Semicentennial of Human Babesiosis, Nantucket Island

Fifty years ago, the index case of human babesiosis due to Babesia microti was diagnosed in a summer resident of Nantucket Island. Human babesiosis, once called “Nantucket fever” due to its seeming restriction to Nantucket and the terminal moraine islands of southern New England, has emerged across the northeastern United States to commonly infect people wherever Lyme disease is endemic. We review the history of babesiosis on Nantucket, analyze its epidemiology and ecology there, provide summaries of the first case histories, and comment on its future public health burden.

Maximum Glacier Extent of the Penultimate Glacial Cycle in the Upper Garonne Basin (Pyrenees): New Chronological Evidence

The Upper Garonne Basin included the longest glacier in the Pyrenees during the Late Pleistocene. During major glacial advances, the Garonne palaeoglacier flowed northwards along ~ 90 km from peaks of the axial Pyrenees exceeding 2,800-3,000 m until the foreland of this mountain range at the Loures-Barouse-Barbazan basin, at only 420–440 m. Here, the palaeoglacier formed a terminal moraine complex that is examined in this work. Based on geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages, we have constrained the timing of the maximum glacial extent as well as the onset of the deglaciation from the end of the Last Glacial Cycle (LGC). Chronological data shows evidence that the external moraines in this basin were abandoned by the ice at the end of the Penultimate Glacial Cycle (PGC) and the onset of the Eemian Interglacial, at ~ 129 ka. No evidence of subsequent glacial advances or standstills occurred during the LGC in this basin were found, as the few existing datable boulders provided in the internal moraine showed inconsistent ages, thus probably being affected by post-glacial processes. The terminal basin was already deglaciated during the global Last Glacial Maximum at 24 − 21 ka, as revealed by exposure ages of polished surfaces at the confluence of the Garonne-La Pique valleys, 13 km south of the entrance of the Loures-Barousse-Barbazan basin. This study introduces the first CRE ages in the Pyrenees for the glacial advance occurred during the PGC and provides also new evidence that glaciers had already significantly shrunk during the LGM.

Reconstruction of the Upper Slope Conditions of an Extraordinary Hydro-Meteorological Event Along the Jamapa Glacier Drainage System, Citlaltépetl (Pico de Orizaba) Volcano, Mexico

A singular precipitation event on the summit glacial slopes of Mexico’s highest volcanic peak, Citlatépetl (also known as Pico de Orizaba), associated with the passage of Hurricane Ernesto across the southern Mexico mainland in August 2012, resulted in a debris flow at altitudes above 4,400 m asl, culminating in a hyperconcentrated flow downstream that had major impacts to a river valley’s channel morphology as well as to communities along a 25 km runout. The lahar originated at the terminal moraine and proglacial ramp of the Little Ice Age (LIA) extent of Citlaltépetl’s Jamapa glacier. Precipitation amounts were estimated based on nearby CONAGUA stations, but also on TRMM satellite images leading to an estimated 106 mm for a 3 day total, with 85 mm (80% of the total) falling on August 9th, the date when the lahar event occurred. The initial debris flow removed a minimum estimated 60,000 m3 of material from the proglacial ramp. A possible causative scenario is that the precipitation event overpressured the groundwater hydrology of an already unstable glacial-melt-saturated moraine. We demonstrate a methodology for the recreation of a pre-event landscape and the environmental conditions at the onset of the lahar, utilizing satellite products, in-situ geomorphological and geological evidence, and UAS technology.

Near-surface glaciotectonic structures in the sediments of an overdeepened glacial valley revealed by a shallow 3D seismic survey

<p>Glaciotectonic structures commonly include thrusting and folding, often as multiphase deformation. Here we present the results of a small-scale 3-D P-wave seismic reflection survey of glacial sediments within an overdeepened glacial valley in which we recognise unusual folding structures in front of push-moraine. The study area is in the Tannwald Basin, in southern Germany, about 50 km north of Lake Constance, where the basin is part of the glacial overdeepened Rhine Valley. The basin was excavated out of Tertiary Molasse sediments during the Hosskirchian stage, and infilled by 200 m of Hosskirchian and Rissian glacioclastics (Dietmanns Fm.). After an unconformity in the Rissian, a ca. 7 m-thick till (matrix-supported diamicton) was deposited, followed by up to 30 m of Rissian/Würmian coarse gravels and minor diamictons (Illmensee Fm.). The terminal moraine of the last Würmian glaciation overlies these deposits to the SW, not 200 m away.</p><p>We conducted a 3-D, 120 x 120 m², P-wave seismic reflection survey around a prospective borehole site in the study area. Source/receiver points and lines were spaced at 3 m and 9 m, respectively. A 10 s sweep of 20-200 Hz was excited by a small electrodynamic, wheelbarrow-borne vibrator twice at every of the 1004 realized shot positions. We recognised that the top layer of coarse gravel above the till is folded, but not in the conventional buckling sense, rather as cuspate-lobate folding. The fold axes are parallel to the terminal moraine front. The wavelength of the folding varies between 40 and 80 m, and the thickness of the folded layer is on average about 20 m. Cuspate-lobate folding is typical for deformation of layers of differing mechanical competence (after Ramsay and Huber 1987; µ<sub>1</sub>/µ<sub>2</sub> less than 10), so this tell us something about the relative competence (or stiffness) of the till layer compared to the coarse clastics above. We also detected small thrust faults that are also parallel to the push-moraine, but these have very little offset and most of the deformation was achieved by folding.</p><p>Ramsay, J.G. and Huber, M. I. (1987): The techniques of modern structural geology, vol. 2: Folds and fractures: Academic Press, London, 700 pp.</p>

