Representation of dissolved organic carbon in the JULES land surface model (vn4.4_JULES-DOCM)

Abstract

Abstract. Current global models of the carbon (C) cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, thus not considering the lateral transport of carbon from the continents to the oceans. Therefore, those models implicitly consider all of the C which is not respired to the atmosphere to be stored on land and hence overestimate the land C sink capability. A model that represents the whole continuum from atmosphere to land and into the ocean would provide a better understanding of the Earth's C cycle and hence more reliable historical or future projections. A first and critical step in that direction is to include processes representing the production and export of dissolved organic carbon in soils. Here we present an original representation of dissolved organic C (DOC) processes in the Joint UK Land Environment Simulator (JULES-DOCM) that integrates a representation of DOC production in terrestrial ecosystems based on the incomplete decomposition of organic matter, DOC decomposition within the soil column, and DOC export to the river network via leaching. The model performance is evaluated in five specific sites for which observations of soil DOC concentration are available. Results show that the model is able to reproduce the DOC concentration and controlling processes, including leaching to the riverine system, which is fundamental for integrating terrestrial and aquatic ecosystems. Future work should include the fate of exported DOC in the river system as well as DIC and POC export from soil.

Fires prime terrestrial organic carbon for riverine export to the global oceans

“…Until a longer timeline of observational data becomes available, it will only be possible to quantify historical and future changes to BC export using models that reliably reproduce the spatial patterns of BC and OC export observed in the available snapshot. Processbased models are already used to investigate the effects of global climate and land use changes on the catchment dynamics of OC, including its riverine export [77][78][79] , yet these have been underutilised for the study of BC dynamics. Modelling of the processes leading to DBC export is especially needed because these processes disconnect the dynamics of BC from the physical mobility of sediments and are instead controlled by a range of interacting hydrological and biogeochemical factors that affect the solubilisation and lateral transfer of organic matter (Fig.…”

Modeling Global Riverine DOC Flux Dynamics From 1951 to 2015

“…Recently, several process‐based biogeochemistry models have been proposed to simulate spatial and temporal dynamic in soil and surface water DOC. Most of these models, the Rothamsted organic carbon turnover model (RothC, Skjemstad et al, ), the dissolved organic carbon dynamics model (Lu & Zhuang, ), Organizing Carbon and Hydrology in Dynamics Ecosystems (ORCHILEAK, Lauerwald et al, ), the Joint UK Land Environment Simulator Dissolved Organic Carbon model (JULES‐DOCM, Nakhavali et al, ) and the integrated catchment model for carbon (INCA‐C) (Futter et al, ), as well as others (Batson et al, ; Dick et al, ), have been built and tested at the catchment or regional scale. Considering the integrated nitrogen model for catchment model as an example, it successfully simulated the DOC dynamics in several catchments, which had a combined effect on the hydrology, carbon biogeochemistry, and land cover types in soil and surface water processes (Futter et al, , ; Futter & de Wit, ; Ledesma et al, ).…”

Carbon leaks from flooded land: do we need to re-plumb the inland water active pipe?

“…Hydrological C export as a significant loss term for terrestrial ecosystems has been considered in more detail only relatively recently (e.g. Ciais et al, 2008) and is included in only a very limited number of global terrestrial models (Tian et al, 2015;Lauerwald et al, 2017;Nakhavali et al, 2018). Terrestrial C budgets at the plot and the continental scales are based on different methods not consistent and precise enough to estimate hydrological C export as a residual flux.…”

“…Ideally, these global geo-referenced databases could also include metabolic parameters such as ecosystem productivity, respiration and CH 4 emission, as well as simplified parameters that describe hydrological connectivity and exposure time to flooding (e.g. Oldham et al, 2013). Process-based models could also be built and validated in individual wetland types, and then aggregated to a global model able to quantify C fluxes between drained land, floodable land, rivers and lakes, and the atmosphere at the continental scale.…”