The impact of global warming on seasonality of ocean primary production

[摘要] The seasonal cycle (i.e. phenology) of oceanic primary production (PP) isexpected to change in response to climate warming. Here, we use output from 6global biogeochemical models to examine the response in the seasonalamplitude of PP and timing of peak PP to the IPCC AR5 warming scenario. Wealso investigate whether trends in PP phenology may be more rapidlydetectable than trends in annual mean PP. The seasonal amplitude of PPdecreases by an average of 1–2% per year by 2100 in most biomes, withthe exception of the Arctic which sees an increase of ~1% peryear. This is accompanied by an advance in the timing of peak PP by~0.5–1 months by 2100 over much of the globe, and particularlypronounced in the Arctic. These changes are driven by an increase in seasonalamplitude of sea surface temperature (where the maxima get hotter faster thanthe minima) and a decrease in the seasonal amplitude of the mixed layer depthand surface nitrate concentration. Our results indicate a transformation ofcurrently strongly seasonal (bloom forming) regions, typically found at highlatitudes, into weakly seasonal (non-bloom) regions, characteristic ofcontemporary subtropical conditions. On average, 36 yr of data are needed todetect a climate-change-driven trend in the seasonal amplitude of PP,compared to 32 yr for mean annual PP. Monthly resolution model output isfound to be inadequate for resolving phenological changes. We conclude thatanalysis of phytoplankton seasonality is not necessarily a shortcut todetecting climate change impacts on ocean productivity.

[学科分类] 地球化学与岩石