In-situ basal melt rate distribution of the floating tongue of 79°N Glacier, Greenland

2020 ◽  
Author(s):  
Ole Zeising ◽  
Daniel Steinhage ◽  
Niklas Neckel ◽  
Julia Christmann ◽  
Veit Helm ◽  
...  
Keyword(s):  
Greenland Ice Sheet ◽  
Repeated Measurements ◽  
Ultra Wideband ◽  
North East ◽  
The North ◽  
Dense Grid ◽  
Phase Sensitive ◽  
Hinge Zone ◽  
Wideband Radar

<p>The 79°N Glacier (79NG) in northeast Greenland, one of the last glaciers in Greenland with a floating ice tongue, plays a crucial role for buttressing the North-East Greenland Ice Stream (NEGIS). Remote-sensing studies indicate high basal melt rates (> 50 m/a) near the grounding line but these methods are limited by the hinge zone, where the floating ice is not in hydrostatic equilibrium. As part of the Greenland Ice Sheet Ocean Interaction (GROCE) project, we have performed a dense grid of repeated measurements with a phase-sensitive radio echo sounder (pRES) accompanied with autonomous pRES (ApRES) stations to estimate basal melt rates focusing on the hinge zone of 79NG. For analysing the pRES measurements, we additionally used ice thickness information derived from AWI’s ultra-wideband radar (UWB) revealing steep channels at the base. The estimated basal melt rates downstream the hinge zone are approximately the same as satellite-derived melt rates. In the hinge zone we found by far larger basal melt rates exceeding 100 m/a next to basal channels.</p>

scholarly journals The effect of the north-east ice stream on the Greenland ice sheet in changing climates

2007 ◽  
Vol 1 (1) ◽  
pp. 41-76 ◽  
Author(s):  
R. Greve ◽  
S. Otsu
Keyword(s):  
Large Scale ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Simulation Code ◽  
North East ◽  
The North ◽  
Ice Stream ◽  
Basal Sliding ◽  
Speed Up ◽  
Fast Flow

Abstract. The north-east Greenland ice stream (NEGIS) was discovered as a large fast-flow feature of the Greenland ice sheet by synthetic aperture radar (SAR) imaginary of the ERS-1 satellite. In this study, the NEGIS is implemented in the dynamic/thermodynamic, large-scale ice-sheet model SICOPOLIS (Simulation Code for POLythermal Ice Sheets). In the first step, we simulate the evolution of the ice sheet on a 10-km grid for the period from 250 ka ago until today, driven by a climatology reconstructed from a combination of present-day observations and GCM results for the past. We assume that the NEGIS area is characterized by enhanced basal sliding compared to the "normal", slowly-flowing areas of the ice sheet, and find that the misfit between simulated and observed ice thicknesses and surface velocities is minimized for a sliding enhancement by the factor three. In the second step, the consequences of the NEGIS, and also of surface-meltwater-induced acceleration of basal sliding, for the possible decay of the Greenland ice sheet in future warming climates are investigated. It is demonstrated that the ice sheet is generally very susceptible to global warming on time-scales of centuries and that surface-meltwater-induced acceleration of basal sliding can speed up the decay significantly, whereas the NEGIS is not likely to dynamically destabilize the ice sheet as a whole.

The waterbodies of the Dallol volcano: A physico-chemical and geo-microbial survey

2020 ◽  
Author(s):  
Hugo Moors ◽  
Miroslav Honty ◽  
Carla Smolders ◽  
Ann Provoost ◽  
Mieke De Craen ◽  
...  
Keyword(s):  
Saline Water ◽  
Halophilic Archaea ◽  
Mining Area ◽  
Ex Situ ◽  
Base Region ◽  
The South ◽  
North East ◽  
The North ◽  
Physico Chemical

