Literatura científica selecionada sobre o tema "Sea ice retreat"
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Artigos de revistas sobre o assunto "Sea ice retreat"
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Dong, K., ØK Kvile, NC Stenseth e LC Stige. "Associations among temperature, sea ice and phytoplankton bloom dynamics in the Barents Sea". Marine Ecology Progress Series 635 (6 de fevereiro de 2020): 25–36. http://dx.doi.org/10.3354/meps13218.
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Variations in physical conditions caused by climate change are likely to have large influences on marine organisms, including phytoplankton. Here, we investigated associations between satellite-derived chlorophyll a data from the Barents Sea and 2 key abiotic factors: sea surface temperature and sea-ice concentration. Specifically, we investigated how climate variability, through the measured physical factors, associated with phytoplankton phenology between 1998 and 2014. Associations between sea surface temperature and phytoplankton bloom dynamics differed depending on the area. The spring phytoplankton bloom occurred earlier and had higher magnitude in warm compared to cold years in the northern part of the Barents Sea, but there was no significant association in the southern part. In seasonally ice-covered regions, the association between the timing of the sea-ice retreat and the phytoplankton peak was nonlinear: sea-ice retreat time before mid-May was not associated with bloom timing, whereas the phytoplankton bloom occurred before or immediately following the ice retreat when the ice retreated after mid-May. Although drivers that are relatively constant across years, such as insolation, probably influenced the spatial gradient in chlorophyll, a space-for-time substitution captured the predicted effects of sea-ice retreat on the timing and magnitude of the phytoplankton bloom quite well.
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Eisenman, Ian, Tapio Schneider, David S. Battisti e Cecilia M. Bitz. "Consistent Changes in the Sea Ice Seasonal Cycle in Response to Global Warming". Journal of Climate 24, n.º 20 (15 de outubro de 2011): 5325–35. http://dx.doi.org/10.1175/2011jcli4051.1.
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Abstract The Northern Hemisphere sea ice cover has diminished rapidly in recent years and is projected to continue to diminish in the future. The year-to-year retreat of Northern Hemisphere sea ice extent is faster in summer than winter, which has been identified as one of the most striking features of satellite observations as well as of state-of-the-art climate model projections. This is typically understood to imply that the sea ice cover is most sensitive to climate forcing in summertime, and previous studies have explained this by calling on factors such as the surface albedo feedback. In the Southern Hemisphere, however, it is the wintertime sea ice extent that retreats fastest in climate model projections. Here, it is shown that the interhemispheric differences in the model projections can be attributed to differences in coastline geometry, which constrain where sea ice can occur. After accounting for coastline geometry, it is found that the sea ice changes simulated in both hemispheres in most climate models are consistent with sea ice retreat being fastest in winter in the absence of landmasses. These results demonstrate that, despite the widely differing rates of ice retreat among climate model projections, the seasonal structure of the sea ice retreat is robust among the models and is uniform in both hemispheres.
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Carr, J. Rachel, Chris Stokes e Andreas Vieli. "Recent retreat of major outlet glaciers on Novaya Zemlya, Russian Arctic, influenced by fjord geometry and sea-ice conditions". Journal of Glaciology 60, n.º 219 (2014): 155–70. http://dx.doi.org/10.3189/2014jog13j122.
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AbstractSubstantial ice loss has occurred in the Russian High Arctic during the past decade, predominantly on Novaya Zemlya, yet the region has been studied relatively little. Consequently, the factors forcing mass loss and the relative contribution of ice dynamics versus surface melt are poorly understood. Here we evaluate the influence of atmospheric/oceanic forcing and variations in fjord width on the behaviour of 38 glaciers on the northern ice cap, Novaya Zemlya. We compare retreat rates on land- versus marine-terminating outlets and on the Kara versus Barents Sea coasts. Between 1992 and 2010, 90% of the study glaciers retreated and retreat rates were an order of magnitude higher for marine-terminating outlets (52.1 ma-1) than for land-terminating glaciers (4.8ma-1). We identify a post-2000 acceleration in marine-terminating glacier retreat, which corresponded closely to changes in sea-ice concentrations. Retreat rates were higher on the Barents Sea coast, which we partly attribute to lower sea-ice concentrations, but varied dramatically between individual glaciers. We use empirical data to categorize changes in along-flow fjord width, and demonstrate a significant relationship between fjord width variability and retreat rate. Results suggest that variations in fjord width exert a major influence on glacier retreat.
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Stern, Harry L., e Kristin L. Laidre. "Sea-ice indicators of polar bear habitat". Cryosphere 10, n.º 5 (14 de setembro de 2016): 2027–41. http://dx.doi.org/10.5194/tc-10-2027-2016.
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Abstract. Nineteen subpopulations of polar bears (Ursus maritimus) are found throughout the circumpolar Arctic, and in all regions they depend on sea ice as a platform for traveling, hunting, and breeding. Therefore polar bear phenology – the cycle of biological events – is linked to the timing of sea-ice retreat in spring and advance in fall. We analyzed the dates of sea-ice retreat and advance in all 19 polar bear subpopulation regions from 1979 to 2014, using daily sea-ice concentration data from satellite passive microwave instruments. We define the dates of sea-ice retreat and advance in a region as the dates when the area of sea ice drops below a certain threshold (retreat) on its way to the summer minimum or rises above the threshold (advance) on its way to the winter maximum. The threshold is chosen to be halfway between the historical (1979–2014) mean September and mean March sea-ice areas. In all 19 regions there is a trend toward earlier sea-ice retreat and later sea-ice advance. Trends generally range from −3 to −9 days decade−1 in spring and from +3 to +9 days decade−1 in fall, with larger trends in the Barents Sea and central Arctic Basin. The trends are not sensitive to the threshold. We also calculated the number of days per year that the sea-ice area exceeded the threshold (termed ice-covered days) and the average sea-ice concentration from 1 June through 31 October. The number of ice-covered days is declining in all regions at the rate of −7 to −19 days decade−1, with larger trends in the Barents Sea and central Arctic Basin. The June–October sea-ice concentration is declining in all regions at rates ranging from −1 to −9 percent decade−1. These sea-ice metrics (or indicators of habitat change) were designed to be useful for management agencies and for comparative purposes among subpopulations. We recommend that the National Climate Assessment include the timing of sea-ice retreat and advance in future reports.
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Danielson, Matthew A., e Philip J. Bart. "The staggered retreat of grounded ice in the Ross Sea, Antarctica, since the Last Glacial Maximum (LGM)". Cryosphere 18, n.º 3 (8 de março de 2024): 1125–38. http://dx.doi.org/10.5194/tc-18-1125-2024.
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Abstract. The retreat of the West Antarctic Ice Sheet (WAIS) in the Ross Sea after the Last Glacial Maximum (LGM) was more significant than for any other Antarctic sector. Here we combined the available chronology of retreat with new mapping of seismically resolvable grounding zone wedges (GZWs). Mapping GZWs is important because they record the locations of former stillstands in the extent of grounded ice for individual ice streams during the overall retreat. Our analysis shows that the longest stillstands occurred early in the deglacial period and had millennial durations. Stillstands ended abruptly with retreat distances measured in the tens to hundreds of kilometers creating deep embayments in the extent of grounded ice across the Ross Sea. The location of embayments shifted through time. The available chronological data show that cessation of WAIS and East Antarctic Ice Sheet (EAIS) stillstands was highly asynchronous across at least 5000 years. There was a general shift to shorter stillstands throughout the deglacial period. The asynchronous collapse of individual catchments during the deglacial period suggests that the Ross Sea sector would have contributed to multiple episodes of relatively small-amplitude sea-level rise as the WAIS and EAIS retreated from the region. The high sinuosity of the modern grounding zone in the Ross Sea suggests that this style of retreat persists.
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Renner, Martin, Sigrid Salo, Lisa B. Eisner, Patrick H. Ressler, Carol Ladd, Kathy J. Kuletz, Jarrod A. Santora, John F. Piatt, Gary S. Drew e George L. Hunt. "Timing of ice retreat alters seabird abundances and distributions in the southeast Bering Sea". Biology Letters 12, n.º 9 (setembro de 2016): 20160276. http://dx.doi.org/10.1098/rsbl.2016.0276.
