Abstract
The concentration of chlorophyll-a (CHL) is an important proxy for
autotrophic biomass and primary production in the ocean. Quantifying
trends and variability in CHL are essential to understanding how marine
ecosystems are affected by climate change. Previous analyses have
focused on assessing trends in CHL mean, but little is known about
observed changes in CHL extremes and variance. Here we apply a quantile
regression model to detect trends in CHL distribution over the period of
1997-2022 for several quantiles. We find that the magnitude of trends in
upper quantiles of global CHL (>90th) are larger than those
in lower quantiles (≤50th) and in the mean, suggesting a growing
asymmetry in CHL distribution. On a regional scale, trends in different
quantiles are statistically significant at high latitude, equatorial,
and oligotrophic regions. Assessing changes in CHL distribution has
potential to yield a more comprehensive understanding of climate change
impacts on CHL.