scholarly journals Aerogeophysical characterization of an active subglacial lake system in the David Glacier catchment, Antarctica

2019 ◽  
Author(s):  
Laura E. Lindzey ◽  
Lucas H. Beem ◽  
Duncan A. Young ◽  
Enrica Quartini ◽  
Donald D. Blankenship ◽  
...  
Keyword(s):  
Water Distribution ◽  
Austral Summer ◽  
Surface Elevation ◽  
Laser Altimetry ◽  
Laser Altimeter ◽  
University Of Texas ◽  
Lake System ◽  
Polar Research Institute ◽  
Subglacial Lakes ◽  
The University

Abstract. In the 2016–2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of characterizing the subglacial water distribution that supports a system of active subglacial lakes and informing the site selection for a potential subglacial access drilling project. This survey overlaps with and expands upon an earlier survey of the Drygalski Ice Tongue and the David Glacier grounding zone from 2011 and 2012 to create a 5 km resolution survey extending 200 km upstream from the grounding zone. The surveyed region covers two active subglacial lakes and includes re-flights of ICESat ground tracks that extend the surface elevation record in the region. While this is not the first aerogeophysical survey of an active lake system, it is one of the most extensive, and provides higher resolution boundary conditions and basal characterizations that will enable process studies of these features. This paper introduces a new helicopter-mounted ice-penetrating radar and laser altimetry system; notes a discrepancy between the original surface-elevation-derived lake outlines and locations of possible water collection based on basal geometry and hydraulic potential; and presents radar- based observations of basal conditions that are inconsistent with large collections of ponded water, despite laser altimetry showing that the hypothesized active lakes are at a high-stand.

scholarly journals Aerogeophysical characterization of an active subglacial lake system in the David Glacier catchment, Antarctica

2020 ◽  
Vol 14 (7) ◽  
pp. 2217-2233
Author(s):  
Laura E. Lindzey ◽  
Lucas H. Beem ◽  
Duncan A. Young ◽  
Enrica Quartini ◽  
Donald D. Blankenship ◽  
...  
Keyword(s):  
Water Distribution ◽  
Austral Summer ◽  
Surface Elevation ◽  
Laser Altimetry ◽  
Laser Altimeter ◽  
University Of Texas ◽  
Lake System ◽  
Polar Research Institute ◽  
Subglacial Lakes ◽  
The University

Abstract. In the 2016–2017 austral summer, the University of Texas Institute for Geophysics (UTIG) and the Korea Polar Research Institute (KOPRI) collaborated to perform a helicopter-based radar and laser altimeter survey of lower David Glacier with the goals of characterizing the subglacial water distribution that supports a system of active subglacial lakes and informing the site selection for a potential subglacial access drilling project. This survey overlaps with and expands upon an earlier survey of the Drygalski Ice Tongue and the David Glacier grounding zone from 2011 and 2012 to create a 5 km resolution survey extending 200 km upstream from the grounding zone. The surveyed region covers two active subglacial lakes and includes reflights of ICESat ground tracks that extend the surface elevation record in the region. This is one of the most extensive aerogeophysical surveys of an active lake system and provides higher-resolution boundary conditions and basal characterizations that will enable process studies of these features. This paper introduces a new helicopter-mounted ice-penetrating radar and laser altimetry system, notes a discrepancy between the original surface-elevation-derived lake outlines and locations of possible water collection based on basal geometry and hydraulic potential, and presents radar-based observations of basal conditions that are inconsistent with large collections of ponded water despite laser altimetry showing that the hypothesized active lakes are at a highstand.

scholarly journals Modeling 5 years of subglacial lake activity in the MacAyeal Ice Stream (Antarctica) catchment through assimilation of ICESat laser altimetry

2011 ◽  
Vol 57 (206) ◽  
pp. 1098-1112 ◽  
Author(s):  
Sasha P. Carter ◽  
Helen A. Fricker ◽  
Donald D. Blankenship ◽  
Jesse V. Johnson ◽  
William H. Lipscomb ◽  
...  
Keyword(s):  
Water Distribution ◽  
Large Scale ◽  
Transport Model ◽  
Laser Altimetry ◽  
Volume Changes ◽  
Ice Streams ◽  
Subglacial Lake ◽  
Lake Volume ◽  
Ice Stream ◽  
Subglacial Lakes

