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1
Dial, Roman J., Colin T. Maher, Rebecca E. Hewitt, Amy M. Wockenfuss, Russell E. Wong, Daniel J. Crawford, Madeline G. Zietlow i Patrick F. Sullivan. "Arctic sea ice retreat fuels boreal forest advance". Science 383, nr 6685 (23.02.2024): 877–84. http://dx.doi.org/10.1126/science.adh2339.
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Climate-induced northward advance of boreal forest is expected to lessen albedo, alter carbon stocks, and replace tundra, but where and when this advance will occur remains largely unknown. Using data from 19 sites across 22 degrees of longitude along the tree line of northern Alaska, we show a stronger temporal correlation of tree ring growth with open water uncovered by retreating Arctic sea ice than with air temperature. Spatially, our results suggest that tree growth, recruitment, and range expansion are causally linked to open water through associated warmer temperatures, deeper snowpacks, and improved nutrient availability. We apply a meta-analysis to 82 circumarctic sites, finding that proportionally more tree lines have advanced where proximal to ongoing sea ice loss. Taken together, these findings underpin how and where changing sea ice conditions facilitate high-latitude forest advance.
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Stern, Harry L., i Kristin L. Laidre. "Sea-ice indicators of polar bear habitat". Cryosphere 10, nr 5 (14.09.2016): 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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Post, Eric, Jeffrey Kerby, Christian Pedersen i Heidi Steltzer. "Highly individualistic rates of plant phenological advance associated with arctic sea ice dynamics". Biology Letters 12, nr 12 (grudzień 2016): 20160332. http://dx.doi.org/10.1098/rsbl.2016.0332.
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We analysed 12 years of species-specific emergence dates of plants at a Low-Arctic site near Kangerlussuaq, Greenland to investigate associations with sea ice dynamics, a potential contributor to local temperature variation in near-coastal tundra. Species displayed highly variable rates of phenological advance, from a maximum of −2.55 ± 0.17 and −2.93 ± 0.51 d yr −1 among a graminoid and forb, respectively, to a minimum of −0.55 ± 0.19 d yr −1 or no advance at all in the two deciduous shrub species. Monthly Arctic-wide sea ice extent was a significant predictor of emergence timing in 10 of 14 species. Despite variation in rates of advance among species, these rates were generally greatest in the earliest emerging species, for which monthly sea ice extent was also the primary predictor of emergence. Variation among species in rates of phenological advance reshuffled the phenological community, with deciduous shrubs leafing out progressively later relative to forbs and graminoids. Because early species advanced more rapidly than late species, and because rates of advance were greatest in species for which emergence phenology was associated with sea ice dynamics, accelerating sea ice decline may contribute to further divergence between early- and late-emerging species in this community.
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Nakanowatari, Takuya, Jun Inoue, Jinlun Zhang, Eiji Watanabe i Hiroshi Kuroda. "A New Norm for Seasonal Sea Ice Advance Predictability in the Chukchi Sea: Rising Influence of Ocean Heat Advection". Journal of Climate 35, nr 9 (1.05.2022): 2723–40. http://dx.doi.org/10.1175/jcli-d-21-0425.1.
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Abstract Predictability of seasonal sea ice advance in the Chukchi Sea has been investigated in the context of ocean heat transport from the Bering Strait; however, the underlying physical processes have yet to be fully clarified. Using the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) reanalysis product (1979–2016), we examined seasonal predictability of sea ice advance in early winter (November–December) and its source using canonical correlation analysis. It was found that 2-month leading (September–October) surface heat flux and ocean heat advection is the major predictor for interannual variability of sea ice advance. Surface heat flux is related to the atmospheric cooling process, which has influenced sea ice area in the southeastern Chukchi Sea particularly in the 1980s and 1990s. Anomalous surface heat flux is induced by strong northeasterly winds related to the east Pacific/North Pacific teleconnection pattern. Ocean heat advection, which is related to fluctuation of volume transport in the Bering Strait, leads to decrease in the sea ice area in the northwestern Chukchi Sea. Diagnostic analysis revealed that interannual variability of the Bering Strait volume transport is governed by arrested topographic waves (ATWs) forced by southeasterly wind stress along the shelf of the East Siberian Sea. The contribution of ocean heat flux to sea ice advance has increased since the 2000s; therefore, it is suggested that the major factor influencing interannual variability of sea ice advance in early winter has shifted from atmospheric cooling to ocean heat advection processes. Significance Statement Predictability of sea ice advance in the marginal Arctic seas in early winter is a crucial issue regarding future projections of the midlatitude winter climate and marine ecosystem. This study examined seasonal predictability of sea ice advance in the Chukchi Sea in early winter using a statistical technique and historical model simulation data. We identified that atmospheric cooling and ocean heat transport are the two main predictors of sea ice advance, and that the impact of the latter has become amplified since the 2000s. Our new finding suggests that the precise information on wind-driven ocean currents and temperatures is crucial for the skillful prediction of interannual variability of sea ice advance under present and future climatic regimes.
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Schroeter, Serena, Will Hobbs i Nathaniel L. Bindoff. "Interactions between Antarctic sea ice and large-scale atmospheric modes in CMIP5 models". Cryosphere 11, nr 2 (24.03.2017): 789–803. http://dx.doi.org/10.5194/tc-11-789-2017.
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Abstract. The response of Antarctic sea ice to large-scale patterns of atmospheric variability varies according to sea ice sector and season. In this study, interannual atmosphere–sea ice interactions were explored using observations and reanalysis data, and compared with simulated interactions by models in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Simulated relationships between atmospheric variability and sea ice variability generally reproduced the observed relationships, though more closely during the season of sea ice advance than the season of sea ice retreat. Atmospheric influence on sea ice is known to be strongest during advance, and it appears that models are able to capture the dominance of the atmosphere during advance. Simulations of ocean–atmosphere–sea ice interactions during retreat, however, require further investigation. A large proportion of model ensemble members overestimated the relative importance of the Southern Annular Mode (SAM) compared with other modes of high southern latitude climate, while the influence of tropical forcing was underestimated. This result emerged particularly strongly during the season of sea ice retreat. The zonal patterns of the SAM in many models and its exaggerated influence on sea ice overwhelm the comparatively underestimated meridional influence, suggesting that simulated sea ice variability would become more zonally symmetric as a result. Across the seasons of sea ice advance and retreat, three of the five sectors did not reveal a strong relationship with a pattern of large-scale atmospheric variability in one or both seasons, indicating that sea ice in these sectors may be influenced more strongly by atmospheric variability unexplained by the major atmospheric modes, or by heat exchange in the ocean.
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Holland, Marika M., i Donald Perovich. "Sea Ice Summer Camp: Bringing Together Sea Ice Modelers and Observers to Advance Polar Science". Bulletin of the American Meteorological Society 98, nr 10 (1.10.2017): 2057–59. http://dx.doi.org/10.1175/bams-d-16-0229.1.
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Abstract Arctic sea ice has undergone significant change with large reductions in thickness and areal extent over the historical record. Numerical models project sea ice loss to continue for the foreseeable future, with the possibility of September ice-free conditions later this century. Understanding the mechanisms behind ice loss and its consequences for the larger Arctic and global systems is important if we are to anticipate and plan for the future. Meeting this challenge requires the collective and collaborative insights of scientists investigating the system from numerous perspectives. One impediment to progress has been a disconnect between the observational and modeling research communities. Advancing the science requires enhanced integration between these communities and more collaborative approaches to understanding Arctic sea ice loss. This paper discusses a successful effort to further these aims: a weeklong sea ice summer camp held in Barrow, Alaska (now known as Utqiaġvik), in May 2016. The camp brought together 25 participants who were a heterogeneous mix of observers and modelers from 13 different institutions at career stages from graduate students to senior researchers. The summer camp provided an accelerated program on sea ice observations and models and also fostered future collaborative interdisciplinary activities. A dialogue with Barrow community members was initiated in order to further understand the local consequences of Arctic sea ice loss. The discussion herein describes lessons learned from this activity and paths forward to advance the understanding and prediction of Arctic climate change.
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Ma¨a¨tta¨nen, Mauri. "Advance in Ice Mechanics in Finland". Applied Mechanics Reviews 40, nr 9 (1.09.1987): 1200–1207. http://dx.doi.org/10.1115/1.3149551.
