Artykuły naukowe (WNGiG)
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Browsing Artykuły naukowe (WNGiG) by Subject "Arctic"
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Item Fossil organic carbon utilization in marine Arctic fjord sediments by subsurface micro-organisms(2023-07) Ruben, Manuel; Hefter, Jens; Schubotz, Florence; Geibert, Walter; Butzin, Martin; Gentz, Torben; Grotheer, Hendrik; Forwick, Matthias; Szczuciński, Witold; Mollenhauer, GesineRock-derived or petrogenic organic carbon has traditionally been regarded as being non-bioavailable and bypassing the active carbon cycle when eroded. However, it has become apparent that this organic carbon might not be so inert, especially in fjord systems where petrogenic organic carbon influxes can be high, making its degradation another potential source of greenhouse gas emissions. The extent to which subsurface micro-organisms use this organic carbon is not well constrained, despite its potential impacts on global carbon cycling. Here, we performed compound-specific radiocarbon analyses on intact polar lipid–fatty acids of live micro-organisms from marine sediments in Hornsund Fjord, Svalbard. By this means, we estimate that local bacterial communities utilize between 5 ± 2% and 55 ± 6% (average of 25 ± 16%) of petrogenic organic carbon for their biosynthesis, providing evidence for the important role of petrogenic organic carbon as a substrate after sediment redeposition. We hypothesize that the lack of sufficient recently synthesized organic carbon from primary production forces micro-organisms into utilization of petrogenic organic carbon as an alternative energy source. The input of petrogenic organic carbon to marine sediments and subsequent utilization by subsurface micro-organisms represents a natural source of fossil greenhouse gas emissions over geological timescales.Item Glacio−meteorology of Ebbabreen, Dickson Land, central Svalbard, during 2008–2010 melt seasons(De Gruyter, 2015-06-25) Małecki, JakubInterior of Svalbard, High Arctic, is relatively arid and warm during the summer, but impact of this quasi-continental climate type on the glacio-meteorology, surface energy balance and melt processes has been seldom researched. This study brings new data from a weather station located on the largest glacier in Dickson Land, Ebbabreen, at 550 m a.s.l from July and August 2008-2010. The paper discusses air temperature and moisture, wind speed, incoming shortwave radiation and estimates of turbulent heat exchange of the melting surface in the background of atmospheric circulation over Svalbard. The results have shown that average insolation in the study area was low with ca. 135 W m-2. Frequent occurrence of strongly negative temperature gradients resulted in mean July-August air temperature of 1.9°C at the measuring site. Relatively low air vapour pressure led to negative latent heat flux, particularly during advection of air masses from the northern and north-eastern sector. The local microclimate supports the sensible heat transfer, which reached its maximum during eastern circulation situations.Item Ice tectonics and bedrock relief control on glacial sedimentation – an example from Hansbreen, Spitsbergen(Pracownia Sztuk Plastycznych Sp. z o.o., 2000) Rachleiwcz, Grzegorz; Szczuciński, WitoldHansbreen, a tidewater glacier in southern Spitsbergen, was investigated to reveal the relationship between its tectonic and mode of deposition. In the land terminating zone the bedrock threshold plays major role in sedimentation by creating compression conditions. It causes the most of sediment to be released supraglacially, and redeposited in form of debris flows. The upward debris transport is done mostly by folding deformation of basal ice layer with a minor participation of thrusts. In observed outcrops no subglacial deformed layer of till was found. The debris occurrence was associated only with the debris-rich basal ice layer. However on the foreland exists subglacial till, partly formed in flutings, also with micromorphological evidence of deformations. Various bedrock morphology is supposed to differentiate basal conditions. The flat, but undulated, regelation favouring conditions, leads to the debris-rich basal ice layer formation, however inclined but non undulated relief prefers deformed subglacial sediments development. No structural or sedimentological evidence of surge events were