Publications by authors named "M R Siegfried"

Observations indicate that groundwater-laden sedimentary aquifers are extensive beneath large portions of the Greenland and Antarctic ice sheets. A reduction in the mechanical loading of aquifers is known to lead to groundwater exfiltration, a discharge of groundwater from the aquifer. Here, we provide a simple expression predicting exfiltration rates under a thinning ice sheet.

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Article Synopsis
  • Ice streams flowing into the Ross Ice Shelf are supported by a complex system of water-saturated sediments and subglacial lakes, which influence microbial life downstream in the West Antarctic Ice Sheet.
  • Recent research at Mercer Subglacial Lake identified high microbial abundance in surface sediments, with distinct communities compared to deeper layers, primarily consisting of chemolithoautotrophs that utilize reduced compounds.
  • The study reveals a subglacial metacommunity linked through ice sheet dynamics, with sediment characteristics such as organic carbon and methane levels significantly shaping microbial diversity and community composition.
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Advanced practice providers (APPs) are trained, licensed health care providers. The American Society of Transplant APP community of practice developed an electronic survey to investigate transplant APP demographics, scope of practice, and academic activities. We defined the top of scope of practice as delivering health care to the fullest extent of APP education and training as allowed by state laws and regulations.

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Antarctica's fast-flowing ice streams drain the ice sheet, with their velocity modulated by subglacial water systems. Current knowledge of these water systems is limited to the shallow portions near the ice-bed interface, but hypothesized deeper groundwater could also influence ice streaming. Here, we use magnetotelluric and passive seismic data from Whillans Ice Stream, West Antarctica, to provide the first observations of deep sub-ice stream groundwater.

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We use Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) laser altimetry crossovers and repeat tracks collected over the North Slope of Alaska to estimate ground surface-height change due to the seasonal freezing and thawing of the active layer. We compare these measurements to a time series of surface deformation from Sentinel-1 interferometric synthetic aperture radar (InSAR) and demonstrate agreement between these independent observations of surface deformation at broad spatial scales. We observe a relationship between ICESat-2-derived surface subsidence/uplift and changes in normalized accumulated degree days, which is consistent with the thermodynamically driven seasonal freezing and thawing of the active layer.

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