摘要：Abstract. Previous studies have suggested that enhanced weathering and benthicphosphorus (P) fluxes, triggered by climate warming, can increase theoceanic P inventory on millennial timescales, promoting ocean productivityand deoxygenation. In this study, we assessed the major uncertainties inprojected P inventories and their imprint on ocean deoxygenation using anEarth system model of intermediate complexity for the same business-as-usualcarbon dioxide (CO2) emission scenario until the year 2300 andsubsequent linear decline to zero emissions until the year 3000. Our set ofmodel experiments under the same climate scenarios but differing in theirbiogeochemical P parameterizations suggest a large spread in the simulatedoceanic P inventory due to uncertainties in (1) assumptions for weatheringparameters, (2) the representation of bathymetry on slopes and shelves inthe model bathymetry, (3) the parametrization of benthic P fluxes and (4) the representation of sediment P inventories. Considering the weatheringparameters closest to the present day, a limited P reservoir and prescribedanthropogenic P fluxes, we find a +30 % increase in the total globalocean P inventory by the year 5000 relative to pre-industrial levels, causedby global warming. Weathering, benthic and anthropogenic fluxes of Pcontributed +25 %, +3 % and +2 %, respectively. The total rangeof oceanic P inventory changes across all model simulations varied between+2 % and +60 %. Suboxic volumes were up to 5 times larger than in amodel simulation with a constant oceanic P inventory. Considerably largeamounts of the additional P left the ocean surface unused by phytoplanktonvia physical transport processes as preformed P. In the model, nitrogenfixation was not able to adjust the oceanic nitrogen inventory to theincreasing P levels or to compensate for the nitrogen loss due to increaseddenitrification. This is because low temperatures and iron limitationinhibited the uptake of the extra P and growth by nitrogen fixers in polarand lower-latitude regions. We suggest that uncertainties in P weathering,nitrogen fixation and benthic P feedbacks need to be reduced to achieve morereliable projections of oceanic deoxygenation on millennial timescales.