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In Finland, 110 years of winter navigation has been a natural initiator of ice mechanics research. It has brought with it sea ice monitoring and statistics, ice forecasting, the testing of mechanical properties, ship and icebreaker model testing and full-scale trials, ice resistant aids-to-navigation, and theoretical modelling and numerical simulations. Lately, a lot of ice mechanics research has been devoted to arctic offshore applications. A summary of the major developments is given in this paper.
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Chu, P. C. "Air-Ice-Ocean Feedback Mechanisms and Ice Oscillation on Millennial Time Scales". Annals of Glaciology 14 (1990): 28–31. http://dx.doi.org/10.3189/s026030550000820x.
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Air-ice-ocean feedback mechanisms, which are not conventionally incorporated within either climate or glacial models, are investigated to illustrate their potential role in generating ice advance/retreat on the time scale of 103–104 years; i.e. for examining the internal causes for the ice oscillation.Three main feedback loops are found from a coupled air-ice-ocean model developed in this paper: (a) ice advance → lower air temperature → ice freezing → ice advance; and (b) ice advance → higher ocean temperature → ice melting → ice retreat; (c) ice advance/retreat → modification of evaporation rate → change of ice accumulation rate and sea-level height → ice advance/retreat. The relative strength of the three feedback mechanisms determines the characteristics of the modes: growing or decaying, oscillatory or non-oscillatory. The solutions show the generation of growing oscillatory modes with the time scale of 103–104 years in certain parameter ranges.
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Chu, P. C. "Air-Ice-Ocean Feedback Mechanisms and Ice Oscillation on Millennial Time Scales". Annals of Glaciology 14 (1990): 28–31. http://dx.doi.org/10.1017/s026030550000820x.
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Air-ice-ocean feedback mechanisms, which are not conventionally incorporated within either climate or glacial models, are investigated to illustrate their potential role in generating ice advance/retreat on the time scale of 103–104 years; i.e. for examining the internal causes for the ice oscillation. Three main feedback loops are found from a coupled air-ice-ocean model developed in this paper: (a) ice advance → lower air temperature → ice freezing → ice advance; and (b) ice advance → higher ocean temperature → ice melting → ice retreat; (c) ice advance/retreat → modification of evaporation rate → change of ice accumulation rate and sea-level height → ice advance/retreat. The relative strength of the three feedback mechanisms determines the characteristics of the modes: growing or decaying, oscillatory or non-oscillatory. The solutions show the generation of growing oscillatory modes with the time scale of 103–104 years in certain parameter ranges.
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Lebrun, Marion, Martin Vancoppenolle, Gurvan Madec i François Massonnet. "Arctic sea-ice-free season projected to extend into autumn". Cryosphere 13, nr 1 (10.01.2019): 79–96. http://dx.doi.org/10.5194/tc-13-79-2019.
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Abstract. The recent Arctic sea ice reduction comes with an increase in the ice-free season duration, with comparable contributions of earlier ice retreat and later advance. CMIP5 models all project that the trend towards later advance should progressively exceed and ultimately double the trend towards earlier retreat, causing the ice-free season to shift into autumn. We show that such a shift is a basic feature of the thermodynamic response of seasonal ice to warming. The detailed analysis of an idealised thermodynamic ice–ocean model stresses the role of two seasonal amplifying feedbacks. The summer feedback generates a 1.6-day-later advance in response to a 1-day-earlier retreat. The underlying physics are the property of the upper ocean to absorb solar radiation more efficiently than it can release heat right before ice advance. The winter feedback is comparatively weak, prompting a 0.3-day-earlier retreat in response to a 1-day shift towards later advance. This is because a shorter growth season implies thinner ice, which subsequently melts away faster. However, the winter feedback is dampened by the relatively long ice growth period and by the inverse relationship between ice growth rate and thickness. At inter-annual timescales, the thermodynamic response of ice seasonality to warming is obscured by inter-annual variability. Nevertheless, in the long term, because all feedback mechanisms relate to basic and stable elements of the Arctic climate system, there is little inter-model uncertainty on the projected long-term shift into autumn of the ice-free season.
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Turner, J., S. A. Harangozo, J. C. King, W. M. Connolley, T. A. Lachlan‐Cope i G. J. Marshall. "An exceptional winter sea‐ice retreat/advance in the Bellingshausen sea, Antarctica". Atmosphere-Ocean 41, nr 2 (czerwiec 2003): 171–85. http://dx.doi.org/10.3137/ao.410205.
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Grumbine, Robert W. "The thermodynamic predictability of sea ice". Journal of Glaciology 40, nr 135 (1994): 277–82. http://dx.doi.org/10.1017/s002214300000736x.
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AbstractStatistical analyses and model experiments suggest that the sea-ice cover is predictable weeks to months in advance. As such, it is one of the most highly predictable components of the climate system. The thermodynamic mechanisms by which this predictability can be realized are examined. It is found that the predictability is dependent on the differential growth/decay of sea ice as a function of thickness. In winter or year-round, for thin ice, the growth/decay rates are a strong function of thickness, which gives a relatively short period of predictability, though still long compared to the atmosphere. In summer, or year-round for thick ice, growth/decay rates are only weak functions of thickness and the period of predictability is comparatively long.
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Grumbine, Robert W. "The thermodynamic predictability of sea ice". Journal of Glaciology 40, nr 135 (1994): 277–82. http://dx.doi.org/10.3189/s002214300000736x.
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AbstractStatistical analyses and model experiments suggest that the sea-ice cover is predictable weeks to months in advance. As such, it is one of the most highly predictable components of the climate system. The thermodynamic mechanisms by which this predictability can be realized are examined. It is found that the predictability is dependent on the differential growth/decay of sea ice as a function of thickness. In winter or year-round, for thin ice, the growth/decay rates are a strong function of thickness, which gives a relatively short period of predictability, though still long compared to the atmosphere. In summer, or year-round for thick ice, growth/decay rates are only weak functions of thickness and the period of predictability is comparatively long.
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Hodgson, Dominic A., Michael J. Bentley, Christoph Schnabel, Andreas Cziferszky, Peter Fretwell, Peter Convey i Sheng Xu. "Glacial geomorphology and cosmogenic 10Be and 26Al exposure ages in the northern Dufek Massif, Weddell Sea embayment, Antarctica". Antarctic Science 24, nr 4 (3.04.2012): 377–94. http://dx.doi.org/10.1017/s0954102012000016.
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AbstractWe studied the glacial geomorphology and geochronology of two ice-free valleys in the Dufek Massif (Antarctic Specially Protected Area 119) providing new constraints on past ice sheet thickness in the Weddell Sea embayment. 10Be and 26Al cosmogenic surface exposure dating provided chronological control. Seven glacial stages are proposed. These include an alpine glaciation, with subsequent (mid-Miocene?) over-riding by a warm-based ice sheet. Subsequent advances are marked by a series of minor drift deposits at 760 m altitude at > 1 Ma, followed by at least two later ice sheet advances that are characterized by extensive drift sheet deposition. An advance of plateau ice field outlet glaciers from the south postdated these drift sheets. The most recent advance involved the cold-based expansion of the ice sheet from the north at the Last Glacial Maximum, or earlier, which deposited a series of bouldery moraines during its retreat. This suggests at most a relatively modest expansion of the ice sheet and outlet glaciers dominated by a lateral ice expansion of just 2–3 km and maintaining a thickness similar to that of the northern ice sheet front. These observations are consistent with other reports of modest ice sheet thickening around the Weddell Sea embayment during the Last Glacial Maximum.
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Lüthgens, Christopher, Jacob Hardt i Margot Böse. "Proposing a new conceptual model for the reconstruction of ice dynamics in the SW sector of the Scandinavian Ice Sheet (SIS) based on the reinterpretation of published data and new evidence from optically stimulated luminescence (OSL) dating". E&G Quaternary Science Journal 69, nr 2 (30.10.2020): 201–23. http://dx.doi.org/10.5194/egqsj-69-201-2020.
