REVIEW | doi:10.20944/preprints201908.0018.v1
Subject: Earth Sciences, Geophysics Keywords: glacial isostatic adjustment; sea level change; fingerprints of past ice melting
Online: 2 August 2019 (08:45:05 CEST)
Along with density and mass variations of the oceans driven by global warming, Glacial Isostatic Adjustment (GIA) in response to the last deglaciation still contributes significantly to present-day sea-level change. Indeed, in order to reveal the impacts of climate change, long term observations at tide gauges and recent absolute altimetry data need to be decontaminated from the effects of GIA. This is now realized by means of global models constrained by the observed evolution of the paleo-shorelines since the Last Glacial Maximum, which account for the complex interactions between the solid Earth, the cryosphere and the oceans. In the recent literature, past and present-day effects of GIA are often expressed in terms of fingerprints describing the spatial variations of several geodetic quantities like crustal deformation, the harmonic components of the Earth's gravity field, relative and absolute sea level. However, since it is driven by the sluggish readjustment occurring within the viscous mantle, GIA shall taint the pattern of sea-level variability also during the forthcoming centuries. The shapes of the GIA fingerprints reflect inextricable deformational, gravitational, and rotational interactions occurring within the Earth system. Using up-to-date numerical modeling tools, our purpose is to revisit and to explore some of the physical and geometrical features of the fingerprints, their symmetries and intercorrelations, also illustrating how they stem from the fundamental equation that governs GIA, i.e., the Sea Level Equation.
ARTICLE | doi:10.20944/preprints202201.0216.v1
Subject: Earth Sciences, Environmental Sciences Keywords: glacial retreat; Walker Glacier; endangered fungi; climate change; mycoflora
Online: 14 January 2022 (15:02:53 CET)
Walker Glacier near the northern coast of Ellesmere Island in the High Canadian Arctic (terrestrial margin of the ‘Last Ice Area’) is undergoing rapid ice attrition in response to climate change. We applied culture and molecular methods to investigate fungal diversity in sediments at the terminus of this glacier. Analysis of the mycoflora composition showed that the Walker Glacier isolates separated into two clusters: the surface of the glacier ice and the glacier foreland. The recently exposed soils of the foreland had a lower fungal diversity and different species from those on the ice, with the exception of five species that occurred in both habitats. This loss of glacial ice in the Arctic is therefore resulting in the loss of habitats for cold-dwelling fungal species. Fungal diversity is a potentially rich biological resource of glacial ecosystems, with unique taxa. The rapid loss of these glacial habitats underscores the urgency for more detailed surveys of fungal diversity in the High Arctic, and the need for further isolation of strains as well as cryopreservation of environmental microbiome samples for future research and conservation.
ARTICLE | doi:10.20944/preprints202104.0578.v1
Subject: Earth Sciences, Atmospheric Science Keywords: glacial ripping; groundwater overpressure; breccia; rubble till; Cambrian quartz-arenite
Online: 21 April 2021 (12:20:51 CEST)
Glacial ripping is a newly recognized process sequence in which subglacial erosion is triggered by groundwater overpressure. Investigations in gneiss terrain in lowland Sweden indicate that ripping involves three stages of (i) hydraulic jacking, (ii) rock disruption under subglacial traction and (iii) glacial transport of rock blocks. Evidence for each stage includes, respectively, dilated fractures with sediment fills, disintegrated roches moutonnées and boulder spreads. Here we ask: can glacial ripping also occur in sedimentary rocks, and, if so, what are its effects? The case study area is in hard, thinly bedded, gently dipping Cambrian quartz-arenites at Loch Eriboll, NW Scotland. Field surveys reveal dilated, sediment filled, bedding-parallel fractures, open joints and brecciated zones, interpreted as markers for pervasive, shallow penetration of the quartz-arenite by water at over-pressure. Other features, including disintegrated rock surfaces, boulder spreads and monomict rubble tills, indicate glacial disruption and short distance subglacial transport. The field results, together with published cosmogenic isotope ages, indicate that glacial ripping operated with high impact close to the former ice margin at Loch Eriboll at 17.6-16.5 ka. Glacial ripping thus can operate effectively in bedded, hard sedimentary rocks and the accompanying brecciation is significant – if not dominant - in till formation. Candidate markers for glacial ripping are identified in other sedimentary terrains in former glaciated areas of the Northern Hemisphere.
