ALBERT

Description: Regional "clear sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57+/-0.02 deg C to 72+/-0.10 deg C per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near 0 deg C during the melt season, and is thus vulnerable to rapid melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue affecting potentially billions of people worldwide. To quantify the ice-surface temperature (IST) of the Greenland Ice Sheet, and to provide an IST dataset of Greenland for modelers that provides uncertainties, we are developing a climate-data record (CDR) of daily "clear-sky" IST of the Greenland Ice Sheet, from 1982 to the present using AVHRR (1982 - present) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data (2000 - present) at a resolution of approximately 5 km. Known issues being addressed in the production of the CDR are: time-series bias caused by cloud cover (surface temperatures can be different under clouds vs. clear areas) and cross-calibration in the overlap period between AVHRR instruments, and between AVHRR and MODIS instruments. Because of uncertainties, mainly due to clouds, time-series of satellite IST do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with automatic-weather station data and with satellite-derived surface-temperature products and biases will be calculated.

Description: A laser tracker (LT) is an important coordinate metrology tool that uses laser interferometry to determine precise distances to objects, points, or surfaces defined by an optical reference, such as a retroreflector. A retroreflector is a precision optic consisting of three orthogonal faces that returns an incident laser beam nearly exactly parallel to the incident beam. Commercial retroreflectors are designed for operation at room temperature and are specified by the divergence, or beam deviation, of the returning laser beam, usually a few arcseconds or less. When a retroreflector goes to extreme cold (.35 K), however, it could be anticipated that the precision alignment between the three faces and the surface figure of each face would be compromised, resulting in wavefront errors and beam divergence, degrading the accuracy of the LT position determination. Controlled tests must be done beforehand to determine survivability and these LT coordinate errors. Since conventional interferometer systems and laser trackers do not operate in vacuum or at cold temperatures, measurements must be done through a vacuum window, and care must be taken to ensure window-induced errors are negligible, or can be subtracted out. Retroreflector holders must be carefully designed to minimize thermally induced stresses. Changes in the path length and refractive index of the retroreflector have to be considered. Cryogenic vacuum testing was done on commercial solid glass retroreflectors for use on cryogenic metrology tasks. The capabilities to measure wavefront errors, measure beam deviations, and acquire laser tracker coordinate data were demonstrated. Measurable but relatively small increases in beam deviation were shown, and further tests are planned to make an accurate determination of coordinate errors.

Description: NASA Langley Research Center (LaRC) and The MITRE Corporation (MITRE) have developed, and successfully demonstrated, an integrated simulation-to-flight capability for evaluating sense and avoid (SAA) system elements. This integrated capability consists of a MITRE developed fast-time computer simulation for evaluating SAA algorithms, and a NASA LaRC surrogate unmanned aircraft system (UAS) equipped to support hardware and software in-the-loop evaluation of SAA system elements (e.g., algorithms, sensors, architecture, communications, autonomous systems), concepts, and procedures. The fast-time computer simulation subjects algorithms to simulated flight encounters/ conditions and generates a fitness report that records strengths, weaknesses, and overall performance. Reviewed algorithms (and their fitness report) are then transferred to NASA LaRC where additional (joint) airworthiness evaluations are performed on the candidate SAA system-element configurations, concepts, and/or procedures of interest; software and hardware components are integrated into the Surrogate UAS research systems; and flight safety and mission planning activities are completed. Onboard the Surrogate UAS, candidate SAA system element configurations, concepts, and/or procedures are subjected to flight evaluations and in-flight performance is monitored. The Surrogate UAS, which can be controlled remotely via generic Ground Station uplink or automatically via onboard systems, operates with a NASA Safety Pilot/Pilot in Command onboard to permit safe operations in mixed airspace with manned aircraft. An end-to-end demonstration of a typical application of the capability was performed in non-exclusionary airspace in October 2011; additional research, development, flight testing, and evaluation efforts using this integrated capability are planned throughout fiscal year 2012 and 2013.

