scholarly journals Gas Hydrate Formation and Dissipation Histories in the Northern Margin of Canada: Beaufort-Mackenzie and the Sverdrup Basins

2012 ◽  
Vol 2012 ◽  
pp. 1-17 ◽  
Author(s):  
Jacek Majorowicz ◽  
Kirk Osadetz ◽  
Jan Safanda
Keyword(s):  
Sea Level ◽  
Canadian Arctic ◽  
Beaufort Sea ◽  
Ice Cover ◽  
Pressure Effects ◽  
Ice Age ◽  
Glacial Ice ◽  
The Holocene ◽  
Surface Temperatures ◽  
Gas Hydrate Formation

Gas hydrates (GHs) are a prominent subsurface feature on the Canadian Arctic continental margin. They occur both onshore and offshore, although they formed generally terrestrially, during the last glacial sea level low-stand, both in a region that was persistently glaciated (Queen Elizabeth Islands Group, Canadian Arctic Archipelago (QEIG)), and in a region that was not persistently glaciated (Mackenzie Delta-Beaufort Sea (MD-BS)). Parts of both regions were transgressed in the Holocene. We study the dynamic permafrost and GH history in both regions using a numerical model to illustrate how changes in setting and environment, especially periodic glacial ice cover, affected GH stability. MD-BS models represent the Mallik wellsite and these models successfully match current permafrost and GH bases observed in the well-studied Mallik wells. The MD-BS models show clearly that GHs have persisted through interglacial episodes. Lower surface temperatures in the more northerly QEIG result in an earlier appearance of GH stability that persists through glacial-interglacial intervals, although the base of GH base stability varies up to 0.2 km during the 100 ka cycles. Because of the persistent glacial ice cover QEIG models illustrate pressure effects attributed to regional ice sheet loading on the bases of both permafrost and GHs since 0.9 MYBP. QEIG model permafrost and GH depths are 572 m and 1072 m, respectively, which is like that observed commonly on well logs in the QEIG. In order to match the observed GH bases in the QEIG it is necessary to introduce ice buildup and thaw gradually during the glacials and interglacials. QEIG sea level rose 100–120 m about 10 ka ago following the most recent glaciation. Shorelines have risen subsequently due to isostatic glacial unloading. Detailed recent history modeling in QEIG coastal regions, where surface temperatures have changed from near zero in the offshore to −20°C in the onshore setting results in a model GH stability base, that is, <0.5 km. These coastal model results are significantly shallower than the inferred average GH base about 1 km in wells, Smith and Judge (1993). QEIG interisland channels are generally shallow and much of the previous shoreline inundated by the Holocene transgression was above the glacial sea level low-stand during the last ice age, resulting in a QEIG setting somewhat analogous to the relict terrestrial GH now transgressed by the shallow Beaufort Sea. It is also possible that the marine conditions were present at emergent shorelines for a shorter time or that the pretransgression subsurface temperatures persisted or were influenced by coastal settings, especially where lateral effects may not be well represented by 1D models.

scholarly journals Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling

1984 ◽  
Vol 5 ◽  
pp. 115-121 ◽  
Author(s):  
N. Reeh
Keyword(s):  
Flow Pattern ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Ice Cover ◽  
Glacial Ice ◽  
North West ◽  
Ice Caps ◽  
Perfectly Plastic

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.

scholarly journals Reconstruction of the Glacial Ice Covers of Greenland and the Canadian Arctic Islands by Three-Dimensional, Perfectly Plastic Ice-Sheet Modelling

1984 ◽  
Vol 5 ◽  
pp. 115-121 ◽  
Author(s):  
N. Reeh
Keyword(s):  
Flow Pattern ◽  
Bottom Topography ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Canadian Arctic ◽  
Ice Cover ◽  
Glacial Ice ◽  
North West ◽  
Ice Caps ◽  
Perfectly Plastic

A three-dimensional perfectly plastic ice-sheet model, developed for determining the surface elevations and the flow pattern of an ice sheet with given bottom topography and ice-margin positions, is applied to the reconstruction of the glacial ice covers of Greenland and the Canadian Arctic islands. In the northern regions, two different reconstructions have been performed with ice margins along the present 600 and 200 m sea-depth contours, respectively. In central Greenland, the ice margin is considered to be at the outermost ice-margin deposits on the coastal shelf to the west, and at the present 200 m sea-depth contour to the east.The main conclusions to be drawn from the reconstructions are: (1). The flow pattern of the glacial ice cover of Greenland shows a great resemblance to the present one, the central ice divide being displaced less than 50 km from its present position and being no more than 200 m higher than today. (2). The main ice divide of the ice sheet covering the Canadian Arctic islands (the Innuitian ice sheet) was located over the highlands of eastern Ellesmere Island with local domes positioned over the present ice caps, indicating that even the deep ice of Wisconsin age in these ice caps is of local origin. This is also the case for the Devon Island ice cap. (3). Even in the not very likely case of a rather extensive glacial ice cover in north-west Greenland, the ice-flow pattern upstream of the Camp Century deep drill site would not have changed radically compared to the present flow pattern. Thus it is concluded that even advanced ice margins in late-Wisconsin time could at most have resulted in an elevation of the deposition site of the late-Wisconsin ice at Camp Century 600 m higher than at present. The consequences of this conclusion are discussed.

