A Modification to the Remotely Sensed Active Layer Thickness (ReSALT) Algorithm to have Self-Consistency

Abstract

Permafrost thaw is an important aspect of Earth's carbon cycles. Initial estimates suggest that permafrost thaw could contribute anywhere between 20 to 500 Gt of CO2 by 2100. These estimates are all fundamentally centered around one number: active layer thickness (ALT). The deeper the ALT, the more emissions. Unfortunately, ALT is a highly spatially heterogeneous number and determined by numerous thermal, soil hydrology, and geomorphological effects. The remotely sensed active layer thickness (ReSALT) algorithm was introduced in 2010 to provide scientists a way to model ALT heterogeneously at meter-scale resolution. However, upon inspection, this work shows that ReSALT's modelling approach is self-inconsistent. This work then introduces SCReSALT (Self-Consistent ReSALT) to solve that problem. SCReSALT is conceptually simple, physics-based, self-consistent, and makes no approximations. Experimental comparisons to a past study in Utqiagvik (formerly Barrow), Alaska show significant improvement and suggest that SCReSALT should replace ReSALT.