<p>The geological extreme Dallol region, located around the Dallol volcano in the north-east of Danakil depression (Ethiopia), is considered as one of the harshest and hottest places on Earth. The geology is made up of years and years of evaporates accumulation. Volcanic activity generates ascending brines that may cross and mix with aquifers from inflowing meteoric water originating from the Ethiopian highlands on the east of the Danakil depression. When these mixtures reach the surface they can generate hydrothermal springs giving rise to waterbodies in the form of small ponds or lakes. During the Europlanet 2018 Danakil field expedition, ten of these saline waterbodies were extensively studied by <em>in situ</em> measurements and <em>ex situ</em> geo–physico-chemical and –microbiological analyses of collected samples, liquids as well as sediments.</p><p>The <em>in situ</em> physico-chemical measurements clearly indicated the extreme nature of all ten investigated lakes. Laboratory analyses of the collected batch samples of liquids and sediments confirmed the extreme character of the waterbodies and complements our geological survey of the region with valuable geo–chemical and –microbiological data.</p><p>Based on our analytical results, the relative small Dallol region can still be subdivided into three geological smaller areas: the outcrop zone, the volcanic base region and the distant south area. The outcrop zone is dominated by sodium, iron and potassium. Oxidation processes in the outflowing superheated ferrous and sulfidic rich brine give rise to some of the most acidic ponds on our planet. In the ponds and lakes of the volcanic base region, incredible high amounts of calcium and/or magnesium can remain in their dissolved form as the most dominant and quasi only available anion is chloride. This region is host for the most saline water body on Earth. Chemical analysis of the lakes of the distant south area show that sodium is by far the most dominant cation. It is therefore no surprise that the large Karum Lake in the south region is economically exploited for the mining of sodium chloride.</p><p>Our mineralogy analyses render results that are completely in line with the observed geochemistry of the waterbodies. Halite and sylvite are the most present minerals in the Dallol outcrop zone associated with some gypsum and in one case with anhydrite. The geology around the waterbodies of volcanic base zone are a little bit more divers. On the shores of the Gaet’ale Pond tachyhydrite, chloromagnesite, halite and sylvite is determined, while the Black Lake is surrounded by bischofite and carnalite. Logically, the mineralogy of the south area, the salt mining area, is dominated by halite and sylvite.</p><p>Apparently, the geochemistry of the outcrop zone and volcanic base region is so harsh that no extremophilic organism is able to survive in these areas. Only in the distant south area did we find indications of the presence of halophiles. Besides the bacterial genus <em>Salinibacter</em>, our 16S rDNA microbiological fingerprinting indicates the presence of halophilic archaea like:  <em>Halobaculum sp., Halobellus sp., Halomicroarcula sp., Halorientalis sp.</em> with the majority of the population being <em>Candidatus Nanosalina sp</em>.</p>

Louis Hunton (1814-1838) - English Pioneer in Ammonite Biostratigraphy

1984 ◽  
Vol 3 (1) ◽  
pp. 58-68 ◽  
Author(s):  
H. Torrens ◽  
T. Getty
Keyword(s):  
Family Business ◽  
Scientific Work ◽  
North East ◽  
The North ◽  
The Family ◽  
The Subject ◽  
First Time ◽  
Practical Demonstration ◽  
Open Cast

In any discussion of the historical development of what was later to be named Biostratigraphy it is often assumed that a modern basis for the subject had already been reached by the cumulative work in the subject up to 1815; culminating in that of William Smith (1769-1839) and Alexandre Brongniart (1770-1847). But to this time fossils had only been used to identify (and discriminate between) often repetitive lithological units or to establish a relationship between rock units in different areas. The practical demonstration that particular lithological units could be regularly subdivided with significant consequences, on the basis of their contained fossils was a later achievement over several generations. One of the first to free stratigraphical palaeontology from such a lithological control was the forgotten Englishman Louis Hunton (1814-1838). In this paper Hunton's origins from a successful alum making family in the north-east of Yorkshire in the north of England and his short life and scientific work are described for the first time. The family business of alum making from the highly fossiliferous local alum shales, which were extracted open-cast, directly introduced Hunton to stratigraphical palaeontology. He followed up this work by study in London, where his pioneering paper was read to the Geological Society of London in 1836. He died less than 2 years later but had helped lay a foundation for major biostratigraphic advances by his insistence that only fossils collected in situ should be used in such work and then that the species, of especially ammonites, in his Yorkshire strata had particularly limited and invariable relative positions within that lithological sequence. His work is also compared with that of his contemporary W.C. Williamson and the conclusion reached that Hunton, because of his emphasis in the merits of ammonites, deserves more to be remembered as a pioneer of Jurassic biostratigraphy.

