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1. Saline Permafrost and Cryopegs as Potentially Important Sources of CO2—Assessing Organic Carbon Mineralization Potentials on the Alaskan Coastal Plain

   https://doi.org/10.1111/gcb.70997  

   Seemann, Fabian; Baysinger, Mackenzie R; Liebner, Susanne; Treat, Claire; Zech, Michael; Jenrich, Maren; Grosse, Guido; Jones, Benjamin M; Strauss, Jens (July 2026, Global Change Biology)

   ABSTRACT Thermokarst lake and drained lake basin (DLB) dynamics are intensifying across the Alaskan Arctic Coastal Plain. Thawing, drainage, and erosion expose surface and deep sediments (> 1 m) to aerobic conditions, with saline deposits being particularly vulnerable due to freeze‐point depression. As organic carbon mineralization remains poorly constrained, we determined potentials with an aerobic one‐year long incubation at 10°C in permafrost upland, lake talik, lake cryopeg, and refrozen saline DLB sediments. We linked CO₂production to biochemical, hydrochemical, and microbial factors, and assessed carbon alteration via repeatedn‐alkane analyses. After 382 days, average CO₂production was 7.0 ± 0.4 mg C g⁻¹dry weight (DW), with DLB surface peat yielding the most (40.5 ± 2.7 mg C g⁻¹DW), and carbon‐poor cryopeg deposits (1.4 ± 0.1 mg C g⁻¹DW) and refrozen saline permafrost (1.5 ± 0.02 mg C g⁻¹DW) the least. Total organic carbon (TOC) was the main driver of CO₂production, while age, nitrogen content, electrical conductivity, water content, pH, and microbial abundance also correlated significantly with CO₂production. Normalizing production to TOC contents, saline permafrost and cryopeg sediments showed similar CO₂production to active layers, stressing the importance of potentially carbon‐rich saline deposits. TOC normalization revealed that carbon characteristics (δ¹³C, alkane content, ACL) also significantly influenced CO₂production. Then‐alkane based quantification of carbon alterations during the incubation further contributes to the understanding of carbon cycling at the molecular level.n‐Alkane contents increased on average by 153% and the carbon preference index (CPI) rose from 13.2 to 15.8, likely due to newly produced alkanes, preferential degradation, and desorption processes. This indicates strong responses of the carbon pool and raises questions about the reliability of the CPI as a degradation proxy. Altogether, our study highlights the overlooked role of salinity in CO₂production from Arctic coastal plains which could substantially shift carbon balances. 

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2. Spatiotemporal landscape dynamics drive organic matter mobilization and degradation in thermokarst terrain of the southern continuous permafrost zone

   https://doi.org/10.1080/15230430.2026.2697545  

   Ebel, Lars; Seemann, Fabian; Grosse, Guido; Marushchak, Maija E; Dietze, Elisabeth; Kanevskiy, Mikhail; Opel, Thomas; Palacin-Lizarbe, Carlos; Ghosh, Sambit; Wolter, Juliane; et al (July 2026, Arctic, Antarctic, and Alpine Research)

   The permafrost carbon cycle in Arctic coastal plains is strongly affected by abrupt thaw processes such as lake and hillslope thermokarst, which are expected to intensify under continued climate warming. Organic matter (OM) degradation may increase if taliks beneath drained lake basins (DLBs) fail to refreeze and retrogressive thaw slump activity accelerates. Thus, we investigated a coastal transect on the Baldwin Peninsula in northwest Alaska spanning a Yedoma upland, a thermokarst lake, a semidrained lake, a DLB, and a nearshore marine unit in proximity of a thaw slump. Using a 70- year aerial imagery analysis (1952–2022) with biogeochemical investigations of sediment cores (0– 1 m), we assessed landscape and OM dynamics. We identified two dominant OM mobilization and decomposition trajectories. First, talik conditions favor OM degradation beneath the lake and the semidrained lake basin, where the talik did not completely refreeze for approximately 60 years following partial drainage. Second, thaw slump driven erosion mobilizes prealtered OM from the inland and transfers it into the marine environment, where further degradation occurs during sediment transport and reworking. In contrast, the upland and refrozen DLB currently preserve and sequester OM; yet, high ground ice contents render these systems vulnerable to future abrupt thaw. 

