Biogeochemical river inputs for global ocean models (RivR2O)

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. v1 -> pre-industrial river inputs with coastal vegetation and burial transformations v2 -> Groundwater DIC discharge was added. v3-> Bugfixes for groundwater discharge and blue carbon inputs. v4 -> Corrected index with list riverexports_list_CN.csv for DIN inputs v5 -> corrected tDOC splits according to R2O-MIP protocol 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 perturbations for every catchment, which were 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). 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 0.51 Pg C yr-1 of DIC, 0.30 Pg C yr-1 of DOC and 0.096 Pg C yr-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 -> 0.51 Pg C yr-1 DIC & Alkalinity (see protocol) DOC_l -> 0.21 Pg C yr-1 DIC DOC_sl -> 0.9 Pg C yr-1 DOC_sl (new ocean model pool) and associated DON and DOP POC -> 0.096 Pg 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/10.1002/2014JG002763.1. 总体概述 本数据集为全球生物地球化学河流输出数据集（RivR2O），是一套整合了前工业时代碳（C）、氮（N）、磷（P）年际海洋输出通量及其历史演变的合成产品，可直接用于全球海洋模型模拟。该数据集将作为河流-海洋模式比对研究（River-2-Ocean Model Intercomparison Study, 简称R2O MIP）的生物地球化学河流输入数据。 数据文件覆盖全球超过10000个流域集水区（catchments），可通过带坐标的列表形式读取，或读取为网格NetCDF文件。数据集涵盖溶解无机碳（DIC）、溶解有机碳（DOC）、颗粒有机碳（POC）、溶解无机磷（DIP）与溶解无机氮（DIN）五类组分。本数据集默认前工业时代为1900年以前，历史数据时段则覆盖1901-2020年。 各版本更新说明如下： v1：包含带海岸植被与埋藏转化过程的前工业时代河流输入数据 v2：新增地下水溶解无机碳（DIC）排放数据 v3：修复了地下水排放与蓝碳（blue carbon）输入相关的程序漏洞 v4：修正了DIN输入对应的riverexports_list_CN.csv列表索引 v5：依据R2O-MIP协议修正了总溶解有机碳（tDOC）的组分拆分方式 1.1 前工业时代输入及其转化过程 前工业时代河流输入数据可通过NetCDF文件（r2o_riverinputs_preindustrial.nc）或流域集水区列表文件获取：其中DIC、DOC、POC、DIN对应文件为riverexports_list_CN.csv，DIP对应文件为riverexports_list_P.csv，均附带坐标信息。上述数据量化了未受显著人为扰动的各流域集水区的年平均通量。 数据集的构建方式如下： DIC、DOC、POC组分 前工业时代DIC、DOC与POC通量通过以下方式得到：以Liu等人（2024）整合的现代河流输出通量为基础，减去Tian等人（2023）估算的1901-2020时段各流域集水区的人为扰动通量。此外，依据Regnier等人（2022）的研究，我们进一步考虑了热带河口与海岸植被生态系统的DOC净源（+0.06 Pg C yr⁻¹）与北半球净汇（-0.03 Pg C yr⁻¹）过程。由于现有模型难以准确表征陆架埋藏过程，本数据集移除了部分POC通量；剩余的再循环POC通量需添加至半难降解DOC库（详见协议文档）。地下水排放携带的DIC通量（0.016 Pg C yr⁻¹）在全球各河口均匀分配。前工业时代全球海洋总河流输入通量为：DIC 0.51 Pg C yr⁻¹、DOC 0.30 Pg C yr⁻¹、POC 0.096 Pg C yr⁻¹。 DIN组分 DIN产品为三个河流氮输出模型的集合平均结果，分别为ORCHIDEE-NLAT（Ma等人，待刊）、DLEM（Yang等人，2015）、IMAGE-GNM（Tian, 个人通信；Beusen等人，2015, 2016）。前工业时代全球海洋DIN输入负荷为11 Tg N yr⁻¹。 DIP组分 DIP产品为IMAGE-GNM（Beusen等人，2016）与Lacroix等人（2020）的流域估算结果的集合平均。前工业时代全球海洋DIP输入负荷为2.19 Tg P yr⁻¹。 