoy record by 0.36-0.57 SD per decade at 4 of 5 buoys, so we do not use it as evidence of intensification. Limitations: buoy anemometer-height changes are not corrected; the test period has 17 seasons and most single-series intervals are wide; CUTI changes product in 2011 (no clear step found); climate modes were not modelled.

coastal upwelling · California Current · Bakun hypothesis · alongshore wind stress · NDBC buoys · CUTI · out-of-sample test · land-sea temperature contrast · eastern boundary upwelling · climate trends