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Timing of spring sea-ice retreat shapes the southeast Bering Sea food web. We compared summer seabird densities and average bathymetry depth distributions between years with early (typically warm) and late (typically cold) ice retreat. Averaged over all seabird species, densities in early-ice-retreat-years were 10.1% (95% CI: 1.1–47.9%) of that in late-ice-retreat-years. In early-ice-retreat-years, surface-foraging species had increased numbers over the middle shelf (50–150 m) and reduced numbers over the shelf slope (200–500 m). Pursuit-diving seabirds showed a less clear trend. Euphausiids and the copepod Calanus marshallae/glacialis were 2.4 and 18.1 times less abundant in early-ice-retreat-years, respectively, whereas age-0 walleye pollock Gadus chalcogrammus near-surface densities were 51× higher in early-ice-retreat-years. Our results suggest a mechanistic understanding of how present and future changes in sea-ice-retreat timing may affect top predators like seabirds in the southeastern Bering Sea.
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Levermann, A., J. Mignot, S. Nawrath e S. Rahmstorf. "The Role of Northern Sea Ice Cover for the Weakening of the Thermohaline Circulation under Global Warming". Journal of Climate 20, n.º 16 (15 de agosto de 2007): 4160–71. http://dx.doi.org/10.1175/jcli4232.1.
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Abstract An increase in atmospheric CO2 concentration and the resulting global warming are typically associated with a weakening of the thermohaline circulation (THC) in model scenarios. For the models participating in the Coupled Model Intercomparison Project (CMIP), this weakening shows a significant (r = 0.62) dependence on the initial THC strength; it is stronger for initially strong overturning. The authors propose a physical mechanism for this phenomenon based on an analysis of additional simulations with the coupled climate models CLIMBER-2 and CLIMBER-3α. The mechanism is based on the fact that sea ice cover greatly reduces heat loss from the ocean. The extent of sea ice is strongly influenced by the near-surface atmospheric temperature (SAT) in the North Atlantic but also by the strength of the THC itself, which transports heat to the convection sites. Consequently, sea ice tends to extend farther south for weaker THC. Initially larger sea ice cover responds more strongly to atmospheric warming; thus, sea ice retreats more strongly for an initially weaker THC. This sea ice retreat tends to strengthen (i.e., stabilize) the THC because the sea ice retreat allows more oceanic heat loss. This stabilizing effect is stronger for runs with weak initial THC and extensive sea ice cover. Therefore, an initially weak THC weakens less under global warming. In contrast to preindustrial climate, sea ice melting presently plays the role of an external forcing with respect to THC stability.
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Meur, E. Le, e Richard C. A. Hindmarsh. "Coupled marine-ice-sheet/Earth dynamics using a dynamically consistent ice-sheet model and a self-gravitating viscous Earth model". Journal of Glaciology 47, n.º 157 (2001): 258–70. http://dx.doi.org/10.3189/172756501781832322.
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AbstractWe use a self-gravitating viscoelastic model of the Earth and a dynamically consistent marine ice-sheet model to study the relationships between marine ice-sheet dynamics, relative sea level, basal topography and bedrock dynamics. Our main conclusion is that sea-level change and lithospheric coupling are likely to have played limited roles in the postglacial retreat of marine ice sheets. The postglacial rise in sea level would only have caused at the most around 100 km of grounding-line retreat for an ice sheet of similar dimensions to the West Antarctic ice sheet, compared with the several hundred km of retreat which has occurred in the Ross Sea. There is no evidence that reverse slopes lead to instability. Incorporating coupling with lithospheric dynamics does not produce markedly different effects. The implication of these studies is that marine ice-sheet retreat is the result of physical mechanisms other than lithospheric coupling and sea-level rise.
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Normandeau, Alexandre, Patrick Lajeunesse, Annie-Pier Trottier, Antoine G. Poiré e Reinhard Pienitz. "Sedimentation in isolated glaciomarine embayments during glacio-isostatically induced relative sea level fall (northern Champlain Sea basin)". Canadian Journal of Earth Sciences 54, n.º 10 (outubro de 2017): 1049–62. http://dx.doi.org/10.1139/cjes-2017-0002.
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The nature of glaciomarine sediments deposited during ice margin retreat can vary according to physiographic setting and relative sea level fluctuations. To understand the effects of these two parameters on sedimentation, we analyzed the sediment records of four lakes located within former isolated glaciomarine embayments of the northern Champlain Sea basin. These lakes were initially inundated by marine water of the Champlain Sea, following deglaciation, and have subsequently experienced basin isolation owing to glacio-isostatic rebound. Three of these lakes reveal a common litho- and acoustic stratigraphic succession, characterized by an IRD-free glaciomarine to marine facies consisting of homogeneous to faintly laminated clayey silts grading into well-laminated silts with rapidly deposited layers. These two units recorded the transitional environment from glaciomarine sedimentation below multiyear shorefast ice to increased terrestrial runoff and rapid glacio-isostatic rebound once the ice margin retreated inland. During ice margin retreat, relative sea level fell concomitantly resulting in the deposition of coarser sediments in marine embayments. Upon the complete retreat of the ice margin, the supply of terrestrial sediments diminished and lake isolation, driven by relative sea level fall, led to higher biogenic content and increased bioturbation. This study provides a framework for sedimentation in isolated glaciomarine embayments which differs from deep-water sedimentation owing to the presence of shorefast sea-ice and their protected location from major ice-stream outlets.
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Yu, Hongju, Eric Rignot, Helene Seroussi e Mathieu Morlighem. "Retreat of Thwaites Glacier, West Antarctica, over the next 100 years using various ice flow models, ice shelf melt scenarios and basal friction laws". Cryosphere 12, n.º 12 (11 de dezembro de 2018): 3861–76. http://dx.doi.org/10.5194/tc-12-3861-2018.
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Abstract. Thwaites Glacier (TG), West Antarctica, has experienced rapid, potentially irreversible grounding line retreat and mass loss in response to enhanced ice shelf melting. Results from recent numerical models suggest a large spread in the evolution of the glacier in the coming decades to a century. It is therefore important to investigate how different approximations of the ice stress balance, parameterizations of basal friction and ice shelf melt parameterizations may affect projections. Here, we simulate the evolution of TG using ice sheet models of varying levels of complexity, different basal friction laws and ice shelf melt to quantify their effect on the projections. We find that the grounding line retreat and its sensitivity to ice shelf melt are enhanced when a full-Stokes model is used, a Budd friction is used and ice shelf melt is applied on partially floating elements. Initial conditions also impact the model results. Yet, all simulations suggest a rapid, sustained retreat of the glacier along the same preferred pathway. The fastest retreat rate occurs on the eastern side of the glacier, and the slowest retreat occurs across a subglacial ridge on the western side. All the simulations indicate that TG will undergo an accelerated retreat once the glacier retreats past the western subglacial ridge. Combining all the simulations, we find that the uncertainty of the projections is small in the first 30 years, with a cumulative contribution to sea level rise of 5 mm, similar to the current rate. After 30 years, the contribution to sea level depends on the model configurations, with differences up to 300 % over the next 100 years, ranging from 14 to 42 mm.
Teses / dissertações sobre o assunto "Sea ice retreat"
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Guo, Wenkai. "The relationship between sea ice retreat and Greenland ice sheet surface-melt". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397692613.
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Himmich, Kenza. "Antarctic sea ice : a seasonal perspective". Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS105.