REVIEW | doi:10.20944/preprints202102.0176.v1
Subject: Life Sciences, Biochemistry Keywords: Bactrian camel; Last Glacial Maximum; Million Years Ago; Human migration
Online: 8 February 2021 (10:30:58 CET)
The Evolutionary history and domestication of Camels are largely unexplored because of the lack of well dated early archaeological records. However, limited records suggest that domestication of Camels likely happened in the late second millennium BCE. Over the time, camels have helped human for their basic needs like meat, milk, wool, dung to long routes transportation. This multifaceted animal has helped the mankind to connect through continents and in trade majorly through the Silk route. In India, both dromedary and Bactrian camels are found and their habitat is entirely different from each other, dromedaries inhabit in hot deserts and Bactrians are found mostly in cold places (Nubra Valley, Ladakh). Fewer studies on Indian dromedaries have been conducted but no such studies are done on Bactrian camels. It is needed to study the genetics of Bactrian camels to find out their genetic affinity and evolutionary history with other Bactrians found in different parts of the world. Furthermore, parallel studies on humans and Bactrian camel are required to understand the co-evolution and migration pattern of humans during their dispersal in different time periods.
Subject: Earth Sciences, Geology Keywords: Last Glacial Maximum; paleoclimate; temperature-index model; Sawatch Range; Colorado
Online: 8 September 2019 (15:59:45 CEST)
Temperature-index modeling is used to determine the magnitude of temperature depression in the northern Sawatch Range required to maintain steady-state mass balances of six reconstructed glaciers at their extent during the local Last Glacial Maximum (LLGM), dated at ~21 ka. Assuming no significant differences in precipitation compared to modern values, mean annual temperatures in the region were on average 8.8 +0.5/–0.8 °C cooler than they are today. Allowing for modest increases or decreases in precipitation, required temperature depressions only differ by ± 0.2 °C. Temperature depression in the northern Sawatch Range are consistent, although slightly greater, with those determined in other ranges in Colorado using similar approaches. The estimates presented here are, however, substantially less than those suggested by several downscaled simulations of global LGM climate, that might be due to the need for improved calibration of such downscalings, or the models from which they are derived. Our estimates of LGM temperature depression are considerably greater than that previously determined in the study area and those in two other ranges in Colorado derived using different methodologies, the latter being most likely responsible for the discrepancies.
ARTICLE | doi:10.20944/preprints201901.0261.v1
Subject: Earth Sciences, Geophysics Keywords: Glacial Isostatic Adjustment; gravimetric land uplift rate modelling; GRACE; independent component analysis
Online: 25 January 2019 (15:08:15 CET)
The mantle mass flow interconnected with the process of Glacial Isostatic Adjustment (GIA) and the reformation of the Earth’s crust constantly perturbs the observed gravity field towards a hypothetic isostatic state. We analyse the temporal changes of the gravity field from the GRACE data, using different mathematical and/or statistical methods to detect the GIA amidst other gravity signals. A number of gravimetric post-glacial land uplift rate (LUR) modelling methods are investigated and compared with the data from a total number of 515 GPS stations and preferred GIA forward models in Fennoscandia and North America. We investigate three mathematical methods, namely regression, principal component, and independent component analysis (ICA) to extracting the GIA signal from the GRACE monthly geoid heights. We use some regularization techniques to exploit the GRACE monthly data to their maximum spatial resolution and to increase the Signal to Noise Ratio of their short wavelengths. Near the centres of the study areas the gravimetric LUR model using the fast-ICA algorithm of Hyvärinen and Oja (2000) is shown to be in a complete agreement with the GPS data and the predictions of the GIA forward models, and for the whole areas, subject to epeirogeny movement of the two regions, their discrepancies reach to the extrema at -1.8 and +3.3, and -4.5 and +7.5 mm/a, respectively. We show that the largest discrepancies between the gravimetric model using the ICA method and the GIA forward model, occur for the sub-regions likely collocated with strong ice mass change signals.
