Rapid Surface Lowering of Benito Glacier, Northern Patagonian Icefield

The Patagonian Icefields, which straddle the Andes below 46?S, are one of the most sensitive ice masses to climate change. However, recent mass loss from the icefields, along with its spatial and temporal variability, is not well constrained. Here we determine surface elevation changes of Benito Glacier, a 163 km2 outlet glacier draining the western flank of the North Patagonian Icefield, using a combination of field and satellite-derived elevation data acquired between 1973 and 2017. Our results demonstrate that, just below the equilibrium line, the glacier dramatically thinned by 139 m in the past 44 years, equivalent to a mean rate of 3.2 ? 0.2 m a-1. However, surface lowering was temporally variable, characterized by a hiatus between 2000 and 2013, and a subsequent increase up to 7.7 ? 3.0 m a-1 between 2013 and 2017. Analysis of Benito Glacier?s flow regime throughout the period indicates that the observed surface lowering was caused by negative surface mass balance, rather than dynamic thinning. The high rate of surface lowering observed over the past half a decade highlights the extreme sensitivity of mid-latitude glaciers to recent atmospheric forcingpublishersversionPeer reviewe

Rock glaciers in central Patagonia

Active rock glaciers are ice and debris-cored landforms common in cold arid mountains. They have not been widely described in the Patagonian Andes of southern South America and here we provide the first rock glacier inventory for the Jeinimeni region to the east of the contemporary North Patagonian Icefield. Detailed analysis of available satellite imagery and fieldwork demonstrates the presence of 89 rock glaciers across the study region, covering a total of 14.18 km2. Elevation is the primary control on rock glacier distribution with 89% existing between 1600 and 1900 m.a.s.l. Aspect also plays a significant role on rock glacier formation with 80% preferentially developed on southerly slopes receiving lower solar insolation

The 2015 Chileno Valley glacial lake outburst flood, Patagonia

Glacial Lake Outburst Floods (GLOFs) have become increasingly common over the past century in response to climate change, posing risks for human activities in many mountain regions. In this paper we document and reconstruct the sequence of events and impact of a large GLOF that took place in December 2015 in the Chileno Valley, Patagonia. Hydrograph data suggests that the flood continued for around eight days with an estimated total discharge of 105.6 × 106 m3 of water. The sequence of events was as follows: (1) A large debris flow entered the lake from two steep and largely non-vegetated mountain gullies located northeast of the Chileno Glacier terminus. (2) Water displaced in the lake by the debris flow increased the discharge through the Chileno Lake outflow. (3) Lake and moraine sediments were eroded by the flood. (4) Eroded sediments were redistributed downstream by the GLOF. The post-GLOF channel at the lake outlet widened in some places by >130 m and the surface elevation of the terrain lowered by a maximum of 38.8 ± 1.5 m. Farther downstream, large amounts of entrained sediment were deposited at the head of an alluvial plain and these sediments produced an ~340 m wide fan with an average increase in surface elevation over the pre-GLOF surface of 4.6 ± 1.5 m. We estimate that around 3.5 million m3 of material was eroded from the flood-affected area whilst over 0.5 million m3 of material was deposited in the downstream GLOF fan. The large debris flow that triggered the GLOF was probably a paraglacial response to glacier recession from its Little Ice Age limits. We suggest that GLOFs will continue to occur in these settings in the future as glaciers further recede in response to global warming and produce potentially unstable lakes. Detailed studies of GLOF events are currently limited in Patagonia and the information presented here will therefore help to inform future glacial hazard assessments in this region

A near 90-year record of the evolution of El Morado Glacier and its proglacial lake, Central Chilean Andes

Using an ensemble of close- and long-range remote sensing, lake bathymetry and regional meteorological data, we present a detailed assessment of the geometric changes of El Morado Glacier in the Central Andes of Chile and its adjacent proglacial lake between 1932 and 2019. Overall, the results revealed a period of marked glacier down wasting, with a mean geodetic glacier mass balance of −0.39 ± 0.15 m w.e.a−1 observed for the entire glacier between 1955 and 2015 with an area loss of 40% between 1955 and 2019. We estimate an ice elevation change of −1.00 ± 0.17 m a−1 for the glacier tongue between 1932 and 2019. The increase in the ice thinning rates and area loss during the last decade is coincident with the severe drought in this region (2010–present), which our minimal surface mass-balance model is able to reproduce. As a result of the glacier changes observed, the proglacial lake increased in area substantially between 1955 and 2019, with bathymetry data suggesting a water volume of 3.6 million m3 in 2017. This study highlights the need for further monitoring of glacierised areas in the Central Andes. Such efforts would facilitate a better understanding of the downstream impacts of glacier downwasting

Reevaluation of the usefulness of spirometrically controlled, quantitative high-resolution computed tomography for the diagnosis of chronic rejection after lung transplantation

