Comment on Zwally and others (2015)-mass gains of the Antarctic ice sheet exceed losses

In their article ‘Mass gains of the Antarctic ice sheet exceed losses’ Zwally and others (2015) choose Vostok Subglacial Lake as an exemplary region to demonstrate their inference of surface height change rates from a portion of the ICESat mission’s laser altimetry data (2003–08). In their appendix, they discuss some of the remarkable differences between their results and those reported by Richter and others (2008, 2013, 2014). However, the selective consideration of our works and the misleading or incorrect interpretation of our results call for clarificationFil: Richter, Andreas Jorg. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Technische Universitaet Dresden; AlemaniaFil: Horwath, M.. Technische Universitaet Dresden; AlemaniaFil: Dietrich, R.. Technische Universitaet Dresden; Alemani

Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth model

Thirty‒one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north‒central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end‒member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end‒member has a mantle viscosity near η =1.6 ×1018 Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995–2012 ice loss at about −11 Gt/yr. In contrast, the other end‒member has much larger viscosity: η = 8.0 ×1018 Pa s, half the post–LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching −25.9 Gt/yr during 1995–2012.Fil: Lange, H.. Technische Universitaet Dresden; AlemaniaFil: Casassa, G.. Centro de Estudios Cientificos; Chile. Universidad de Magallanes; ChileFil: Ivins, E. R.. Institute of Technology. Jet propulsion Laboratory; Estados UnidosFil: Schroeder, L.. Technische Universitaet Dresden; AlemaniaFil: Fritsche, M.. Technische Universitaet Dresden; AlemaniaFil: Richter, Andreas Jorg. Technische Universitaet Dresden; Alemania. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Groh, A.. Technische Universitaet Dresden; AlemaniaFil: Dietrich, R.. Technische Universitaet Dresden; Alemani

Congress of neurological surgeons systematic review and evidence-based guidelines update on the role of chemotherapeutic management and antiangiogenic treatment of newly diagnosed glioblastoma in adults

QUESTION: What is the role of temozolomide in the management of adult patients (aged 65 and under) with newly diagnosed glioblastoma? TARGET POPULATION: These recommendations apply to adult patients diagnosed with newly diagnosed glioblastoma. RECOMMENDATION: Level I: Concurrent and post-irradiation Temozolomide (TMZ) in combination with radiotherapy and post-radiotherapy as described by Stupp et al. is recommended to improve both PFS and OS in adult patients with newly diagnosed GBM. There is no evidence that alterations in the dosing regimen have additional beneficial effect. QUESTION: Is there benefit to adjuvant temozolomide treatment in elderly patients (\u3e 65 years old?). TARGET POPULATION: These recommendations apply to adult patients diagnosed with newly diagnosed glioblastoma. RECOMMENDATION: Level III: Adjuvant TMZ treatment is suggested as a treatment option to improve PFS and OS in adult patients (over 70 years of age) with newly diagnosed GBM. QUESTION: What is the role of local regional chemotherapy with BCNU biodegradable polymeric wafers in adult patients with newly diagnosed glioblastoma? TARGET POPULATION: These recommendations apply to adult patients diagnosed with newly diagnosed glioblastoma. RECOMMENDATION: Level III: There is insufficient evidence for the use of BCNU wafers following resection in patients with newly diagnosed glioblastoma who undergo the Stupp protocol after surgery. Further studies of higher quality are suggested to understand the role of BCNU wafer and other locoregional therapy in the setting of Stupp Protocol. QUESTION: What is the role of bevacizumab in the adult patient with newly diagnosed glioblastoma? TARGET POPULATION: These recommendations apply to adult patients diagnosed with newly diagnosed glioblastoma. RECOMMENDATION: Level I: Bevacizumab in general is not recommended in the initial treatment of adult patients with newly diagnosed GBM. It continues to be strongly recommended that patients with newly diagnosed GBM be enrolled in properly designed clinical trials to assess the benefit of novel chemotherapeutic agents compared to standard therapy

The hydrostatic control of load-induced height changes above subglacial Lake Vostok

