Phytoplankton Chlorophyll trends in the Arctic (1998-2022) at the local, regional, and pan-Arctic scales
Abstract
We analyzed the temporal trends (1998-2022) of surface phytoplankton Chlorophyll (Chl) concentration in the Arctic at the local, regional, and pan-Arctic scales. We used four empirically-derived Chl satellite ocean color products: two global merged products and two MODIS products, one calibrated to the Arctic. At the local level, between 10-40% of the area with valid pixels showed statistically significant Chl trends, with ~2/3 of those pixels showing increases, and the other third indicating a decrease. At the regional level, only the Barents and Chukchi Seas had consistent Chl increases across products. At the pan-Arctic level, most products showed Chl increases in the months of July and September (0.3-0.9% Chl year-1), even after removing the effect of new open water pixels. Overall, Chl is changing in the Arctic, although trends vary threefold depending on the product and spatial-averaging assumptions used.