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Abstract. We propose a new concept of the Weichselian ice dynamics in the south-western sector of the Baltic Sea depression. The review of existing geochronological data from Germany, Denmark and southernmost Sweden in combination with new optically stimulated luminescence (OSL) data from the German Oder Lobe area is the basis for a reassessment and an improvement of previous ice dynamic models. Factors like the pre-existing topography, glaciotectonic features and the occurrence of till beds and inter-till deposits of varying origin are also taken into consideration for our process-based reconstruction of the sedimentary environments close to the ice margin and hence the ice dynamics of the Scandinavian Ice Sheet (SIS). During the early MIS 3 (marine isotope stage), the late MIS 3 and MIS 2, the SIS advanced into present-day terrestrial areas around the south-western Baltic Sea Basin. The first ice advance during the warming phase in early MIS 3 is poorly documented as the Ellund–Warnow Advance in Germany but may be correlated with the numerically dated Ristinge Advance in Denmark and Sweden. The late MIS 3 advance in contrast is reliably documented. It shaped the landforms of the Brandenburg Advance and the maximum Weichselian ice extent in the Oder Lobe area in north-eastern Germany and occurred contemporaneously with the Klintholm Advance in southern Sweden and Denmark. The lack of a corresponding till in various cliff profiles along the Baltic Sea coastline between southern Schleswig-Holstein and the island of Rügen can be explained by the distinct lobate structure of this ice advance, which was strongly guided by the pre-existing low-lying topography. We propose the horst of Bornholm, Denmark, acting as an ice divide, with ice-dammed lakes existing on the lee side between two glacier lobes. This lobate structure had not been considered in previous conceptual models, which led to seemingly conflicting chronological and stratigraphical interpretations. Our introduction of the lobate structure for the first time resolves these contradictions and integrates the data in a coherent model. The dynamics of the MIS 2 readvance to the Last Glacial Maximum (LGM) extent were clearly different to the previous advance and were most likely characterized by a more uniformly advancing ice front with a less lobate structure which also overrode the horst of Bornholm and the island of Rügen. This advance reached the maximum Weichselian ice extent in some parts of the south-western SIS, but, in the Oder Lobe area, it is proven to have terminated at a lesser extent than the early MIS 3 advance, but it did shape the most prominent morphological landform record of the last glacial cycle. In order to advance the reconstruction of Weichselian ice dynamics in the future, we strongly suggest using both an MIS-based terminology and a process-based approach in the interpretation of geochronological data to live up to the dynamic nature of continental ice sheets.
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Zhang, Yong-Fei, Cecilia M. Bitz, Jeffrey L. Anderson, Nancy Collins, Jonathan Hendricks, Timothy Hoar, Kevin Raeder i François Massonnet. "Insights on Sea Ice Data Assimilation from Perfect Model Observing System Simulation Experiments". Journal of Climate 31, nr 15 (sierpień 2018): 5911–26. http://dx.doi.org/10.1175/jcli-d-17-0904.1.
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Simulating Arctic sea ice conditions up to the present and predicting them several months in advance has high stakeholder value, yet remains challenging. Advanced data assimilation (DA) methods combine real observations with model forecasts to produce sea ice reanalyses and accurate initial conditions for sea ice prediction. This study introduces a sea ice DA framework for a sea ice model with a parameterization of the ice thickness distribution by resolving multiple thickness categories. Specifically, the Los Alamos Sea Ice Model, version 5 (CICE5), is integrated with the Data Assimilation Research Testbed (DART). A series of perfect model observing system simulation experiments (OSSEs) are designed to explore DA algorithms within the ensemble Kalman filter (EnKF) and the relative importance of different observation types. This study demonstrates that assimilating sea ice concentration (SIC) observations can effectively remove SIC errors, with the error of total Arctic sea ice area reduced by about 60% annually. When the impact of SIC observations is strongly localized in space, the error of total volume is also modestly improved. The largest simulation improvements are produced when sea ice thickness (SIT) and SIC are jointly assimilated, with the error of total volume decreased by more than 70% annually. Assimilating multiyear sea ice concentration (MYI) can reduce error in total volume by more than 50%. Assimilating MYI produces modest improvements in snow depth (errors are reduced by around 16%), while assimilating SIC and SIT has no obvious influence on snow depth. This study also suggests that different observation types may need different localization distances to optimize DA performance.
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Bernard, Kim S., Lacey A. Gunther, Sean H. Mahaffey, Katelyn M. Qualls, Monisha Sugla, Benjamin T. Saenz, Anthony M. Cossio, Jennifer Walsh i Christian S. Reiss. "The contribution of ice algae to the winter energy budget of juvenile Antarctic krill in years with contrasting sea ice conditions". ICES Journal of Marine Science 76, nr 1 (18.10.2018): 206–16. http://dx.doi.org/10.1093/icesjms/fsy145.
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AbstractKrill overwintering strategies vary with ontogeny and year; understanding this variability is essential to predicting how the species will respond to climate change in the future. Overwintering studies have focused on larval and adult krill, but we know little about how juvenile krill overwinter. The late winter diet of juvenile krill is important because it will determine their growth and development rates and consequently their reproductive potential the following spring. A diet rich in ice algae would promote growth and reproductive development. The Bransfield Strait (northern Antarctic Peninsula, AP) is an important overwintering ground for krill; it has been proposed this region offers a food-rich winter environment. We examined the contribution of ice algae to the energy budget of overwintering juvenile krill during 2 years with contrasting sea ice conditions. Grazing on ice algae contributed ∼146% to their winter energy budget in 2015, even though ice concentrations were ≤50% and consisted of newly formed pancake ice. However, when sea ice advanced late in the Bransfield Strait (2016), ice algae contributed significantly less (∼16%) to the winter energy budget of juvenile krill. Delayed sea ice advance may negatively affect growth and reproductive development of overwintering juvenile krill.
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Wen, Xiao, Zhenghao Liu, Mengzi Yang i Ju Ding. "Numerical study of the brash ice effects on propeller performance with different advance speeds". Journal of Physics: Conference Series 2756, nr 1 (1.05.2024): 012040. http://dx.doi.org/10.1088/1742-6596/2756/1/012040.
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Abstract In this paper, the effects of brash ice on propeller performance with different advanced speeds are numerically analysed based on the CFD-DEM method. The results show that in the ice-water environment, the thrust and torque of the propeller oscillate violently due to the interaction between the ice and the propeller, and as the advanced speed increases, the oscillation becomes more and more intense. Moreover, under the blocking effect of sea ice, the average value of the thrust and torque of the propeller obviously increase and cause a large loss of propeller performance under high advance speed conditions, which would seriously affect the ice-breaking ability of polar ships.
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Jacobs, S. S., D. R. Macayeal i J. L. Ardai. "The Recent Advance of the Ross Ice Shelf Antarctica". Journal of Glaciology 32, nr 112 (1986): 464–74. http://dx.doi.org/10.1017/s0022143000012181.
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AbstractThe seaward edge of the Ross Ice Shelf advanced northward at a minimum average velocity of 0.8 km a–1between 1962 and 1985. That advance approximated velocities that have been obtained from glaciological data, indicating little recent wastage by iceberg calving. West of long. 178° E., the ice shelf has attained its most northerly position in the past 145 years, and has not experienced a major calving episode for at least 75 years. Since 1841 the ice-front position has advanced and retreated within a zone from about lat. 77° 10’S. (near long. 171° E.) to lat. 78° 40’ S. (near long. 164° W.). The central ice front is now farthest south but has the highest advance rate. Calving may occur at more frequent intervals in that sector, which also overlies the warmest ocean currents that flow into the sub-ice-shelf cavity. Available information on ice-shelf advance, thickness, spreading rate, and surface accumulation indicates a basal melting rate around 3 m a–1near the ice front. These data and independent estimates imply that basal melting is nearly as large a factor as iceberg calving in maintaining the ice-shelf mass balance. In recent years, the Ross, Ronne, and Filchner Ice Shelves have contributed few icebergs to the Southern Ocean, while projections from a contemporaneous iceberg census are that circumpolar calving alone may exceed accumulation on the ice sheet. Large-scale ice-shelf calving may have preceded historical sightings of increased numbers of icebergs at sea.
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Jacobs, S. S., D. R. Macayeal i J. L. Ardai. "The Recent Advance of the Ross Ice Shelf Antarctica". Journal of Glaciology 32, nr 112 (1986): 464–74. http://dx.doi.org/10.3189/s0022143000012181.