Lake Vostok, East Antarctica, represents an extensive water surface at the base of the ice sheet. Snow, ice and atmospheric pressure loads applied anywhere within the lake area produce a hydrostatic response, involving deformations of the ice surface, ice-water interface and particle horizons. A modelling scheme is developed to derive height changes of these surfaces for a given load pattern. It is applied to a series of load scenarios, and predictions based on load fields derived from a regional climate model are compared to observational datasets. Our results show that surface height changes due to snow-buildup anomalies are damped over the lake area, reducing the spatial standard deviation by one-third. The response to air pressure variations, in turn, adds surface height variability. Atmospheric pressure loads may produce height changes of up to ±4 cm at daily resolution, but decay rapidly with integration time. The hydrostatic load response has no significant impact neither on ICESat laser campaign biases determined over the lake area nor on vertical particle movements derived from GNSS observations.Fil: Richter, Andreas Jorg. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; ArgentinaFil: Schröder, Ludwig. Technische Universität Dresden; AlemaniaFil: Scheinert, Mirko. Technische Universität Dresden; AlemaniaFil: Popov, Sergey V.. Polar Marine Geosurvey Expedition; Rusia. Saint Petersburg State University; RusiaFil: Groh, Andreas. Technische Universität Dresden; AlemaniaFil: Willen, Matthias. Technische Universität Dresden; AlemaniaFil: Horwath, Martin. Technische Universität Dresden; AlemaniaFil: Dietrich, Reinhard. Technische Universität Dresden; Alemani

Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth model

Thirty‒one GPS geodetic measurements of crustal uplift in southernmost South America determined extraordinarily high trend rates (> 35 mm/yr) in the north‒central part of the Southern Patagonian Icefield. These trends have a coherent pattern, motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations. Two end‒member models provide good fits: both require a lithospheric thickness of 36.5 ± 5.3 km. However, one end‒member has a mantle viscosity near η =1.6 ×1018 Pa s and an ice collapse rate from the Little Ice Age (LIA) maximum comparable to a lowest recent estimate of 1995–2012 ice loss at about −11 Gt/yr. In contrast, the other end‒member has much larger viscosity: η = 8.0 ×1018 Pa s, half the post–LIA collapse rate, and a steadily rising loss rate in the twentieth century after AD 1943, reaching −25.9 Gt/yr during 1995–2012.Facultad de Ciencias Astronómicas y Geofísica

The rapid and steady mass loss of the patagonian icefields throughout the GRACE Era: 2002-2017

We use the complete gravity recovery and climate experiment (GRACE) Level-2 monthly time series to derive the ice mass changes of the Patagonian Icefields (Southern Andes). The glacial isostatic adjustment is accounted for by a regional model that is constrained by global navigation satellite systems (GNSS) uplift observations. Further corrections are applied concerning the effect of mass variations in the ocean, in the continental water storage, and of the Antarctic ice sheet. The 161 monthly GRACE gravity field solutions are inverted in the spatial domain through the adjustment of scaling factors applied to a-priori ice mass change patterns based on published remote sensing results for the Southern and Northern Patagonian Icefields, respectively. We infer an ice mass change rate of -24.4 ± 4.7 Gt/a for the Patagonian Icefields between April 2002 and June 2017, which corresponds to a contribution to the eustatic sea level rise of 0.067 ± 0.013 mm/a. Our time series of monthly ice mass changes reveals no indication for an acceleration in ice mass loss. We find indications that the Northern Patagonian Icefield contributes more to the integral ice loss than previously assumed.Fil: Richter, Andreas Jorg. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Technische Universität Dresden; AlemaniaFil: Groh, Andreas. Technische Universität Dresden; AlemaniaFil: Horwath, Martin. Technische Universität Dresden; AlemaniaFil: Ivins, Erik. California Institute of Technology; Estados UnidosFil: Marderwald, Eric Rodolfo. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Hormaechea, José Luis. Estacion Astronomica Rio Grande; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Perdomo, Raúl. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Dietrich, Reinhard. Technische Universität Dresden; Alemani

Do crustal deformations observed by GPS in Tierra del Fuego (Argentina) reflect glacial-isostatic adjustment?

Vertical site velocities determined by geodetic GPS observations in the Lago Fagnano area, Tierra del Fuego main island, are interpreted with respect to their potential relation with the glacial-isostatic crustal response to ice mass changes. The spatial pattern of the uplift rates, in combination with the horizontal crustal deformation pattern, point towards a fault-tectonic rather than glacial-isostatic origin of the determined vertical crustal deformations. This implies rather small GIA effects pointing towards relatively small Holocene ice-mass changes in Tierra del Fuego. However, these findings are considered to be preliminary. They should be confirmed by additional observations covering an extended area with GPS sites.Facultad de Ciencias Astronómicas y Geofísica

Present-day crustal deformation along the Magallanes-Fagnano Fault System in Tierra del Fuego from repeated GPS observations