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La banquise antarctique a subi une réduction brutale en 2016, après plus de quatre décennies d'une lente augmentation. Une telle évolution pourrait avoir de larges conséquences, compte tenu de l'importance de la banquise antarctique pour le climat, l'océan et l'écosystème marin polaire local. Pourtant, les modèles climatiques ne parviennent pas à reproduire les changements observés, laissant planer une incertitude considérable quant à leur origine et à leurs conséquences. Cette déficience des modèles est en partie due à une mauvaise compréhension des processus fondamentaux liés à la banquise antarctique. Dans cette thèse, nous contribuons à faire progresser cette compréhension, en adoptant une perspective saisonnière. Les processus moteurs de l'avancée et du retrait saisonniers de la banquise sont explorés. En particulier, les rôles possibles d'un préconditionnement thermodynamique, des flux de chaleur air-glace-mer et de la dynamique de la banquise sont étudiés. Nous montrons, dans l'état moyen, que les dates d'avancée et de retrait de la banquise sont largement contrôlées par des processus thermodynamiques, à travers un préconditionnement respectif du contenu thermique de la couche de mélange et de l'épaisseur de la banquise. Les variations des flux de chaleur air-glace-mer et la dynamique de la banquise ont une importance significative mais secondaire. Ces conclusions sont étayées par un modèle thermodynamique simple, des analyses d'observations et un modèle glace-océan (NEMO). Nous montrons également que les changements récents dans la saisonnalité de la banquise sont principalement dus à des processus thermodynamiques, comme pour l'état moyen. La réduction de la banquise antarctique suivant l'année 2016 coïncide avec un recul plus précoce et une avancée plus tardive de la banquise, à l'échelle quasi-circompolaire. Notre analyse relie ces changements à une glace plus fine en hiver, une fonte plus rapide au printemps et un océan de surface plus chaud en été, en accord avec les processus de la rétroaction glace-albédo. L'empreinte circumpolaire de ces changements leur suggère une cause océaniqueAntarctic sea ice has undergone an abrupt reduction in 2016, following more than four decades of a slow increase. This could have wide-ranging consequences given the importance of Antarctic sea ice for climate, ocean, and local ecosystem. Yet, climate models fail to capture this observed evolution, leaving considerable uncertainty regarding its origin, impacts and future evolution. Models failure relates, but not only, to a poor understanding of fundamental Antarctic sea ice processes. In this thesis, we contribute to progress understanding of Antarctic sea ice, adopting a seasonal perspective. We investigate the drivers of seasonal sea ice edge advance and retreat, analyzing the roles of thermodynamic preconditioning, air-ice-sea heat fluxes and sea ice dynamics. We show that, in the mean state, timings of ice edge advance and retreat are largely controlled by thermodynamics, via preconditioning from mixed layer heat content and sea ice thickness, respectively. Variations in air-ice-sea heat fluxes and sea ice dynamics have a significant but secondary importance. This conclusion is supported by a simple thermodynamic model, observational analyses and the NEMO ice-ocean model. We also show that recent changes in sea ice seasonality are mainly driven by thermodynamics, similar to the mean state. The reduction in Antarctic sea ice following 2016 coincides with nearly circumpolar earlier retreat and later advance of the ice edge. Our analysis links these changes to thinner ice in winter, faster melt in spring and warmer upper ocean in summer, in line with ice-albedo feedback processes. Based on the circumpolar footprint of these changes, we argue that they likely have an oceanic origin
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Halsted, Christopher T. "Determining the Timing and Rate of Southeastern Laurentide Ice Sheet Thinning During the Last Deglaciation with 10Be Dipsticks". Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108215.
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Thesis advisor: Jeremy D. ShakunThe deglacial extent chronology of the southeastern Laurentide Ice Sheet as it retreated through the northeastern United States and southern Quebec has been well constrained by multiple lines of evidence. By comparison, few data exist to constrain the thinning history of the southeastern Laurentide, resulting in lingering uncertainty about volume changes and dynamics of this ice mass during the deglacial period. To address the lack of thinning information, my team collected 120 samples for in-situ `10Be exposure dating from various elevations at numerous mountains in New England and southern Quebec. Monte Carlo regression analyses using the analytical uncertainties of exposure ages from each mountain are used to determine the most-likely timing and rate of ice thinning for that location, a technique known as the ‘dipstick approach’. While this larger project is ongoing, I have processed and measured 10Be concentrations of 42 samples for this thesis and present my preliminary results and interpretation here. Exposure ages from Peekamoose Mt. in southern NY suggest ice thinning early in the deglacial period (~19.5 – 17.5 ka), near the onset of the Heinrich Stadial I cold period. Samples from Franconia Notch, NH, and Mt. Mansfield, VT, suggest ice thinning from approximately 15 – 13 ka in northern New England, roughly coincident with the Bølling-Allerød warm period. Exposure ages from each of the northern New England dipsticks are nearly identical within 1σ internal uncertainty, indicating that ice thinning was rapid. Higher elevation (>1200 m a.s.l.) samples from the northern New England mountains appear to contain inherited 10Be from previous periods of exposure, indicating a lack of glacial erosion on these surfaces. My high-elevation samples with inherited 10Be suggest that these summit landscapes were preserved beneath cold-based, non-erosive ice during the last glacial and deglacial periods. 40 samples that have yet to be processed will provide more information on ice thinning around Killington Mt., VT, Mt. Greylock, MA, Mt. Bigelow, ME, and Mt. Jacques-Cartier, Quebec. Ultimately, this information will be used to create probabilistic reconstructions of the lowering southeastern Laurentide ice surface during its retreat
Thesis (MS) — Boston College, 2018
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Earth and Environmental Sciences
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Huang, Yiyi, Xiquan Dong, Baike Xi, Erica K. Dolinar e Ryan E. Stanfield. "The footprints of 16 year trends of Arctic springtime cloud and radiation properties on September sea ice retreat". AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/623224.
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The most prominent September Arctic sea ice decline over the period of 2000-2015 occurs over the Siberian Sea, Laptev Sea, and Kara Sea. The satellite observed and retrieved sea ice concentration (SIC) and cloud/radiation properties over the Arctic (70 degrees-90 degrees N) have been used to investigate the impact of springtime cloud and radiation properties on September SIC variation. Positive trends of cloud fractions, cloud water paths, and surface downward longwave flux at the surface over the September sea ice retreat areas are found over the period of 1 March to 14 May, while negative trends are found over the period of 15 May to 28 June. The spatial distributions of correlations between springtime cloud/radiation properties and September SIC have been calculated, indicating that increasing cloud fractions and downward longwave flux during springtime tend to enhance sea ice melting due to strong cloud warming effect. Surface downward and upward shortwave fluxes play an important role from May to June when the onset of sea ice melting occurs. The comparison between linearly detrended and nondetrended of each parameter indicates that significant impact of cloud and radiation properties on September sea ice retreat occurs over the Chukchi/Beaufort Sea at interannual time scale, especially over the period of 31 March to 29 April, while strongest climatological trends are found over the Laptev/Siberian Sea.
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Bulthuis, Kevin. "Towards robust prediction of the dynamics of the Antarctic ice sheet: Uncertainty quantification of sea-level rise projections and grounding-line retreat with essential ice-sheet models". Doctoral thesis, Universite Libre de Bruxelles, 2020. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/301049.
