Der globale Kohlenstoffkreislauf im Anthropozän. Betrachtung aus meereschemischer Perspektive

By burning of fossil fuels humankind emits more than 8 billion tons of carbon (Gt C) in the form of CO₂ to the atmosphere. Since the onset of the industrial revolution the cumulative emissions have led to an increase of the atmospheric CO₂ concentration which corresponds to an additional radiative forcing in the atmosphere. Of the three reservoirs which exchange carbon on the time scale of centuries – atmosphere, terrestrial biosphere, and ocean – the ocean is by far the largest. The marine CO₂ system comprises the chemical species HCO₃^–, CO₃^2–, and CO₂(aq). This gives rise to the pH‐buffering nature of seawater as well as its high uptake capacity for anthropogenic CO₂. Four measurement parameters of the marine CO₂ system are available for an accurate analytical characterization. These parameters also provide a means of sensing the role of physical, chemical, and biological drivers for the marine carbon cycle. The marine carbon cycle features major natural processes that exchange carbon with the atmosphere and re‐distribute it throughout the ocean. These are known as “pumps” and driven by physical and biological factors. While the “physical pump” is inevitably enhanced by the oceanic uptake of anthropogenic CO₂, even the sign of the response is currently not clear for the “biological pumps”. A host of potential consequences of global change (temperature rise, ocean carbonation, ocean acidification) have been identified. These are currently studied intensively with respect to their climate sensitivity as well as the climate feedback potential.