scholarly journals In Anticipation of Extirpation

2020 ◽  
Vol 12 (1) ◽  
pp. 113-131 ◽  
Author(s):  
Patrick D. Nunn
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Age ◽  
Optimal Solutions ◽  
The Holocene ◽  
The Past ◽  
Coastal Cities ◽  
The People ◽  
Northwest Europe ◽  
Last Ice Age

Abstract As concern about sea level rise grows and optimal solutions are sought to address its causes and effects, little attention has been given to past analogs. This article argues that valuable insights into contemporary discussions about future sea level rise can be gained from understanding those of the past, specifically the ways in which coastal peoples and societies reacted during the period of postglacial sea level rise. For much of the Holocene, most continental people eschewed coastal living in favor of inland areas. In many places large coastal settlements appeared only after the development of polities and associated crosswater networks. Postglacial sea level rise affected coastal living in ways about which we remain largely ignorant. Yet, millennia-old stories from Australia and northwest Europe show how people responded, from which we can plausibly infer their motivations. Stories from Australia say the people have succeeded in halting sea level rise, whereas those from northwest Europe indicate that people have failed, leading to the drowning of coastal cities such as Ys (Brittany) and Cantre’r Gwaelod (Wales). This distinction is explained by the contrasting duration of postglacial sea level rise in these regions; around Australia, sea level stopped rising 7,000 years ago, while along many coasts of northwest Europe it has risen unceasingly since the last ice age ended. The nature of past human and societal responses to postglacial sea level rise holds important insights for the future.

scholarly journals Sedimentary archives of climate and sea-level changes during the Holocene in the Rhone prodelta (NW Mediterranean Sea)

2016 ◽  
Author(s):  
Anne-Sophie Fanget ◽  
Maria-Angela Bassetti ◽  
Christophe Fontanier ◽  
Alina Tudryn ◽  
Serge Berné
Keyword(s):  
Sea Level ◽  
Water Depth ◽  
Late Holocene ◽  
Ice Age ◽  
Sea Level Changes ◽  
The Holocene ◽  
The Core ◽  
Core Site ◽  
Nw Mediterranean ◽  
And Sea Level

Abstract. A 7.38 m-long sediment core was collected from the eastern part of the Rhone prodelta (NW Mediterranean) at 67 m water depth. A multi-proxy study (sedimentary facies, benthic foraminifera and ostracods, clay mineralogy, and major elements from XRF) provides a multi-decadal to century-scale record of climate and sea-level changes during the Holocene. The early Holocene is marked by alternative silt and clay layers interpreted as distal tempestites deposited in a context of rising sea level. This interval contains shallow infra-littoral benthic meiofauna (e.g. Pontocythere elongata, Elphidium spp., Quinqueloculina lata) and formed between ca. 20 and 50 m water depth. The middle Holocene (ca. 8.3 to 4.5 ka cal. BP), is characterized, at the core site, by a period of sediment starvation (accumulation rate of ca. 0.01 cm yr−1) resulting from the maximum landward shift of the shoreline and the Rhone outlet(s). From a sequence stratigraphic point of view, this condensed interval, about 35 cm-thick, is a Maximum Flooding Surface that can be identified on seismic profiles as the transition between delta retrogradation and delta progradation. It is marked by very distinct changes in all proxy records. Following the stabilization of the global sea level, the late Holocene is marked by the establishment of prodeltaic conditions at the core site, as shown by the lithofacies and by the presence of benthic meiofauna typical of the modern Rhone prodelta (e.g. Valvulineria bradyana, Cassidulina carinata, Bulimina marginata). Several periods of increased fluvial discharge are also emphasized by the presence of species commonly found in brackish and shallow water environments (e.g. Leptocythere). Some of these periods correspond to the multi-decadal to centennial late Holocene humid periods recognized in Europe (i.e. the 2.8 ka event and the Little Ice Age). Two other periods of increased runoffs at ca. 1.3 and 1.1 ka cal. BP are recognized, and are likely to reflect periods of regional climate deterioration that are observed in the Rhone watershed.