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Recent progress in the modelling of the dynamics of the Antarctic ice sheet has led to a paradigm shift in the perception of the Antarctic ice sheet in a changing climate. New understanding of the dynamics of the Antarctic ice sheet now suggests that the response of the Antarctic ice sheet to climate change will be driven by instability mechanisms in marine sectors. As concerns have grown about the response of the Antarctic ice sheet in a warming climate, interest has grown simultaneously in predicting with quantified uncertainty the evolution of the Antarctic ice sheet and in clarifying the role played by uncertainties in predicting the response of the Antarctic ice sheet to climate change. Essential ice-sheet models have recently emerged as computationally efficient ice-sheet models for large-scale and long-term simulations of the ice-sheet dynamics and integration into Earth system models. Essential ice-sheet models, such as the fast Elementary Thermomechanical Ice Sheet (f.ETISh) model developed at the Université Libre de Bruxelles, achieve computational tractability by representing essential mechanisms and feedbacks of ice-sheet thermodynamics through reduced-order models and appropriate parameterisations. Given their computational tractability, essential ice-sheet models combined with methods from the field of uncertainty quantification provide opportunities for more comprehensive analyses of the impact of uncertainty in ice-sheet models and for expanding the range of uncertainty quantification methods employed in ice-sheet modelling. The main contributions of this thesis are twofold. On the one hand, we contribute a new assessment and new understanding of the impact of uncertainties on the multicentennial response of the Antarctic ice sheet. On the other hand, we contribute new methods for uncertainty quantification of geometrical characteristics of the spatial response of physics-based computational models, with, as a motivation in glaciology, a focus on predicting with quantified uncertainty the retreat of the grounded region of the Antarctic ice sheet. For the first contribution, we carry out new probabilistic projections of the multicentennial response of the Antarctic ice sheet to climate change using the f.ETISh model. We apply methods from the field of uncertainty quantification to the f.ETISh model to investigate the influence of several sources of uncertainty, namely sources of uncertainty in atmospheric forcing, basal sliding, grounding-line flux parameterisation, calving, sub-shelf melting, ice-shelf rheology, and bedrock relation, on the continental response on the Antarctic ice sheet. We provide new probabilistic projections of the contribution of the Antarctic ice sheet to future sea-level rise; we carry out stochastic sensitivity analysis to determine the most influential sources of uncertainty; and we provide new probabilistic projections of the retreat of the grounded portion of the Antarctic ice sheet. For the second contribution, we propose to address uncertainty quantification of geometrical characteristics of the spatial response of physics-based computational models within the probabilistic context of the random set theory. We contribute to the development of the concept of confidence sets that either contain or are contained within an excursion set of the spatial response with a specified probability level. We propose a new multifidelity quantile-based method for the estimation of such confidence sets and we demonstrate the performance of the proposed method on an application concerned with predicting with quantified uncertainty the retreat of the Antarctic ice sheet. In addition to these two main contributions, we contribute to two additional pieces of research pertaining to the computation of Sobol indices in global sensitivity analysis in small-data settings using the recently introduced probabilistic learning on manifolds (PLoM) and to a multi-model comparison of the projections of the contribution of the Antarctic ice sheet to global mean sea-level rise.Les progrès récents effectués dans la modélisation de la dynamique de la calotte polaire de l'Antarctique ont donné lieu à un changement de paradigme vis-à-vis de la perception de la calotte polaire de l'Antarctique face au changement climatique. Une meilleure compréhension de la dynamique de la calotte polaire de l'Antarctique suggère désormais que la réponse de la calotte polaire de l'Antarctique au changement climatique sera déterminée par des mécanismes d'instabilité dans les régions marines. Tandis qu'un nouvel engouement se porte sur une meilleure compréhension de la réponse de la calotte polaire de l'Antarctique au changement climatique, un intérêt particulier se porte simultanément vers le besoin de quantifier les incertitudes sur l'évolution de la calotte polaire de l'Antarctique ainsi que de clarifier le rôle joué par les incertitudes sur le comportement de la calotte polaire de l'Antarctique en réponse au changement climatique. D'un point de vue numérique, les modèles glaciologiques dits essentiels ont récemment été développés afin de fournir des modèles numériques efficaces en temps de calcul dans le but de réaliser des simulations à grande échelle et sur le long terme de la dynamique des calottes polaires ainsi que dans l'optique de coupler le comportement des calottes polaires avec des modèles globaux du sytème terrestre. L'efficacité en temps de calcul de ces modèles glaciologiques essentiels, tels que le modèle f.ETISh (fast Elementary Thermomechanical Ice Sheet) développé à l'Université Libre de Bruxelles, repose sur une modélisation des mécanismes et des rétroactions essentiels gouvernant la thermodynamique des calottes polaires au travers de modèles d'ordre réduit et de paramétrisations. Vu l'efficacité en temps de calcul des modèles glaciologiques essentiels, l'utilisation de ces modèles en complément des méthodes du domaine de la quantification des incertitudes offrent de nombreuses opportunités afin de mener des analyses plus complètes de l'impact des incertitudes dans les modèles glaciologiques ainsi que de développer de nouvelles méthodes du domaine de la quantification des incertitudes dans le cadre de la modélisation glaciologique. Les contributions de cette thèse sont doubles. D'une part, nous contribuons à une nouvelle estimation et une nouvelle compréhension de l'impact des incertitudes sur la réponse de la calotte polaire de l'Antarctique dans les prochains siècles. D'autre part, nous contribuons au développement de nouvelles méthodes pour la quantification des incertitudes sur les caractéristiques géométriques de la réponse spatiale de modèles physiques numériques avec, comme motivation en glaciologie, un intérêt particulier vers la prédiction sous incertitudes du retrait de la région de la calotte polaire de l'Antarctique en contact avec le lit rocheux. Dans le cadre de la première contribution, nous réalisons de nouvelles projections probabilistes de la réponse de la calotte polaire de l'Antarctique au changement climatique au cours des prochains siècles à l'aide du modèle numérique f.ETISh. Nous appliquons des méthodes du domaine de la quantification des incertitudes au modèle numérique f.ETISh afin d'étudier l'impact de différentes sources d'incertitude sur la réponse continentale de la calotte polaire de l'Antarctique. Les sources d'incertitude étudiées sont relatives au forçage atmosphérique, au glissement basal, à la paramétrisation du flux à la ligne d'ancrage, au vêlage, à la fonte sous les barrières de glace, à la rhéologie des barrières de glace et à la relaxation du lit rocheux. Nous réalisons de nouvelles projections probabilistes de la contribution de la calotte polaire de l'Antarctique à l'augmentation future du niveau des mers; nous réalisons une analyse de sensibilité afin de déterminer les sources d'incertitude les plus influentes; et nous réalisons de nouvelles projections probabilistes du retrait de la région de la calotte polaire de l'Antarctique en contact avec le lit rocheux.Dans le cadre de la seconde contribution, nous étudions la quantification des incertitudes sur les caractéristiques géométriques de la réponse spatiale de modèles physiques numériques dans le cadre de la théorie des ensembles aléatoires. Dans le cadre de la théorie des ensembles aléatoires, nous développons le concept de régions de confiance qui contiennent ou bien sont inclus dans un ensemble d'excursion de la réponse spatiale du modèle numérique avec un niveau donné de probabilité. Afin d'estimer ces régions de confiance, nous proposons de formuler l'estimation de ces régions de confiance dans une famille d'ensembles paramétrés comme un problème d'estimation de quantiles d'une variable aléatoire et nous proposons une nouvelle méthode de type multifidélité pour estimer ces quantiles. Finalement, nous démontrons l'efficacité de cette nouvelle méthode dans le cadre d'une application relative au retrait de la région de la calotte polaire de l'Antarctique en contact avec le lit rocheux. En plus de ces deux contributions principales, nous contribuons à deux travaux de recherche additionnels. D'une part, nous contribuons à un travail de recherche relatif au calcul des indices de Sobol en analyse de sensibilité dans le cadre de petits ensembles de données à l'aide d'une nouvelle méthode d'apprentissage probabiliste sur des variétés géométriques. D'autre part, nous fournissons une comparaison multimodèle de différentes projections de la contribution de la calotte polaire de l'Antarctique à l'augmentation du niveau des mers.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Shipp, Stephanie Staples. "Retreat history of the last glacial maximum ice sheet in Ross Sea, Antarctica". Thesis, 1999. http://hdl.handle.net/1911/19449.
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High-resolution geophysical and geologic data were acquired in western and central Ross Sea, Antarctica, to determine the: (1) maximum extent and configuration of the ice sheet during the Last Glacial Maximum (LGM); (2) conditions and processes at the base of the expanded ice sheet and their role in ice stream activity; and (3) relative retreat history of the ice sheet. This information can provide geologic constraints for modeling of ice-sheet retreat. The research formed the basis for development of a public Web site (http://www.glacier.rice.edu) and for middle-school earth-science instructional materials.
Based on identification of isolated grounding-zone wedges and consistency of mega-scale glacial lineations, the LGM ice edge reached the Coulman Island region in western Ross Sea. The maximum extent in central Ross Sea occurred at the continental-shelf edge, based on the presence of mega-scale glacial lineations, glacio-tectonic features, and shelf-edge gullies.
Streaming ice, overlying a deforming bed typically <5 m in thickness, filled the troughs. Thinner, divergent, slower moving ice, not underlain by deforming sediment, occupied the bank tops. The ice sheet eroded and conveyed sediment from the inner regions toward the outer shelf, where the material was deposited at the grounding line. No features associated with meltwater occur; water available to the subglacial system probably was incorporated into a deforming unit.
The ice sheet may have undergone an initial phase of mass wasting, based the large, arcuate iceberg furrows associated with the grounding zones. Ice retreated first from western Ross Sea, possibly because of a diminished contribution from the East Antarctic Ice Sheet. Ice retreat from central Ross Sea lagged that of western Ross Sea. The banks remained ice covered after ice retreat from the troughs; ice shelves may have covered the troughs. During retreat, the grounded ice reworked the substrate into back-stepping grounding-zone wedges and corrugation moraines. The latter features exhibit a spacing on the order of 40 to 100 m and may record annual retreat. This argues for gradual retreat and negates catastrophic collapse of the ice sheet.
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Tan, Wenxia. "An Examination of Sea Ice Spring and Summer Retreat in the Canadian Arctic Archipelago: 1989 to 2010". Thesis, 2013. http://hdl.handle.net/10012/7724.