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AbstractThe seaward edge of the Ross Ice Shelf advanced northward at a minimum average velocity of 0.8 km a–1 between 1962 and 1985. That advance approximated velocities that have been obtained from glaciological data, indicating little recent wastage by iceberg calving. West of long. 178° E., the ice shelf has attained its most northerly position in the past 145 years, and has not experienced a major calving episode for at least 75 years. Since 1841 the ice-front position has advanced and retreated within a zone from about lat. 77° 10’S. (near long. 171° E.) to lat. 78° 40’ S. (near long. 164° W.). The central ice front is now farthest south but has the highest advance rate. Calving may occur at more frequent intervals in that sector, which also overlies the warmest ocean currents that flow into the sub-ice-shelf cavity. Available information on ice-shelf advance, thickness, spreading rate, and surface accumulation indicates a basal melting rate around 3 m a–1 near the ice front. These data and independent estimates imply that basal melting is nearly as large a factor as iceberg calving in maintaining the ice-shelf mass balance. In recent years, the Ross, Ronne, and Filchner Ice Shelves have contributed few icebergs to the Southern Ocean, while projections from a contemporaneous iceberg census are that circumpolar calving alone may exceed accumulation on the ice sheet. Large-scale ice-shelf calving may have preceded historical sightings of increased numbers of icebergs at sea.
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England, John. "The late Quaternary history of Greely Fiord and its tributaries, west-central Ellesmere Island". Canadian Journal of Earth Sciences 27, nr 2 (1.02.1990): 255–70. http://dx.doi.org/10.1139/e90-025.
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Moraines and meltwater channels mark the limit of the last glaciation that interfingered with the sea around the perimeter of Greely Fiord and its tributaries. The extent of this ice advance was dictated predominantly by its proximity to the sea. Consequently, the large tidewater glaciers at the fiord heads today were so constrained by calving that they advanced only 5–10 km. Similarly, grounding-line deposits from widespread plateau ice caps also terminate just below marine limit. The most extensive outlet glaciers, which advanced 20–35 km beyond present margins, are simply those that had access to the most extensive terrain above marine limit, i.e., the northwest margin of the Agassiz Ice Cap.Forty-one new 14C dates are presented. The onset of the last ice advance must predate marine shells collected from sediments overlying a former grounding line when sea level was 122 m higher than present. At this site, the lowermost shells collected from glaciomarine silts dated 38 070 ± 410 BP, whereas a surface sample 13 m above them dated 22 900 ± 190 BP. Although both dates may be minimum estimates, they are nonetheless associated with an ice margin that retreated only a few kilometres by 7850 BP, suggesting the maintenance of the glacioisostatic loading (and relative sea level) during the interim. Nearby, shells in growth position overlying bedrock confirm that relative sea level was > 83 m asl by 38 010 ± 410 BP (minimum age). These marine deposits lie outside the last ice limit and are not overlain by glacigenic sediments.Distal to the last ice limit, Greely Fiord was occupied by the full glacial sea, whose limit is marked by discontinuous beaches and wave-cut benches. The full glacial sea rises from 116 m north of Greely Fiord to a maximum elevation of 148 m bordering its south shore from which it descends to 112 m asl near the head of Cañon Fiord. Numerous 14C dates on shells collected within 8 m of marine limit show that the full glacial sea remained stable from at least 8400 to 7400 BP. Several other shell samples collected ~20 m below marine limit are much older (> 22 000 BP). The position of relative sea level between ca. 8000 and > 22 000 BP is uncertain; however, stratigraphic evidence for an intervening regression has not been found.The modest extent of the last ice limit encircling Greely Fiord, together with its occupancy by the full glacial sea, is fully compatible with the paleogeography previously reported from northeast Ellesmere Island and northwest Greenland. Furthermore, this data base provides a reinterpretation of a 500 km transect previously reported along west-central Ellesmere Island to the south and affirms that the Innuitian Ice Sheet, defined sensu stricto for the last glaciation, is supplanted by the full glacial Innuitian Sea, which penetrated the Queen Elizabeth Islands, constraining the last ice limit.
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Moen, M. A. N., A. P. Doulgeris, S. N. Anfinsen, A. H. H. Renner, N. Hughes, S. Gerland i T. Eltoft. "Comparison of automatic segmentation of full polarimetric SAR sea ice images with manually drawn ice charts". Cryosphere Discussions 7, nr 3 (13.06.2013): 2595–634. http://dx.doi.org/10.5194/tcd-7-2595-2013.
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Abstract. In this paper we investigate the performance of an algorithm for automatic segmentation of full polarimetric, synthetic aperture radar (SAR) sea ice scenes. The algorithm uses statistical and polarimetric properties of the backscattered radar signals to segment the SAR image into a specified number of classes. This number was determined in advance from visual inspection of the SAR image and by available in-situ measurements. The segmentation result was then compared to ice charts drawn by ice service analysts. The comparison revealed big discrepancies between the charts of the analysts, and between the manual and the automatic segmentations. In the succeeding analysis, the automatic segmentation chart was labeled into ice types by sea ice experts, and the SAR features used in the segmentation were interpreted in terms of physical sea ice properties. Studies of automatic and robust estimation of the number of ice classes in SAR sea ice scenes will be highly relevant for future work.
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Ackley, S. F., S. Stammerjohn, T. Maksym, M. Smith, J. Cassano, P. Guest, J. L. Tison i in. "Sea-ice production and air/ice/ocean/biogeochemistry interactions in the Ross Sea during the PIPERS 2017 autumn field campaign". Annals of Glaciology 61, nr 82 (11.06.2020): 181–95. http://dx.doi.org/10.1017/aog.2020.31.
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AbstractThe Ross Sea is known for showing the greatest sea-ice increase, as observed globally, particularly from 1979 to 2015. However, corresponding changes in sea-ice thickness and production in the Ross Sea are not known, nor how these changes have impacted water masses, carbon fluxes, biogeochemical processes and availability of micronutrients. The PIPERS project sought to address these questions during an autumn ship campaign in 2017 and two spring airborne campaigns in 2016 and 2017. PIPERS used a multidisciplinary approach of manned and autonomous platforms to study the coupled air/ice/ocean/biogeochemical interactions during autumn and related those to spring conditions. Unexpectedly, the Ross Sea experienced record low sea ice in spring 2016 and autumn 2017. The delayed ice advance in 2017 contributed to (1) increased ice production and export in coastal polynyas, (2) thinner snow and ice cover in the central pack, (3) lower sea-ice Chl-a burdens and differences in sympagic communities, (4) sustained ocean heat flux delaying ice thickening and (5) a melting, anomalously southward ice edge persisting into winter. Despite these impacts, airborne observations in spring 2017 suggest that winter ice production over the continental shelf was likely not anomalous.
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Hodgson, Dominic A., Kelly Hogan, James M. Smith, James A. Smith, Claus-Dieter Hillenbrand, Alastair G. C. Graham, Peter Fretwell i in. "Deglaciation and future stability of the Coats Land ice margin, Antarctica". Cryosphere 12, nr 7 (20.07.2018): 2383–99. http://dx.doi.org/10.5194/tc-12-2383-2018.
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Abstract. The East Antarctic Ice Sheet discharges into the Weddell Sea via the Coats Land ice margin. We have used geophysical data to determine the changing ice-sheet configuration in this region through its last glacial advance and Holocene retreat and to identify constraints on its future stability. Methods included high-resolution multibeam bathymetry, sub-bottom profiles, seismic-reflection profiles, sediment core analysis and satellite altimetry. These provide evidence that Coats Land glaciers and ice streams merged with the palaeo-Filchner Ice Stream during the last glacial advance. Retreat of this ice stream from 12 848 to 8351 cal. yr BP resulted in its progressive southwards decoupling from Coats Land outlet glaciers. Moraines and grounding-zone wedges document the subsequent retreat and thinning of these glaciers, their loss of contact with the bed and the formation of ice shelves, which re-advanced to pinning points on topographic highs at the distal end of the troughs. Once fully detached from the bed, these ice shelves were predisposed to rapid retreat back to coastal grounding lines. This was due to reverse-bed slopes, the consequent absence of further pinning points in the troughs and potentially to the loss of structural integrity resulting from weaknesses inherited at the grounding line. These processes explain why there are no large ice shelves in the eastern Weddell Sea between 75.5 and 77∘ S.
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Peng, Ge, Michael Steele, Angela Bliss, Walter Meier i Suzanne Dickinson. "Temporal Means and Variability of Arctic Sea Ice Melt and Freeze Season Climate Indicators Using a Satellite Climate Data Record". Remote Sensing 10, nr 9 (21.08.2018): 1328. http://dx.doi.org/10.3390/rs10091328.
