Abstract
Abstract. Northwestern Alaska has been highly affected by changing climatic patterns with new temperature and precipitation maxima over the recent years. In particular, the Baldwin and northern Seward peninsulas are characterized by an abundance of thermokarst lakes that are highly dynamic and prone to lake drainage like many other regions at the southern margins of continuous permafrost. We used Sentinel-1 synthetic aperture radar (SAR) and Planet CubeSat optical remote sensing data to analyze recently observed widespread lake drainage. We then used synoptic weather data, climate model outputs and lake ice growth simulations to analyze potential drivers and future pathways of lake drainage in this region. Following the warmest and wettest winter on record in 2017/2018, 192 lakes were identified as having completely or partially drained by early summer 2018, which exceeded the average drainage rate by a factor of ∼ 10 and doubled the rates of the previous extreme lake drainage years of 2005 and 2006. The combination of abundant rain- and snowfall and extremely warm mean annual air temperatures (MAATs), close to 0 ∘C, may have led to the destabilization of permafrost around the lake margins. Rapid snow melt and high amounts of excess meltwater further promoted rapid lateral breaching at lake shores and consequently sudden drainage of some of the largest lakes of the study region that have likely persisted for millennia. We hypothesize that permafrost destabilization and lake drainage will accelerate and become the dominant drivers of landscape change in this region. Recent MAATs are already within the range of the predictions by the University of Alaska Fairbanks' Scenarios Network for Alaska and Arctic Planning (UAF SNAP) ensemble climate predictions in scenario RCP6.0 for 2100. With MAAT in 2019 just below 0 ∘C at the nearby Kotzebue, Alaska, climate station, permafrost aggradation in drained lake basins will become less likely after drainage, strongly decreasing the potential for freeze-locking carbon sequestered in lake sediments, signifying a prominent regime shift in ice-rich permafrost lowland regions.
Highlights
Permafrost is widespread (20 % to 25 % of the land area) in the northern high latitudes (Brown et al, 1997; Obu et al, 2019) and is primarily a result of past and present cold climatic conditions (Shur and Jorgenson, 2007)
We focus on the northern Seward Peninsula (NSP) and the Baldwin Peninsula (BP) in western Alaska
Of the five large drained lakes, four are of thermokarst origin, and the largest is a lagoon on the BP, which likely is affected by episodic flooding and drying
Summary
Permafrost is widespread (20 % to 25 % of the land area) in the northern high latitudes (Brown et al, 1997; Obu et al, 2019) and is primarily a result of past and present cold climatic conditions (Shur and Jorgenson, 2007). The rapidly warming Arctic climate is already reducing the stability and distribution of near-surface permafrost. Warming of permafrost at the global scale has been observed over recent decades from borehole temperature measurements (Romanovsky et al, 2010; Biskaborn et al, 2019), while local to regional permafrost degradation has been observed in many studies of varying scales across the permafrost domain (Nitze et al, 2018a). Permafrost degradation may lead to long-term surface subsidence (Streletskiy et al, 2017), change in hydrological regimes (Liljedahl et al, 2016) and release of greenhouse gases including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (Elberling et al, 2013; Walter Anthony et al, 2018; Repo et al, 2009). The stability of permafrost is crucial for local communities which are dependent on ground stability for infrastructure, food security and water supply (Chambers et al, 2007; White et al, 2007; Melvin et al, 2017; Hjort et al, 2018)
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