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The sea ice extent change and variability of the Canadian Arctic Archipelago (CAA) are quite different compared to the Arctic as a whole due to its unique geographic settings. In this thesis, the sea ice retreat processes, the connection with other Arctic regions, and the linkages to the surface radiation flux in the CAA are examined.
The sea ice retreat processes in the CAA follow a four-phase process: a slow ice melt phase that usually lasts until early June (phase 1); a quick melt phase with large daily sea ice extent change which lasts close to half-a-month (phase 2); a slow melt phase that looks like slow sea ice melt or even a small ice increase that lasts another half-a-month (phase 3); and a steady ice decrease phase (phase 4). With the help of Moderate-Resolution Imaging Spectroradiometer (MODIS) data, it is identified that the quick melt in phase 2 is actually melt ponding, with melt ponds being falsely identified as open water by passive microwave.
A simplified data assimilation method is then developed to improve the passive microwave sea ice concentration estimation by fusion with MODIS ice surface temperature data. The ice concentration from the analysis is found to improve the original passive microwave sea ice concentration estimation, with the largest improvements during sea ice melt.
The sea ice retreat patterns in the CAA region are correlated with the sea ice retreat patterns in other regions of the Arctic. A decision tree classifier is designed to segment the sea ice retreat patterns in the CAA into several classes and classification maps are generated. These maps are effective in identifying the geographic locations that have large changes in the sea ice retreat patterns through the years.
The daily progressions of the surface radiation components are described in detail. Due to the lack of multiple reflection, the percentage of shortwave radiation at the top of atmosphere that reaches the surface is influenced by the form of melt ponds over ice surface. The roles that each surface radiation component plays in forcing sea ice retreat are different in different years.
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Mosola, Amanda Beth. "Growth and retreat of the West Antarctic Ice Sheet from the last glacial maximum to the present in the eastern Ross Sea, Antarctica". Thesis, 2004. http://hdl.handle.net/1911/18671.
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Marine geological evidence supports rapid retreat of the West Antarctic Ice Sheet in the eastern Ross Sea before the last glacial maximum. As the only accessible marine record of a major drainage outlet of the West Antarctic Ice Sheet (WAIS), this central and eastern Ross Sea dataset provides a unique opportunity to test the hypothesis of WAIS instability, assess its regulating role in eustasy, and explore the geological record of paleo-ice stream behavior. As the last vast marine-based ice sheet on the planet, the WAIS is seen as a key source of potentially rapid sea level rise. The collapse and disintegration of the WAIS would raise sea level by 5--6 m, a major threat to the world's coastal cities.
Marine geological data were collected along the axis of large bathymetric troughs during a 1999 cruise of the R/V Nathanial B. Palmer. Thick till sheets, extensive lineations, and multiple grounding zone wedges imaged on seismic profiles and multibeam bathymetric records, indicate that troughs in the Ross Sea were occupied by paleo-ice streams during the last glacial maximum. Ice stream boundaries in the eastern Ross Sea are characterized by laterally accreting sedimentary strata indicating lateral migration of ice streams. The abrupt transition from lineated to non-lineated morphologies reflects sharp ice stream margins.
Sediment cores recovered glacial-marine deposits overlying till, a facies succession that indicates an abrupt transition from subglacial to open marine deposition. High concentrations of ice rafted debris in the glacial-marine units and iceberg furrows suggest mass wasting of the ice sheet and iceberg calving from the grounding line during retreat. Corrected radiocarbon ages of samples taken above the contact between subglacial (till) and glacial-marine sediments range from 23.4 to 26.0 ka. B.P., indicating pre-LGM ice sheet withdrawal in the eastern Ross Sea. This was long before the ice sheet retreated from the western Ross Sea and is inconsistent with previous models for ice sheet retreat in the region.
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Kirshner, Alexandra. "Sedimentological Investigations of Paleo-Ice Sheet Dynamics in West Antarctica". Thesis, 2013. http://hdl.handle.net/1911/71973.
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Modern Pine Island and Thwaites Glaciers, which both drain into Pine Island Bay, are some of the fastest moving portions of the cryosphere and may be the most unstable ice streams in Antarctica. I examined over 133 cores to conduct a detailed sedimentological facies analysis. These data, augmented by new radiocarbon and 210Pb dates, and bathymetric data, are used to reconstruct the post-LGM deglacial history of PIB and gain a better understanding of the causes of ice sheet retreat.
My results record a clear retreat stratigraphy in PIB composed of, from top to base; terrigenous sandy silt (plumite), pebbly sandy mud (ice-proximal glacimarine), and till. Initial retreat from the outer-continental shelf began shortly after the LGM and before 16.4 k cal yr BP, in response to rising sea level. Bedforms in outer PIB document episodic retreat in the form of back-stepping grounding zone wedges and are associated with proximal glacimarine sediments. A sub-ice shelf facies is observed in central PIB that spans ∼12.3–10.6 k cal yr BP. Widespread impingement of warm water onto the continental shelf caused an abrupt change from sub-ice shelf sedimentation to distal glacimarine sedimentation dominated by dispersal of terrigenous silt between 7.8 and 7.0 k cal yr BP. The uppermost sediments in Pine Island Bay were hydrodynamically sorted by meltwater plumes. Inner Pine Island Bay contains several large basins that are linked by channels. The most recent release of sediment coincides with rapid retreat of the grounding line, and has an order of magnitude greater flux relative to the entire unit, indicating episodic sedimentation. This is the first identification of a meltwater-derived deposit in Antarctica and demonstrates that punctuated meltwater-intensive glacial retreat occurred at least three times throughout the Holocene in this region.
Quartz sand grains were used to conduct an analysis of mode of transport for sediments in the Antarctic Peninsula region from the Eocene to present to record the onset of glaciation. Glacial transport imparts a unique suite of microtextures on quartz grains from high shear-stresses. Eocene samples are free of glacial influence. Late Eocene samples show the inception of glacially derived high-stress microtextures, marking the onset of alpine glaciation. Oligocene grains are similar to the late Eocene samples. Middle Miocene microtextures are characteristic of transport from far-field large ice sheets, originating from ice rafting from the West Antarctic Ice Sheet. The Pliocene and Pleistocene samples indicate the existence of the northern Antarctic Peninsula Ice Sheet at this time, consistent with other proxies.
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Milliken, Kristy Lynn Tramp. "Holocene sea-level history and the evolution of Sabine Lake and Calcasieu Lake; east Texas and west Louisiana, USA and the glacial retreat history of Maxwell Bay, South Shetland Islands, Antarctica: Implications for ice cap thickness, retreat, and climate change". Thesis, 2008. http://hdl.handle.net/1911/22264.
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The history of relative sea-level rise along the northern Gulf of Mexico must be constrained in order to determine the relative effects of eustatic sea-level rise, subsidence, antecedent topography, and sediment supply variations on fluvial--bay-shoreline sedimentary systems. This study adds important additional sea-level indicators for the past 10 kyrs in addition to compiling the extensive pre-existing data from the literature. The northern Gulf of Mexico data from the modern shoreline is compared western and eastern Gulf of Mexico datasets to determine the relative difference in subsidence rates over the past 4 kyrs. Subsidence differences are negligible.
Furthermore, quantification of the antecedent topography provides a means to account for its effects on sedimentary architecture and the evolution of the Sabine and Calcasieu river-bay systems. The record of eustasy potentially indicates 3 to 4 meter-scale rapid rise intervals during the early Holocene. Subsequent to 7.5 ka, the progradation and retrogradation of the sedimentary systems must be attributed to sediment supply variations (climate change). From 7.5 ka to ∼3 ka, the east Texas, west Louisiana climate oscillated between sub-humid to sub-arid to produce greater than modern sediment flux manifested as deltaic deposits in the modern estuaries. Important future applications of this study include comparison to the nature and timing of fluvial-deltaic retreat in other estuaries along the Gulf of Mexico and Atlantic coasts.
The South Shetland Islands, off the western side of the Antarctic Peninsula, are separated by glacial troughs carved during glacial maxima. These glacial troughs are currently fjords which contain a glaciomarine sedimentary record. Age constraining the sediments provides a retreat history of the ice cap for the past 15 kyrs including rates and magnitude of retreat for sub-polar glacial systems. Furthermore, the timing of the migration of sub-glacial polar (cold-based) glacial conditions southward is constrained to ∼10kyr. This has important implications for Holocene glacial flow rates and ice shelf stability in the Antarctic Peninsula region.