AbstractSubglacial lakes beneath Antarctica’s fast-moving ice streams are known to undergo ∼1 km3 volume changes on annual timescales. Focusing on the MacAyeal Ice Stream (MacIS) lake system, we create a simple model for the response of subglacial water distribution to lake discharge events through assimilation of lake volume changes estimated from Ice, Cloud and land Elevation Satellite (ICESat) laser altimetry. We construct a steady-state water transport model in which known subglacial lakes are treated as either sinks or sources depending on the ICESat-derived filling or draining rates. The modeled volume change rates of five large subglacial lakes in the downstream portion of MacIS are shown to be consistent with observed filling rates if the dynamics of all upstream lakes are considered. However, the variable filling rate of the northernmost lake suggests the presence of an undetected lake of similar size upstream. Overall, we show that, for this fast-flowing ice stream, most subglacial lakes receive >90% of their water from distant distributed sources throughout the catchment, and we confirm that water is transported from regions of net basal melt to regions of net basal freezing. Our study provides a geophysically based means of validating subglacial water models in Antarctica and is a potential way to parameterize subglacial lake discharge events in large-scale ice-sheet models where adequate data are available.

Not a “Nonissue”: Perceptions and Realities of Campus Carry at The University of Texas at Austin

2020 ◽  
pp. 1-13
Author(s):  
SAMPO RUOPPILA ◽  
ALBION M. BUTTERS
Keyword(s):  
Publicly Funded ◽  
Campus Life ◽  
University Of Texas ◽  
The Law ◽  
The University

As a publicly funded institution,The University of Texas at Austin had to implement the state's legislation to allow concealed handguns on campus. Yet its own Campus Carry policy has sought to erase the matter from everyday campus life. The administration deems it a “nonissue,” presuming that students have become accustomed to the idea, do not think about it actively, and have a low interest in acquiring a handgun license. This paper, based on a survey of the university's undergraduates, questions these ideas. It shows that a majority of students think that the issue is important and examines in what sense the students are troubled by its effects. While opinions differ between supporters and opponents of Campus Carry, divergences also exist within their ranks, such as among supporters of the law regarding where guns should specifically be allowed at the university. On the basis of the survey, the essay also examines how many licensed carriers are actually on campus, compared to the university's estimates.

scholarly journals 44. Antibiotic Class-Based Distribution and Analysis of Reported Beta-Lactam Allergies amongst Hospitalized Patients

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S45-S45
Author(s):  
Joseph Patrik Hornak ◽  
David Reynoso
Keyword(s):  
Bacterial Infections ◽  
Drug Resistant ◽  
Beta Lactam ◽  
Resistance Development ◽  
Texas Medical ◽  
University Of Texas ◽  
Icd 10 ◽  
Mrsa Infection ◽  
The University ◽  
Alternative Antibiotic

Abstract Background Reported β-lactam allergy (BLA) is very common, yet less than 10% of these patients exhibit true hypersensitivity. When faced with reported BLAs, physicians often choose alternative antibiotics which can be associated with C. difficile infection, drug-resistance development, poorer outcomes, & increased costs. Effective identification of these patients is necessary for subsequent, appropriate BLA “de-labeling.” Here, we conducted a single-center analysis of alternative antibiotic utilization amongst patients reporting BLA and compare the frequency of drug-resistant infections and C. difficile infection in allergic & non-allergic patients. Methods This is a retrospective review of adult patients hospitalized at The University of Texas Medical Branch from 1/1/2015 to 12/31/2019. Pooled electronic medical records were filtered by antibiotic orders and reported allergies to penicillins or cephalosporins. Patients with drug-resistant and/or C. difficile infection (CDI) were identified by ICD-10 codes. Microsoft Excel & MedCalc were used for statistical calculations. Results Data were available for 118,326 patients and 9.3% (11,982) reported a BLA, with the highest rates seen in those receiving aztreonam (85.9%, 530/617) & clindamycin (33.7%, 3949/11718). Amongst patients reporting BLA, high ratios-of-consumption (relative to all patients receiving antibiotics) were seen with aztreonam (7.0), clindamycin (2.7), cephalosporin/β-lactamase inhibitors (2.4), & daptomycin (2.1). Compared to the non-BLA population, BLA patients more frequently experienced MRSA infection (3.0% vs 1.5%, OR 1.99, 95% CI 1.79–2.23, p< 0.0001), β-lactam resistance (1.2% vs 0.6%, OR 2.07, 95% CI 1.72–2.49, p< 0.0001), and CDI (1.2% vs 0.7%, OR 1.85, 95% CI 1.54–2.23, p< 0.0001). Conclusion Our measured BLA rate matches approximate expectations near 10%. Moreover, these patients experienced significantly higher frequencies of drug-resistant bacterial infections and CDI. Targeted inpatient penicillin allergy testing stands to be particularly effective in those patients receiving disproportionately utilized alternative agents (e.g. aztreonam, clindamycin, daptomycin). β-lactam allergy “de-labeling” in these patients is likely a valuable antimicrobial stewardship target. Disclosures All Authors: No reported disclosures

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