Geophysical evidence for a large Holocene ice marginal moraine of Skeiðarárjökull, SE Iceland

2020 ◽  
Author(s):  
Devin Harrison ◽  
Neil Ross ◽  
Andrew Russell ◽  
Stuart Jones
Keyword(s):  
Surface Morphology ◽  
Environmental History ◽  
Sea Level ◽  
Low Frequency ◽  
Ice Age ◽  
The Holocene ◽  
Geophysical Surveys ◽  
History Of ◽  
Ground Penetrating ◽  
Surface Geomorphology

&lt;p&gt;The sedimentary record of Icelandic ice-contact environments provides valuable information about glacier margin dynamics and position, relative sea-level and the geomorphic processes driving proglacial environments. This important archive has been little exploited, however, with most glacier and sea level reconstructions based on limited sedimentary exposures and surface geomorphic evidence. Although geophysical surveys of Icelandic sandur have been conducted, they have often been of limited spatial scale and focused on specific landforms. Here, we report an extensive (42 km of data) detailed low-frequency (40 and 100 MHz) ground-penetrating radar (GPR) survey of the Sandgig&amp;#250;r moraine complex, SE Iceland, which transforms our understanding of this landform, with implications for the Holocene history of Skei&amp;#240;ar&amp;#225;rsandur and SE Iceland.&lt;/p&gt;&lt;p&gt;The Sandgig&amp;#250;r moraines are located on Skei&amp;#240;ar&amp;#225;rsandur, SE Iceland, down-sandur of large Little Ice Age-moraines of Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull. They have a relatively subtle surface geomorphic expression (typically 125 m wide and 7 m high), and knowledge of their formation is limited, with no dating control on their age or detailed geomorphic or sedimentological investigations. &amp;#160;GPR investigations reveal a much larger (60 m high and 1200 m wide) and extensive buried moraine complex than that suggested by surface morphology, suggesting that the moraine was a major Holocene ice margin of Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull.&lt;/p&gt;&lt;p&gt;GPR reflections interpreted as large progradational foresets (up to 20 m in height) beneath the morainic structure are consistent with a sub-aqueous depositional environment before moraine formation, providing potential controls on former sea-level. &amp;#160;The GPR data also provide information on the internal structure of the moraine, with evidence for glacitectonism within the proximal side of the moraine, multiphase moraine formation, and possible buried ice at depth. A 30-40 m thick package of down-sandur dipping GPR reflections drape the leeside of the moraine, evidencing glaciofluvial deposition during and after moraine development. Potential moraine breaches, possibly caused by glaciofluvial (e.g. j&amp;#246;kulhlaup) events, are also apparent within the GPR data and the surface geomorphology.&lt;/p&gt;&lt;p&gt;We combine GPR-derived subsurface architecture with the current surface morphology to develop a conceptual model detailing the geomorphic evolution of the moraines and surrounding region, from pre-moraine morphology, to their formation and breaching, resulting in the subsequent present-day morphology. These results provide new insights into the Holocene to present-day evolution of Skei&amp;#240;ar&amp;#225;rsandur and Skei&amp;#240;ar&amp;#225;rj&amp;#246;kull, with implications for reconstructions of the Holocene environmental history of SE Iceland.&lt;/p&gt;

Geological, Paleoclimatological, and Archaeological History of the Baltic Sea Region Since the Last Glaciation

2020 ◽  
Author(s):  
Jan Harff ◽  
Hauke Jöns ◽  
Alar Rosentau
Keyword(s):  
Baltic Sea ◽  
Sea Level Rise ◽  
Sea Level ◽  
Little Ice Age ◽  
Environmental Changes ◽  
Ice Age ◽  
The Baltic Sea ◽  
The Holocene ◽  
Socioeconomic System ◽  
The Baltic