Capítulos de livros sobre o assunto "Sea ice retreat"
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Lancelot, Christiane, Sylvie Mathot, Cornelis Veth e Hein de Baar. "On the factors controlling phytoplankton ice edge blooms in the marginal ice zone of the northwestern Weddell Sea during sea ice retreat 1988". In Weddell Sea Ecology, 333. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-77595-6_39.
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Cadée, G. C. "Organic carbon in the upper layer and its sedimentation during the ice-retreat period in the Scotia-Weddell Sea, 1988". In Weddell Sea Ecology, 253–59. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77595-6_29.
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Lebedev, S. A., A. G. Kostianoy e S. K. Popov. "Satellite altimetry of the Barents sea". In THE BARENTS SEA SYSTEM, 194–212. Shirshov Institute of Oceanology Publishing House, 2021. http://dx.doi.org/10.29006/978-5-6045110-0-8/(16).
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Satellite altimetry data are used for investigation of the sea level variability and sea ice cover retreat in the Barents Sea in 1992−2018. The data from ERS−1/2, ENVISAT, SARAL/AltiKa, and Sentinel-3A/3B satellites were used in this study. An increasing trend of the sea level of about 2.31 mm/yr was observed in this time period, which caused a total increase in the Barents Sea level by about 6 cm. Linear trends of the sea level change varied from 1.84 mm/yr in July to 4.29 mm/yr in September. The average velocity of the ice edge retreat along the tracks in the northeastern direction is of 10.9 km/yr for the same period. It was found that the ice edge displacement rate tends to increase by 0.30 km/yr per a degree in longitude in the eastward direction. Thus, the ice edge retreat along the “eastern” tracks goes faster than along the “western” ones, which is likely explained by a change in the water dynamics in the Barents Sea.
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Fogg, G. E. "Sea ice as a habitat and ecological interface". In The Biology of Polar Habitats, 157–81. Oxford University PressOxford, 1998. http://dx.doi.org/10.1093/oso/9780198549543.003.0007.
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Abstract The profound effects of sea ice on the climatic and oceanographic environments in which polar organisms live have been outlined in Chapter 1. It is more variable and heterogeneous in structure than land ice and since it is in contact with liquid water and consequently does not reach such low temperatures as does land ice, it provides a variety of niches for active life. Sea ice has a unique ecological role. It interposes a solid interface between two fluid phases—biologically productive seawater and air, unproductive but allowing exceptional mobility to animals able to take advantage of it. It modifies environmental conditions in the sea below and also provides a platform on which air-breathing birds and mammals can live, breed, and base foraging forays into the water. Although its annual cycle of advance and retreat is a recurrent pattern, the distribution and local structure is irregular. Its variations from year to year affect all levels in the marine ecosystem.
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Bay-Larsen, Ingrid, Erlend A.T. Hermansen e Tone G. Bjørndal. "Den menneskeskapte iskanten – Om vitenskapelig sannhetssøken og uavhengighet i en kunnskapsbasert forvaltning". In Interessekonflikter i forskning, 131–52. Cappelen Damm Akademisk/NOASP, 2019. http://dx.doi.org/10.23865/noasp.63.ch6.
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In this chapter we explore how the geographical position of the marginal ice zone in the Barents Sea became the center of a hot political debate. In 2015, new data sets on the retreat of sea ice were introduced by the Norwegian government, indicating how petroleum drilling could take place without conflicting with the vulnerable ice ecosystem. In the public debate that followed, four different definitions of the ice edge zone were introduced, each providing different geographical positions of the ice edge. These multiple definitions directly corresponded to various political views on the exploration of petroleum in the Barents Sea. The analysis shows how ethical principles connected to scientific rigor and independence may be put on trial when conflicts of interests escalate in policy debates. This chapter demonstrates the mismatch between ethical ideals and practice in knowledge-based management, and discusses what their democratic implications might be.
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Bianchi, Thomas S. "The Holocene and Global Climate Change". In Deltas and Humans. Oxford University Press, 2016. http://dx.doi.org/10.1093/oso/9780199764174.003.0008.
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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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Maslin, Mark. "3. Evidence for climate change". In Climate Change: A Very Short Introduction, 29–45. Oxford University Press, 2014. http://dx.doi.org/10.1093/actrade/9780198719045.003.0003.
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‘Evidence for climate change’ considers both past and recent climate change through changes in temperature, precipitation, and relative global sea level to show that significant changes in climate have been recorded. These include a 0.85°Celsius (C) increase in average global temperatures over the last 150 years, sea-level rise of over 20 cm, significant shifts in the seasonality and intensities of precipitation, changing weather patterns, and significant retreat of Arctic sea ice and nearly all continental glaciers. The IPCC 2013 report states that the evidence for global warming is unequivocal and that there is very high confidence that this warming is due to human emissions of greenhouse gases.
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Smith, Raymond C., e William R. Fraser. "Climate Variability and Ecological Response of the Marine Ecosystem in the Western Antarctic Peninsula (WAP) Region". In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0018.
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The Antarctic Peninsula, a relatively long, narrow extension of the Antarctic continent, defines a strong climatic gradient between the cold, dry continental regime to its south and the warm, moist maritime regime to its north. The potential for these contrasting climate regimes to shift in dominance from season to season and year to year creates a highly variable environment that is sensitive to climate perturbation. Consequently, long-term studies in the western Antarctic Peninsula (WAP) region, which is the location of the Palmer LTER (figure 9.1), provide the opportunity to observe how climate-driven variability in the physical environment is related to changes in the marine ecosystem (Ross et al. 1996; Smith et al. 1996; Smith et al. 1999). This is a sea ice–dominated ecosystem where the annual advance and retreat of the sea ice is a major physical determinant of spatial and temporal change in its structure and function, from total annual primary production to the breeding success and survival of seabirds. Mounting evidence suggests that the earth is experiencing a period of rapid climate change, and air temperature records from the last half century confirm a statistically significant warming trend within the WAP during the past half century (King 1994; King and Harangozo 1998; Marshall and King 1998; Ross et al. 1996; Sansom 1989; Smith et al. 1996; Stark 1994; van den Broeke 1998; Weatherly et al. 1991). Air temperature–sea ice linkages appear to be very strong in the WAP region (Jacka 1990; Jacka and Budd 1991; King 1994; Smith et al. 1996; Weatherly et al. 1991), and a statistically significant anticorrelation between air temperatures and sea ice extent has been observed for this region. Consistent with this strong coupling, sea ice extent in the WAP area has trended down during this period of satellite observations, and the sea ice season has shortened. In addition, both air temperature and sea ice have been shown to be significantly correlated with the Southern Oscillation Index (SOI), which suggests possible linkages among sea ice, cyclonic activity, and global teleconnections.
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Macintosh Wilson, Alistair. "Symphonies Of Stone". In The Infinite In The Finite, 1–18. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780198539506.003.0001.
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Abstract Around 10 000 BC, the glaciers of the Great Ice Age began to retreat from off the face of the continent of Europe. As the land was freed from their grip, people started to move back northward. At first these were small tribes of hunters and gatherers, following the herds, coming together where the hunting was good, breaking apart to search for food where it was not. Slowly these tribes pressed further north and west, finally reaching the natural barriers of the continent: the coast of the North Sea and the Atlantic, and the islands of the sea—Britain and Ireland. There was no further to go. The wanderers settled, beginning to cultivate the land, and raise livestock. As further immigrants arrived, the population began to rise.
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Holman, J. Alan. "Introductio". In Pleistocene Amphibians and Reptiles in Britain and Europe. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195112320.003.0005.
