Journal Article

Permafrost slows Arctic riverbank erosion

Avouac, Jean-Philippe, Douglas, Madison M., Geyman, Emily C., Lamb, Michael P.

2024

Overview

The rate of river migration affects the stability of Arctic infrastructure and communities 1 , 2 and regulates the fluxes of carbon 3 , 4 , nutrients 5 and sediment 6 , 7 to the oceans. However, predicting how the pace of river migration will change in a warming Arctic 8 has so far been stymied by conflicting observations about whether permafrost 9 primarily acts to slow 10 , 11 or accelerate 12 , 13 river migration. Here we develop new computational methods that enable the detection of riverbank erosion at length scales 5–10 times smaller than the pixel size in satellite imagery, an innovation that unlocks the ability to quantify erosion at the sub-monthly timescales when rivers undergo their largest variations in water temperature and flow. We use these high-frequency observations to constrain the extent to which erosion is limited by the thermal condition of melting the pore ice that cements bank sediment 14 , a requirement that will disappear when permafrost thaws, versus the mechanical condition of having sufficient flow to transport the sediment comprising the riverbanks, a condition experienced by all rivers 15 . Analysis of high-resolution data from the Koyukuk River, Alaska, shows that the presence of permafrost reduces erosion rates by 47%. Using our observations, we calibrate and validate a numerical model that can be applied to diverse Arctic rivers. The model predicts that full permafrost thaw may lead to a 30–100% increase in the migration rates of Arctic rivers. Analysis of the sub-seasonal patterns of river migration reveals that permafrost reduces erosion rates and suggests that full permafrost thaw may lead to a 30–100% increase in the migration rates of Arctic rivers.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/106/694 / 704/2151/215 / 704/242 / Alaska / Arctic Regions / Bank erosion / Calibration / Cements / Confounding (Statistics) / Erosion rates / Floodplains / Freezing / Geologic Sediments - analysis / Geologic Sediments - chemistry / Ground ice / Humanities and Social Sciences / Ice - analysis / Landsat satellites / Mathematical models / Models, Theoretical / multidisciplinary / Numerical models / Oceans / Permafrost / Permafrost - chemistry / Permafrost thaws / Reproducibility of Results / River banks / River erosion / Rivers / Rivers - chemistry / Satellite imagery / Satellite Imagery - methods / Satellite Imagery - standards / Science / Science (multidisciplinary) / Sediments / Soil erosion / Soil Erosion - prevention & control / Soil Erosion - statistics & numerical data / Temperature / Temperature requirements / Thaws / Water Movements / Water temperature