Global climate-change trends detected in indicators of ocean ecology
B. B. Cael, Kelsey Bisson, Emmanuel Boss, Stephanie Dutkiewicz, Stephanie Henson
Abstract
Abstract Strong natural variability has been thought to mask possible climate-change-driven trends in phytoplankton populations from Earth-observing satellites. More than 30 years of continuous data were thought to be needed to detect a trend driven by climate change 1 . Here we show that climate-change trends emerge more rapidly in ocean colour (remote-sensing reflectance, R rs ), because R rs is multivariate and some wavebands have low interannual variability. We analyse a 20-year R rs time series from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite, and find significant trends in R rs for 40% of the global surface ocean. The climate-change signal in R rs emerges after 20 years in similar regions covering a similar fraction of the ocean in a state-of-the-art ecosystem model 2 , which suggests that our observed trends indicate shifts in ocean colour—and, by extension, in surface-ocean ecosystems—that are driven by climate change. On the whole, low-latitude oceans have become greener in the past 20 years.