Characteristics of recessional moraines at a temperate glacier in SE Iceland: Insights into patterns, rates and drivers of glacier retreat
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The ittle ce ge behaviour of glaciers in the central ritish olumbia oast ountains, anada, was described by conducting lichenometric surveys of hizocarpon spp. found on recently deposited moraines in the itimat and acific ranges. At attullo lacier in the southern itimat ange, surveys across four sets of nested lateral moraines describe advances prior to the late thirteenth century, 1550–1610, 1680–1710, and 1850 ad. In the onarch cefield area in the northern acific ange, ittle ce ge moraines stabilized prior to 1380–1430 ad, the mid‐seventeenth and mid‐eighteenth centuries, and in the mid‐nineteenth century. The timing of these moraine‐building episodes corresponds closely to the intervals of glacier expansion recorded in complementary studies in the region. These findings indicate that most glaciers in the region reached their maximum downvalley ittle ce ge extent prior to 1780 ad, and suggest that climate forcing likely contributed to regionally synchronous glacier fluctuations.
Little ice age
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Glacier morphology
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Abstract 18 new radiocarbon dates were obtained for organic materials, associated mainly with soils buried by till, from sites in the lateral moraines of Mount Cook glaciers, particularly the Tasman. The 23 New Zealand (i.e., Institute of Nuclear Sciences, DSIR, Lower Hutt) dates now available from the Tasman Glacier, taken at face value, indicate that there were glacier expansion periods there about 3450-3000, 2280, 1800-1620, 1200-900, 860, 680, 340, and < 250 radiocarbon years ago. Taking into account the statistical counting error, the ages of some of the date sets overlap. Excluding a few problematical age determinations, and those on whole soil samples, the full range of dates now available from moraines of Mount Cook glaciers (including those from the New Zealand laboratory and a laboratory in Hannover, West Germany), taken at face value, shows that glacier expansion episodes have occurred: c. 8000 years ago, probably in the 6th millennium B.P., c. 3690-3000, c. 2550-2280, c. 2110-1620, c. 1255-900, c. 860, c. 680, c. 550, c. 340, and < 250 radiocarbon years ago. The dates and the associated geomorphic evidence indicate that the glacier shrinkage which ensued from about A.D. 1900 to at least A.D. 1984 has been the most profound for at least the last 3500 years.
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Abstract Glacier monitoring has been internationally coordinated for more than 125 years. Despite this long history, there is no authoritative answer to the popular question: ‘Which glaciers are the largest in the world?’ Here, we present the first systematic assessment of this question and identify the largest glaciers in the world – distinct from the two ice sheets in Greenland and Antarctica but including the glaciers on the Antarctic Peninsula. We identify the largest glaciers in two domains: on each of the seven geographical continents and in the 19 first-order glacier regions defined by the Global Terrestrial Network for Glaciers. Ranking glaciers by area is non-trivial. It depends on how a glacier is defined and mapped and also requires differentiating between a glacier and a glacier complex, i.e. glaciers that meet at ice divides such as ice caps and icefields. It also depends on the availability of a homogenized global glacier inventory. Using separate rankings for glaciers and glacier complexes, we find that the largest glacier complexes have areas on the order of tens of thousands of square kilometers whereas the largest glaciers are several thousands of square kilometers. The world's largest glaciers and glacier complexes are located in the Antarctic, Arctic and Patagonia.
Glacier morphology
Rock glacier
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Tidewater glacier cycle
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<p>Glacial moraines represent one of the most spatially diverse climate archives on earth. Moraine dating and numerical modeling are used to effectively reconstruct past climate from mountain ranges at the global scale. But because moraines are often located downvalley from steep mountain headwalls, it is possible that debris-covered glaciers emplaced many moraines preserved in the landscape today.</p><p>Before we can understand the effect of debris cover on the moraine recored we need to understand how debris modulates glacier response to climate change. To help address this need, we developed a numerical model that links feedbacks between mountain glaciers, climate change, hillslope erosion, and landscape evolution. Our model uses parameters meant to represent glaciers in the Khumbu region of Nepal, though the model physics are relevant for mountain glaciers elsewhere.</p><p>We compare simulated debris-covered and debris-free glaciers and their length evolution. We explore the effect of climate-dependent hillslope erosion. We also allow temperature change to control frost cracking and permafrost in the headwall above simulated glaciers. Including these effects holds special implications for glacial evolution during deglaciation and the long-term evolution of mountain landscapes.</p><p>Because debris cover suppresses melt, debris-covered glaciers can advance independent of climate change. When debris cover is present during cold periods, moraine emplacement can lag debris-free glacier moraine emplacement by hundreds of years. We develop a suite of tools to help determine whether individual moraines were formed by debris-covered glaciers. Our analyses also point to how we might interpret moraine ages and estimate past climate states from debris-perturbed settings.</p>
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Terminal moraine
Deglaciation