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3. Geochemical characterization and material properties of coastal permafrost near Drew Point, Alaska

   https://doi.org/10.6073/pasta/cc4d53a91ed873765224fcb6d09f5eb7  

   Bristol, Emily M; Connolly, Craig T; Lorenson, Thomas D; Richmond, Bruce M; Ilgen, Anastasia G; Choens, Robert Charles; Bull, Diana L; Kanevskiy, Mikhail; Iwahana, Go; Jones, Benjamin M; et al (January 2020, Environmental Data Initiative)

   Permafrost cores (4.5-7.5 m long) were collected April 10th-19th, 2018, along a geomorphic gradient near Drew Point, Alaska to characterize active layer and permafrost geochemistry and material properties. Cores were collected from a young drained lake basin, an ancient drained lake basin, and primary surface that has not been reworked by thaw lake cycles. Measurements of total organic carbon (TOC) and total nitrogen (TN) content, stable carbon isotope ratios (δ13C) and radiocarbon (14C) analyses of bulk soils/sediments were conducted on 45 samples from 3 permafrost cores. Porewaters were extracted from these same core sections and used to measure salinity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), anion (Cl-, Br-, SO4 2-, NO3 -), and trace metal (Ca, Mn, Al, Ba, Sr, Si, and Fe) concentrations. Radiogenic strontium (87Sr/86Sr) was measured on a subset of porewater samples. Cores were also sampled for material property measurements such as dry bulk density, water content, and grain size fractions. 

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4. Sedimentary insights into organic matter alteration in Arctic Alaska's saline permafrost

   https://doi.org/10.5194/bg-23-3675-2026  

   Seemann, Fabian; Zech, Michael; Jenrich, Maren; Grosse, Guido; Jones, Benjamin M; Treat, Claire; Schirrmeister, Lutz; Liebner, Susanne; Strauss, Jens (June 2026, Biogeosciences)

   Abstract. In Arctic coastal lowland regions such as northernmost Alaska, thermokarst landscapes are often underlain by saline deposits, a factor frequently overlooked when assessing permafrost thaw risks. To evaluate the influence of thaw and salinity on organic matter degradation and landscape dynamics, we analyzed six sediment cores from representative landforms near Utqiaġvik (Alaska) using a multiproxy, carbon-focused approach, with emphasis on n-alkane biomarkers. Undisturbed tundra uplands contained well-preserved, organic-rich Holocene sediments (∼140 cm thick) overlying brackish late Pleistocene deposits, indicating the presence of saline permafrost. Thermokarst lake subsidence into these substrates led to enhanced organic matter degradation, as reflected by lower n-alkane carbon preference index (CPI) values. While West Twin Lake talik sediments exhibited brackish porewater, East Twin Lake sediments were characterized by predominantly saline porewater, indicating the presence of a cryopeg driven by salt-induced thaw-point depression. Lagoonal environments, receiving both terrestrial and lacustrine inputs, accumulate sediments under unfrozen hypersaline conditions, presenting a high potential for organic matter decomposition. Carbon proxy signatures statistically distinguish perennially frozen uplands, unfrozen lake sediments, refrozen drained lake basins, and lagoonal settings. Our results demonstrate that salt-bearing deposits, as found in all investigated sites, are vulnerable to active layer deepening, talik and cryopeg formation, and lake/coastal shoreline erosion. These processes accelerate organic matter degradation and alter landscape trajectories. Our study underscores the need to better understand the role of saline permafrost in Arctic coastal lowlands and its broader implications under ongoing climate change. 

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5. 14C (Carbon-14) ages of Holocene lake drainage events on the North Slope of Alaska, 2019-2020

   https://doi.org/10.18739/A2VH5CK1N  

   Farquharson, Louise; Jones, Benjamin; Kanveskiy, Mikhail; Gaglioti, Benjamin; Bergstedt, Helena; Hinkel, Kenneth (January 2021, NSF Arctic Data Center)

   Lakes are abundant features on coastal plains of the Arctic, providing important fish and wildlife habitat and water supply for villages and industry, but also interact with frozen ground (permafrost) and the carbon it stores. Most of these lakes are termed "thermokarst" because they form in ice-rich permafrost and gradually expand over time. The dynamic nature of thermokarst lakes also makes them prone to catastrophic drainage and abrupt conversion to wetlands, called drained thermokarst lake basins (DTLBs). Together, thermokarst lakes and DTLBs cover up to 80% of arctic lowland regions, making understanding their response to ongoing climate change essential for coastal plain environmental assessment. Dating the timing of lake drainage can improve our understanding of the causes and consequences of DTLB formation. This suite of 14C (Carbon-14) ages provides insight into the timing of lake drainage on the North Slope of Alaska across a range of ecosystems and surficial geology types. 

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