The correlation of climate variability; the change environment, in particular the change of coastlines; and the development of human societies during the last millennia can be studied exemplarily in the Baltic area. The retreat of the Scandinavian ice-sheet vertical crustal movement (glacio-isostatic adjustment), together with climatically controlled sea-level rise and a continuously warming atmosphere, determine a dramatic competition between different forcings of the environment that advancing humans are occupying step by step after the glaciation. These spatially and temporally changing life conditions require a stepwise adjustment of survival strategies. Changes in the natural environment can be reconstructed from sedimentary, biological proxy data and archaeological information. According to these reconstructions, the main shift in the Baltic area’s environment happened about 8,500 years before present (BP) when the Baltic Sea became permanently connected to the Atlantic Ocean via the Danish straits and the Sound, and changed the environment from lacustrine to brackish-marine conditions. Human reaction to environmental changes in prehistoric times is mainly reconstructed from remains of ancient settlements—onshore in the uplifting North and underwater in the South dominated by sea-level rise. According to the available data, the human response to environmental change was mainly passive before the successful establishment of agriculture. But it became increasingly active after people settled down and the socioeconomic system changed from hunter-gatherer to farming communities. This change, mainly triggered by the climatic change from the Holocene cool phase to the warming period, is clearly visible in Baltic basin sediment cores as a regime shift 6,000 years (BP). But the archaeological findings prove that the relatively abrupt environmental shift is reflected in the socioeconomic system by a period of transition when hunter-gatherer and farming societies lived in parallel for several centuries. After the Holocene warming, the permanent regression in the Northern Baltic Sea and the transgression in the South did affect the socioeconomic response of the Baltic coastal societies, who migrated downslope at the regressive coast and upslope at the transgressive coast. The following cooling phases, in particular the Late Antique Little Ice Age (LALIA) and the Little Ice Age (LIA), are directly connected with migration and severe changes of the socioeconomic system. After millennia of passive reaction to climate and environmental changes, the Industrial Revolution finally enabled humans to influence and protect actively the environment, and in particular the Baltic Sea shore, by coastal constructions. On the other hand, this ability also affected climate and environment negatively because of the disturbance of the natural balance between climate, geosystem, and ecosystem.

Late Quaternary seismic stratigraphy of the inner shelf seaward of the Tuktoyaktuk Peninsula, Canadian Beaufort Sea

1989 ◽  
Vol 26 (10) ◽  
pp. 1990-2002 ◽  
Author(s):  
Arnaud Héquette ◽  
Philip R. Hill
Keyword(s):  
Sea Level ◽  
Land Surface ◽  
Large Scale ◽  
Late Quaternary ◽  
Lower Boundary ◽  
Beaufort Sea ◽  
Seismic Stratigraphy ◽  
Inner Shelf ◽  
The Holocene ◽  
Late Wisconsinan

This paper describes the seismic stratigraphy of the Quaternary sediments on the inner shelf (< 20 m water depth) of the Canadian Beaufort Sea, seaward of the Tuktoyaktuk Peninsula. Two regional unconformities and three seismic sequences are defined from the high-resolution seismic records. The deeper sequence (sequence III) is characterized by large-scale cross-beds. This sequence has been correlated with the Tingmiark Sand lithostratigraphic unit, which was previously defined farther offshore and is thought to be a glaciofluvial unit deposited during lower-than-present sea-level conditions in the Late Wisconsinan. The lower boundary of the overlying sequence (sequence II) is an unconformity (u/c 2), interpreted as the pre-transgression land surface. Sequence II is discontinuous and consists of localized basin-fill and channel-fill units. Most of these are remnants of thermokarst lakes partially eroded during the Holocene transgression. This sequence is separated from the uppermost sequence (sequence I) by another unconformity (u/c 1), which is the shoreface erosion surface generated by the Holocene sea-level rise. Sequence I is composed of a transgressive sand sheet overlain, in deeper areas, by recent marine muds. Seaward of Hutchison Bay, a large subbottom depression within sequence III in interpreted as a Late Wisconsinan fluviatile channel. According to our seismic interpretation, the Tuk Phase morainal and glaciofluvial deposits existing onland on the Tuktoyaktuk Peninsula, previously assigned to the Early Wisconsinan, would be of Late Wisconsinan age.

scholarly journals The Quaternary geology of the Narssaq area, South Greenland

1979 ◽  
Vol 86 ◽  
pp. 1-24
Author(s):  
S Funder
Keyword(s):  
Sea Level ◽  
Ice Cover ◽  
Quaternary Geology ◽  
Ice Age ◽  
Ice Thickness ◽  
Glacial Deposit ◽  
Rock Types ◽  
Local Topography ◽  
Bedrock Surface ◽  
Minimum Estimate