Description: Villarrica is one of the most active volcanoes in Chile, has a persistent lava lake within its crater, and is presently characterized by continuous degassing and high-level seismicity. We use a multiparameter approach based on high time-resolution gas flux measurements and seismic data to characterize magmatic and tectonic processes controlling the volcanic activity. The instrumentation includes 3 ground-based NOVAC-type scanning Mini-DOAS spectrometers for the quantification of SO2 fluxes, installed at the volcano in March 2009, which are complemented with seismic data from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS in Spanish) and from the SFB 574 temporary volcanic network. During the last three years, we have detected activity variations at Villarrica occurring on several time scales, which can be related to distinct processes at depth. The monthly averages in degassing rates increased from 400 tons/d SO2 before December 2009, to about 1200 tons/d SO2 in April 2010. Superimposed on this pattern are strong pulses of seismic LP events occurring every 3 to 4 months, accompanied by peaks in degassing rates, interpreted as periodic influx of fresh magma batches to the deeper levels of the plumbing system. The degassing rates further show cyclic variations with a periodicity of 5 to 7 days. We interpret the latter variations to represent the turnover time for a conduit convection cycle of magma from a mid-crustal reservoir, where the degassing peaks correspond to the arrival of comparatively undegassed magma at shallow levels. In addition, irregular regional earthquake events are typically followed by increased degassing activity at Villarrica 2-4 days later, interpreted as due to increased bubble nucleation in the magmatic system at depth. The period of strongly increasing degassing rates between December 2009 and April 2010 encompasses the M 8.8 Maule earthquake, which occurred on February 27, 2010. However, the degassing variations show a complex pattern, including a steady increase already 3 months before the Maule earthquake. Degassing rates dropped off sharply 7 days before the earthquake, and was followed by several weeks of comparatively low degassing during the aftershock phase. At the end of March, degassing rates picked up to a factor of 3 above the pre-earthquake level culminating with a peak of 2800 tons/d SO2 at the beginning of April. The persistence of high degassing rates even two years later indicates a permanent change in the magma plumbing system. Further, the observation that the Maule earthquake rather interrupted than enhanced the trend of increased degassing requires a fundamental increase in the magma supply to Villarrica commencing months before the rupture event. We tentatively assign the increased availability of magma to pre-rupture creep in the lower crust or at mantle depths, enabling a pressure gradient for influx of magma. We suggest that such a change in the volume of incoming magma would probably have led to an eruptive cycle at a closed vent system like e.g. the neighboring Llaima volcano.

Description: Llaima and Villarrica are two of the most actives volcanoes in the Southern Volcanic Zone in the Chilean Andes, with different type of activity and edifice. Llaima is a close vent volcano with constant seismic activity, while Villarrica is an open vent volcano with lava lake at the summit and constant degassing. The relation between volcano eruptions following a great earthquake has been studied in different cases around the world, and it has been the case for the 1960 Valdivia earthquake in southern Chile, where Llaima and Villarrica presented eruptions on the following months to years. This study characterize the volcano-seismic activity in the months before and after the M8.8 Maule earthquake. Time series for tremors, long period and volcano tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS in Spanish) and from the continuous record of the SFB 574 temporary volcanic networks. In Villarrica volcano, peaks of activity of tremor and long period events were observed months prior to and after the earthquake, followed by degassing activity, which is consistent with an increase in the activity related to fluids (gas and magma). While in Llaima volcano, a high increase in the volcano tectonic activity was observed directly after the earthquake, a possible structural adjustment response. Pressure change and normal stress were calculated for the Maule earthquake (M8.8) giving results two orders of magnitude lower in comparison to the ones obtained for Valdivia earthquake (M9.5). Giving the sustained activity and the nature of response, it is possible to state that the Maule earthquake affected these volcanoes in some way, but given the location and the insufficient critical state of both edifices, it was not possible to generate a great eruption.

