Improved soil physics for simulating high latitude permafrost regions by the JSBACH terrestrial ecosystem model

Abstract

State-of-the-art climate models postulate disproportionately large climate warming in the northern latitudes. Ground and satellite observations indicate recent warming is already altering the environment, evidenced by increasing permafrost temperature, deepening active layers, accelerating glacier melt and increasing river runoff. It is es-5 timated that the circum-arctic regions contain vast amounts of soil organic carbon, whose fate is governed by climate; if temperature continues to rise, thawing of per-mafrost could release historic carbon initiating a positive climate-carbon cycle feed-back. Consequently, projecting the future state of ecosystems in permafrost regions under changing environmental conditions is a major research challenge, but most of 10 the associated processes are not yet adequately represented in current Earth sys-tem models. The new version of JSBACH incorporates phenomena specific to high latitudes: freeze/thaw processes, coupling thermal and hydrological processes in a lay-ered soil scheme, defining a multi-layer snow representation and an insulating moss cover. Evaluations using the most comprehensive Arctic datasets show improvements 15 at the site, basin, continental and circum-arctic scales. Such improvements highlight the need to include processes relevant to high latitude systems in order to capture the dynamics, and therefore realistically predict the evolution of this climatically critical biome.