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Sediment discharged from the Greenland Ice Sheet delivers nutrients to marine ecosystems around Greenland and shapes seafloor habitats. Current estimates of the total sediment flux are constrained by observations from land-terminating glaciers only. Addressing this gap, our study presents a budget derived from observations at 30 marine-margin locations. Analyzing sediment cores from nine glaciated fjords, we assess spatial deposition since 1950. A significant correlation is established between mass accumulation rates, normalized by surface runoff, and distance down-fjord. This enables calculating annual sediment flux at any fjord point based on nearby marine-terminating outlet glacier melt data. Findings reveal a total annual sediment flux of 1.324 + /- 0.79 Gt yr-1 over the period 2010-2020 from all marine-terminating glaciers to the fjords. These estimates are valuable for studies aiming to understand the basal ice sheet conditions and for studies predicting ecosystem changes in Greenlands fjords and offshore areas as the ice sheet melts and sediment discharge increase.

Through the Sediment, Ice, & Learning on the Tanana (SILT) project, a team of university scientists engaged two middle school student groups in testing innovative environmental research technologies to measure sediment flowing underneath river ice. The culturally responsive, place-based pilot program tests these technologies as a strategy to increase students' science interest and science self-efficacy. Over a series of three workshops, 39 students built and deployed low-cost turbidity sensors to measure sediment flowing underneath river ice and designed model payload attachment systems to attach the sensors to drones for measuring sediment fluxes during spring river ice breakup. Students' changes in science interest and self-efficacy were measured using both a true pre- and post-program survey and a retrospective pre-program survey.

Abstract Sediment discharged from the Greenland Ice Sheet delivers nutrients to marine ecosystems around Greenland and shapes seafloor habitats. Current estimates of the total sediment flux are constrained by observations from land-terminating glaciers only. Addressing this gap, our study presents a budget derived from observations at 30 marine-margin locations. Analyzing sediment cores from nine glaciated fjords, we assess spatial deposition since 1950. A significant correlation is established between mass accumulation rates, normalized by surface runoff, and distance down-fjord. This enables calculating annual sediment flux at any fjord point based on nearby marine-terminating outlet glacier melt data. Findings reveal a total annual sediment flux of 1.324 + /− 0.79 Gt yr-1 over the period 2010-2020 from all marine-terminating glaciers to the fjords. These estimates are valuable for studies aiming to understand the basal ice sheet conditions and for studies predicting ecosystem changes in Greenland’s fjords and offshore areas as the ice sheet melts and sediment discharge increase.

We present a highly stable, easy-to-use, table-top coherent XUV source delivering a brightness of >1kW/(mm²sr)/1%BW at 130eV (9.5nm). It is based on high-harmonic generation driven by an ultrastable ytterbium-based fiber laser and a multipass-cell-based post- compression to 35fs.

Ice formation is generally considered to exclude many particles and most solutes and thus be relatively pure compared to ambient waters. Because river ice forms by a combination of thermal and mechanical processes, some level of sediment entrainment in the ice column is likely, though reports of sediment in river ice are limited. We observed high and sporadic levels of silt and sand in ice of the Kuskokwim and Tanana rivers (Alaska, the United States) during routine field studies. These observations led us to make a more comprehensive survey of sediment entrainment in river ice of the Kuskokwim and Yukon rivers and several of their tributaries. We collected and subsampled 48 ice cores from 19 different river locations in March 2023, which included concurrent measurements of water turbidity, velocity, and depth. Approximately 60% of cores contained detectable levels of sediment, averaging 438 mg/L with median concentrations exceeding 1000 mg/L in three cores from the Yukon and Kuskokwim main stems. Many cores had even higher concentrations at certain intervals, with seven cores having subsamples exceeding 2000 mg/L; these were often located in the middle or lower portion of the ice column. Jumble ice, formed mechanically by frazil‐pan jamming during freeze‐up, was generally the best predictor of higher sediment entrainment, and these locations often had higher under‐ice velocities and depths. Our observation of high and widespread sediment entrainment in northern river ice, particularly in jumble‐ice fields, may have implications for sediment transport regimes, ice strength and transportation safety, and how rivers break up in the springtime. [ABSTRACT FROM AUTHOR]

