Terminus-driven retreat of a major southwest Greenland tidewater glacier during the early 19th century : insights from glacier reconstructions and numerical modelling

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Jakobshavn Isbræ, West Greenland: the 2002–2003 collapse and nomination for the UNESCO World Heritage List

Jakobshavn Isbræ (also known as Sermeq Kujalleq or Ilulissat Isbræ) is situated at about 69°10′N and 50°00′W in West Greenland. This major outlet from the Inland Ice has an extremely high rate of movement (nearly 1 m/hour) and thus a high production of icebergs, which via the icefjord float westwards through Disko Bugt to Davis Strait (Fig. 1). Estimates of the iceberg production are in the range of 35 ± 10 km3 ice per year, more than 10% of the entire calf-ice production of the Inland Ice (e.g. Bauer l968; Bindschadler 1984). The icefjord into which Sermeq Kujalleq calves is Kangia, best known in glaciological literature as Jakobshavn Isfjord. Spectacular changes of the glacier were observed during 2002 and 2003 at the same time as it was nominated for inclusion in the UNESCO World Heritage List under the name ‘Ilulissat Icefjord’

Neoglacial and historical glacier changes around Kangersuneq fjord in southern West Greenland

The Nuup Kangerlua region in southern West Greenland became eglaciated in the early Holocene and by the mid-Holocene, the margin of the Inland Ice was located east of its present position. Discussion of late Holocene changes in the frontal positions of outlets relies on descriptions, paintings, photographs, maps, data from investigations of Norse ruins, aerial photographs and satellite images.The Kangiata Nunaata Sermia glacier system has receded over 20 km during the last two centuries, indicating a marked response to climatic fluctuations during and since the Little Ice Age (LIA). A large advance between 1700 and 1800 was followed by rapid recession in the first half of the 1800s. Limited data from c. 1850–1920 indicate that although the long-term position of the glacier front remained c. 10–12 km behind the LIA maximum, the late 1800s and the early 1900s may have seen a recession followed by an advance that resulted in a pronounced moraine system. The ice-dammed lake Isvand formed during the LIA maximum when meltwater from the western side of Kangiata Nunaata Sermia drained to the Ameralla fjord in the west. This is in contrast to the drainage pattern before the 1700s, when water probably drained to Kangersuneq in the north. Thinning of Kangiata Nunaata Sermia resulted in total drainage of Isvand between 2000 and 2010 and the discharge of water through Austmannadalen has now returned to the same level as that in medieval times.Other outlets in the region, such as Akullersuup Sermia and Qamanaarsuup Sermia have varied in phase with Kangiata Nunaata Sermia, but with amplitudes of only a few kilometres. In contrast, Narsap Sermia has been nearly stationary and Kangilinnguata Sermia may have advanced until the middle of the 1900s.Lowland marine outlets in south-western Greenland were characterised by large amplitude changes during the Neoglacial. Extreme examples, in addition to Kangiata Nunaata Sermia, are Eqalorutsit Killiit Sermiat at the head of Nordre Sermilik fjord in southern Greenland and Jakobshavn Isbræ in Disko Bugt, central West Greenland. The Neoglacial advances appear to have occurred at different times, although this may in part reflect the limited information about fluctuations prior to the 1930s. The differences could also reflect variations in mass balance of different sectors of the ice sheet, different subglacial dynamics or topographical factors. The lowland areas are separated by uplands and highlands that extend below the marginal part of the Inland Ice; in such areas, the outlets have been advancing almost up to the present, so that the position of the glacier front around AD 2000 broadly coincides with the LIA maximum. Charting the fluctuations of the outlets thus illustrates the large variability of the glaciers’ response to changing climate but it is notable that the number of advancing outlets has decreased markedly in recent years

Использование вейвлет-преобразования при локализации последовательностей символов

В статье предложен метод автоматического определения масштаба вейвлет-преобразования при локализации квазипериодических последовательностей (текстур, областей с символьной информацией и т.д.) путем анализа функции энергии коэффициентов вейвлет-преобразования. Реализация предложенного метода при разработке приложений, связанных с локализацией и распознаванием символьной информации, повысила универсальность таких систем за счет повышения точности локализации символьной информации путем автоматизации выбора масштаба вейвлет-преобразования.У статті запропоновано метод автоматичного визначення масштабу вейвлет-перетворення при локалізації квазіперіодичних послідовностей (текстур, областей з символьною інформацією (СІ) тощо) шляхом аналізу функції енергії коефіцієнтів вейвлет-перетворення. Реалізація методу при розробці додатків, які пов’язані з локалізацією та розпізнаванням символьної інформації, підвищила універсальність таких систем за рахунок збільшення точності локалізації СІ шляхом автоматизації вибору масштабу вейвлет-перетворення.Method of automatically determining wavelet transform scale on the base of analyzing the function of the energy wavelet transform coefficients is proposed. It is used for localization of quasiperiodic sequences (patterns, areas with character information, etc.). The proposed method is used in image processing systems related to the localization and recognition of the symbolic information. It is allowed to increase versatility of such systems by improving the accuracy localization of the symbolic information by automating choice of scale wavelet transform

Greenland surface mass-balance observations from the ice-sheet ablation area and local glaciers