The topography and glacial striations in the Narssaq area indicate that the ice age glacial regime in this part of Greenland was characterized by ice movement constrained by the local topography, and a shallow depth of the ice cover. Erratics observed 1200 m above sea level provide a minimum estimate for the ice thickness. The most widespread type of glacial deposit consists of scattered boulders Iying on the glacially abraded bedrock surface with loose fillings of sand and gravet washed into depressions; this deposit probably reflects the debris content of the ice cover in a final short lasting phase of stagnation and melting. Counting of the boulders and stones shows that the travelling distances generally are short: rock types which are exposed as bedrock less than 1 km away comprise on average 72 % of the material. Some rock types, i.e. the syenites of the Precambrian Ilimaussaq Intrusion, decrease very rapidly in their frequencies as erratics downstream from their exposures, indicating that they were selectively crushed during transportation. The large spatial variation in the 'boulder communities' supports the idea of ice movement being directed by the topography, and poor mixing in the ice sheet. The low altitudes of the marine limits (47-60 m above sea level) also may be interpreted to reflect shallow ice thicknesses, while the few available dates for the timing of the isostatic upheaval, indicate that the Narssaq area was free of ice c. 11 000 years ago.

scholarly journals Will Florida be saved?

2016 ◽  
Vol 3 (2) ◽  
pp. 251-260
Author(s):  
Robert G. Johnson
Keyword(s):  
Global Warming ◽  
Sea Level ◽  
Fossil Fuel ◽  
Barents Sea ◽  
Coastal Areas ◽  
Tipping Point ◽  
Ice Age ◽  
Small Scale ◽  
Glacial Ice ◽  
Rising Sea Level

The state of Florida is typical of all the low-lying densely populated coastal areas around the world that are threatened by present and future rising sea level. These coastal areas will become destructively flooded by sea level rise due to melting of the world's glacial ice if fossil fuel consumption and resulting global warming are not strongly limited. Efforts to achieve this limitation in a timely way might not be successful because of cultural inertia, opposition by vested interests, and the difficulties in developing alternative sources of renewable energy on a large scale. However, the rising sea level could be reversed to a more rapidly falling sea level at least temporarily if a previously unrecognized tipping point in the changing climate is reached in coming decades. This tipping point is the onset of rapid new glacial ice sheet growth in northeastern Canada, Greenland, and the Barents Sea. The cause would be an order of magnitude increase in regional precipitation. Much evidence for that event is found in the geological records of the initiation of the last ice age 120,000yrs ago. The precursors for a similar future event are in place and are identified in modern oceanic records. These precursors include the increasing salinity of the Mediterranean Sea and the observed increasing penetration of the Spitsbergen-Atlantic Current into the polar ocean, which suggests that the tipping point may be reached before the end of this century. If so, the flooding may occur on only a small scale. However if so, a sharp 500yr cooling would be expected in eastern Canada and northern Europe, and greenhouse warming elsewhere would continue unless fossil fuel usage is reduced. This paper supports the suggestion by Giff Miller and Anne de Vernal in a 1992 letter to Nature that global warming and an ice age may occur simultaneously.

The Holocene and Global Climate Change

2016 ◽  
Author(s):  
Thomas S. Bianchi
Keyword(s):  
Climate Change ◽  
Sea Level ◽  
Global Climate Change ◽  
Global Climate ◽  
Warm Period ◽  
Ice Age ◽  
The Holocene ◽  
The World ◽  
The Last Glacial

The Pleistocene Epoch, often referred to as the Ice Age, lasted from approximately 2.6 million to 11,700 years ago. The last major ice advance began about 110,000 years ago, and the most recent episode of maximum ice coverage, the Last Glacial Maximum, began about 26,500 years ago and ended approximately 19,000 years ago. Thereafter, glacier retreat began, largely ending by about 11,700 years ago. That marked the beginning of the Holocene interglacial geologic epoch, which continues to the present. During the last glacial period, sea level was much lower because so much water was locked up in ice sheets, largely at the poles. This lowering of the sea level exposed the margins of the continents (the continental shelves) around the world. When the Ice Age ended, sea level started to rise during the deglacial period, a process that continued into the Holocene. Deltaic regions received meltwaters from the thawing glaciers, along with glacier- derived sediments. Of particular note in the late Holocene is a climate episode called the Medieval Warm Period, originally identified by the English botanist Hubert Lamb. The Medieval Warm Period was a time of warm climate in the North Atlantic region and may have also impacted other areas around the world. It lasted from about the years 950 to 1250. Later in this chapter, I will discuss this climate anomaly, along with something called the “Hockey Stick” debate, which relates to exceptional warming during recent centuries of the Holocene (i.e., global warming). In any case, all modern and paleodeltas formed during periods of peak sea level in the Holocene. These new deltas had fertile soils that were constantly irrigated by the flow of fresh water, which promoted early settlement by humans. So, the Holocene started near the end of the retreat of the Pleistocene glaciers, and human civilizations arose entirely in the Holocene Epoch. To view the Holocene, simply look around you today. In this chapter, I will explore the natural and human-induced causes of global climate change and how they impact deltaic regions.

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