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<p>Rock walls in high-alpine glacial environments are becoming increasingly unstable due to climate warming. This instability increases the erosion of headwalls above glaciers modifying glacial surface debris cover and mass balance and, thus, affecting the response of glaciers to climate change. As debris is deposited on glaciers, it is passively transported downglacier forming medial moraines where two glaciers join.</p><p>We assess headwall erosion by systematic downglacier-debris sampling of medial moraines and by computing headwall erosion rates from their <sup>10</sup>Be-cosmogenic nuclide concentrations. Around Pigne d&#8217;Arolla in Switzerland, we collected a total of 39 downglacier medial moraine debris samples from five adjacent glaciers. We explicitly chose medial moraines with source headwalls that vary in size, orientation and morphology, to investigate how different debris source area characteristics may express themselves in medial moraine cosmogenic nuclide concentrations. At the same time, the downglacier-debris sampling enables us to derive headwall erosion rate estimates through time, as medial moraine deposits tend to be older downglacier.</p><p>Preliminary results reveal systematic differences in <sup>10</sup>Be concentrations for the studied glaciers. At Glacier d&#8217;Otemma, Glacier du Brenay, and Glacier de Cheilon <sup>10</sup>Be concentrations average at 17x10<sup>3</sup>, 31x10<sup>3</sup>, and 4x10<sup>3</sup> atoms g<sup>-1</sup>, respectively. Downglacier <sup>10</sup>Be concentrations at Glacier d&#8217;Otemma vary systematically and headwall erosion rates tend to increase towards the present. At both Glacier du Brenay and Glacier de Cheilon downglacier <sup>10</sup>Be concentrations are more uniform, suggesting that headwall erosion rates did not evolve significantly through time. Results for Glacier de Tsijiore Nouve and Glacier de Pi&#232;ce will follow soon. In addition, samples at Glacier d&#8217;Otemma were collected along two parallel medial moraines sourced by different but adjacent headwalls. Yet, their downglacier <sup>10</sup>Be concentrations deviate and our analyses suggest that at Glacier d&#8217;Otemma both differences in headwall orientation and headwall deglaciation history may account for the deviation of the two medial moraine records. For all five glaciers, we currently explore how lithology, slope angles, exposition, deglaciation, and elevation vary between the debris source areas and how differences therein could result in the observed differences in <sup>10</sup>Be concentrations.</p>
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Glacier variations over the past centuries are still poorly documented on the southern slope of the Greater Caucasus. In this paper, the change of Chalaati Glacier in the Georgian Caucasus from its maximum extent during the Little Ice Age has been studied. For the first time in the history of glaciological studies of the Georgian Caucasus, 10 Be in situ Cosmic Ray Exposure (CRE) dating was applied. The age of moraines was determined by tree-ring analysis. Lichenometry was also used as a supplementary tool to determine the relative ages of glacial landforms. In addition, the large-scale topographical maps (1887, 1960) were used along with the satellite imagery – Corona, Landsat 5 TM, and Sentinel 2B. Repeated photographs were used to identify the glacier extent in the late XIX and early XX centuries. 10 Be CRE ages from the oldest lateral moraine of the Chalaati Glacier suggest that the onset of the Little Ice Age occurred ~0.73±0.04 kyr ago (CE ~1250–1330), while the dendrochronology and lichenometry measurements show that the Chalaati Glacier reached its secondary maximum extent again about CE ~1810. From that time through 2018 the glacier area decreased from 14.9±1.5 km 2 to 9.9±0.5 km 2 (33.8±7.4% or ~0.16% yr −1 ), while its length retreated by ~2280 m. The retreat rate was uneven: it peaked between 1940 and 1971 (~22.9 m yr −1 ), while the rate was slowest in 1910– 1930 (~4.0 m yr −1 ). The terminus elevation rose from ~1620 m to ~1980 m above sea level in ~1810–2018.
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Regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data
Very few global‐scale ice volume estimates are available for mountain glaciers and ice caps, although such estimates are crucial for any attempts to project their contribution to sea level rise in the future. We present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from ∼123,000 glaciers from a recently extended World Glacier Inventory. We compute glacier volumes and their sea level equivalent (SLE) for 19 glacierized regions containing all mountain glaciers and ice caps on Earth. On the basis of total glacierized area of 741 × 10 3 ± 68 × 10 3 km 2 , we estimate a total ice volume of 241 × 10 3 ± 29 × 10 3 km 3 , corresponding to 0.60 ± 0.07 m SLE, of which 32% is due to glaciers in Greenland and Antarctica apart from the ice sheets. However, our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried, i.e., Antarctica, North America, Greenland, and Patagonia. This emphasizes the need for more volume observations, especially of large glaciers and a more complete World Glacier Inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps.
Glacier morphology
Glacier mass balance
Accumulation zone
Meltwater
Glacier ice accumulation
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The study of moraines at the Avacha volcano group revealed that glaciers changes at all volcanoes within the group happened almost synchronously. Glacial deposits could be grouped into three generations, corresponding to three periods of glacier fluctuations in Neoholocene. The largest glaciation within the group occurred ~2000 years ago. Fragments of moraine, corresponding to that period were found only in the moraine complex of the Ditmar Glacier which was 15% larger then today at that time. The most of moraines at the Avacha volcano group were formed during the Little Ice Age, which in the studied region continued up to the first decades of XX centuries. The maximal advance of glaciers probably happened in XVII century. The moraine corresponding to that period was found at the Kozelsky Glacier valley. At present time the total area of glaciers which moraines were described and dated approaches 21.46 km2. The area of reconstructed moraines corresponding to the Little Ice Age is estimated to be 2.79 km2, therefore at that period the total glaciation area reaches 24,25 км2 exceeding the present area by 13%. It could be claimed that in general during the time past the Little Ice Age the glaciation nature and glacier types did not change sufficiently. The rate of glacier degradation at various parts of the group is different and depends mainly on exposition. At the valleys of four glaciers we found moraines formed in the middle of XX century. They may appear in 1941–1952 when the unfavorable weather conditions leaded to stable negative anomalies in accumulation have happened.
Cirque glacier
Terminal moraine
Glacier morphology
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