The ebb and flow of carbon within Earth’s systems are complex occurrences. Carbon is a nomadic element. It travels between the atmosphere, ocean, and the soil, rock and ice of the planet. It changes forms along the way. Much of this cycling takes place in the ocean, partially through a biological carbon pump.
Atmospheric carbon is fixed through phytoplankton growing at the surface of the sea, in the BCP. Carbon particles sink from the surface to deep ocean waters, when the phytoplankton dies. This carbon can remain for hundreds of years before returning to the atmosphere.
BCP has been treated as a constant, previously. But the variability of sinking carbon particles has been observed in sediment trap sampling over the past few decades. Now scientists looked how the changing seasons can alter the amount and rate of carbon and other nutrients that sink into deep ocean waters.
Scientists used a global ocean biogeochemical model. They wanted to see how the amount of carbon particles reaching the deep ocean would change with variations in seasonality. They looked at how both the pattern and the strength of the seasonality would affect the sinking speed of carbon particles and their attenuation throughout the water column.
They compared the modelled seasonal results to nonseasonal scenarios. They found that there was an increase of up to 196% of carbon particle transfer when seasonal variations were taken into consideration.
The model was a simplified version of a complicated biogeochemical system. They found that particle fluxes in BCP are sensitive to the strength of seasonal fluxes, especially in high-latitude regions. Scientists noted that this study highlights the importance of seasonality on carbon flux. This includes the sinking speed and amount of detritus moving through the water column.
They added that if other scientists assume BCP is constant, they may be underestimating how much carbon can be sequestered in the ocean. Future work should collect new observations. It will unravel how seasonality can affect detrital sinking speeds. Scientists also noted that more nuanced inputs of other factors such as water temperature and phytoplankton sizes and species could reveal more details about BCP related to seasonal fluxes.