How to Combine SST and Chlorophyll Charts

SST alone finds a temperature edge; chlorophyll alone finds a productivity edge. Neither one alone tells the whole story: where both edges line up in the same place is a stronger signal than either layer by itself, and that overlap is the whole point of using both.

Why one layer isn't enough

A temperature break marks a water-mass boundary, but not every temperature boundary is biologically productive: some are just two masses of equally barren water at different temperatures. A chlorophyll edge marks a productivity boundary, but productivity alone doesn't tell you whether the water is structurally distinct enough to hold bait against a current. Read together, the two layers cross-check each other.

What it means when both edges line up

A location where a sharp temperature break and a sharp chlorophyll edge sit at the same line is where two different water masses meet: one of them nutrient-rich, and the boundary itself concentrating whatever's feeding on that nutrient load. This is the strongest version of an offshore structure signal a satellite chart can offer, and it's exactly the kind of place upwelling or an eddy typically produces.

The workflow on Chlorofishy

Compare mode puts SST in one pane and chlorophyll in the other with a synced camera and region, so you can pan the same area on both layers at once and look for where the two edges align. See using compare mode for how the two panes sync, and finding temperature breaks for the pin-and-scrub technique that works the same way on either layer.

Open compare mode on the SST map to try this today, or see pricing for satellite pass access in your region. Back to Learn.