Description: Llaima and Villarrica are two of the most actives volcanoes in the Southern Volcanic Zone in the Chilean Andes, with different type of activity and edifice. Llaima is a closed vent volcano with constant seismic activity, while Villarrica is an open vent volcano with a constantly degassing lava lake at the summit. Since 2009, seismic networks have been deployed at Llaima and Villarrica, and mini-DOAS stations continuously recording SO2 degassing were installed in 2010 and 2009, respectively. The response of Llaima and Villarrica volcanoes to local volcano-seismic activity, to regional events, and also to the tectonic activity related to the great Maule earthquake (M8.8) in February 2010 are investigated. Time series for tremors, long period and volcano tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS in Spanish) and from the continuous record of the SFB 574 temporary volcanic network. At Villarrica volcano, peaks of activity of tremor and long period events were observed months prior to and after the earthquake, which is consistent with an increase in the activity related to fluids (gas and magma). Degassing at Villarrica followed a complex pattern, where increased degassing rates preceded the M8.8 Maule earthquake by three months. Days before the earthquake, there was a strong decrease in degassing, and finally by a persistent degassing maximum about one month after the earthquake. At Llaima, a high increase in the volcano tectonic activity was observed directly after the earthquake, consistent with a possible structural adjustment response. Also, continuous low fumarolic degassing was observed during and after the earthquake at Llaima, but this activity could be related to the closing of the eruption cycle started in January 2008. We aim at a better understanding of the volcanic systems through the combination of both degassing and seismic data, and also detection of satellite-based thermal anomalies. Ongoing work focuses on the quantification of magma volumes involved, location of chambers and finally on tomographic structures of Villarrica.

Description: Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state.

Description: Villarrica is one of the most active volcanoes in Chile and is presently characterized by continuous degassing, high-level seismicity and a persistent lava lake within its crater. Three stationary NOVAC-type scanning Mini-DOAS UV spectrometers for the quantification of SO2 fluxes were installed at the volcano in March 2009. Seismic stations used for this study include the OVDAS (Observatorio Volcanológico de los Andes del Sur) volcano monitoring network, and 7 dedicated short period and broadband seismometers that were deployed in the region for more than one year. We have registered several cases of correlation between SO2 fluxes and seismic activity (LP events). Seismic events have in several cases been followed by an increase in degassing activity. The response seems to occur on two different time scales. Regional earthquake events in 2009 and 2010, and the 2011 Araucania event which occurred on January 2 and had a magnitude of 7.1, were followed by strongly increased degassing activity at Villarrica 2-4 days later, interpreted as due to increased bubble nucleation in the magmatic system at depth. The large Maule earthquake on February 27, 2010 with a magnitude of 8.8 had little immediate effect, but was followed several weeks later by an immense increase in degassing activity of about one order of magnitude compared to the baseline level. We speculate that this was a result of changing stress fields in the lower crust and at mantle depths caused by the Maule event, possibly changing melting conditions temporarily. Numerical models based on seismic, petrologic and gas flux data are used to demonstrate the feasibility of the time-lag between seismicity and degassing. We thus aim at gaining insight into the interface between magmatic and volcano-tectonic processes, especially factors playing a role for the onset of volcanic unrest. www.ifm-geomar.de

Description: ABSTRACT FINAL ID: V44C-02 Villarrica is one of the most active volcanoes in Chile and is presently characterized by activity from open continuously degassing conduit. The twohundred meter diameter crater contains a persistent lava lake which has a diameter of approximately ten meters. For the quantification of SO2 fluxes three stationary NOVAC-type scanning Mini-DOAS UV spectrometers were installed at the volcano in March 2009. To validate the ground-based gas measurements we compared them to thermal anomalies detected by the MODVOLC algorithm which is provided by the Hawai'i Institute of Geophysics and Planetology (http://modis.higp.hawaii.edu). The MODVOLC algorithm (WRIGHT et al., 2002) uses data from the space-based Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the National Aeronautics and Space Administration’s Terra and Aqua platforms and it exhibits the possibility to monitor volcanic heat sources. Although it was not intended to detect low intensity activity from open vent degassing, we find that in the case of Villarrica the detected thermal anomalies seem to originate from the heat carried by the gas phase. Additionally we have registered correlation between SO2 fluxes and thermal activity during the whole period of our ground-based gas-monitoring. Thermal anomalies detected by the MODVOLC algorithm coincide with observed periods of increased gas flux, enabling us to estimate gas fluxes indirectly from thermal data. Wright R. et al. (2002) Remote Sensing of Environment 82, 135-155