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There is disagreement about the time of the beginning of the Pleistocene. For instance, Repenning (1987), a North American, puts the beginning date at 1.9 million ybp. On the other hand, some modern Europeans studying the subject (e.g., Gibbard et al., 1991; Kolfschoten and Meulen, 1986; Roebroeks and Kolfschoten, 1995; Zagwijn, 1985, 1992) consider the epoch to have begun about 2.3 million ybp. The system used here, however, follows Sanchiz (in press), who accepts the official usage of Harland et al. (1990), who put the beginning of the Pleistocene at 1.64 million ybp. Evidence that the Pleistocene ended about 10,000 ybp (Meltzer and Mead, 1983) is widely accepted. This ending date correlates very closely with the terminal extinction of many large land mammal species. The Pleistocene is characterized by climatic oscillations and a series of glacial and interglacial events where great continental ice sheets advanced and retreated many times. The ice sheets were massive forces, sculpting the topography of the land and carrying much sedimentary material, including huge boulders and even megablocks of land up to 4 km in diameter, as far as 250 km in the Canadian prairies (MacStalker, 1977). In Britain and Europe, as well as in North America, the advance and retreat of ice sheets had a marked effect on the distribution of plant and animal life. Huge tracts of habitat were alternately obliterated and reopened several times, but other effects perhaps arc not so well known. For instance, during glacial times, so much atmospheric water was tied up in the formation of the ice that sea levels worldwide lowered markedly. On the other hand, sea levels rose during interglacial times when water was melting off the ice sheets. The most interesting and controversial biological event that took place in the Pleistocene was the sudden, almost worldwide, extinction of large land mammals, and to a lesser extent birds, that took place by the end of the epoch 10,000 years ago. At least 200 mammalian genera became extinct, among them large herbivores, the carnivores that preyed on them, and the scavengers that fed on the remains of both groups.
Trabalhos de conferências sobre o assunto "Sea ice retreat"
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Wadhams, Peter. "Arctic Sea Ice Changes under Global Warming". In SNAME 8th International Conference and Exhibition on Performance of Ships and Structures in Ice. SNAME, 2008. http://dx.doi.org/10.5957/icetech-2008-140.
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In this review we summarise the latest results on the rapid changes that are occurring to Arctic sea ice thickness and extent, the reasons for them, and the methods being used to monitor the changing ice thickness. Arctic sea ice extent has been reducing at a relatively modest rate of 3-4% per decade (annually averaged) but since 1996 this has speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million sq km. Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may arise from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques which show the greatest promise on different spatial and temporal scales, and for different purposes. We show results from some very recent work from submarines.
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Sershen, Benjamin J., e Alex D. Crawford. "CAN HEAT FLUX DATA FROM OCEAN REANALYSES PREDICT SEASONAL ARCTIC SEA ICE RETREAT?" In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-318898.
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Prothro, Lindsay O., Yusuke Yokoyama, Lauren M. Simkins, John B. Anderson, Wojciech Majewski, Masako Yamane e Naohiko Ohkouchi. "TIMING AND SEA LEVEL CONTRIBUTIONS OF THE DECONVOLVING ANTARCTIC ICE SHEET DURING POST-LGM RETREAT OF THE ROSS SEA SECTOR". In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-301400.
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Kuznetsov, Dmitry, Dmitry Kuznetsov, Anatoliy Kamalov, Anatoliy Kamalov, Nataliya Belova, Nataliya Belova, Nataliya Shabanova, Nataliya Shabanova, Stanislav Ogorodov e Stanislav Ogorodov. "MONITORING THE DYNAMICS OF THERMOABRASION COASTS AT KHARASAVEY AREA, WESTERN YAMAL (KARA SEA)". In Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.31519/conferencearticle_5b1b93ffdcdfd1.86932804.
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The dynamics of thermoabrasion coasts on loose sediments under permafrost conditions are highly variable due to several factors: length of the dynamic period of the year, mechanic composition of the frozen ground and its ice content, hydrometeorological conditions, and human impact. Multiannual monitoring of the coastal zone was carried out by Lab. Geoecology of the North (Moscow State University) at the 22 km long Kharasavey deposit site, Western Coast of Yamal Peninsula (Kara Sea). The methods include direct measurements and observations (repeated topographic survey of shore transects from 1981 to 2012) along with remote sensing data analysis (images from 1964 to 2011). This allowed producing detailed characteristics of coastal dynamics. At the site, thermoabrasion coasts occupy the most part, and accumulative coasts are present in the north. Data on natural relief forming factors and ground composition are included in the detailed geomorphologic map of the site. Shore retreat rate shows correlation to amounts of wind-wave energy and to specific wind directions. Human impact on the coast includes dredging at the port channel, mining of sand, driving motor vehicles, and deposition of construction debris. Relations between shore retreat rate and aforementioned factors were studied, including dependencies on ice content, and shore segmentation was carried out. This allows for coastal dynamics forecasts in the region.
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Kuznetsov, Dmitry, Dmitry Kuznetsov, Anatoliy Kamalov, Anatoliy Kamalov, Nataliya Belova, Nataliya Belova, Nataliya Shabanova, Nataliya Shabanova, Stanislav Ogorodov e Stanislav Ogorodov. "MONITORING THE DYNAMICS OF THERMOABRASION COASTS AT KHARASAVEY AREA, WESTERN YAMAL (KARA SEA)". In Managing risks to coastal regions and communities in a changing world. Academus Publishing, 2017. http://dx.doi.org/10.21610/conferencearticle_58b4315237f1f.
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The dynamics of thermoabrasion coasts on loose sediments under permafrost conditions are highly variable due to several factors: length of the dynamic period of the year, mechanic composition of the frozen ground and its ice content, hydrometeorological conditions, and human impact. Multiannual monitoring of the coastal zone was carried out by Lab. Geoecology of the North (Moscow State University) at the 22 km long Kharasavey deposit site, Western Coast of Yamal Peninsula (Kara Sea). The methods include direct measurements and observations (repeated topographic survey of shore transects from 1981 to 2012) along with remote sensing data analysis (images from 1964 to 2011). This allowed producing detailed characteristics of coastal dynamics. At the site, thermoabrasion coasts occupy the most part, and accumulative coasts are present in the north. Data on natural relief forming factors and ground composition are included in the detailed geomorphologic map of the site. Shore retreat rate shows correlation to amounts of wind-wave energy and to specific wind directions. Human impact on the coast includes dredging at the port channel, mining of sand, driving motor vehicles, and deposition of construction debris. Relations between shore retreat rate and aforementioned factors were studied, including dependencies on ice content, and shore segmentation was carried out. This allows for coastal dynamics forecasts in the region.
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Caissie, Beth E., Sarah D. Zellers, Ellen A. Cowan, Juliane Müller, Jacob W. Pratt e Anna Nesterovich. "SEA ICE AND PRIMARY PRODUCTIVITY IN THE GULF OF ALASKA DURING RETREAT OF BERING ICE STREAM FROM THE LAST GLACIAL MAXIMUM". In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-313268.
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Григорьев, М., e M. Grigor'ev. "LAPTEV AND EAST SIBERIAN SEA COASTAL DYNAMICS, SEDIMENT FLUXES, AND COASTAL DATABASE". In Sea Coasts – Evolution ecology, economy. Academus Publishing, 2018. http://dx.doi.org/10.31519/conferencearticle_5b5ce3c4d160c7.32509546.
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The coastal zones of the Laptev and East-Siberian seas are characterized by the highest erosion rates in the Arctic. Thermal abrasion is the leading geomorphological process in the region, with average rates of 1 to 4 m/yr. On the basis of shore segmentation, coastal erosion rates were analysed for each segment of coast. The mean rate of coastal retreat for the Laptev and East-Siberian seas was calculated and estimated to be 0,8 m/yr.
In recent decades, the Laptev and East-Siberian sea regions have experienced a warming trend. Under these conditions, erosion rates of ice rich coasts on several key sites have increased 1,5–2 times during the last 10–12 years. Sediment and organic material inputs for the Laptev and East-Siberian seas were estimated and found to be respectively (1,6 and 2,4 103 t/yr for sediment and 62,2 and 90,2 103 t/yr for organic material). The data obtained were compiled into an electronic coastal database for the study region. Using the database, 16 lithologic, morphologic, morphometric and dynamic parameters were determined for each coastal section.
The processes of cryogenic morphogenesis form rather specific coastal landscapes within the studied coasts. In studied region the rates of coastal transformation is much faster then in other Arctic areas. This study has shown that 10,7 km2/yr of land is lost annually along the Arctic seas of East Siberia.
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Bervid, Heather D., Anders E. Carlson, Maureen H. Walczak, Ingrid Hendy e Joseph Stoner. "RAPID RETREAT OF THE WESTERN MARGIN OF THE NORTHERN AND SOUTHERN CORDILLERAN ICE SHEET IN RESPONSE TO ABRUPT DEGLACIAL SEA-SURFACE TEMPERATURE WARMING". In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-306898.
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Brazo, Julia, Joseph Licciardi e Alia J. Lesnek. "USING 10BE SURFACE EXPOSURE DATING TO RECONSTRUCT THE LATE PLEISTOCENE HISTORY OF ICE SHEET RETREAT AND RELATIVE SEA-LEVEL CHANGES IN THE SEACOAST REGION OF NEW HAMPSHIRE". In Northeastern Section - 57th Annual Meeting - 2022. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022ne-375012.