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Information on the timing of Arctic snow and ice melt onset, sea ice opening, retreat, advance, and closing, can be beneficial to a variety of stakeholders. Sea ice modelers can use information on the evolution of the ice cover through the rest of the summer to improve their seasonal sea ice forecasts. The length of the open water season (as derived from retreat/advance dates) is important for human activities and for wildlife. Long-term averages and variability of these dates as climate indicators are beneficial to business strategic planning and climate monitoring. In this study, basic characteristics of temporal means and variability of Arctic sea ice climate indicators derived from a satellite-based climate data record from March 1979 to February 2017 melt and freeze seasons are described. Our results show that, over the Arctic region, anomalies of snow and ice melt onset, ice opening and retreat dates are getting earlier in the year at a rate of more than 5 days per decade, while that of ice advance and closing dates are getting later at a rate of more than 5 days per decade. These significant trends resulted in significant upward trends for anomalies of inner and outer ice-free periods at a rate of nearly 12 days per decade. Small but significant downward trends of seasonal ice loss and gain period anomalies were also observed at a rate of −1.48 and −0.53 days per decade, respectively. Our analyses also demonstrated that the means of these indicators and their trends are sensitive to valid data masks and regional averaging methods.
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Yan, Qingyun, i Weimin Huang. "Sea Ice Remote Sensing Using GNSS-R: A Review". Remote Sensing 11, nr 21 (1.11.2019): 2565. http://dx.doi.org/10.3390/rs11212565.
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Knowledge of sea ice is critical for offshore oil and gas exploration, global shipping industries, and climate change studies. During recent decades, Global Navigation Satellite System-Reflectometry (GNSS-R) has evolved as an efficient tool for sea ice remote sensing. In particular, thanks to the availability of the TechDemoSat-1 (TDS-1) data over high-latitude regions, remote sensing of sea ice based on spaceborne GNSS-R has been rapidly growing. The goal of this paper is to provide a review of the state-of-the-art methods for sea ice remote sensing offered by the GNSS-R technique. In this review, the fundamentals of these applications are described, and their performances are evaluated. Specifically, recent progress in sea ice sensing using TDS-1 data is highlighted including sea ice detection, sea ice concentration estimation, sea ice type classification, sea ice thickness retrieval, and sea ice altimetry. In addition, studies of sea ice sensing using airborne and ground-based data are also noted. Lastly, applications based on various platforms along with remaining challenges are summarized and possible future trends are explored. In this review, concepts, research methods, and experimental techniques of GNSS-R-based sea ice sensing are delivered, and this can benefit the scientific community by providing insights into this topic to further advance this field or transfer the relevant knowledge and practice to other studies.
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Howell, Stephen E. L., Randall K. Scharien, Jack Landy i Mike Brady. "Spring melt pond fraction in the Canadian Arctic Archipelago predicted from RADARSAT-2". Cryosphere 14, nr 12 (21.12.2020): 4675–86. http://dx.doi.org/10.5194/tc-14-4675-2020.
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Abstract. Melt ponds form on the surface of Arctic sea ice during spring, influencing how much solar radiation is absorbed into the sea ice–ocean system, which in turn impacts the ablation of sea ice during the melt season. Accordingly, melt pond fraction (fp) has been shown to be a useful predictor of sea ice area during the summer months. Sea ice dynamic and thermodynamic processes operating within the narrow channels and inlets of the Canadian Arctic Archipelago (CAA) during the summer months are difficult for model simulations to accurately resolve. Additional information on fp variability in advance of the melt season within the CAA could help constrain model simulations and/or provide useful information in advance of the shipping season. Here, we use RADARSAT-2 imagery to predict and analyze peak melt pond fraction (fpk) and evaluate its utility to provide predictive information with respect to sea ice area during the melt season within the CAA from 2009–2018. The temporal variability of RADARSAT-2 fpk over the 10-year record was found to be strongly linked to the variability of mean April multi-year ice area with a statistically significant detrended correlation (R) of R=-0.89. The spatial distribution of RADARSAT-2 fpk was found to be in excellent agreement with the sea ice stage of development prior to the melt season. RADARSAT-2 fpk values were in good agreement with fpk observed from in situ observations but were found to be ∼ 0.05 larger compared to MODIS fpk observations. Dynamically stable sea ice regions within the CAA exhibited higher detrended correlations between RADARSAT-2 fpk and summer sea ice area. Our results show that RADARSAT-2 fpk can be used to provide predictive information about summer sea ice area for a key shipping region of the Northwest Passage.
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Kim, Stacy, Ben Saenz, Jeff Scanniello, Kendra Daly i David Ainley. "Local climatology of fast ice in McMurdo Sound, Antarctica". Antarctic Science 30, nr 2 (15.02.2018): 125–42. http://dx.doi.org/10.1017/s0954102017000578.
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AbstractFast ice plays important physical and ecological roles: as a barrier to wind, waves and radiation, as both barrier and safe resting place for air-breathing animals, and as substrate for microbial communities. While sea ice has been monitored for decades using satellite imagery, high-resolution imagery sufficient to distinguish fast ice from mobile pack ice extends only back to c. 2000. Fast ice trends may differ from previously identified changes in regional sea ice distributions. To investigate effects of climate and human activities on fast ice dynamics in McMurdo Sound, Ross Sea, the sea and fast ice seasonal events (1978–2015), ice thicknesses and temperatures (1986–2014), wind velocities (1973–2015) and dates that an icebreaker annually opens a channel to McMurdo Station (1956–2015) are reported. A significant relationship exists between sea ice concentration and fast ice extent in the Sound. While fast/sea ice retreat dates have not changed, fast/sea ice reaches a minimum later and begins to advance earlier, in partial agreement with changes in Ross Sea regional pack ice dynamics. Fast ice minimum extent within McMurdo Sound is significantly correlated with icebreaker arrival date as well as wind velocity. The potential impacts of changes in fast ice climatology on the local marine ecosystem are discussed.
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Huybers, Kathleen, Gerard Roe i Howard Conway. "Basal topographic controls on the stability of the West Antarctic ice sheet: lessons from Foundation Ice Stream". Annals of Glaciology 58, nr 75pt2 (5.06.2017): 193–98. http://dx.doi.org/10.1017/aog.2017.9.
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ABSTRACT Using observations of basal topography, ice thickness and modern accumulation rates, we use theory and a dynamic flowline model to examine the sensitivity of Antarctica's Foundation Ice Stream to changes in sea level, accumulation and buttressing at the grounding line. Our sensitivity studies demonstrate that the steep, upward-sloping basal topography inland from the grounding line serves to stabilize retreat of the ice stream, while the upward-sloping submarine topography downstream from the grounding line creates the potential for significant advance under conditions of modest sea-level lowering and/or increased accumulation rate. Extrapolating from Foundation Ice Stream, many nearby Weddell Sea sector ice streams are in a similar configuration, suggesting that the historical and projected responses of this sector's ice streams may contrast with those in the Amundsen or Ross Sea sectors. This work reaffirms that the greatest concerns for rapid West Antarctic Ice Sheet (WAIS) retreat are locations of reverse slopes, muted basal topography and limited lateral support.
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Kimura, Noriaki, i Masaaki Wakatsuchi. "Processes controlling the advance and retreat of sea ice in the Sea of Okhotsk". Journal of Geophysical Research: Oceans 104, nr C5 (15.05.1999): 11137–50. http://dx.doi.org/10.1029/1999jc900004.
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Bell, Trevor, Robert J. Rogerson i Flemming Mengel. "Reconstructed ice-flow patterns and ice limits using drift pebble lithology, outer Nachvak Fiord, northern Labrador". Canadian Journal of Earth Sciences 26, nr 3 (1.03.1989): 577–90. http://dx.doi.org/10.1139/e89-049.
