DOI: 10.5281/zenodo.13684982
title: Biogeochemical river inputs for global ocean models (RivR2O)

description: 1. General Description

The global biogeochemical riverine export dataset (RivR2O) uploaded here is a synthesis product for yearly means of preindustrial C, N and P exports to the ocean and their historical evolutions, which are ready-to-use for global ocean models. They will serve as biogeochemical river inputs in the River-2-Ocean Model Intercomparison Study (R2O MIP). The files cover >10000 global catchments which can be read as lists with coordinates, or as gridded netcdf files. They cover the compounds DIC, DOC, POC, DIP and DIN. The assumed pre-industrial era is assumed to be pre-1900, whereas historical data will cover 1901-2020. 

In this v2 version, groundwater DIC discharge was added to the dataset.  

1.1. Preindustrial inputs and their transformations

The files are for preindustrial river inputs can be downloaded as netcdf (r2o_riverinputs_preindustrial.nc), or as catchment lists (DIC,DOC,POC,DIN: riverexports_list_CN.csv , DIP: riverexports_list_P.csv) with given coordinates. They quantify yearly means for every catchment without a significant anthropogenic perturbation. They were constructed in the following ways:

DIC, DOC, POC

Preindustrial DIC, DOC and POC were obtained by subtracting the estimated anthropogenic perturbation for every catchment, which was determined for the 1901-2020 time period by Tian et al. (2023), from the synthesis of present-day exports by Liu et al. (2024). We further accounted for a net DOC source in the tropics (+0.06 Pg C yr-1), and a sink in the Northern Hemisphere (-0.03 Pg C yr-1) from estuaries and coastal vegetated ecosystems based on Regnier et al. (2022). A fraction of POC was also removed from the dataset due to models misrepresenting burial on shelf and the remaining fraction (recycled POC) should be added to the semi-refractory DOC pool (see protocol). Similarly, a fraction of highly refractory DOC (2 TgC yr-1, REF) was removed from the Liu et al. (2024) DOC dataset. DIC inputs from groundwater discharge (0.016 Pg C yr-1) were distributed globally homogeneously at every river mouth. Globally, this then amounts to a total of 512 gCyr-1 of DIC, 300 gCyr-1 of DOC and 95 gCyr-1 of POC export to the ocean over the preindustrial time period. 

DIN 

The DIN product averages over three river N exports models (ORCHIDEE-NLAT: Ma et al., in review; DLEM: Yang et al., 2015; Tian, pers. Com., IMAGE-GNM: Beusen et al., 2015, 2016) for every catchment. The resulting preindustrial DIN load to the ocean is 11 TgNyr-1. 

DIP

The DIP product averages catchment estimates from IMAGE-GNM (Beusen et al., 2016) and Lacroix et al. (2020). The resulting preindustrial DIP load to the ocean is 2.19 TgPyr-1.

1.2. Anthropogenic Perturbation (1901-2020)

Not yet available, to be added.

2. Use for modelers within the R2O MIP 

We only briefly describe most important information on how to apply the river input data here and refer to the official R2O MIP protocol for more detail on our general simulation guidelines.



We firstly recommend the addition of two terrestrial dissolved organic carbon pools in the ocean models: tDOC semi-labile (DOC_sl) and tDOC semi-refractory (DOC_sr).  Their only source should be that of the river inputs, which are given separately in the river inputs files, and it should be degraded with a first order constant of k_sl = 1 / 1.5yr and k_sr = 1/20yr (based on Hansell et al., 2012). The other tDOC compound given in the dataset, tDOC labile (tdoc_l), is assumed to be rapidly degraded and should therefore be added to the ocean model DIC pool.

The inputs should be added to the closest ocean model grid points where the ocean model has freshwater inputs. Note that the inputs are given as 10^6 C/N/P per year, and this should be taken into account in the addition of the inputs at the model timestep. We recommend scaling the inputs to the seasonality of the freshwater inputs.

The inputs from the riverine files should be added to the corresponding pool based on the following table:








River Input

(as named in rivr2o_riverinputs_preindustrial.nc)



Global Load (preindustrial)



Ocean Model Pool





 



 



 





DIC ->



512 Tg C yr-1



DIC & Alkalinity (see protocol)





DOC_l ->



155 Tg C yr-1



DIC





DOC_sl ->



130 Tg C yr-1



DOC_sl (new ocean model pool) and associated DON and DOP





DOC_sr ->



15 Tg C yr-1



DOC_sr (new ocean model pool) and associated DON and DOP





POC ->



95 Tg C yr-1



marine DOC and associated nutrients (DON, DOP, see protocol)





DIP ->



2.19 Tg P yr-1



DIP / Phosphate





DIN ->



11 Tg N yr-1



DIN / Nitrate







 

3. References

Beusen, A. H. W., L. P. H. Van Beek, A. F. Bouwman, J. M. Mogollón, and J. J. Middelburg. Coupling Global Models for Hydrology and Nutrient Loading to Simulate Nitrogen and Phosphorus Retention in Surface Water-description of IMAGE–GNM and Analysis of Performance. Geoscientific Model Development, 8, no. 12 (2015): 4045–67. https://doi.org/10.5194/gmd-8-4045-2015. 

Beusen, A. H. W., Bouwman, A. F., Van Beek, L. P. H., Mogollón, J. M., and Middelburg, J. J.: Global riverine N and P transport to ocean increased during the 20th century despite increased retention along the aquatic continuum, Biogeosciences, 13, 2441–2451, https://doi.org/10.5194/bg-13-2441-2016, 2016.

Hansell, D. A., C. A. Carlson, and R. Schlitzer (2012), Net removal of major marine dissolved organic carbon fractions in the subsurface ocean, Global Biogeochem. Cycles, 26, GB1016, doi:10.1029/2011GB004069.

Lacroix, F., Ilyina, T., and Hartmann, J.: Oceanic CO2 outgassing and biological production hotspots induced by pre-industrial river loads of nutrients and carbon in a global modeling approach, Biogeosciences, 17, 55–88, https://doi.org/10.5194/bg-17-55-2020, 2020.

Liu et al. (2024). Global riverine land-to-ocean carbon export constrained by observations and multi-model assessment, Nature Geoscience, https://www.nature.com/articles/s41561-024-01524-z

Ma, M., Zhang, H., Lauerwald, R., Ciais, P., and Regnier, P.: Estimating lateral nitrogen transfer through the global river network using a land surface model, Earth Syst. Dynam. Discuss. [preprint], https://doi.org/10.5194/esd-2024-29, in review, 2024.

Regnier, P., Resplandy, L., Najjar, R.G. et al. The land-to-ocean loops of the global carbon cycle. Nature 603, 401–410 (2022). https://doi.org/10.1038/s41586-021-04339-9

Tian, H., Yao, Y., Li, Y., Shi, H., Pan, S., Najjar, R. G., et al. (2023). Increased terrestrial carbon export and CO2 evasion from global inland waters since the preindustrial era. Global Biogeochemical Cycles, 37, e2023GB007776. https://doi.org/10.1029/2023GB007776

Yang, Qichun, Hanqin Tian, Marjorie A. M. Friedrichs, Charles S. Hopkinson, Chaoqun Lu, and Raymond G. Najjar.: Increased Nitrogen Export from Eastern North America to the Atlantic Ocean Due to Climatic and Anthropogenic Changes during 1901–2008. Biogeosciences,120, no. 6 (2015): 1046–68. https://doi.org/10.1002/2014JG002763.