A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff erosion in the Arctic

Abstract

Eroding permafrost coasts are likely indicators and integrators of changes in the Arctic System as they are susceptible to the combined effects of declining sea ice extent, increases in open water duration, more frequent and impactful storms, sea-level rise, and warming permafrost. However, few observation sites in the Arctic have yet to link decadal-scale erosion rates with changing environmental conditions due to temporal data gaps. This study increases the temporal fidelity of coastal permafrost bluff observations using near-annual high spatial resolution (<1 m) satellite imagery acquired between 2008-2017 for a 9 km segment of coastline at Drew Point, Beaufort Sea coast, Alaska. Our results show that mean annual erosion for the 2007-2016 decade was 17.2 m yr −1 , which is 2.5 times faster than historic rates, indicating that bluff erosion at this site is likely responding to changes in the Arctic System. In spite of a sustained increase in decadal-scale mean annual erosion rates, mean open water season erosion varied from 6.7 m yr −1 in 2010 to more than 22.0 m yr −1 in 2007, 2012, and 2016. This variability provided a range of coastal responses through which we explored the different roles of potential environmental drivers. The lack of significant correlations between mean open water season erosion and the environmental variables compiled in this study indicates that we may not be adequately capturing the environmental forcing factors, that the system is conditioned by long-term transient effects or extreme weather events rather than annual variability, or that other not yet considered factors may be responsible for the increased erosion occurring at Drew Point. Our results highlight an increase in erosion at Drew Point in the 21st century as well as the complexities associated with unraveling the factors responsible for changing coastal permafrost bluffs in the Arctic.

Permafrost-carbon mobilization in Beringia caused by deglacial meltwater runoff, sea-level rise and warming

“…As a consequence, fluvial transport of permafrostderived particulate organic matter amplifies. Moreover, rising sea-level and warming can induce massive destruction of permafrost along coastlines by physical erosion and thermal collapse of coastal bluffs (Vonk et al 2012, Jones et al 2018. Together these processes increase the deposition rates of permafrost carbon in marine sediments .…”

Rapid CO2 Release From Eroding Permafrost in Seawater

“…In short, the mechanisms of erosion at the Arctic coast are multifaceted but all contribute to the release of OC to the nearshore zone. The current mean circum-Arctic erosion rate is 0.57 m/year but can exceed 20 m/year at specific locations (Jones et al, 2018), inducing the transfer of large masses of sediment (430 Tg/year) and OC (up to 14 Tg/year; Wegner et al, 2015) to the nearshore Figure 1. Lateral erosion of permafrost coasts in the Arctic.…”

Rapid retreat of permafrost coastline observed with aerial drone photogrammetry

“…Our study reach lies within the slightly larger coastal reach 3 unit considered by Radosavljevic et al (2016); consequently, differences in reach length and historic image co-registration result in some slight differences between the erosion rates reported herein and those previously reported for the historic imagery. Coastal retreat rates in the neighbouring Alaskan Beaufort Sea were typically 0.7 to 2.4 m a −1 depending on coast type (Jorgenson and Brown, 2005), with extremes of up to 25 m a −1 (Jones et al, 2009b). Yet, the Alaskan Beaufort Sea coastline is more similar to the western formerly non-glaciated part of the Yukon Coast, with low cliffs, overall strong erosion rates, and longer sea ice cover (Irrgang et al, 2018;Jorgenson and Brown, 2005;Ping et al, 2011).…”