The present-day deformation of the earth crust in the Argentine part of Tierra del Fuego main island (southernmost South America) is here investigated based on repeated geodetic GPS observations. The island is traversed by the active transform boundary between the South American and Scotia tectonic plates, represented by the Magallanes-Fagnano fault system. Since 1993 a regional network comprising to date 29 GPS sites has been observed almost every year. The complete set of accumulated observations was processed using the Bernese GPS software and state-of-the-art processing strategies and models. The utilization of homogeneous GPS products resulting from a reprocessing of the global IGS network warrants a stable realization of a global reference frame. For each GPS site 3-D positions and linear velocities with error estimates were obtained. A strain analysis of the horizontal velocity components revealed the zones of major deformation activity. A 30-km-wide deformation belt centred on the main trace of the fault system was identified. This belt is bordered to the north (South America) and south (Scotia) by geodynamically stable zones, which move horizontally with a relative average velocity of 4.4 ± 0.6 (east) and -0.3 ± 0.4 (north) mm a-1. Within the deformation belt a maximum strain rate in the order of 0.25 μstrain per year has been detected. A pronounced change in the deformation style from transtension (east) to transpression (west) is observed. The area of predominating shortening of the crust coincides with a local rotation minimum and relative uplift. Throughout the period covered by the GPS observations the displacements and deformations occurred to be linear with time.Facultad de Ciencias Astronómicas y Geofísica

Present-day crustal deformation along the Magallanes-Fagnano Fault System in Tierra del Fuego from repeated GPS observations

The present-day deformation of the earth crust in the Argentine part of Tierra del Fuego main island (southernmost South America) is here investigated based on repeated geodetic GPS observations. The island is traversed by the active transform boundary between the South American and Scotia tectonic plates, represented by the Magallanes-Fagnano fault system. Since 1993 a regional network comprising to date 29 GPS sites has been observed almost every year. The complete set of accumulated observations was processed using the Bernese GPS software and state-of-the-art processing strategies and models. The utilization of homogeneous GPS products resulting from a reprocessing of the global IGS network warrants a stable realization of a global reference frame. For each GPS site 3-D positions and linear velocities with error estimates were obtained. A strain analysis of the horizontal velocity components revealed the zones of major deformation activity. A 30-km-wide deformation belt centred on the main trace of the fault system was identified. This belt is bordered to the north (South America) and south (Scotia) by geodynamically stable zones, which move horizontally with a relative average velocity of 4.4 ± 0.6 (east) and -0.3 ± 0.4 (north) mm a-1. Within the deformation belt a maximum strain rate in the order of 0.25 μstrain per year has been detected. A pronounced change in the deformation style from transtension (east) to transpression (west) is observed. The area of predominating shortening of the crust coincides with a local rotation minimum and relative uplift. Throughout the period covered by the GPS observations the displacements and deformations occurred to be linear with time.Facultad de Ciencias Astronómicas y Geofísica

Horizontal and vertical deformation rates linked to the Magallanes‐Fagnano Fault, Tierra del Fuego: Reconciling geological and geodetic observations by modeling the current seismic cycle

We integrate geodetic, geological and seismological observations in Tierra del Fuego,into a consistent and quantitative analysis, to better understand the current crustaldeformation associated to the Magallanes-Fagnano Fault, i.e., the transform boundarybetween the South American and Scotia plates at the southern tip of Patagonia. Toobtain reliable geodetic estimates of the thickness of the seismogenic layer, we modelthe current seismic cycle from the great 1949 Mw 7.7 earthquake to the present,including the lasting effects of postseismic relaxation. The model parameters are con-strained by GNSS velocities obtained by reprocessing 24 years of observations in theisland with up-to-date models and satellite products. We combine the observed de-formation rates with long-term geological estimates of the slip rate in this transformsystem during the Holocene. The modeling results point to a seismogenic layer thick-ness of 15 ± 3 km and to fault planes inclined 63◦ ± 4◦ , dipping to the South. Alongthe sections of the Magallanes-Fagnano Fault in the island these results are consistentwith a seismic moment deficit rate, per unit of length, of 3.2±0.8×1012 N m a−1 km−1,and a cumulative seismic moment, to date, equivalent to an earthquake of magnitudeMw ´7. The postseismic viscoelastic relaxation, probably related to viscous flow inthe mantle, affects the entire region up to ∼ 200 km away from the Magallanes-FagnanoFault, and more than 60 years after the earthquake.Fil: Mendoza, Luciano Pedro Oscar. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Richter, Andreas Jorg. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; Argentina. Technische Universität Dresden; AlemaniaFil: Marderwald, Eric Rodolfo. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Laboratorio Maggia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Departamento de Astrometría; ArgentinaFil: Hormaechea, José Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Estación Astronómica Río Grande; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Connon, Gerardo Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Estación Astronómica Río Grande; ArgentinaFil: Scheinert, M.. Technische Universität Dresden; AlemaniaFil: Dietrich, R.. Technische Universität Dresden; AlemaniaFil: Perdomo, Raul Anibal. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin