Resilience and vulnerability of permafrost to climate changeThis article is one of a selection of papers from The Dynamics of Change in Alaska’s Boreal Forests: Resilience and Vulnerability in Response to Climate Warming.

TLDR

Permafrost resilience and vulnerability hinge on interactions among topography, water, soil, vegetation, and snow, allowing persistence up to mean annual air temperatures of +2 °C and degradation down to –20 °C, with groundwater temperatures of 2–7 °C further influencing lateral and internal thaw. The study aims to evaluate how these interactions influence permafrost by compiling existing data and modeling the effects of varying conditions on mean annual surface temperatures (MASTs) and 2 m deep temperatures (MADTs). Using compiled datasets, the authors modeled how changes in topographic, hydrologic, vegetative, and snow conditions affect MASTs and MADTs. The model shows that surface water exerts the strongest influence, raising sediment temperatures ~10 °C above MAAT, while snow depth, elevation, aspect, and vegetation structure also modulate MASTs and MADTs by several degrees, and that vegetation succession and surface water act as opposing negative feedbacks that can either stabilize permafrost against warming or increase its vulnerability even at low temperatures.

Abstract

The resilience and vulnerability of permafrost to climate change depends on complex interactions among topography, water, soil, vegetation, and snow, which allow permafrost to persist at mean annual air temperatures (MAATs) as high as +2 °C and degrade at MAATs as low as –20 °C. To assess these interactions, we compiled existing data and tested effects of varying conditions on mean annual surface temperatures (MASTs) and 2 m deep temperatures (MADTs) through modeling. Surface water had the largest effect, with water sediment temperatures being ~10 °C above MAAT. A 50% reduction in snow depth reduces MADT by 2 °C. Elevation changes between 200 and 800 m increases MAAT by up to 2.3 °C and snow depths by ~40%. Aspect caused only a ~1 °C difference in MAST. Covarying vegetation structure, organic matter thickness, soil moisture, and snow depth of terrestrial ecosystems, ranging from barren silt to white spruce ( Picea glauca (Moench) Voss) forest to tussock shrub, affect MASTs by ~6 °C and MADTs by ~7 °C. Groundwater at 2–7 °C greatly affects lateral and internal permafrost thawing. Analyses show that vegetation succession provides strong negative feedbacks that make permafrost resilient to even large increases in air temperatures. Surface water, which is affected by topography and ground ice, provides even stronger negative feedbacks that make permafrost vulnerable to thawing even under cold temperatures.