Subject: Earth Sciences, Geology Keywords: Last Glacial Maximum; paleoclimate; temperature-index model; Blanca Massif; Sangre de Cristo Mountains; Colorado
Online: 11 June 2021 (15:02:15 CEST)
Temperature-index modeling is used to determine the magnitude of temperature depression on the Blanca Massif, Colorado, required to maintain steady-state mass balances of nine reconstructed glaciers at their extent during the Last Glacial Maximum (LGM). The mean temperature depression thus determined is ~8.6 +0.7/–0.9 °C where the uncertainties account for those inherent in the glacier reconstructions, in model parameters (e.g. melt factors), and possible modest changes in LGM precipitation. Associated equilibrium-line altitudes (ELAs) exhibit a statistically significant directional dependency being lower toward the north and east. Under the assumption that regional temperature change was uniform, required changes in precipitation vary systematically – also exhibiting a directional dependency coinciding with that in ELAs – and indicate increases (over modern) occurred on the eastern side of the massif while decreases occurred on the western side. This disparity represents a strengthening of a precipitation asymmetry, particularly winter precipitation, that exists today. The modern precipitation asymmetry may be a consequence of snow being blown over to the eastern side of the massif (advective transport) by southwesterly flow. Intensification of this flow during the LGM would have enhanced advection, and augmented snow accumulation on glaciers, thus explaining the lower ELAs and increased precipitation on that side of the massif.
HYPOTHESIS | doi:10.20944/preprints202007.0100.v2
Subject: Medicine & Pharmacology, Allergology Keywords: amyotrophic lateral sclerosis; ALS; glacial; lake; clay; mineral; United States; Canada; Finland; Vermont; New Hampshire; Maine; Ohio; Wisconsin; Indiana; Minnesota; North Dakota; Montana, Idaho; Washington; Oregon; Colorado; Iowa; Utah
Online: 15 December 2020 (10:21:51 CET)
Amyotrophic lateral sclerosis (ALS) disease clusters are found in several countries worldwide. In the United States, ALS clusters are found in many states, largely within the northern United States. The cause of the increased rates of ALS in these areas remains indefinite. It is reported here that many ALS clusters are associated with sites of current or prior glacial lakes, or regions containing an abundance of silts and clay minerals. The potential significance of these findings in ALS is discussed.
ARTICLE | doi:10.20944/preprints201808.0176.v1
Subject: Earth Sciences, Environmental Sciences Keywords: persistent pollutants; risk assessment; arctic; glacial melt; climate change; human health; alaska; alpine glacier; Alaska Range
Online: 9 August 2018 (00:40:50 CEST)
To assess the presence of organochlorine pollutants (OCP) in Alaskan sub-Arctic latitudes, we analyzed ice core and meltwater samples from Jarvis Glacier, a polythermal glacier in Interior Alaska. Jarvis Glacier is receding as atmospheric warming continues throughout the region, increasing opportunity for OCP transport both englacially and into the proglacial watershed. Across all meltwater and ice core samples we identify the pesticides DDT, DDE and DDD, α- HCH and ϒ-HCH. OCP concentrations in ice core samples were highest at the 7-14 m depth (0.51 ng/L of DDT) and decreased gradually approaching the bedrock at 79m. Meltwater concentrations from the proglacial creek slightly exceeded concentrations found in the ice core, potentially indicating aggregate OCP glacial loss, with peak OCP concentration (1.12 ng/L of DDD) taken in July and potentially associated to peak melt. Ongoing use of DDT to fight Malaria in Asia, and the extended atmospheric range of HCH may account for concentrations in near-surface ice, correlating with use and atmospheric transport. The opportunity for biota bioaccumulation of OCPs, or human uptake of OCPs from glacial meltwater, may increase as glacial melt continues.