1.2 人为扰动（1901-2020） 该部分数据暂未发布，待后续补充。 2. 供R2O MIP建模者使用 本文仅简要说明河流输入数据的核心应用要点，详细的通用模拟指南请参见官方R2O MIP协议文档。 我们建议在海洋模型中新增两类陆地溶解有机碳库：半易变总溶解有机碳（tDOC_sl）与半难降解总溶解有机碳（tDOC_sr）。两类碳库的唯一来源为数据集提供的河流输入通量，且需分别以一级动力学常数k_sl=1/1.5 yr⁻¹、k_sr=1/20 yr⁻¹进行降解（依据Hansell等人，2012的研究）。数据集中的另一类tDOC组分——易变总溶解有机碳（tdoc_l）被假设为快速降解，因此需直接添加至海洋模型的DIC库中。 河流输入通量需匹配至海洋模型中设置淡水输入的最近网格点。请注意，数据集中的通量单位为每年10⁶ C/N/P，在模型时间步长中添加通量时需注意单位转换。我们建议依据淡水输入的季节变化对通量进行缩放。 需依据下表将河流输入通量添加至对应的模型碳/营养盐库中： | 河流输入（在rivr2o_riverinputs_preindustrial.nc中的命名） | 全球总负荷（前工业时代） | 海洋模型对应库 | | -------------------------------------------------------- | ------------------------ | -------------- | | DIC | 0.51 Pg C yr⁻¹ | DIC与碱度（详见协议文档） | | DOC_l | 0.21 Pg C yr⁻¹ | DIC | | DOC_sl | 0.9 Pg C yr⁻¹ | tDOC_sl（新增海洋模型库）及关联的溶解有机氮（DON）、溶解有机磷（DOP） | | POC | 0.096 Pg C yr⁻¹ | 海洋DOC库及关联营养盐（DON、DOP，详见协议文档） | | DIP | 2.19 Tg P yr⁻¹ | DIP/磷酸盐 | | DIN | 11 Tg N yr⁻¹ | DIN/硝酸盐 | 3. 参考文献 1. Beusen, A. H. W., Van Beek, L. P. H., Bouwman, A. F., Mogollón, J. M., & Middelburg, J. J. 耦合水文与营养盐负荷全球模型以模拟地表水中氮磷滞留——IMAGE-GNM模型描述与性能分析. 地球科学模型开发, 8(12), 4045–4067 (2015). https://doi.org/10.5194/gmd-8-4045-2015. 2. Beusen, A. H. W., Bouwman, A. F., Van Beek, L. P. H., Mogollón, J. M., & Middelburg, J. J. 尽管水生连续体滞留增加，20世纪全球河流氮磷海洋输出通量仍显著上升. 生物地球科学, 13, 2441–2451 (2016). https://doi.org/10.5194/bg-13-2441-2016. 3. Hansell, D. A., Carlson, C. A., & Schlitzer, R. 次表层海洋中主要溶解有机碳组分的净移除. 全球生物地球化学循环, 26, GB1016 (2012). https://doi.org/10.1029/2011GB004069. 4. Lacroix, F., Ilyina, T., & Hartmann, J. 全球模型框架下前工业时代河流营养盐与碳输入诱导的海洋CO₂脱气与生物生产热点. 生物地球科学, 17, 55–88 (2020). https://doi.org/10.5194/bg-17-55-2020. 5. Liu, et al. 基于观测与多模型评估的全球陆地-海洋河流碳输出约束. 自然地球科学, (2024). https://www.nature.com/articles/s41561-024-01524-z 6. Ma, M., Zhang, H., Lauerwald, R., Ciais, P., & Regnier, P. 基于陆面模型估算全球河网侧向氮传输. 地球系统动力学讨论, 预印本, https://doi.org/10.5194/esd-2024-29, 待刊 (2024). 7. Regnier, P., Resplandy, L., Najjar, R. G., et al. 全球碳循环的陆地-海洋循环环路. 自然, 603, 401–410 (2022). https://doi.org/10.1038/s41586-021-04339-9. 8. Tian, H., Yao, Y., Li, Y., Shi, H., Pan, S., & Najjar, R. G., et al. 前工业时代以来全球内陆水体的陆地碳输出与CO₂脱气均显著上升. 全球生物地球化学循环, 37, e2023GB007776 (2023). https://doi.org/10.1029/2023GB007776. 9. Yang, Q., Tian, H., Friedrichs, M. A. M., Hopkinson, C. S., Lu, C., & Najjar, R. G. 1901-2008年气候与人为变化导致北美东部向大西洋的氮输出增加. 生物地球科学, 120(6), 1046–1068 (2015). https://doi.org/10.1002/2014JG002763.