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The geology of outer Nachvak Fiord provides an opportunity to differentiate lithologies originating in the Churchill Structural Province (central and inner fiord) from those in the sedimentary Ramah Group and the Nain Structural Province (outer fiord). As a result, the distribution of glacial erratics from the central and inner fiord depicts the former presence of regional Laurentide ice in the outer fiord, whereas the distribution of glacial deposits characterized by locally derived lithologies delimits the area of local glacier expansion.Based upon these criteria, the suggestion is made that regional ice at some time covered the deeply weathered mountain summits (900 m asl) in outer Nachvak Fiord. A later advance, confined to the fiord and valleys, deposited the highest moraines and till (180–115 m asl) recorded in the area. On the basis of geomorphic relationships, this advance is considered a discrete glacial event, separate from a later glaciation that was responsible for moraines and sediments at lower elevations (130–80 m asl). Two hypotheses are presented to explain the character of glacial features and sediments in the lower valleys.Hypothesis I requires that regional ice advanced through the study area and floated as ice shelves in the outer fiord and adjacent distributary valley. Sea level at this time was approximately 70 m higher than at present. Radiocarbon dates and amino-acid ratios from the shells in associated marine and glaciomarine sediments suggest a Middle Wisconsinan age for this event. During the Late Wisconsinan, regional Laurentide ice was restricted to the inner fiord while the sea (29–40 m above present) occupied the outer fiord area. The expansion of local cirque glaciers in upland areas may have occurred during both regional glaciations.In hypothesis II, the Middle Wisconsinan was characterized by extensive local glacier activity, depositing predominantly local material in the lower valleys, south of the fiord. Related fossiliferous sediments (same as above) provide the dating framework for this event. Late Wisconsinan regional ice advanced to the outer fiord and entered the distributary valley south of the fiord. Till deposited during this event is distinguished from the earlier local glaciation by the predominance of regional lithologies. Both Middle and Late Wisconsinan glaciations resulted in the formation of ice-shelf moraines at similar elevations. This implies similar relative sea-level responses to loading of the crust during both events, and consequently it is suggested that regional Laurentide ice had also advanced during the Middle Wisconsinan.Neither hypothesis conforms to a recently proposed Late Wisconsinan ice model for northern Labrador that requires extensive regional ice coverage in the outer fiord and on the Labrador Shelf.
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Moen, M. A. N., A. P. Doulgeris, S. N. Anfinsen, A. H. H. Renner, N. Hughes, S. Gerland i T. Eltoft. "Comparison of feature based segmentation of full polarimetric SAR satellite sea ice images with manually drawn ice charts". Cryosphere 7, nr 6 (7.11.2013): 1693–705. http://dx.doi.org/10.5194/tc-7-1693-2013.
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Abstract. In this paper we investigate the performance of an algorithm for automatic segmentation of full polarimetric, synthetic aperture radar (SAR) sea ice scenes. The algorithm uses statistical and polarimetric properties of the backscattered radar signals to segment the SAR image into a specified number of classes. This number was determined in advance from visual inspection of the SAR image and by available in situ measurements. The segmentation result was then compared to ice charts drawn by ice service analysts. The comparison revealed big discrepancies between the charts of the analysts, and between the manual and the automatic segmentations. In the succeeding analysis, the automatic segmentation chart was labeled into ice types by sea ice experts, and the SAR features used in the segmentation were interpreted in terms of physical sea ice properties. Utilizing polarimetric information in sea ice charting will increase the efficiency and exactness of the maps. The number of classes used in the segmentation has shown to be of significant importance. Thus, studies of automatic and robust estimation of the number of ice classes in SAR sea ice scenes will be highly relevant for future work.
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Goosse, Hugues, Sofia Allende Contador, Cecilia M. Bitz, Edward Blanchard-Wrigglesworth, Clare Eayrs, Thierry Fichefet, Kenza Himmich i in. "Modulation of the seasonal cycle of the Antarctic sea ice extent by sea ice processes and feedbacks with the ocean and the atmosphere". Cryosphere 17, nr 1 (31.01.2023): 407–25. http://dx.doi.org/10.5194/tc-17-407-2023.
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Abstract. The seasonal cycle of the Antarctic sea ice extent is strongly asymmetric, with a relatively slow increase after the summer minimum followed by a more rapid decrease after the winter maximum. This cycle is intimately linked to the seasonal cycle of the insolation received at the top of the atmosphere, but sea ice processes as well as the exchanges with the atmosphere and ocean may also play a role. To quantify these contributions, a series of idealized sensitivity experiments have been performed with an eddy-permitting (1/4∘) NEMO-LIM3 (Nucleus for European Modelling of the Ocean–Louvain-la-Neuve sea ice model version 3) Southern Ocean configuration, including a representation of ice shelf cavities, in which the model was either driven by an atmospheric reanalysis or coupled to the COSMO-CLM2 regional atmospheric model. In those experiments, sea ice thermodynamics and dynamics as well as the exchanges with the ocean and atmosphere are strongly perturbed. This perturbation is achieved by modifying snow and ice thermal conductivities, the vertical mixing in the ocean top layers, the effect of freshwater uptake and release upon sea ice growth and melt, ice dynamics, and surface albedo. We find that the evolution of sea ice extent during the ice advance season is largely independent of the direct effect of the perturbation and appears thus mainly controlled by initial state in summer and subsequent insolation changes. In contrast, the melting rate varies strongly between the experiments during the retreat, in particular if the surface albedo or sea ice transport are modified, demonstrating a strong contribution of those elements to the evolution of ice coverage through spring and summer. As with the advance phase, the retreat is also influenced by conditions at the beginning of the melt season in September. Atmospheric feedbacks enhance the model winter ice extent response to any of the perturbed processes, and the enhancement is strongest when the albedo is modified. The response of sea ice volume and extent to changes in entrainment of subsurface warm waters to the ocean surface is also greatly amplified by the coupling with the atmosphere.
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Shabanov, Pavel, Alexander Osadchiev, Natalya Shabanova i Stanislav Ogorodov. "Decline in Ice Coverage and Ice-Free Period Extension in the Kara and Laptev Seas during 1979–2022". Remote Sensing 16, nr 11 (24.05.2024): 1875. http://dx.doi.org/10.3390/rs16111875.
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The duration of ice-free periods in different parts of the Arctic Ocean plays a great role in processes in the climate system and defines the most comfortable sea ice conditions for economic activity. Based on satellite-derived sea ice concentration data acquired by passive microwave instruments, we identified the spatial distribution of the dates of sea ice retreat (DOR), dates of sea ice advance (DOA), and the resulting ice-free period duration (IFP) between these days for the Kara and Laptev seas during 1979–2022. The monthly decline in sea ice extent was detected from June to October in both seas, i.e., during the whole ice-free period. The annual mean sea ice extent during 2011–2021 decreased by 19.0% and 12.8% relative to the long-term average during 1981–2010 in the Kara and Laptev seas, respectively. The statistically significant (95% confidence level) positive IFP trends were detected for the majority of areas of the Kara and Laptev seas. Averaged IFP trends were estimated equal to +20.2 day/decade and +16.2 day/decade, respectively. The observed DOR tendency to earlier sea ice melting plays a greater role in the total IFP extension, as compared to later sea ice formation related to the DOA tendency. We reveal that regions of inflow of warm Atlantic waters to the Kara Sea demonstrate the largest long-term trends in DOA, DOR, and IFP associated with the decrease in ice coverage, that highlights the process of atlantification. Also, the Great Siberian Polynya in the Laptev Sea is the area of the largest long-term decreasing trend in DOR.
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Briner, Jason P., i Darrell S. Kaufman. "Late Pleistocene Glaciation of the Southwestern Ahklun Mountains, Alaska". Quaternary Research 53, nr 1 (styczeń 2000): 13–22. http://dx.doi.org/10.1006/qres.1999.2088.
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AbstractGlacial deposits in the southwestern Ahklun Mountains, southwestern Alaska, record two major glacier advances during the late Pleistocene. The Arolik Lake and Klak Creek glaciations took place during the early and late Wisconsin, respectively. During the Arolik Lake glaciation, outlet glaciers emanated from an ice cap centered over the central portion of the Ahklun Mountains and expanded beyond the present coast. During the Klak Creek glaciation, ice-cap outlet glaciers terminated ∼60 km upvalley from Arolik Lake moraines. The area also supported numerous alpine glaciers that expanded from small massifs. During both episodes of glaciation, these alpine glaciers apparently reached their maximum positions sometime after the retreat of the ice-cap outlet glaciers. Equilibrium-line altitudes for reconstructed alpine glaciers of the Klak Creek glaciation average ∼390 ± 100 m elevation in the western Ahklun Mountains, which is at most 500 m, and possibly only 200 m, below the estimated modern equilibrium-line altitude. The maximum late Pleistocene advance in the southwestern Ahklun Mountains occurred during the early Wisconsin, similar to advances elsewhere in western Alaska, but in contrast to the isotopic signal in the deep-sea record of global ice volume. The restricted extent of Klak Creek glaciers might reflect the increased distance to the Bering Sea resulting from eustatic sea-level regression and decreased evaporation resulting from lower sea-surface temperatures and increased sea-ice extent.
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Glok, N. I., G. V. Alekseev i A. E. Vyazilova. "Seasonal forecast of sea ice extent in the Barents sea". Arctic and Antarctic Research 65, nr 1 (8.04.2019): 5–14. http://dx.doi.org/10.30758/0555-2648-2019-65-1-5-14.
