Changing Nutrient Inputs Down Rivers

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Variable River Inputs over Time

Karl Follmi, who compiled estimates of P burial over time.

Constraining River Fluxes over Geological Time

Experiments with varying the initial conditions and perturbing the nutrient models show that they exert a fairly robust regulation of the nutrient levels in the ocean. A further experiment is to try varying a "forcing" or "driving" input to the system, to see how well the system automatically compensates for variations in its forcing. In the case of the nutrient models this can be done by varying the amounts of nutrients flowing down rivers and into the sea. Unfortunately it is not easy to accurately reconstruct these fluxes from geological data. As nutrients flowed down ancient rivers they didn't leave behind little tell-tale indicators in sediments. Therefore we don't have any clear idea about how much phosphorus, nitrogen, silicate or carbon were flowing down rivers in earlier times. There are however less direct methods. Following an idea by Tim Lenton, we have used an alternative dataset to reconstruct river input.

Karl Follmi, who compiled estimates of P burial over time.

What goes in, must come out. The residence time of phosphorus in the oceans is order 50,000 years, and therefore, over timescales longer than this, we would expect any variations in phosphorus inputs to be balanced by corresponding changes in phosphorus outputs. Fortunately Karl Follmi, a Swiss geologist (see picture above), has compiled a dataset of phosphorus outputs from the ocean. From numerous measurements of the phosphorus contents in marine rocks through the ages and spread across different continents, he has obtained an estimate of how the global burial flux of phosphorus has changed over geological time. The image to the right shows Follmi's estimate of how P burial changed over time. We have used this record of P burial as an indication of P inputs.

Using the JModels to Examine Response to Time-Variable River Inputs

Follmi's dataset extends over 100 million years. It is feasible to run the phosphorus model for this length of time, but

This website is in its early stages of use. If you find it difficult to run a model in the way described, or find any other problems, your feedback will help us improve the site for future users.

Further reading

  • K. Follmi et al. <from assignment>

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