Oceanography http://doi.org/bksd (2016)

During the winter of 2013–2014, a warm-water anomaly formed in the northeastern Pacific Ocean, persisting until early 2016. This 'blob', as it became known, altered the physical properties of the marine environment. For example, increasing stratification in the region — impacting mixing and upwelling, which affect the marine ecosystem.

Letícia Cavole and colleagues at Scripps Institution of Oceanography, University of California San Diego, USA synthesize the biological impacts of the warm anomaly, and consider how representative the event may be of future climate. In the south, the increased stratification reduced the mixing of nutrient-rich waters to the surface and there was an observed reduction in phytoplankton biomass. This decrease in food source, along with higher temperatures, resulted in zooplankton and invertebrates species shifting northward to cooler waters, followed by the predators. Although there was a decrease in phytoplankton in the south, there was an unprecedented increase in harmful algal bloom species in the north.

The elevated temperatures seen during this period were comparable with those expected in the second half of this century under climate change. Although the blob was confined the surface waters, and climate change will see more generalized warming, there is still expected to be an increase in stratification and other physical changes such as those observed. As such, the observed changes are an indication of what may be ahead.