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Earlier, the authors established a close relationship between the temperature of water coming from the North Atlantic and the sea ice extent (SIE) in the Barents Sea, which accounts for up to 75 % of the inter-annual variability of the monthly SIE from January to June. In turn, temperature variations of the incoming Atlantic water are affected from anomalies of sea surface temperature (SST) in the low latitudes of the North Atlantic. These dependences served as the basis for the development of a forecast method. The empirical orthogonal functions decomposition of the SIE set from January to June for 1979–2014 was used. The main component of decomposition reflects 83 % of the inter-annual variability of SIE from January to June. Regression model of forecast is based on the relation of the main component with SST anomalies taking into account the delay. Comparison of prognostic and actual values of the climatic component for each of the 6 months showed the correctness of forecasts with a lead time of 27 to 32 months is 83 %, and for the prediction of the initial values of SIE 79 %. Appealing to the second predictor — SST anomalies in the Norwegian Sea allowed to improve the quality of the forecast of the observed values of SIE. At the same time, the forecast advance time was reduced to 9–14 months.
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Syvitski, James P. M., i Dan B. Praeg. "Quaternary Sedimentation in the St. Lawrence Estuary and Adjoining Areas, Eastern Canada: An Overview Based on High-Resolution Seismo-Stratigraphy". Géographie physique et Quaternaire 43, nr 3 (18.12.2007): 291–310. http://dx.doi.org/10.7202/032784ar.
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ABSTRACT The regional Quaternary seismo-stratigraphy of NW Gulf of St. Lawrence, based on 5700 line km of high resolution seismic reflection profiles, is described. The Quaternary sequence can be locally missing or can exceed 1.3 km in thickness. Five major stratigraphic units are recognized, which vary in their character and distribution so that at any location a variety of bedrock types may be overlain by a distinctive Quaternary sequence. These units relate to the advance and retreat of the Late Wisconsinan Ice Sheet. We interpret these units as: Unit 1, recording the presence of grounded glacial ice, including ice-loaded and ice-deposited sediments. Unit 2, ice-proximal coarse-grained sediment deposited either as a thin, conformable layer during the rapid retreat of an ice terminus, or as a wedge-shaped fan marking the position of an ice front still stand. Unit 3, ice-distal fine-grained sediment deposited from meltwater plumes at times of elevated sea levels and rapidly ablating sea ice. Unit 4, paraglacial deltaic sediment marking the melting of terrestrially-based ice caps, and the concommittant growth of deltas, rapidly prograding into a seaway undergoing rapidly falling sea levels. Unit 5, postglacial sediment reflecting the winnowing of shallow areas and deposition of organic-rich mud in deep basins, under modern sea level and océanographie conditions. A conceptual model dealing with the deposition of sediment associated with the withdrawal of a continental ice sheet is developed. The model includes the dynamics associated with the initial ice advance, terminal ice dynamics, retreat of the ice terminus, stable ice-fronts during the recessional phase, ice sheets ablating on land, and postglacial sedimentation under conditions of fluctuating sea levels.
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Chevallier, Matthieu, i David Salas-Mélia. "The Role of Sea Ice Thickness Distribution in the Arctic Sea Ice Potential Predictability: A Diagnostic Approach with a Coupled GCM". Journal of Climate 25, nr 8 (10.04.2012): 3025–38. http://dx.doi.org/10.1175/jcli-d-11-00209.1.
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Abstract The intrinsic seasonal predictability of Arctic sea ice is investigated in a 400-yr-long preindustrial simulation performed with the Centre National de Recherches Météorologiques Coupled Global Climate Model, version 3.3 (CNRM-CM3.3). The skill of several predictors of the pan-Arctic sea ice area was quantified: the sea ice area itself, the pan-Arctic sea ice volume, and some areal predictors built from the subgrid ice thickness distribution (ITD). Sea ice area provides a potential predictability of about 3 months, which is consistent with previous studies using model and observation data. Sea ice volume predictive skill for winter sea ice area prediction is weak. Nevertheless, there is a higher potential to predict the September ice area with the June volume anomaly than with the June area anomaly. Using ITD-based predictors, two “regimes” of predictability were highlighted. The first one, a “persistence regime,” applies to winter/early spring sea ice seasonal predictability. The winter sea ice cover can be predicted in late fall/early winter from the amount of young ice formed since the freeze-up onset in the margins. However, sea ice area itself is potentially the best predictor of winter sea ice area at seasonal time scales. The second regime is a “memory regime.” It applies to the predictability of summer sea ice area. An ice area anomaly in September is potentially predictable up to 6 months in advance, using the area covered by ice thicker than a critical thickness lying between 0.9 and 1.5 m. Results of this study are preliminary; however, they provide information for the design of future prediction systems and highlight the need for observations and a state-of-the-art sea ice model.
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Easterbrook, Don J. "Advance and Retreat of Cordilleran Ice Sheets in Washington, U.S.A." Géographie physique et Quaternaire 46, nr 1 (23.11.2007): 51–68. http://dx.doi.org/10.7202/032888ar.
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ABSTRACT Cordilleran Ice Sheet glaciations show characteristic patterns of advance and retreat, consisting of (1) advance out outwash, (2) glacial scouring, (3) deposition of till, (4) deposition of recessional outwash south of Seattle in the southern Puget Lowland, glaciomarine drift in the northern lowland, and eskers, kames, and small moraines on the Columbia Plateau. Radiocarbon dates show that the Puget and Juan de Fuca lobes advanced and retreated synchronously. The Puget lobe backwasted to Seattle by 13.4-14 ka yrs BP, where the thinning ice floated in seawater northward to Canada by 13 ka yrs BP depositing glaciomarine drift contemporaneously over 18,000 km2. Compelling evidence against the backwasting, calving, terminus model for the origin of the glaciomarine drift includes: 1) abundant 14C dates demonstrate simultaneous deposition of glaciomarine drift over the entire area; 2) stagnant-ice deposits closely related to glaciomarine drift are not consistent with an actively-calving, backwasting terminus; 3) irrefutable evidence for the nonmarine origin of Deming sand shows that Cordilleran ice was absent immediately prior to deposition of the overlying glaciomarine drift. The pattern of events in the northern Puget Lowland includes: 1) glacial loading under 1800 m of ice during the Vashon maximum; 2) rapid glacial thinning and floating of the ice deposited Kulshan glaciomarine drift 12-13 ka yrs BP; 3) emergence and deposition of fluvial Deming sand 11.5 ka yrs BP; 4) resubmer-gence and deposition of Bellingham glaciomarine drift up to -200 m, well beyond global eustatic sea level rise; 5) emergence 10.5-11.5 ka yrs BP and deposition of Sumas outwash on Bellingham glaciomarine drift; 6) Holocene eustatic sea level rise kept pace with isostatic rebound, thus, post-Sumas marine terraces are absent.
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Phillips, F. "Glacial chronology of the Sierra Nevada, California, from the Last Glacial Maximum to the Holocene". Cuadernos de Investigación Geográfica 43, nr 2 (15.09.2017): 527. http://dx.doi.org/10.18172/cig.3233.
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During the Last Glacial Maximum the Sierra Nevada in California, USA, supported a mountain glacier/ice cap complex that covered over 20,000 km2. The history of this ice cover can be reconstructed using 14C and cosmogenic-nuclide surface-exposure dating. These show that the glaciers reached their maximum extent for the last glacial cycle between 21 and 18 ka, i.e., during the global Last Glacial Maximum. This is termed the Tioga 3 advance. A slow retreat began at 18 ka and accelerated rapidly at about 17 ka. After retreating an unknown distance, the glaciers began to readvance at about 16.7 ka, reaching the Tioga 4 limit at 16.2 ka. They then rapidly retreated to the crest of the range, probably within 500 to 1000 years. There is no indication of subsequent glacial expansion until the Recess Peak advance between 14.0 and 12.5 ka. Unfortunately, chronological control is not adequate to determine whether this advance was during the early Younger Dryas or slightly preceded it. The equilibrium-line-altitude reduction during the Tioga 3 was about 1200 m, that during the Tioga 4 about 800 m, and during the Recess Peak 100 to 200 m. The Tioga 4 advance coincided with the expansion of nearby pluvial Lake Lahontan to its maximum size. The Sierra Nevada advances correlate well with the glacial chronology of the Alps during the same period, and also with the episodes of melting and advance of the European and Laurentide Ice Sheets. Times of glacial advance in the Sierra Nevada may be connected to the melting history of the ice sheets, and to Heinrich events, by expansion and contraction of sea ice in the southern North Atlantic.