Seasonal sea ice impacts Arctic delta morphology by limiting wave and river influences and altering river‐to‐ocean sediment pathways. However, the long‐term effects of sea ice on delta morphology remain poorly known. To address this gap, 1D morphologic and hydrodynamic simulations were set up in Delft3D to study the 1500‐year development of Arctic deltas during the most energetic Arctic seasons: spring break‐up/freshet, summer open‐water, and autumn freeze‐up. The model focused on the deltaic clinoform (i.e., the vertical cross‐sectional view of a delta) and used a floating barge structure to mimic the effects of sea ice on nearshore waters. From the simulations we find that ice‐affected deltas form a compound clinoform morphology, that is, a coupled subaerial and subaqueous delta separated by a subaqueous platform that resembles the shallow platform observed offshore of Arctic deltas. Nearshore sea ice affects river dynamics and promotes sediment bypassing during sea ice break‐up, forming an offshore depocenter and building a subaqueous platform. A second depocenter forms closer to shore during the open‐water season at the subaerial foreset that aids in outbuilding the subaerial delta and assists in developing the compound clinoform morphology. Simulations of increased wave activity and reduced sea‐ice, likely futures under a warming Arctic climate, show that deltas may lose their shallow platform on centennial timescales by (a) sediment infill and/or (b) wave erosion. This study highlights the importance of sea ice on Arctic delta morphology and the potential morphologic transitions these high‐latitude deltas may experience as the Arctic continues to warm. Plain Language Summary: The shape of a river delta is affected by river, wave, and tidal forces. In the Arctic, the presence of seasonal sea ice is also thought to play an important role in shaping high‐latitude deltas. To investigate the effects of sea ice on Arctic delta shape, we used a popular computer model with a new representation of sea ice to examine delta growth. Our results showed that sea ice limits delta growth near the shoreline, but accelerates growth further away at sea. It leads to a large underwater platform, which is consistent with the morphology (shape) of Arctic deltas. The results were used to test future Arctic warming conditions when a reduction in sea ice coverage is likely. Future modeled simulations showed that Arctic deltas may lose the shallow underwater platform from increases in infilling by river sediments or increases in wave erosion. These results shed light on the impacts sea ice has on shaping Arctic deltas and potential changes that may occur to these delta systems as the Arctic continues to warm. Key Points: 1D Delft3D simulations of delta growth under sea‐ice show compound clinoform developmentNearshore sea‐ice promotes sediment bypassing and the development of a shallow subaqueous topset (2‐m deep)Arctic deltas may lose the shallow 2‐m‐deep topset if future sea ice coverage continues to decline and river and wave influence grows [ABSTRACT FROM AUTHOR]

Capes and cape-associated shoals represent sites of convergent sediment transport, and can provide points of relative coastal stability, navigation hazards, and offshore sand resources. Shoal evolution is commonly impacted by the regional wave climate. In the Arctic, changing sea-ice conditions are leading to (a) longer open-water seasons when waves can contribute to sediment transport, and (b) an intensified wave climate (related to duration of open water and expanding fetch). At Blossom Shoals offshore of Icy Cape in the Chukchi Sea, these changes have led to a five-fold increase in the amount of time that sand is mobile at a 31-m water depth site between the period 1953-1989 and the period 1990-2022. Wave conditions conducive to sand transport are still limited to less than 2% of the year, however--and thus it is not surprising that the overall morphology of the shoals has changed little in 70 years, despite evidence of active sand transport in the form of 1-m-scale sand waves on the flanks of the shoals which heal ice keel scours formed during the winter. Suspended-sediment transport is relatively weak due to limited sources of mud nearby, but can be observed in a net northeastward direction during the winter (driven by the Alaska Coastal Current under the ice) and in a southwestward direction during open-water wind events. Longer open-water seasons mean that annual net northeastward transport of fine sediment may weaken, with implications for the residence time of fine-grained sediments and particle-associated nutrients in the Chukchi Sea. Plain Language Summary Offshore of coastal headlands, large sand ridges (on the scale of 1-10 m high) commonly occur. These features can change shape and migrate over decades to centuries, especially as conditions change in the ocean--for example, when wave energy increases and/or sea level rises. Here we explore the shape and sediments of Blossom Shoals offshore of Icy Cape in northwestern Alaska. These ridges are dominated by sands, though muds travel through the system during storms (and are likely sourced from the adjacent lagoons) and during the winter when sea ice covers the ocean. These shoals appear to have changed little in shape over the past 70 years, though stronger waves in the present climate mean that sands in the shoals are mobile for more time each year, which means the shoals may change shape and/or location in the future. Muddy sediments tend to flow northeastward (on average) over the course of a year, but longer open-water seasons mean that these sediments may spend a greater portion of each year traveling southwestward--representing a possible change in the typical pathway of sediments and related nutrients (like carbon). [ABSTRACT FROM AUTHOR]

As an overarching geriatric syndrome, frailty describes a potentially reversible transitional stage between functional autonomy and irreversible disability. Thus, frailty addresses a "window of opportunity" in which functional limitations can be successfully treated. This article provides an overview of the therapeutic approaches and their scientific evidence., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)

Frailty increases the older adult's vulnerability to suffer adverse health outcomes. To date, no gold standard for the diagnosis of frailty exists. This article provides an overview of the most relevant frailty instruments and their scope of application., Competing Interests: Die Autorinnen/Autoren geben an, dass kein Interessenkonflikt besteht., (Thieme. All rights reserved.)