found in the tributary glaciers (Fuglebreen, Tuvbreen), hence this phenomenon is thought to be limited to the main ice stream.Item Post−surge geometry and thermal structure of Hørbyebreen, central Spitsbergen(De Gruyter, 2013-10-05) Małecki, Jakub; Faucherre, Samuel; Strzelecki, MateuszHørbyebreen surged in the 19th or early 20th century, as suggested by geomorphological evidences and looped medial moraines. In this study, we investigate its wide-spread geometry changes and geodetic mass balance with 1960 contour lines, 1990 and 2009 digital elevation models, in order to define the present-day state of the glacier. We also study its thermal structure from ground-penetrating radar data. Little is known on the glacier behaviour in the first part of the 20th century, but from the surge maximum until 1960 it has been retreating and losing its area. In the period 1960-1990, fast frontal thinning (2-3 m a-1) and a slow mass build-up in the higher zones (~0.15 m a-1) have been noted, resulting in generally negative mass balance (-0.40 ± 0.07 m w. eq. a-1). In the last studied period 1990-2009, the glacier showed an acceleration of mass loss (-0.64 m ± 0.07 w. eq. a-1) and no build-up was observed anymore. We conclude that Hørbyebreen system under present climate will not surge anymore and relate this behaviour to a considerable increase in summer temperature in Svalbard after 1990. Radar soundings indicate that the studied glacial system is polythermal, with temperate ice below 100-130 m depth. It has therefore not (or not yet) switched to cold-bedded, as has been suggested in previous works for some small Svalbard surge-type glaciers in a negative mass balance mode.Item Sedimentary evidence for a mid-Holocene iceberg-generated tsunami in a coastal lake, west Greenland(2015-12) Long, Antony J.; Szczuciński, Witold; Lawrence, ThomasWe report sedimentological evidence for a tsunami from a coastal lake at Innaarsuit, Disko Bugt (west Greenland), which was most likely generated by a rolling iceberg. The tsunami invaded the lake c. 6000 years ago, during a period of time when relative sea level (RSL) was falling quickly because of isostatic rebound. We use the background rate of RSL fall, together with an age model for the sediment sequence, to infer a minimum wave run-up during the event of c. 3.3 m. The stratigraphic signature of the event bears similarities to that described from studies of the early-Holocene Storegga slide tsunami in Norwegian coastal basins. Conditions conducive to iceberg tsunami include a supply of icebergs, deep water close to the shore, a depositional setting protected from storms or landslide tsunami, and a coastal configuration that has the potential to amplify the height of tsunami waves as water depths shallow and the waves approach and impact the coast. Future warming of polar regions will lead to increased calving and iceberg production, at a time when human use of polar coasts will also grow. We predict, therefore, that iceberg-generated tsunami will become a growing hazard in polar coastal waters, especially in areas adjacent to large, fast-flowing, marine-terminating ice streams that are close to human populations or infrastructure.Item Sedimentological characteristics of debris flow Deposits within ice−cored moraine of Ebbabreen, central Spitsbergen(De Gruyter / © Polish Academy of Sciences, 2016-06-25) Pleskot, KrzysztofThe Ebbabreen ice−cored moraine area is covered with a sediment layer of up to 2.5 m thick, which mostly consists of massive diamicton. Due to undercutting by lateral streams, debris flow processes have been induced in marginal parts of this moraine. It was recognized that the sedimentology of deposits within the deposition area of debris flows is the effect of: (1) the origin of the sediments, (2) the nature of the debris flow, and (3) post−debris flow reworking. Analysis of debris flow deposits in microscale (thin sections) suggests a common mixing during flow, even though a small amount of parent material kept its original structure. The mixing of sediments during flow leads to them having similar sedimentary characteristics across the deposition area regardless of local conditions (i.e. slope angle, water content, parent material lithology). After the deposition of sediments that were transported by the debris flow, they were then reworked by a further redeposition process, primarily related to meltwater stream action.