Plumbing of the biological pump


Nutrient transport and biological teleconnections of Ocean surface regions are diagnosed in a data-assimilated circulation model coupled to a jointly optimized simple phosphorus cycling model. These teleconnections paint the plumbing of the biological pump: phytoplankton takes up phosphate (PO4) in the euphotic layer, pumps it as dissolved organic phosphorus (DOP) through the whole water column, until it is remineralized in the ocean depths and ultimately transported to the surface where it is available again for uptake. The biological pump efficiency (39%) is redefined and computed. Ocean surface regions where biological production takes its origin are defined, out of which major contributors as well as biological leaks are determined: The high latitude ocean regions provide a large quantity of phosphate to other oceans, but contribute very lightly themselves to the biological pump. While the easternmost part of the tropical oceans produce large quantities of utilized phosphorus which is pumped for long average transit times. Using Green functions and adjoint techniques, flow rates, masses in transit, and timescales of biologically utilized nutrients between surface regions of interest are computed: the easternmost part of tropical ocean basins provide the majority of the biology, which reemerges predominantly in the high latitudes. Time-dependent path densities of major teleconnections are then computed, which paint a very detailed and quantitative picture of the phosphorus cycle within the ocean interior: paths associated with long transit times (>1000 yrs) spread through the entire ocean, but are concentrated in the deep Northernmost Pacific, while paths associated with short transit times (<500 yrs) are more localised, and restricted mostly to the surface currents.

UNSW, Sydney, Australia
Benoît Pasquier
Research Associate

My research interests include mathematics, oceanography, and computer science.