Glacier surface mass-balance measurements on Greenland started more than a century ago, but no compilation exists of the observations from the ablation area of the ice sheet and local glaciers. Such data could be used in the evaluation of modelled surface mass balance, or to document changes in glacier melt independently from model output. Here, we present a comprehensive database of Greenland glacier surface mass-balance observations from the ablation area of the ice sheet and local glaciers. The database spans the 123 a from 1892 to 2015, contains a total of similar to 3000 measurements from 46 sites, and is openly accessible through the PROMICE web portal (http://www.promice.dk). For each measurement we provide X, Y and Z coordinates, starting and ending dates as well as quality flags. We give sources for each entry and for all metadata. Two thirds of the data were collected from grey literature and unpublished archive documents. Roughly 60% of the measurements were performed by the Geological Survey of Denmark and Greenland (GEUS, previously GGU). The data cover all regions of Greenland except for the southernmost part of the east coast, but also emphasize the importance of long-term time series of which there are only two exceeding 20 a. We use the data to analyse uncertainties in point measurements of surface mass balance, as well as to estimate surface mass-balance profiles for most regions of Greenland

Quaternary glaciation history and glaciology of Jakobshavn Isbræ and the Disko Bugt region,

The Disko Bugt region in central West Greenland is characterised by permanent ice streams, of which Jakobshavn Isbræ is by far the most important. The first thorough studies on the glaciology of the region were conducted over 150 years ago by H.J. Rink, who introduced the terms ‘ice streams’ and ‘Inland Ice’. Rink’s work inspired new field work, which has continued to the present, and the long series of observations are unique for an Arctic region.Cooling during the Cenozoic led to ice-sheet growth in Greenland. A number of interglacial occurrences have been reported from the Disko Bugt region, and during the penultimate glacial stage, the Greenland ice-sheet margin extended to the shelf break. During the last glacial maximum, the ice margin probably extended only to the inner part of the banks on the continental shelf, and large floating glaciers may have been present at this time. During the Younger Dryas cold period, the ice margin may have been located at a marked basalt escarpment west of Disko Bugt.Disko Bugt was deglaciated rapidly in the early Holocene, around 10 500 – 10 000 years before present (10.5–10 ka B.P.), but when the ice margin reached the eastern shore of the bay, recession paused, and major moraine systems were formed. With renewed recession, the present ice-margin position was attained around 8–6 ka B.P., and by c. 5 ka B.P. the ice margin was located east of its present position. The subsequent Neoglacial readvance generally reached a maximum during the Little Ice Age, around AD 1850. This was followed by recession that has continued to the present day.The relative sea-level history shows a rapid sea-level fall in the early Holocene, and a slow rise in the late Holocene. This development mainly reflects a direct isostatic response to the ice-margin history.Jakobshavn Isbræ is the main outlet from the Greenland ice sheet. It drains c. 6.5% of the present Inland Ice, and produces c. 35–50 km3 of icebergs per year, corresponding to more than 10% of the total output of icebergs from the Inland Ice. The velocity of the central part of the ice stream at the front has been around 7 km/year since records began, but has nearly doubled in recent years. Other calf-ice producing glacier outlets in Disko Bugt produce c. 18 km3 per year. The large calf-ice production of Jakobshavn Isbræ may have been initiated at about 8 ka B.P. when the glacier front receded from the iceberg bank (Isfjeldsbanken) near Ilulissat. Ice streams in inner and outer Egedesminde Dyb may have been active during the early Holocene and during the last glacial maximum

Quaternary glaciation history and glaciology of Jakobshavn Isbræ and the Disko Bugt region, West Greenland: a review

The Disko Bugt region in central West Greenland is characterised by permanent ice streams, of which Jakobshavn Isbræ is by far the most important. The first thorough studies on the glaciology of the region were conducted over 150 years ago by H.J. Rink, who introduced the terms 'ice streams' and 'Inland Ice'. Rink's work inspired new field work, which has continued to the present, and the long series of observations are unique for an Arctic region. Cooling during the Cenozoic led to ice-sheet growth in Greenland. A number of interglacial occurrences have been reported from the Disko Bugt region, and during the penultimate glacial stage, the Greenland ice-sheet margin extended to the shelf break. During the last glacial maximum, the ice margin probably extended only to the inner part of the banks on the continental shelf, and large floating glaciers may have been present at this time. During the Younger Dryas cold period, the ice margin may have been located at a marked basalt escarpment west of Disko Bugt. Disko Bugt was deglaciated rapidly in the early Holocene, around 10 500–10 000 years before present (10.5–10 ka B.P.), but when the ice margin reached the eastern shore of the bay, recession paused, and major moraine systems were formed. With renewed recession, the present ice-margin position was attained around 8–6 ka B.P., and by c. 5 ka B.P. the ice margin was located east of its present position. The subsequent Neoglacial readvance generally reached a maximum during the Little Ice Age, around AD 1850. This was followed by recession that has continued to the present day. The relative sea-level history shows a rapid sea-level fall in the early Holocene, and a slow rise in the late Holocene. This development mainly reflects a direct isostatic response to the ice-margin history. Jakobshavn Isbræ is the main outlet from the Greenland ice sheet. It drains c. 6.5% of the present Inland Ice, and produces c. 35–50 km3 of icebergs per year, corresponding to more than 10% of the total output of icebergs from the Inland Ice. The velocity of the central part of the ice stream at the front has been around 7 km/year since records began, but has nearly doubled in recent years. Other calf-ice producing glacier outlets in Disko Bugt produce c. 18 km3 per year. The large calf-ice production of Jakobshavn Isbræ may have been initiated at about 8 ka B.P. when the glacier front receded from the iceberg bank (Isfjeldsbanken) near Ilulissat. Ice streams in inner and outer Egedesminde Dyb may have been active during the early Holocene and during the last glacial maximum