Noch immer ist die chronische Abstoßung (CLAD = chronic lung allograft dysfunction) einer der entscheidenden limitierenden Faktoren für das Langzeitüberleben nach Lungentransplantation. Gefordert ist eine möglichst frühzeitige Diagnose, um mit einer Intensivierung des Therapieregimes die Transplantatfunktion zu erhalten. Diese Arbeit diskutiert in diesem Zusammenhang die quantitative hochauflösende Computertomographie (HR-CT). Zugrunde liegt eine frühere Untersuchung an 49 Lungentransplantierten 8 bis 87 Monate postoperativ mittels spirometrisch gesteuerter pulmonaler HR-CT. Es wurde neben einer visuellen Auswertung typischer Veränderungen auch die mittlere Dichte in drei repräsentativen Schichten (Höhe der Carina, 5 cm darüber bzw. darunter) und drei Atemlagen (20 %, 50 %, 80 % der Vitalkapazität) bestimmt und alles im Vergleich zu den Ergebnissen jeweils zweier Lungenfunktionsuntersuchungen (Zeitpunkt der CT und ein Jahr danach) ausgewertet. Die Ergebnisse wurden jetzt unter aktuellen Gesichtspunkten und im Hinblick auf die seither gewonnenen Erkenntnisse reevaluiert, mit einer Überlebenszeitanalyse verknüpft und mögliche Fehlerquellen und Mängel im Studiendesign identifiziert. Die mittlere Lungendichte wies zum Zeitpunkt der CT keine signifikante Korrelation zur Lungenfunktion auf. Auch die visuellen Kriterien zeigten zwar teilweise eine Tendenz, es gab aber letztlich keines, welches überzeugte. Anders das Bild ein Jahr nach der CT: Die Patientinnen und Patienten, die ein Jahr nach der CT die Kriterien eines BOS erfüllten, hatten ein Jahr zuvor bei der CT eine signifikant niedrigere Lungendichte als jene ohne. Es konnte ein Cut-Off-Punkt von –819 HE bestimmt werden (basale Schicht, Atemmittellage), unterhalb dessen ein signifikant erhöhtes Risiko für das Entwickeln eines BOS binnen Jahresfrist besteht. Hinsichtlich des Überlebens und des Transplantat-bedingten Überlebens konnte zwar eine Tendenz, aber kein signifikanter Unterschied zwischen diesen Gruppen bestimmt werden. Einschränkend an unserem Studiendesign könnte vor allem die fehlende Identifikation von Fällen der restriktiven Form einer chronischen Abstoßung (RAS) gewesen sein, welche zu diesem Zeitpunkt noch nicht definiert worden war. Zudem wird die Bestimmung der mittleren Dichte einem disseminierten Prozess wie der CLAD vermutlich nicht gerecht. Eine Dichtewertverteilung in Form von Histogrammen könnte hier ein wertvoller Parameter zur Quantifizierung sein. Gleichzeitig fehlt eine Verlaufsuntersuchung, auch um Veränderungen im späteren Krankheitsverlauf, die mit einer höheren Dichte einhergehen und Bereiche mit niedriger Dichte maskieren, zu erfassen. Zuletzt wäre ein Abgleich mit dem Therapieregime essenziell zur Verlaufsbeurteilung wie auch zur Erfassung der Effektivität therapeutischer Interventionen. Es wird deshalb der Vorschlag für ein aktualisiertes, verbessertes Studiendesign gemacht, um die standardisierte, quantitative HR-CT der Lunge unter Nutzung aktueller Technik als Erweiterung des diagnostischen Arsenals im Kampf gegen die chronische Abstoßung neu zu überprüfen.Chronic lung allograft dysfunction (CLAD) is one of the main limiting factors for long-term survival after lung transplantation. Diagnosing it as early as possible is decisive to maintain the transplant function. In this thesis, quantitative high-resolution computed tomography (HR-CT) is discussed in this context. It is based on an earlier examination of 49 lung transplant recipients with a post transplantation period of 7 to 87 months using spirometrically gated pulmonary HR-CT. In addition to a visual evaluation, the mean attenuation (ME) in three representative anatomic levels (carina + 5cm above and below) and three levels of inspiration (20 %, 50 %, 80 % VC) was evaluated in comparison to the results of two pulmonary function tests (around CT and one year after). The results have now been re-evaluated from the current point of view and regarding the knowledge gained since then. A survival time analysis was performed and possible sources of error and deficiencies in the study design were identified. ME at the time of the CT showed no significant correlation to lung function. Some visual criteria showed a tendency, but ultimately none was convincing. One year after CT the results change substantially: The patients who met the criteria of a BOS had a significantly lower ME on the CT a year earlier than those without. A cut-off point of –819HE could be determined (basal level, 50 % VC), below which there is a significantly increased risk of developing BOS within a year. Regarding survival and graft-related survival a tendency could be determined but no significant difference between these groups. The main limiting factor in our study design could have been the lack of identification of patients with RAS (restrictive CLAD), which was not yet defined at this point. Furthermore, ME probably does not sufficiently represent a disseminated process such as CLAD. Histograms showing the attenuation frequency distribution could be a more valuable parameter for quantification here. Study also lacks follow-up examinations to record changes in the later course of disease that are associated with higher attenuation and mask areas of decreased attenuation. Finally, a parallel glance on the therapy regimen would be essential for assessing the progress and recording the effectiveness of therapeutic interventions. A proposal is therefore made for an updated, improved study design using current technology to reevaluate the standardized, quantitative pulmonary HR-CT as an additional diagnostic option in the fight against CLAD