Risk management and response process of moraine lakes GLOF in southwestern Tibet (China)

<p>The southwestern part of Tibet in China is one of the hardest-hit areas where Glacier Lake Outburst Flood (GLOF) occurs frequently in the Moraine Lakes of Himalayas. In the face of the increasingly severe GLOF threat of Moraine Lakes, it is urgent to build a risk management and response process of moraine lakes GLOF in this region.  Therefore, we propose a multi-module, process-oriented approach to GLOF risk response (Monitoring-Evaluation-Simulation), which integrates remote sensing, field surveys, Geographic Information Science (GIS), mathematical evaluation models, and hydrodynamic models to carry out the monitoring and analysis of GLOF, susceptibility evaluation, and numerical simulation work in Moraine Lakes.  In the monitoring section (remote sensing and field surveys), we find that typical Moraine Lakes in southwestern Tibet continue to expand in area and are prone to GLOF, which is mainly due to significant area expansion, large-scale ice/avalanches and landslides, and overflow or seepage at the terminal moraine dam. In the assessment part, based on the susceptibility evaluation factor of the glacial lake obtained by monitoring. We creatively use the grey correlation model to filter the GLOF susceptibility evaluation factors, so that the constructed GLOF susceptibility evaluation model has achieved good results (the model evaluation accuracy rate reached 84%, and the AUC value reached 0.874). In the modeling part, the GLOF modeling was carried out for the glacial lakes with high GLOF susceptibility determined by the assessment. It is also the first time that the FLO-2D model is used to construct the GLOF process of a typical Moraine Lake in the Himalayas. The simulation results show the effective simulation capability of the FLO-2D model (the simulated flow depth and flow velocity errors are both within 10%). In short, realizing the organic combination of monitoring, evaluation and simulation are one of the main advantages of the "Monitoring-Evaluation-Simulation" method. This approach effectively supports the prevention and control of GLOF in Moraine Lakes in southwestern Tibet and provides a new application idea for the risk management and response of GLOF in regional Moraine Lakes.</p><p> </p>

Structural Controls on Himalayan Glacial Lake Expansion

<p>As glaciers in the Himalaya have lost mass, their proglacial lakes have expanded. Despite increasing interest in hazard assessment and mitigation of Glacial Lake Outburst Floods (GLOFs) over more than the last two decades, the role of glacier structures in controlling patterns and rates of glacier recession, and subsequently of lake expansion, have not yet been investigated in detail. This study aims to identify and map glacier structures over a 20-year period and investigate their significance in ice front recession. Four glacial lakes and their associated debris-covered glaciers have been examined in the Everest Region of Nepal and China: Imja Tsho, Tsho Rolpa, Lumdin Tsho, and Dang Pu Tsho. Lake area was mapped between 2000 and 2020 using images acquired from Landsat 5/7/8 and Sentinel 2. Discrete glacier flow units were identified and specific structures were digitised using the finest-resolution panchromatic bands. We reveal a distinct pattern of transverse features across each glacier that can be related to ice frontal position through time. While this is not the only controlling factor contributing towards ice front recession from lake-terminating glaciers in the Himalaya, it is clear that pre-existing structures influence the ice front shape and are involved in ice front deterioration. These observations could be used to indicate future ice front positions and behaviour, and rates of glacier recession and of lake expansion.  This would also enable GLOF hazard assessments to include more detailed glaciological factors and help in the recognition of such legacy structures in the behaviour of stagnant debris-covered ice masses that are part of terminal moraine complexes.</p>

Luminescence dating of the last glaciation maximum in the southern Black Forest, Germany: Preliminary results

