Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. This study seeks to better understand the ...impact of extreme snowfall events on the resilience of very small glaciers and ice patches in the southeastern European Alps, an area with the highest mean annual precipitation in the entire Alpine chain. Mean annual precipitation here is up to 3300 mm water equivalent, and the winter snow accumulation is approximately 6.80 m at 1800 m asl averaged over the period 1979–2018. As a consequence, very small glaciers and ice/firn patches are still present in this area at rather low altitudes (1830–2340 m). We performed repeated geodetic mass balance measurements on 14 ice bodies during the period 2006–2018 and the results show an increase greater than 10% increase in ice volume over this period. This is in accordance with several extreme winter snow accumulations in the 2000s, promoting a positive mass balance in the following years. The long-term evolution of these very small glaciers and ice bodies matches well with changes in mean temperature of the ablation season linked to variability of Atlantic Multidecadal Oscillation. Nevertheless, the recent behaviour of such residual ice masses in this area where orographic precipitation represents an important component of weather amplification is somehow different to most of the Alps. We analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the influence and modification of atmospheric planetary waves and Arctic Amplification, with further positive feedbacks due to change in local sea surface temperature and its interactions with low level flows and the orography. Although further summer warming is expected in the next decades, we conclude that modification of storm tracks and more frequent occurrence of extreme snowfall events during winter are crucial in ensuring the resilience of small glacial remnants in maritime alpine sectors.
This study analysed the actively surging Shisper Glacier in the Karakoram region of Pakistan using earth observation data from Landsat 8 OLI and Planet images. Changes in the surface glacier ...velocity, supraglacial moraines and debris cover were assessed using Landsat 8 data at monthly time-steps from January 2018 to May 2019. High resolution data from Planet Labs was used to precisely detect the snout advance and ice-dammed lake expansion. Downstream cross-section profiles of the valley were generated using a moderate resolution digital elevation model to assess the inundation in the event of rapid ice-dammed lake drainage. Correlation Image Analysis Software working on the principle of normalized cross-correlation was used to generate time series monthly surface velocity profiles for Shisper Glacier. Manual digitization at 1:30000 scale was used to delineate supraglacial moraines and supraglacial debris cover. The glacier surface velocity profiles indicate that the ablation zone of the glacier continues to be in an active surge phase resulting in advance of the snout and expansion of the ice-dammed lake. Surface glacier velocities are as high as 48 m d−1. Between 18 December 2018 and 8 May 2019, the glacier snout advanced at ~6 m d−1 with a total overall advance of 860 m. The lake formed due to damming of an outflow stream from Mochowar Glacier expanded to its maximum area (29.69 ha) in May 2019 before drainage started on 23 June 2019. Our estimates indicate that the peak discharge in case of rapid drainage could vary between 5033 m3 s−1 and 6167 m3 s−1 and potentially affect infrastructure downstream.
•Remote sensing methods reveal monthly changes in the velocity of Shisper Glacier.•Glacier surge impacted the distribution of supraglacial debris cover.•The snout of the glacier advanced by 1047 m (February 2018–September 2019).•Ice-dammed lake drained steadily damaging a part of Karakoram highway.
Abstract
Ice streams regulate most ice mass loss in Antarctica. Determining ice stream response to warmer conditions during the Pliocene could provide insights into their future behaviour, but this ...is hindered by a poor representation of subglacial topography in ice-sheet models. We address this limitation using a high-resolution model for Dronning Maud Land (East Antarctica). We show that contrary to dynamic thinning of the region’s ice streams following ice-shelf collapse, the largest ice stream, Jutulstraumen, thickens by 700 m despite lying on a retrograde bed slope. We attribute this counterintuitive thickening to a shallower Pliocene subglacial topography and inherent high lateral stresses at its flux gate. These conditions constrict ice drainage and, combined with increased snowfall, allow ice accumulation upstream. Similar stress balances and increased precipitation projections occur across 27% of present-day East Antarctica, and understanding how lateral stresses regulate ice-stream discharge is necessary for accurately assessing Antarctica’s future sea-level rise contribution.
Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first ...global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity – rather unexpectedly – have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century.
It is widely believed that the last glaciers in the British Isles disappeared at the end of the Younger Dryas stadial (12.9–11.7 cal. kyr BP). Here, we use a glacier–climate model driven by data from ...local weather stations to show for the first time that glaciers developed during the Little Ice Age (LIA) in the Cairngorm Mountains. Our model is forced from contemporary conditions by a realistic difference in mean annual air temperature of −1.5°C and an increase in annual precipitation of 10%, and confirmed by sensitivity analyses. These results are supported by the presence of small boulder moraines well within Younger Dryas ice limits, and by a dating programme on a moraine in one cirque. As a result, we argue that the last glaciers in the Cairngorm Mountains (and perhaps elsewhere in upland Britain) existed in the LIA within the last few hundred years, rather than during the Younger Dryas.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study presents a 1:25,000 geomorphological map of the northern sector of Ulu Peninsula, James Ross Island, Antarctic Peninsula. The map covers an area of c. 250 km
2
, and documents the ...landforms and surficial sediments of one of the largest ice-free areas in Antarctica, based on remote sensing and field-based mapping. The large-scale landscape features are determined by the underlying Cretaceous sedimentary and Neogene volcanic geology, which has been sculpted by overlying ice masses during glacial periods. Paraglacial and periglacial features are superimposed upon remnant glacial features, reflecting the post-glacial evolution of the landscape. The study area can be broadly separated into three geomorphological sectors, according to the dominant contemporary Earth-surface processes; specifically, a glacierised southern sector, a paraglacial-dominated eastern sector, and a periglacial-dominated central/northern sector. This map provides a basis for further interdisciplinary research, and insight into the potential future landscape evolution of other parts of the Antarctic Peninsula as the climate warms.
Abstract
The impact of late Cenozoic climate on the East Antarctic Ice Sheet is uncertain. Poorly constrained patterns of relative ice thinning and thickening impair the reconstruction of past ...ice-sheet dynamics and global sea-level budgets. Here we quantify long-term ice cover of mountains protruding the ice-sheet surface in western Dronning Maud Land, using cosmogenic Chlorine-36, Aluminium-26, Beryllium-10, and Neon-21 from bedrock in an inverse modeling approach. We find that near-coastal sites experienced ice burial up to 75–97% of time since 1 Ma, while interior sites only experienced brief periods of ice burial, generally <20% of time since 1 Ma. Based on these results, we suggest that the escarpment in Dronning Maud Land acts as a hinge-zone, where ice-dynamic changes driven by grounding-line migration are attenuated inland from the coastal portions of the East Antarctic Ice Sheet, and where precipitation-controlled ice-thickness variations on the polar plateau taper off towards the coast.
This paper presents InSAR-derived ice shelf velocities and observations of surface debris deformation on the McMurdo Ice Shelf (MIS). Ice shelf velocities show that the MIS has a low surface ...velocity, with debris-laden parts of the ice shelf in the area known as the ‘swirls’ averaging speeds of c. 3 m a-1 increasing to c. 16 m a-1 at the ice front. Analysis of the fold patterns within moraine ridges on the ice surface reveals a deformational history inconsistent with the present velocity measurements. Polyphase, isoclinal folding within moraine ridges at the surface are interpreted to have formed through intense deformation by past ice flow in a NNW orientation. The velocities and styles of deformation indicate that the majority of debris on the ice shelf was originally transported into the area by a large and dynamic ice sheet/ice shelf system entirely different to that of the present configuration. Although the age of this event is unknown, it is possible that this debris has been exposed on the surface of the ice shelf since the last glacial maximum.
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