Texto completo da fonteRelatórios de organizações sobre o assunto "Sea ice retreat"
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Kerr, D. E. Reconnaissance surficial geology, Tinney Hills, Nunavut, NTS 76-J. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/321821.
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The Tinney Hills map area consists primarily of glacially and meltwater scoured bedrock, discontinuous till in the southwest and central-east, and postglacial marine sediments in coastal lowlands and along river valleys inland. The boundaries of many till deposits are cut to bedrock by widespread subglacial meltwater erosion. Ridged till in particular, is often associated with eskers and other glaciofluvial sediments and meltwater erosion. Striations and streamlined till landforms indicate regional ice flow towards the north-northwest and northwest, and later crosscutting relationships recording minor variations locally. Orientation of eskers and outwash plains suggest ice recession was primarily southeastward. Small, isolated glacial lakes formed where retreating or stagnant ice temporarily blocked local drainage. Below 200 to 220 m elevation, the region was inundated by the sea during ice retreat. Glaciomarine and marine sediments consist of littoral beach and offshore sediments, winnowed till surfaces, and isolated deltas. Isostatic rebound caused marine regression, recorded by deltas and beaches at 210 to 220 m elevation, and decreasing to current sea level.
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McMartin, I., M. S. Gauthier e A. V. Page. Updated post-glacial marine limits along western Hudson Bay, central mainland Nunavut and northern Manitoba. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330940.
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A digital compilation of updated postglacial marine limits was completed in the coastal regions of central mainland Nunavut and northern Manitoba between Churchill and Queen Maud Gulf. The compilation builds on and updates previous mapping of the marine limits at an unprecedented scale, making use of high-resolution digital elevation models, new field-based observations of the marine limit and digital compilations of supporting datasets (i.e. marine deltas and marine sediments). The updated mapping also permits a first-hand, knowledgedriven interpolation of a continuous limit of marine inundation linking the Tyrrell Sea to Arctic Ocean seawaters. The publication includes a detailed description of the mapping methods, a preliminary interpretation of the results, and a GIS scalable layout map for easy access to the various layers. These datasets and outputs provide robust constraints to reconstruct the patterns of ice retreat and for glacio-isostatic rebound models, important for the estimation of relative sea level changes and impacts on the construction of nearshore sea-transport infrastructures. They can also be used to evaluate the maximum extent of marine sediments and associated permafrost conditions that can affect land-based infrastructures, and potential secondary processes related to marine action in the surficial environment and, therefore, can enhance the interpretation of geochemical anomalies in glacial drift exploration methods. A generalized map of the maximum limit of postglacial marine inundation produced for map representation and readability also constitutes an accessible output relevant to Northerners and other users of geoscience data.
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Roberts, Andrew, Elizabeth Hunke, Mark Petersen, Wilbert Weijer, Carmela Veneziani, Nicole Jeffery, Hailong Wang, Aixue Hu, Deborah Sulsky e Wieslaw Maslowski. Slides for DOE BER to present to Congress April 2024 addressing the question: How much sea ice retreat will it take for the climate of the Arctic region to become irreversible, and are there any thresholds to avoid? Office of Scientific and Technical Information (OSTI), abril de 2024. http://dx.doi.org/10.2172/2340852.
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Guest, Peter S., Christopher W. Fairall e P. O. Persson. Office of Naval Research (ONR), Arctic and Global Prediction Program Department Research Initiative (DRI), Sea State and Boundary Layer Physics of the Emerging Arctic Ocean Quantifying the Role of Atmospheric Forcing in Ice Edge Retreat and Advance Including Wind-Wave Coupling. Fort Belvoir, VA: Defense Technical Information Center, setembro de 2014. http://dx.doi.org/10.21236/ada616467.
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Blais-Stevens, A., A. Castagner, A. Grenier e K D Brewer. Preliminary results from a subbottom profiling survey of Seton Lake, British Columbia. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/332277.
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Seton Lake is a freshwater fiord located in southwestern British Columbia, roughly 4 km west of Lillooet and 250 km north-northeast of Vancouver. Located in the Coast Mountains, it is an alpine lake about 22-km long and roughly 1-1.5 km wide. It is separated from nearby Anderson Lake, located to the west, by a large pre-historic rock avalanche deposit at Seton Portage. The lake stands at about 243 m above sea level and is up to about 150 m deep (BC gov., 1953). Water level is controlled by a hydroelectric dam (i.e., Seton dam) located at the eastern end of the lake. Here, the lake drains east into Seton Canal, a 5 km diversion of the flow of the Seton River, which begins at the Seton dam. The Seton Canal pushes water to the Seton Powerhouse, a hydroelectric generating station at the Fraser River, just south of the community of Sekw'el'was and confluence of the Seton River, which drains into the Fraser River at Lillooet. Seton Portage, Shalatlh, South Shalatlh, Tsal'alh (Shalath), Sekw'el'was (Cayoosh Creek), and T'it'q'et (Lillooet) are communities that surround the lake. Surrounded by mountainous terrain, the lake is flanked at mid-slope by glacial and colluvial sediments deposited during the last glacial and deglacial periods (Clague, 1989; Jakob, 2018). The bedrock consists mainly of mafic to ultramafic volcanic rocks with minor carbonate and argillite from the Carboniferous to Middle Jurassic periods (Journeay and Monger, 1994). As part of the Public Safety Geoscience Program at the Geological Survey of Canada (Natural Resources Canada), our goal is to provide baseline geoscience information to nearby communities, stakeholders and decision-makers. Our objective was to see what kind of sediments were deposited and specifically if we could identify underwater landslide deposits. Thus, we surveyed the lake using a Pinger SBP sub bottom profiler made by Knudsen Engineering Ltd., with dual 3.5 / 200 kHz transducers mounted to a small boat (see photo). This instrument transmits sound energy down through the water column that reflects off the lake bottom surface and underlying sediment layers. At the lake surface, the reflected sound energy is received by the profiler, recorded on a laptop computer, and integrated with GPS data. These data are processed to generate a two-dimensional image (or profile) showing the character of the lake bottom and underlying sediments along the route that the boat passed over. Our survey in 2022 recorded 98 profiles along Seton Lake. The red transect lines show the locations of the 20 profiles displayed on the poster. The types of sediments observed are mostly fine-grained glaciolacustrine sediments that are horizontally bedded with a subtle transition between glaciolacustrine to lacustrine (e.g., profiles A-A'; C-C'; F-F'; S-S'). Profile S-S' displays this transition zone. The glaciolacustrine sediments probably were deposited as the Cordilleran Ice Sheet retreated from the local area (~13,000-11,000 years ago; Clague, 2017) and the lacustrine sediments, after the ice receded to present-day conditions. Some of the parallel reflections are interrupted, suggesting abrupt sedimentation by deposits that are not horizontally bedded; these are interpreted as landslide deposits (see pink or blue deposits on profiles). The deposits that show disturbance in the sedimentation found within the horizontal beds are thought to be older landslides (e.g., blue arrows/deposits in profiles C-C'; E-E'; F-F'; G-G'; I-I'; J-J'; K-K'; N-N'; P-P'; Q-Q'; R-R'; T-T'; U-U'), but the ones that are found on top of the horizontally laminated sediments (red arrows/pink deposits), and close to the lake wall, are interpreted to be younger (e.g., profiles B-B'; C-C'; H-H'; K-K'; M-M'; O-O'; P-P'; Q-Q'). At the fan delta just west of Seton dam, where there was no acoustic signal penetration, it is interpreted that the delta failed and brought down coarser deposits at the bottom of the lake (e.g., profiles H-H'; M-M'; and perhaps K-K'). However, these could be glacial deposits, bedrock, or other coarser deposits. Some of the deposits that reflect poor penetration of the acoustic signal, below the glaciolacustrine sediments, could represent glacial deposits, old landslide deposits, or perhaps the presence of gas (orange arrows; e.g, B-B'; D-D'; J-J'; O-O', T-T'). The preliminary results from sub bottom profiling reveal that there are underwater landslides deposits of widely varying ages buried in the bottom of the lake. However, the exact timing of these is not known. Hence our preliminary survey gives an overview of the distribution of landslides where there seems to be a larger number of landslides recorded in the narrower eastern portion of the lake.