scholarly journals Petroleum potential of the Upper Jurassic Hareelv Formation, Jameson Land, East Greenland

2018 ◽  
pp. 85-113 ◽  
Author(s):  
Jørgen A. Bojesen-Koefoed ◽  
Morten Bjerager ◽  
H. Peter Nytoft ◽  
Henrik I. Petersen ◽  
Stefan Piasecki ◽  
...  
Keyword(s):  
Significant Proportion ◽  
Upper Jurassic ◽  
Geochemical Data ◽  
Eastern Canada ◽  
Petroleum Potential ◽  
East Greenland ◽  
North East ◽  
The North ◽  
Clay Formation

The marine, mudstone-dominated Hareelv Formation (Upper Jurassic) of Jameson Land, East Greenland is a representative of the widespread Kimmeridge Clay Formation equivalents, sensu lato, known from the greater North Atlantic region, western Siberia and basins off eastern Canada. These deposits constitute the most important petroleum source-rock succession of the region. The present study reports petroleum geochemical data from the 233.8 m thick succession penetrated by the fully cored Blokelv-1 borehole, and includes supplementary data from outcrop samples and other boreholes in Jameson Land. The succession consists of basinal mudstone intercalated with a significant proportion of gravity-flow sandstones, both in situ and remobilised as injectites. The mudstones are generally rich in organic carbon with values of TOC reaching nearly 19 wt% and high pyrolysis yields reaching values of S2 up to nearly 43 kg HC/ton. Hydrogen Indices are up to 363. The data presented herein demonstrate that weathering of abundant pyritic sulfur adversely affects the petroleum potential of the kerogen in outcrop samples. The succession is thermally immature to early mature, except where intrusions have locally heated adjacent mudstones. The documentation of rich gas/oil-prone Upper Jurassic successions in Jameson Land is important for the assessment of the regional petroleum potential, including the North-East Greenland continental shelf.

Marine geophysical evidence for former expansion and flow of the Greenland Ice Sheet across the north-east Greenland continental shelf

2009 ◽  
Vol 24 (3) ◽  
pp. 279-293 ◽  
Author(s):  
Jeffrey Evans ◽  
Colm Ó Cofaigh ◽  
Julian A. Dowdeswell ◽  
Peter Wadhams
Keyword(s):  
Continental Shelf ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
East Greenland ◽  
North East ◽  
The North

II. On a Section of the Lower Chalk near Ely

1864 ◽  
Vol 1 (4) ◽  
pp. 150-154
Author(s):  
Harry Seeley
Keyword(s):  
North East ◽  
The North ◽  
Boulder Clay ◽  
The City ◽  
River Banks

Ely stands on a hill extending somewhat beyond the city as a ridge to the north; and a mile north-east of the Cathedral, at a spot variously named Roslyn or Roswell Hole, its flank is reached at a well-known pit, where the Kimmeridge Clay is dug for mending the river-banks; and the excavation shows some Boulder-clay and Chalk. What the relative positions and relations of these latter deposits may be has been long disputed; some holding that the Chalk is there in sitû, let down by a fault; others maintaining that it is merely such a drifted mass, included in the Boulder-clay, as those which form so strange a feature in the Drift of the Norfolk Coast.† Professor Sedgwick has long been convinced that this latter view is a groundless hyothesis; for when the railway was made from Ely to Lynn, it exposed at about 100 yards off a section showing Kimmeridge Clay and Chalk side by side, and Boulder-clay between them; so the conclusion inevitably followed that there had been a great fault; letting down the Chalk for at least two or three hundred feet. This section was still to be seen in the spring of 1860, when I examined it. The faulted faces of both stratified formations were perfectly erect, parted by a column of Boulder-clay, some twelve feet wide, which from a distance looked like a basaltic dyke.

