In search of long‐term trends in ocean color

There is an ongoing debate regarding the role of phytoplankton within the ocean carbon cycle, and the role of biology in possibly capturing part of the excess CO2 produced by human activities. Without entering this debate, this article takes a few simple facts as granted; e.g., that the transfer of CO2 from the atmosphere toward the ocean interior mediated by photosynthesis (the so‐called “biological pump”) is active, so that any evolution of its strength or structure could impact the CO2 exchange between the ocean and the atmosphere.