ORCHIDEE MICT-LEAK (r5459), a global model for the production, transport and transformation of dissolved organic carbon from Arctic permafrost regions, Part 1: Rationale, model description and simulation protocol

Abstract

Abstract. Few Earth System models adequately represent the unique permafrost soil biogeochemistry and its respective processes; this significantly contributes to uncertainty in estimating their responses, and that of the planet at large, to warming. Likewise, the riverine component of what is known as the "boundless carbon cycle" is seldom recognized in Earth System modeling. Hydrological mobilization of organic material from a ~ 1330–1580 PgC carbon stock to the river network results either in sedimentary settling or atmospheric "evasion", processes widely expected to increase with amplified Arctic climate warming. Here, the production, transport and atmospheric release of dissolved organic carbon (DOC) from high-latitude permafrost soils into inland waters and the ocean is explicitly represented for the first time in the land surface component (ORCHIDEE) of a CMIP6 global climate model (IPSL). The model, ORCHIDEE MICT-LEAK, mechanistically represents (a) vegetation and soil physical processes for high latitude snow, ice and soil phenomena, and (b) the cycling of DOC and CO2, including atmospheric evasion, along the terrestrial-aquatic continuum from soils through the river network to the coast, at 0.5° to 2° resolution. This paper, the first in a two-part study, presents the rationale for including these processes in a high latitude specific land surface model, then describes the model with a focus on novel process implementations, followed by a summary of the model configuration and simulation protocol. The results of these simulation runs, conducted for the Lena River basin, are evaluated against observational data in the second part of this study.

Spatio-temporal patterns and drivers of terrestrial Dissolved Organic Carbon (DOC) leaching to the European river network

“…Assuming a realistic representation of DOC reactivity in the river network, which is to be evaluated against observations as well, this model-data comparison of riverine DOC fluxes represents a valuable, additional possibility to assess the validity of simulated soil DOC leaching. So far, ORCHILEAK has been successfully tested and applied on large, near-natural river systems such as the Amazon (Lauerwald et al 2017, Hastie et al 2019, the Congo (Hastie et al 2021) and the Lena Rivers with a version also including some specific permafrost related mechanisms (Bowring et al 2019(Bowring et al , 2020. In this study, for the first time, ORCHILEAK is applied to, and evaluated for, the European river network which is subject to direct impacts of agricultural land use, in contrast to more natural river basins.…”