scholarly journals Seamount physiography and biology in the north-east Atlantic and Mediterranean Sea

2013 ◽  
Vol 10 (5) ◽  
pp. 3039-3054 ◽  
Author(s):  
T. Morato ◽  
K. Ø. Kvile ◽  
G. H. Taranto ◽  
F. Tempera ◽  
B. E. Narayanaswamy ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Biological Diversity ◽  
Morphological Characteristics ◽  
East Atlantic ◽  
Late 19Th Century ◽  
North East ◽  
The North ◽  
The Mediterranean ◽  
Area North

Abstract. This work aims at characterising the seamount physiography and biology in the OSPAR Convention limits (north-east Atlantic Ocean) and Mediterranean Sea. We first inferred potential abundance, location and morphological characteristics of seamounts, and secondly, summarized the existing biological, geological and oceanographic in situ research, identifying examples of well-studied seamounts. Our study showed that the seamount population in the OSPAR area (north-east Atlantic) and in the Mediterranean Sea is large with around 557 and 101 seamount-like features, respectively. Similarly, seamounts occupy large areas of about 616 000 km2 in the OSPAR region and of about 89 500 km2 in the Mediterranean Sea. The presence of seamounts in the north-east Atlantic has been known since the late 19th century, but overall knowledge regarding seamount ecology and geology is still relatively poor. Only 37 seamounts in the OSPAR area (3.5% of all seamounts in the region), 22 in the Mediterranean Sea (9.2% of all seamounts in the region) and 25 in the north-east Atlantic south of the OSPAR area have in situ information. Seamounts mapped in both areas are in general very heterogeneous, showing diverse geophysical characteristics. These differences will likely affect the biological diversity and production of resident and associated organisms.

scholarly journals Decadal Dynamics of the CO2 System and Associated Ocean Acidification in Coastal Ecosystems of the North East Atlantic Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Jean-Philippe Gac ◽  
Pierre Marrec ◽  
Thierry Cariou ◽  
Emilie Grosstefan ◽  
Éric Macé ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Ocean Acidification ◽  
Dissolved Inorganic Carbon ◽  
Coastal Ecosystems ◽  
Total Alkalinity ◽  
East Atlantic ◽  
North East ◽  
The North ◽  
The Impact

Weekly and bi-monthly carbonate system parameters and ancillary data were collected from 2008 to 2020 in three coastal ecosystems of the southern Western English Channel (sWEC) (SOMLIT-pier and SOMLIT-offshore) and Bay of Brest (SOMLIT-Brest) located in the North East Atlantic Ocean. The main drivers of seasonal and interannual partial pressure of CO2 (pCO2) and dissolved inorganic carbon (DIC) variabilities were the net ecosystem production (NEP) and thermodynamics. Differences were observed between stations, with a higher biological influence on pCO2 and DIC in the near-shore ecosystems, driven by both benthic and pelagic communities. The impact of riverine inputs on DIC dynamics was more pronounced at SOMLIT-Brest (7%) than at SOMLIT-pier (3%) and SOMLIT-offshore (<1%). These three ecosystems acted as a weak source of CO2 to the atmosphere of 0.18 ± 0.10, 0.11 ± 0.12, and 0.39 ± 0.08 mol m–2 year–1, respectively. Interannually, air-sea CO2 fluxes (FCO2) variability was low at SOMLIT-offshore and SOMLIT-pier, whereas SOMLIT-Brest occasionally switched to weak annual sinks of atmospheric CO2, driven by enhanced spring NEP compared to annual means. Over the 2008–2018 period, monthly total alkalinity (TA) and DIC anomalies were characterized by significant positive trends (p-values < 0.001), from 0.49 ± 0.20 to 2.21 ± 0.39 μmol kg−1 year−1 for TA, and from 1.93 ± 0.28 to 2.98 ± 0.39 μmol kg–1 year–1 for DIC. These trends were associated with significant increases of calculated seawater pCO2, ranging from +2.95 ± 1.04 to 3.52 ± 0.47 μatm year–1, and strong reductions of calculated pHin situ, with a mean pHin situ decrease of 0.0028 year–1. This ocean acidification (OA) was driven by atmospheric CO2 forcing (57–66%), Sea surface temperature (SST) increase (31–37%), and changes in salinity (2–5%). Additional pHin situ data extended these observed trends to the 2008–2020 period and indicated an acceleration of OA, reflected by a mean pHin situ decrease of 0.0046 year–1 in the sWEC for that period. Further observations over the 1998–2020 period revealed that the climatic indices North Atlantic Oscillation (NAO) and Atlantic Multidecadal Variability (AMV) were linked to trends of SST, with cooling during 1998–2010 and warming during 2010–2020, which might have impacted OA trends at our coastal stations. These results suggested large temporal variability of OA in coastal ecosystems of the sWEC and underlined the necessity to maintain high-resolution and long-term observations of carbonate parameters in coastal ecosystems.