<p>During the last glaciation maximum, an ice cap and its more than 20 kilometres-long outlet glaciers covered the highest summit of the Black Forest, the Feldberg (1493 m above sea-level), and the surrounding region (Hofmann et al., 2020). This event is tentatively correlated with the global last glacial maximum (at ca. 22-19 ka). However, this hypothesis has never been tested by applying up-to-date geochronological techniques to glacial deposits or landforms. Due to the lack of significant topographic control, the climate probably mainly controlled the mass balance of the ice cap. Dating its last maximum extent may thus have important implications for the reconstruction of atmospheric circulations patterns during the Pleistocene. A last glaciation maximum out of phase with the Alps would strengthen the hypothesis that a meridional atmospheric circulation prevailed over Europe during the last glaciation maximum in the Alps (at ca. 25 ka).</p><p>We aim at filling this gap by re-investigating a well-preserved multi-ridged terminal moraine complex several kilometres north-west of the Feldberg. Since the beginning of the twentieth century, this landform is undisputedly assigned to the last glaciation maximum. As units of sorted sediments occur in two sections on one ridge of the terminal moraine complex, luminescence dating was deemed a suitable technique to infer the age of the landform.</p><p>Luminescence dating was applied to both feldspar and quartz for suitable comparison, as these dosimeters have different drawbacks. Since quartz from crystalline source areas often shows no or only a relatively weak luminescence signal, we anticipated that this also applies to the sampled sediments from the crystalline part of the Black Forest. Optically-stimulated luminescence (OSL) measurements revealed a bright signal in quartz as well as equivalent doses in the order of 200 Gy considerably below the saturation level. We did not observe any obvious signs for partial bleaching, but this possibility has to be confirmed via further OSL measurements, since the sampled sediments were not transported over large distances. Component analysis will also be performed.</p><p>Infrared-stimulated luminescence (IRSL) measurements on feldspar revealed higher preliminary luminescence ages. It is expected that anomalous fading and partial bleaching will be two major future challenges. To overcome the first problem, post-infrared IRSL dating will be applied. As resetting of this signal is more difficult when compared to IRSL and OSL signals, problems associated with incomplete bleaching may arise in future work.</p><p>Our preliminary quartz OSL ages tentatively suggest that the last glaciation maximum in the southern Black Forest preceded the last glaciation maxima in other formerly glaciated uplands in Central Europe and the global last glacial maximum. This result needs to be evaluated by luminescence dating of other ice-marginal landforms correlative with the last glaciation maximum. Other geochronological techniques, such as <sup>10</sup>Be cosmic-ray exposure dating, will also be applied to reveal their age.</p><p> </p><p><strong>Reference</strong></p><p>Hofmann, F. M., Rauscher, F., McCreary, W., Bischoff, J.-P., and Preusser, F.: Revisiting Late Pleistocene glacier dynamics north-west of the Feldberg, southern Black Forest, Germany, E&G Quaternary Science Journal, 69, 61–87, https://doi.org/10.5194/egqsj-69-61-2020, 2020.</p><p> </p><p> </p><p> </p>

Physicochemical Impacts of Dust Storms on Aerosol and Glacier Meltwater on the Northern Margin of the Taklimakan Desert

To analyze the impacts of dust storms on the atmospheric and meltwater environment, intensive and simultaneous sampling for aerosols and meltwater on the terminal moraine (41°73′ N, 79°88′ E, 3,789 m a.s.l.) of Qingbingtan Glacier No. 72 (Glacier No. 72) on the northern margin of the Taklamakan Desert were conducted during the summer of 2008. Aerosol and meltwater chemistry (including the species of Na+, K+, Mg2+, Ca2+, NH4+, Cl−, SO42−, and NO3−) was analyzed by ion chromatography. The results indicated that the major anions and cations in the samples were SO42− and Ca2+, respectively. In the dust event, the average value of aerosol ions was 566.91 neq·m−3, which was nearly five times that under nondust conditions (115.58 neq·m−3). In addition, in the meltwater samples, the sum of ion concentrations ranged from 31.26 to 180.98 mg·L−1, with an average of 76.40 mg·L−1. When a dust storm occurred, the ion concentrations in these two media increased significantly and simultaneously, but with different trends due to the different influencing factors. That is, the atmospheric environment was significantly affected by the dust storm. According to the correlation analysis and principal component analysis, the water-soluble ions, such as SO42−, Cl−, Na+, K+, Mg2+, and Ca2+, originated from natural sources, while NH4+ and NO3− originated from anthropogenic sources. The results of the air mass trajectory suggested that the regional dust storms caused by the air masses originating from Eastern Europe and Siberia had a significant influence on the glacial environment.

Reconstructing the History of Glacial Lake Outburst Floods (GLOF) in the Kanchenjunga Conservation Area, East Nepal: An Interdisciplinary Approach

An interdisciplinary field investigation of historic glacial lake outburst floods (GLOFs) in the Kanchenjunga region of Nepal was conducted between April and May, 2019. Oral history and field measurements suggested that at least six major GLOFs have occurred in the region since 1921. A remote sensing analysis confirmed the occurrence of the six GLOFs mentioned by informants, including two smaller flood events not mentioned that had occurred at some point before 1962. A numerical simulation of the Nangama GLOF suggested that it was triggered by an ice/debris avalanche of some 800,000 m3 of material, causing a surge wave that breached the terminal moraine and released an estimated 11.2 × 106 m3 ± 1.4 × 106 m3 of water. Debris from the flood dammed the Pabuk Khola river 2 km below the lake to form what is today known as Chheche Pokhari lake. Some concern has been expressed for the possibility of a second GLOF from Nangama as the result of continued and growing landslide activity from its right lateral moraine. Regular monitoring of all lakes and glaciers is recommended to avoid and/or mitigate the occurrence of future GLOF events in the region. Collectively, the paper demonstrates the benefits and utility of interdisciplinary research approaches to achieving a better understanding of past and poorly documented GLOF events in remote, data-scarce high mountain environments.