The importance of terrestrial weathering changes in multimillennial recovery of the global carbon cycle: a two-dimensional perspective

Abstract

Abstract. In this paper, we describe the development and application of a new spatially explicit weathering scheme within the University of Victoria Earth System Climate Model (UVic ESCM). We integrated a dataset of modern-day lithology with a number of previously devised parameterizations for weathering dependency on temperature, primary productivity, and runoff. We tested the model with simulations of future carbon cycle perturbations, comparing a number of emission scenarios and model versions with each other and with zero-dimensional equivalents of each experiment. Overall, we found that our two-dimensional weathering model versions were more efficient in restoring the carbon cycle to its pre-industrial state following the pulse emissions than their zero-dimensional counterparts; however, in either case the effect of this weathering negative feedback on the global carbon cycle was small on timescales of less than 1000 years. According to model results, the largest contribution to future changes in weathering rates came from the expansion of tropical and mid-latitude vegetation in grid cells dominated by weathering-vulnerable rock types, whereas changes in temperature and river runoff had a more modest direct effect. Our results also confirmed that silicate weathering is the only mechanism that can lead to a full recovery of the carbon cycle to pre-industrial levels on multimillennial timescales.

The capacity of northern peatlands for long-term carbon sequestration

“…The limits to northern peatlands carbon stock were estimated here for the first time, although the methodology for obtaining such estimates were developed more than 30 years ago by Clymo (1984). We adapted this methodology for use at the Earth System scale based on gridded data (Hengl et al, 2014) representing geomorphological aspects of peat bog growth.…”

“…This rate suggests that northern peatlands, occupying 2.4-4 million square kilometers (Yu, 2011), may, during the next 20 000 years, accumulate an amount of carbon comparable to the expected cumulative anthropogenic carbon emissions, corresponding to a 2.5 • C warming (Raupach et al, 2014), i.e., ranging from 864 (18 g C m −2 yr −1 × 2.4 × 10 12 m 2 × 2 × 10 4 years) to 2240 (28 g C m −2 yr −1 × 4 × 10 12 m 2 × 2 × 10 4 years) Pg C. There has been little research, however, on the estimation of the potential magnitude of the cumulative carbon removal from the atmosphere associated with the natural development of peatland ecosystems. Individual peatland development may lead to reduction of the carbon sequestra-tion potential under the assumptions of constant production and decomposition rates (Clymo, 1984). The closer the peatland ecosystem is to its steady state, i.e., to the equilibrium between organic matter production and decomposition, the lower the carbon sink magnitude is.…”

“…The process of reaching equilibrium can be conceptualized as follows (see Clymo, 1984;Alexandrov et al, 2016). Peat is accumulated due to protection of organic matter in the catotelm, the lower layer of a peat deposit that is permanently saturated with water.…”

Soil Warming Accelerates Biogeochemical Silica Cycling in a Temperate Forest

“…We also suspect that weathering inputs to soil DSi are increased by warming, as mineral silicate weathering typically increases with temperature as a result of reaction kinetics (Velbel, 1993; Brady and Carroll, 1994; White and Blum, 1995). Plants also influence mineral weathering through the physical and chemical alteration of soils (Lovering, 1959; Drever, 1994; Berner, 1997; Porder, 2019); thus, NPP enhancements may potentially lead to weathering increases in certain ecosystems (Kelly et al, 1998; Brault et al, 2017). In our study, this could lead to greater weathering inputs and leaching outputs of silica with warming, in addition to our observed enhancement of internal silica recycling.…”

Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

“…Chemical weathering is the break-up of rock through chemical processes and is characterised by the break-up of the cleavage of bonds in the mineral lattice by water with the presence of a secondary weathering agent such as carbonic acid (Brault, Matthews, & Mysak, 2017). Weathering is a major component of the geochemical cycle (Fig.…”