ARTICLE | doi:10.20944/preprints201806.0430.v1
Subject: Earth Sciences, Geology Keywords: Tisza, Tisa, Pannonian Basin, fluvial evolution, terrace development, tectonic impact, local conditions, last glacial, OSL-dating
Online: 26 June 2018 (15:55:33 CEST)
External impact on the development of fluvial systems is generally exerted by changes in sea level, climate and tectonic movements. In this study it is shown that regional to local differentiation of fluvial response may be caused by semi-direct effects of climate change and tectonic movement, as for instance vegetation cover, frozen soil, snow cover and longitudinal gradient. Such semi-direct effects may be responsible for specific fluvial activity resulting in proper drainage patterns, sedimentation series and erosion-accumulation rates. These conclusions are exemplified by the study of the Tis(z)a catchment in the Pannonian Basin in Hungary and Serbia from the middle of the last glacial to the Pleistocene-Holocene transition. Previous investigations in that catchment are supplemented here by new geomorphological-sedimentological data and OSL-dating. Specific characteristics of this catchment in comparison with other regions are the preponderance of meandering systems during the last glacial and the presence of very large meanders in given time intervals.
ARTICLE | doi:10.20944/preprints202007.0555.v1
Subject: Earth Sciences, Geoinformatics Keywords: UAS, debris-covered glacier, trans-Himalaya, aerial photogrammetry, structure from motion, DSM differencing, point cloud differencing, glacial mass balance, ice-cliffs
Online: 23 July 2020 (12:00:27 CEST)
Debris-covered glaciers are a notable feature in the greater Himalaya, and their ongoing mass loss under changing climate will affect the water resources of over a billion people. The current knowledge of the mass balance of Himalayan glaciers is restricted by the paucity of in-situ measurements of glaciers in both space and time, as well as the resolution of satellite remote sensing imageries. Recently, the use of Unmanned Aerial System (UAS) imagery has shown the potential to bridge this gap by enabling very detailed monitoring of inaccessible glacial areas. UAS imagery-based monitoring of Himalayan glaciers has so far been limited to a single glacier in the entire Himalaya, providing a limited understanding of spatial variability in glacier mass balance and driving factors. In the first UAS based glacial mass change estimation in the trans-Himalaya, we conducted two Unmanned Aerial System (UAS) surveys (May and November 2019) over the debris-covered Annapurna III glacier in the Himalaya. We performed Structure-from-Motion (SfM) analysis and utilized differential GPS field observations to derive geometrically accurate point clouds, ortho-mosaics and digital surface models (DSMs). The glacial volumetric loss was estimated from DSM differencing, and the magnitude and spatial variability of glacier surface change was derived from 3-D differencing of point clouds. Results revealed a heterogeneous glacial melt pattern, with an average elevation loss of 0.89 m during the monitored time period. The majority of the glacial tongue exhibited surface lowering except the area above and around the glacial snout that surprisingly exhibited significant elevation gain. Both the highest magnitude of mass loss and the highest spatial variability in mass change was observed in areas with exposed ice-cliffs and supraglacial ponds. Glacial surface velocity derived from manual feature tracking showed velocity ranging from 0-4.1 m. A detailed evaluation of specific areas allowed an improved understanding of the complex interplay of factors leading to observed surface change. Our findings expand the extent of UAS based monitoring of debris-covered glaciers in the Himalaya and conclude that UAS derived 3D topographic products will become increasingly important for monitoring of thinning debris-covered glaciers.