Validation of GIA models in north-east Greenland using densified GNSS measurements and refined estimates of present-day ice-mass changes

2021 ◽  
Author(s):  
Maria Theresia Kappelsberger ◽  
Undine Strößenreuther ◽  
Mirko Scheinert ◽  
Martin Horwath ◽  
Andreas Groh ◽  
...  
Keyword(s):  
Greenland Ice Sheet ◽  
Repeated Measurements ◽  
East Greenland ◽  
Satellite Gravimetry ◽  
Isostatic Adjustment ◽  
North East ◽  
Elastic Load ◽  
Uplift Rates ◽  
Grace Satellite Gravimetry ◽  
Gnss Measurements

<p>Models of glacial-isostatic adjustment (GIA) exhibit large differences in north-east Greenland, reflecting uncertainties about glacial history and solid Earth rheology. The GIA uncertainties feed back to uncertainties in present-day mass-balance estimates from satellite gravimetry. We present results from repeated and continuous GNSS measurements which provide direct observables of the bedrock displacement. The repeated measurements were conducted within five measurement campaigns between 2008 and 2017. They reveal uplift rates in north-east Greenland in the range of 2.8 to 8.9 mm yr<sup>-1</sup>. We used the observed uplift rates to validate different GIA models in conjunction with estimates of the elastic load deformation induced by present-day ice-mass changes and ocean mass redistribution. To determine present-day ice-mass changes for both the Greenland Ice Sheet and the peripheral glaciers, we combined CryoSat-2 satellite altimetry data with GRACE satellite gravimetry data. The different GIA models were consistently used in all processing steps. Our comparison between observed and predicted uplift rates clearly favours GIA models that show low rates (0.7 to 4.4 mm yr<sup>-1</sup> at the GNSS sites) over GIA models with higher rates of up to 8.3 mm yr<sup>-1</sup>. Applying the correction predicted by the GIA model favoured in north-east Greenland we estimate an ice-mass loss of 233 ± 43 Gt yr<sup>-1</sup> for entire Greenland (including peripheral glaciers) over the period July 2010 to June 2017.</p>

2. On the Destructive Effects of the Waves of the Sea on the North-East Shores of Shetland

1862 ◽  
Vol 4 ◽  
pp. 200-201
Author(s):  
Thomas Stevenson
Keyword(s):  
North Sea ◽  
Present Communication ◽  
North East ◽  
The North ◽  
The North Sea ◽  
The One ◽  
The Waves

The author stated, that the present communication might be regarded as supplementary to the one describing the results of his marine dynamometer, which would be found in the 14th volume of the “Transactions.” On the Bound Skerry of Whalsey, which is only exposed to the waves of the North Sea or German Ocean, he had found, on first landing in 1852, masses of rock, weighing 9½ tons and under, heaped together by the action of the waves at the level of no less than 62 feet above the sea; and others, ranging from 6 to 13½ tons, were found to have been quarried out of their positions in situ, at levels of from 70 to 74 feet above the sea.

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