Spatial variations in nutrient uptake, remineralisation and elemental ratios in a global ocean model and their role for marine biogeochemical cycles
Many oceanic biogeochemical cycles, like the carbon cycle, are driven by the biological pump. Organic matter is created at the ocean surface and sinks into the depths of the ocean where it is remineralised, or in other words, converted from organic matter back to the inorganic matter from which it was originally created. The ocean’s biological pump is, itself, composed of three major parts: organic matter production, its remineralisation, and the processes that control how much of a particular nutrient or gas is exchanged.
Our ability to simulate ocean biogeochemical cycles is therefore dependent on our ability to simulate the biological pump. Put in the context of climate, if we want to accurately simulate carbon exchange between the ocean and atmosphere, then we must be confident that the biological pump is being simulated accurately. In large part, however, the equations that govern global biogeochemical models that are in use today were developed many decades ago. Seminal research from the early 20th century is used to explain nutrient cycles and carbon storage in past climates, and to predict changes into the future. These experiments guide our understanding of the climate, which eventually informs policy and humanities actions in the coming years.
Recently, the fields of ocean biogeochemical modelling and marine microbial research have begun to coalesce. New equations have been proposed. These are dynamic equations that attempt to capture variations in the character of microbial communities and how they function. One curve, one ratio, does not hold across the varied face of the ocean. The proposal of these equations marks an important opportunity, a bedground for testing and developing our biogeochemical models. How do these new, fan-dangled equations compare to the traditional, static equations that have been used to simulate the ocean’s biological pump for decades?