Bottom warmth had positive copepod contrast slopes at fixed surface temperature in four US shelf samples in 1977-2023

We tested whether bottom temperature adds a repeated signal to a copepod abundance contrast at fixed surface temperature. We used 19,850 EcoMon tows in two latitude bands and two periods from 1977 to 2023. Four models controlled location by month, year, bottom depth, date and time of day. Bottom slopes were positive, from 0.183 to 0.417 log contrast units per degree C. All four three-year block intervals were above zero after correction for four primary tests. Five-year intervals also stayed above zero, but one nearly reached zero. The contrast mainly reflected lower Calanus finmarchicus abundance, not a repeated increase in Centropages typicus. Salinity, shallow-depth and timing checks kept positive slopes. Finer cells gave one interval that included zero. Missing measurements, catch bias, one survey system and unmeasured water transport limit inference. These are conditional habitat associations, not causal climate effects. Pollution and heatwave duration were not tested. The package includes code, aggregate evidence, source hashes and tested retrieval instructions.