## 1 Introduction
The global, OCO-2 based SIF product (GOSIF) that [PERSON] and [PERSON] [31] developed, freely available at our data repository ([[http://globalecology.unth.edu](http://globalecology.unth.edu)]([http://globalecology.unth.edu](http://globalecology.unth.edu))), provides fine-resolution SIF estimates (\(0.05^{\circ}\) spatial resolution and 8-day time step) from 2000 to present for carbon cycle and ecological studies. Having well-established and robust SIF-GPP relationships is the prerequisite for directly and accurately converting gridded SIF to GPP estimates. Although the strong relationship between SIF and GPP is widely recognized by the scientific community [11; 17; 32; 33; 34], there has been some controversy on the form of the SIF-GPP relationship. The first controversy on the SIF-GPP relationship is whether it varies with biomes or universal across biomes. Previous studies based on coarse-resolution SIF (GOSATor GOME-2) and gridded GPP products showed biome-dependent SIF-GPP relationships [10; 21; 22]. Based on OCO-2 SIF with much smaller ground-pixel size and tower GPP from three EC flux sites, [PERSON] et al. [26] found a universal SIF-GPP relationship across different biomes: cropland, grassland and temperate forest. [PERSON] et al. [17] conducted the first global analysis of the SIF-GPP relationship based on OCO-2 SIF and flux tower GPP for 64 EC flux sites, and found that SIF was strongly correlated with GPP at the ecosystem scale for a wide variety of boimes and there was a strong and nearly universal SIF-GPP relationship across seven biomes. The previously observed SIF-GPP relationships that were dependent upon biome types was possibly due to the fact that gridded GPP products typically have systematic biases [26]. In a letter to the editor, [PERSON] et al. [35] argued that the nearly universal SIF-GPP relationship found in our previous study [17] may be complicated by viewing geometries of OCO-2 SIF observations. By only using the SIF retrievals measured by the nadir mode, wefound that a universal SIF-GPP relationship still exists among the seven biomes [36]. The universal SIF-GPP relationship across a wide variety of biomes that we demonstrated [17] has not yet been used to map GPP globally from satellite-based SIF data despite its great potential. Meanwhile, it remains unclear how the forms of the SIF-GPP relationships (universal or biome-specific) influence the estimation of GPP. In addition, the SIF-GPP relationship can also be slightly altered when forcing the linear fitting through the origin or not (zero intercept or non-zero intercept) [35; 36]. The relationship with an intercept is based on the samples with optimal linear fitting, while the relationship without intercept is derived by assuming that when the plants have no photosynthetic activity (e.g., during the non-growing season) the SIF values approach zero. How the treatment of the intercept term influences the estimation of GPP also remains unclear. Here, we mapped GPP globally from 2000 to 2017 at 8-day intervals and on a \(0.05^{\circ}\times 0.05^{\circ}\) grid based on the fine-resolution GOSIF product and SIF-GPP relationships. We used eight different SIF-GPP relationships by considering several factors that could bias the resulting GPP estimates, including whether the relationship is universal across biomes or biome-specific, whether the linear regression is forced to pass the origin or not, and at what spatial scale (site or grid cell) the relationship is developed. We then used the ensemble GPP estimates to examine the magnitude, spatial patterns, and temporal variations of GPP. To our knowledge, our study is the first effort to develop a global fine-resolution GPP product based on fine-resolution gridded SIF estimates, and we also first illuminate how the slight change in the slope or intercept of the SIF-GPP relationship affects the GPP estimation for one grid cell and eventually the global annual GPP. Although we used multiple variables to produce the GOSIF product [31], the GPP estimation in this study is solely based on the GOSIF.