Supra‐permafrost submarine groundwater discharge (SGD) in the Arctic is potentially important for coastal biogeochemistry and will likely increase over the coming decades owing to climate change. Despite this, land‐to‐ocean material fluxes via SGD in Arctic environments have seldom been quantified. This study used radium (Ra) isotopes to quantify SGD fluxes to an Arctic coastal lagoon (Simpson Lagoon, Alaska) during five sampling periods between 2021 and 2023. Using a Ra mass balance model, we found that the SGD water flux was substantial and dependent on environmental conditions. No measurable SGD was detected during the spring sampling period (June 2022), when the lagoon was partially ice‐covered. During ice‐free periods, the main driver of SGD in this location is wind‐driven lagoon water level changes, not tides, which control surface water recirculation through sediments along the lagoon boundary. A combination of wind strength and direction led to low SGD fluxes in July 2022, with an SGD flux of (6 ± 3) × 106 m3 d−1, moderate fluxes in August 2021 and July 2023, which had an average flux of (17 ± 9) × 106 m3 d−1, and high fluxes in October 2022, at (79 ± 16) × 106 m3 d−1. This work demonstrates how soil and environmental conditions in the Arctic impact Ra mobilization, laying a foundation for future SGD studies in the Arctic and shedding light on the major processes driving Ra fluxes in this important environment.
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Abstract Free, publicly-accessible full text available June 1, 2025 -
Abstract Radium‐226(226Ra) and barium (Ba) exhibit similar chemical behaviors and distributions in the marine environment, serving as valuable tracers of water masses, ocean mixing, and productivity. Despite their similar distributions, these elements originate from distinct sources and undergo disparate biogeochemical cycles, which might complicate the use of these tracers. In this study, we investigate these processes by analyzing a full‐depth ocean section of226Ra activities (
T 1/2 = 1,600 years) and barium concentrations obtained from samples collected along the US GEOTRACES GP15 Pacific Meridional Transect during September–November 2018, spanning from Alaska to Tahiti. We find that surface waters possess low levels of226Ra and Ba due to export of sinking particulates, surpassing inputs from the continental margins. In contrast, deep waters have higher226Ra activities and Ba concentrations due to inputs from particle regeneration and sedimentary sources, with226Ra inputs primarily resulting from the decay of230Th in sediments. Further, dissolved226Ra and Ba exhibit a strong correlation along the GP15 section. To elucidate the drivers of the correlation, we used a water mass analysis, enabling us to quantify the influence of water mass mixing relative to non‐conservative processes. While a significant fraction of each element's distribution can be explained by conservative mixing, a considerable fraction cannot. The balance is driven using non‐conservative processes, such as sedimentary, rivers, or hydrothermal inputs, uptake and export by particles, and particle remineralization. Our study demonstrates the utility of226Ra and Ba as valuable biogeochemical tracers for understanding ocean processes, while shedding light on conservative and myriad non‐conservative processes that shape their respective distributions.Free, publicly-accessible full text available June 1, 2025 -
Radium isotopes are continuously produced at ocean boundaries and are soluble in seawater. Radium therefore serves as an analogue for similarly sourced shelf-derived materials, including biologically important elements such as carbon, nutrients, and trace metals. To test the hypothesis that climate change is leading to increased delivery of terrestrially-derived solutes to the Arctic Ocean, radium levels will be measured on bi-annual cruises along the Laptev and East Siberian Sea margins (to capture interannual changes) and on a first-of-its kind in situ radium isotope sampler (to capture seasonal changes). These sampling efforts will be complemented by an international network of collaborators that will contribute data to create an Arctic Radium Isotope Observing Network (ARION) that spans the Arctic Ocean and will serve the greater scientific community. This dataset contains the results of the water column measurements made on the first ARION cruise, which took place in Sept-Oct 2021 along the slopes of the East Siberian and Laptev Seas in collaboration with the Nansen and Amundsen Basin Observational Systems (NABOS) program. Parameters measured include radium-228, radium-226, oxygen-18, deuterium, and salinity.more » « less
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Radium isotopes (radium-228 and radium-226), water isotopes (oxygen-18 and deuterium), and salinity were measured on the slope of the East Siberian Sea in coordination with the 2018 Nansen and Amundsen Basins Observational System (NABOS) expedition. Radium is continuously produced at ocean boundaries and is soluble in seawater, thus it serves as an analogue for similarly sourced sediment-derived materials. Because the Eastern Arctic shelves are the origin of the Transpolar Drift, monitoring the radium levels in this region improves our understanding of potential climate-driven changes on the transport of shelf-derived materials offshore.more » « less
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Water column dissolved radium-226 and radium-228 from Leg 2 (Hilo, HI to Papeete, French Polynesia) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1815) on R/V Roger Revelle from October to November 2018. In this dataset version (v3), the radium-226 data have been updated from the previous version of the dataset.more » « less
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Water column dissolved radium-226 and radium-228 from Leg 1 (Seattle, WA to Hilo, HI) of the US GEOTRACES Pacific Meridional Transect (PMT) cruise (GP15, RR1814) on R/V Roger Revelle from September to October 2018. In this dataset version (v3), the radium-226 data have been updated from the previous version of the dataset.more » « less
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Supra-permafrost submarine groundwater discharge (SGD) in the Arctic is poorly understood, yet has the potential to increase over the coming decades due to climate change. This study uses radium (Ra) isotopes to investigate this process by constraining seasonal SGD inputs to an Arctic coastal lagoon (Simpson Lagoon, AK). Within this dataset are 224Ra, 223Ra, 228Ra, and 226Ra activities for surface water samples (lagoon, rivers) and groundwater samples across three seasons: thaw (June 2022), open water (August 2021 and July 2022), and freeze up (September/October 2022). Experimentally determined valued for Ra desorption from riverine suspended sediments and diffusive fluxes from bottom sediments are also included.more » « less