Numerical model to simulate long-term soil organic carbon and ground ice budget with permafrost and ice sheets (SOC-ICE-v1.0)

Abstract

Abstract. The degradation of permafrost is a large source of uncertainty in understanding the behaviour and projecting the future impacts of Earth's climate system. The spatial distributions of soil organic carbon (SOC) and ground ice (ICE) provide essential information for the assessment and projection of risks and impacts of permafrost degradation. However, uncertainties regarding the geographical distribution and estimated range of the total amount of stored carbon and ice are still substantial. A numerical soil organic carbon–ground ice budget model, SOC-ICE-v1.0, that considers essential aspects of carbon and hydrological processes in above-ground and subsurface environments and permanently frozen ground (permafrost) and land cover changes (ice sheets and coastlines) was developed to calculate the long-term evolution of local SOC and ICE. The model was integrated to cover the last 125 kyr – from the last interglacial to date for areas north of 50∘ N at 1∘ resolution – to simulate the balance between accumulation and dissipation of SOC and ICE. Model performance was compared with observation-based data and evaluated to assess allogenic (external) impacts on soil carbon dynamics in the circum-Arctic region on a glacial–interglacial timescale. Despite the limitation of forcing climate data being constructed on the basis of a single Greenland ice core dataset, the simulated results successfully reproduced temporal changes in northern SOC and ICE, consist with current knowledge. The simulation also captured regional differences in different geographical and climatic characteristics within the circum-Arctic region. The model quantitatively demonstrated allogenic controls on soil carbon evolution represented by a key parameter that reflects climatological and topo-geographical factors. The resulting circum-Arctic set of simulated time series can be compiled to produce snapshot maps of SOC and ICE distributions for past and present assessments or future projection simulations. Examples of 1∘ resolution maps for the Last Glacial Maximum and mid-Holocene periods were provided. Despite a simple modelling framework, SOC-ICE-v1.0 provided substantial information on the temporal evolution and spatial distribution of circum-Arctic SOC and ICE. Model improvements in terms of forcing climate data, improvement of SOC and ICE dynamics, and choice of initial values are, however, required for future research.

High-resolution predictions of ground ice content for the Northern Hemisphere permafrost region

“…The compiled observations represented ground ice content at one point of time, and we did not consider the potential changes in ice content over time. Whatsoever, considering that accumulation of ground ice at the targeted depth range has typically occurred during several millennia (e.g., Saito et al, 2021) we argue that any aggradation of ground ice over annual to decadal periods would have had a small effect on the average ice content across the entire depth range. For example, Kokelj and Burn (2003) found that a decadal-scale ice aggradation of segregated ice beneath the permafrost table was 395 limited, and that the aggraded permafrost had similar ice content to that in underlying permafrost.…”

“…Ground ice content has also been simulated by process-based land surface models. For example, Saito et al (2021) used a land surface model to simulate long-term ground ice budget across the circumarctic permafrost region. Others have used the IPA map (Brown et al, 1997) to derive excess ice estimates at coarse resolution for land surface model simulations (e.g., Lee et al, 2014;Cai et al, 2020).…”

Estimation of Permafrost Ground Ice to 10 m Depth on the Qinghai‐Tibet Plateau

“…The spatialization of permafrost ground ice is challenging. Accumulation of ground ice in the target depth range typically developed over thousands of years [51], and its distribution patterns are related to climatic, hydrological, and geomorphological characteristics over that time period. Although the predicted results based on contemporary climate and geomorphological conditions performed well in the RF model validation, the performance in practical applications (e.g., in evaluating the impacts of ground ice meltwater on the basin water balance) is difficult to directly assess.…”

Impacts of Permafrost Degradation on Carbon Stocks and Emissions under a Warming Climate: A Review

“…Permafrost C stocks, biodegradability, and emission of permafrost carbon are baselines of simulating permafrost C feedback to climate warming. Their studies can help make alerts for the risks of environmental changes and assure the economic and productive safety for policy makers [115][116][117][118][119][120][121][122][123][124][125][126][127][128][129].…”