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This dataset describes measurements of river migration rates (averaged over the period 2016-2022) in three locations within the Yukon River Watershed: Huslia, Alaska (AK) (65.700 N, 156.387 W), Beaver, AK (66.362 N, 147.398 W), and Alakanuk, AK (62.685 N, 164.644 W). Huslia is located on the Koyukuk River and Beaver and Alakanuk are located on the Yukon River. The river migration rates are quantified from sub-pixel correlation of optical satellite imagery (Sentinel-2 imagery, 10 meter (m) spatial resolution), following the methodology of Geyman et al. (2024). The methodology allows for the detection of riverbank erosion at scales approximately 5-10 times smaller than the pixel size, so the detection threshold is 1-2 m over the approximately 7-year interval, corresponding to a migration rate of 0.1 to 0.3 m/year. The motion of the eroding and accreting sides of the river are quantified separately. The river migration rate datasets are made available as georeferenced shapefiles. 

This document describes geomorphic relative age mapping and radiocarbon (14C) measurements used to construct floodplain age models for three locations within the Yukon River Watershed: Huslia, Alaska (65.700 N, 156.387 W), Alakanuk, Alaska (62.685 N, 164.644 W), and Beaver, Alaska (66.362 N, 147.398 W). We describe the field sampling protocols, geomorphic mapping of cross-cutting relationships (aided by digital elevation models (DEMs) and high-resolution satellite imagery), 14C and optically stimulated luminescence (OSL) lab analyses, Markov Chain Monte Carlo (MCMC) interpolation through the geomorphic–radiogenic age constraints, and the resulting floodplain terrain age models. 

The carbon stored in permafrost deposits represents the single largest soil carbon reservoir on Earth. Concerns about the instability and dynamics of this carbon reservoir during permafrost thaw associated with polar amplification of climate warming contribute a large part of the uncertainty in forecasting future climate. We have been studying the carbon dynamics of permafrost deposits contained in the floodplains of large Arctic rivers. Across Arctic floodplains, accelerating bank erosion can liberate permafrost organic carbon (OC) as carbon dioxide (CO2) or methane (CH4), and/or redeposit it in fluvial units. These different fates have very different implications for climate feedback. Determining OC stocks and their dynamics in Arctic floodplain cutbanks and point bars, as well as the OC load in fluvial transport, is essential to better understand the recycling and export of permafrost carbon. As part of a National Science Foundation (NSF) funded project to better understand the effects of erosion in the Yukon River Basin, floodplain sediments were collected between June and September 2022 at two locations underlain by discontinuous permafrost within the Yukon River Basin in Alaska: Beaver (65.700° North (N), 156.387° West (W)) and Huslia (66.362° N, 147.398° W). This dataset mainly reports OC contents for collected subsurface sediments in floodplains measured by elemental analyzer. The coupled mercury content can be found in Isabel et al., 2024 (https://doi.org/10.18739/A2RF5KH5J). 

Due to atmospheric circulation and preservation of organic matter, large amounts of mercury (Hg) are stored in permafrost regions. Due to rapid warming and thawing permafrost in the Arctic, this Hg may be released, potentially degrading water quality and impacting human health. River bank erosion in particular has the ability to quickly mobilize large amounts of Hg-rich floodplain sediments. As part of a National Science Foundation (NSF) funded project to better understand the effects of erosion in the Yukon River Basin, floodplain sediments were collected between June and September 2022 at two locations underlain by discontinuous permafrost within the Yukon River Basin: Beaver, Alaska (AK) (65.700 N, 156.387 W) and Huslia, AK (66.362N, 147.398 W). This dataset contains mercury contents for collected floodplain sediments measured by direct thermal decomposition. Sample metadata also includes information recorded in the field (location, visual grain size description, and sample collection depth) and collected post sample processing (water content and dry density). 

This dataset includes field measurements of above-ground biomass made between May and October, 2023 in three locations within the Yukon River Watershed: Huslia, Alaska(AK) (65.700 N, 156.387W), Beaver, AK (66.362 N, 147.398W), and Alakanuk, AK (62.685N, 164.644W). We measured a total of 11,335 trees, distributed in 190 field plots (approximately 10 meter (m) x 10 m). We apply allometric scaling relations to convert measurements of tree diameter to kilograms of dry biomass. We then link these filed measurements of above-ground biomass density to the mean forest canopy height (MCH), derived from airborne Light Detection and Ranging (LiDAR) data. We derive empirical regressions linking MCH to above-ground biomass in each of the field sites, and then apply these empirical relationships to the LiDAR datasets to obtain maps of above-ground biomass density. This dataset includes both the field observations (coordinates, tree type, and tree diameter of the 11,335 inventoried trees) and the processed above-ground biomass maps (georeferenced TIFF files, with a spatial resolution of 10 m). 

Abstract Permafrost degradation is altering biogeochemical processes throughout the Arctic. Thaw‐induced changes in organic matter transformations and mineral weathering reactions are impacting fluxes of inorganic carbon (IC) and alkalinity (ALK) in Arctic rivers. However, the net impact of these changing fluxes on the concentration of carbon dioxide in the atmosphere (pCO₂) is relatively unconstrained. Resolving this uncertainty is important as thaw‐driven changes in the fluxes of IC and ALK could produce feedbacks in the global carbon cycle. Enhanced production of sulfuric acid through sulfide oxidation is particularly poorly quantified despite its potential to remove ALK from the ocean‐atmosphere system and increasepCO₂, producing a positive feedback leading to more warming and permafrost degradation. In this work, we quantified weathering in the Koyukuk River, a major tributary of the Yukon River draining discontinuous permafrost in central Alaska, based on water and sediment samples collected near the village of Huslia in summer 2018. Using measurements of major ion abundances and sulfate () sulfur (³⁴S/³²S) and oxygen (¹⁸O/¹⁶O) isotope ratios, we employed the MEANDIR inversion model to quantify the relative importance of a suite of weathering processes and their net impact onpCO₂. Calculations found that approximately 80% of in mainstem samples derived from sulfide oxidation with the remainder from evaporite dissolution. Moreover,³⁴S/³²S ratios,¹³C/¹²C ratios of dissolved IC, and sulfur X‐ray absorption spectra of mainstem, secondary channel, and floodplain pore fluid and sediment samples revealed modest degrees of microbial sulfate reduction within the floodplain. Weathering fluxes of ALK and IC result in lower values ofpCO₂over timescales shorter than carbonate compensation (∼10⁴ yr) and, for mainstem samples, higher values ofpCO₂over timescales longer than carbonate compensation but shorter than the residence time of marine (∼10⁷ yr). Furthermore, the absolute concentrations of and Mg²⁺in the Koyukuk River, as well as the ratios of and Mg²⁺to other dissolved weathering products, have increased over the past 50 years. Through analogy to similar trends in the Yukon River, we interpret these changes as reflecting enhanced sulfide oxidation due to ongoing exposure of previously frozen sediment and changes in the contributions of shallow and deep flow paths to the active channel. Overall, these findings confirm that sulfide oxidation is a substantial outcome of permafrost degradation and that the sulfur cycle responds to permafrost thaw with a timescale‐dependent feedback on warming.