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Lange, Manfred A., i Heinz Kohnen. "Ice Front Fluctuations in the Eastern and Southern Weddell Sea". Annals of Glaciology 6 (1985): 187–91. http://dx.doi.org/10.3189/1985aog6-1-187-191.
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We report new data on the position of ice edges in the eastern and southern Weddell Sea for the years 1983 and 1984. The data are derived from ship-borne radar measurements of individual points along the ice edge together with ship’s positions obtained by a satellite navigation system. They are accurate within 0.23 to 0.4 nm (426 - 741 m). Comparisons of ice shelf margins for the years 1980, 1983 and 1984 allow estimates of apparent ice advance rates during this period. Together with quantitative ice edge velocity estimates first conclusions about net changes along the ice front and the ablation along the margin of ice shelves in the eastern and southern Weddell Sea are derived.
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Lange, Manfred A., i Heinz Kohnen. "Ice Front Fluctuations in the Eastern and Southern Weddell Sea". Annals of Glaciology 6 (1985): 187–91. http://dx.doi.org/10.1017/s0260305500010314.
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We report new data on the position of ice edges in the eastern and southern Weddell Sea for the years 1983 and 1984. The data are derived from ship-borne radar measurements of individual points along the ice edge together with ship’s positions obtained by a satellite navigation system. They are accurate within 0.23 to 0.4 nm (426 - 741 m). Comparisons of ice shelf margins for the years 1980, 1983 and 1984 allow estimates of apparent ice advance rates during this period. Together with quantitative ice edge velocity estimates first conclusions about net changes along the ice front and the ablation along the margin of ice shelves in the eastern and southern Weddell Sea are derived.
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Quetin, Langdon B., Robin M. Ross, Christian H. Fritsen i Maria Vernet. "Ecological responses of Antarctic krill to environmental variability: can we predict the future?" Antarctic Science 19, nr 2 (22.05.2007): 253–66. http://dx.doi.org/10.1017/s0954102007000363.
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AbstractAntarctic krill are a key species in the Southern Ocean ecosystem, and their life cycle appears to be correlated with, and by implication dependent upon, seasonal sea ice dynamics. Moving from correlations with environmental parameters to an understanding of the mechanisms that lead to these correlations may allow predictions of the consequences of climate change on the distribution of favourable habitat for Antarctic krill. During winter cruises in 2001 and 2002 in the region west of the Antarctic Peninsula, one of the most rapidly warming regions on the planet, ice camps were established for periods of 3–9 days. Timing of sea ice advance, chlorophyll a concentrations in ice cores, and growth rates and pigment content of larval krill all differed significantly between winters. Growth rates and pigment content of larval krill from the same ice floe were correlated, suggesting that growth rates in winter are a function of the biomass of the sea ice microbial community. Apossible mechanism underlying the correlation between recruitment success and timing of ice advance is proposed. In conjunction with other postulated habitat requirements, this proposed mechanism allows for speculation about future changes in the geographic location of favourable habitat for Antarctic krill.
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Serreze, Mark C., Alex D. Crawford, Julienne C. Stroeve, Andrew P. Barrett i Rebecca A. Woodgate. "Variability, trends, and predictability of seasonal sea ice retreat and advance in the Chukchi Sea". Journal of Geophysical Research: Oceans 121, nr 10 (październik 2016): 7308–25. http://dx.doi.org/10.1002/2016jc011977.
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Loose, B., W. R. McGillis, D. Perovich, C. J. Zappa i P. Schlosser. "A parameter model of gas exchange for the seasonal sea ice zone". Ocean Science Discussions 10, nr 4 (23.07.2013): 1169–204. http://dx.doi.org/10.5194/osd-10-1169-2013.
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Abstract. Carbon budgets for the polar oceans require better constraint on air-sea gas exchange in the sea ice zone (SIZ). Here, we utilize recent advances in the theory of turbulence, mixing and air-sea flux in the ice-ocean boundary layer (IOBL) to formulate a simple model for gas exchange when the surface ocean is partially covered by sea ice. The gas transfer velocity (k) is related to shear-driven and convection-driven turbulence in the aqueous mass boundary layer, and to the mean-squared wave slope at the air–sea interface. We use the model to estimate k along the drift track of Ice-Tethered Profilers (ITPs) in the Arctic. Individual estimates of daily-averaged k from ITP drifts ranged between 1.1 and 22 m d−1, and the fraction of open water (f) ranged from 0 to 0.83. Converted to area-weighted effective transfer velocities (keff), the minimum value of keff was 10−5 m d−1 near f = 0 with values exceeding keff = 5 m d−1 at f = 0.4. The largest values of k occurred during the periods when ice cover around the ITP was changing rapidly; either in advance or retreat. The model indicates that effects from shear and convection in the sea ice zone contribute an additional 40% to the magnitude of keff, beyond what would be predicted from an estimate of keff based solely upon a windspeed parameterization. Although the ultimate scaling relationship for gas exchange in the sea ice zone will require validation in laboratory and field studies, the basic parameter model described here demonstrates that it is feasible to formulate estimates of k based upon properties of the IOBL using data sources that presently exist.
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Hodell, David A., Sharon L. Kanfoush, Aldo Shemesh, Xavier Crosta, Christopher D. Charles i Thomas P. Guilderson. "Abrupt Cooling of Antarctic Surface Waters and Sea Ice Expansion in the South Atlantic Sector of the Southern Ocean at 5000 cal yr B.P." Quaternary Research 56, nr 2 (wrzesień 2001): 191–98. http://dx.doi.org/10.1006/qres.2001.2252.
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AbstractAntarctic surface waters were warm and ice free between 10,000 and 5000 cal yr B.P., as judged from ice-rafted debris and microfossils in a piston core at 53°S in the South Atlantic. This evidence shows that about 5000 cal yr B.P., sea surface temperatures cooled, sea ice advanced, and the delivery of ice-rafted detritus (IRD) to the subantarctic South Atlantic increased abruptly. These changes mark the end of the Hypsithermal and onset of Neoglacial conditions. They coincide with an early Neoglacial advance of mountain glaciers in South America and New Zealand between 5400 and 4900 cal yr B.P., rapid middle Holocene climate changes inferred from the Taylor Dome Ice Core (Antarctica), cooling and increased IRD in the North Atlantic, and the end of the African humid period. The near synchrony and abruptness of all these climate changes suggest links among the tropics and both poles that involved nonlinear response to gradual changes in Northern Hemisphere insolation. Sea ice expansion in the Southern Ocean may have provided positive feedback that hastened the end of the Hypsithermal and African humid periods in the middle Holocene.
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Morioka, Yushi, Liping Zhang, Thomas L. Delworth, Xiaosong Yang, Fanrong Zeng, Masami Nonaka i Swadhin K. Behera. "Multidecadal variability and predictability of Antarctic sea ice in the GFDL SPEAR_LO model". Cryosphere 17, nr 12 (8.12.2023): 5219–40. http://dx.doi.org/10.5194/tc-17-5219-2023.
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Abstract. Using a state-of-the-art coupled general circulation model, physical processes underlying Antarctic sea ice multidecadal variability and predictability are investigated. Our model simulations constrained by atmospheric reanalysis and observed sea surface temperature broadly capture a multidecadal variability in the observed sea ice extent (SIE) with a low sea ice state (late 1970s–1990s) and a high sea ice state (2000s–early 2010s), although the model overestimates the SIE decrease in the Weddell Sea around the 1980s. The low sea ice state is largely due to the deepening of the mixed layer and the associated deep convection that brings subsurface warm water to the surface. During the high sea ice period (post-2000s), the deep convection substantially weakens, so surface wind variability plays a greater role in the SIE variability. Decadal retrospective forecasts started from the above model simulations demonstrate that the Antarctic sea ice multidecadal variability can be skillfully predicted 6–10 years in advance, showing a moderate correlation with the observation. Ensemble members with a deeper mixed layer and stronger deep convection tend to predict a larger sea ice decrease in the 1980s, whereas members with a larger surface wind variability tend to predict a larger sea ice increase after the 2000s. Therefore, skillful simulation and prediction of the Antarctic sea ice multidecadal variability require accurate simulation and prediction of the mixed layer, deep convection, and surface wind variability in the model.
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Mudryk, Lawrence R., Chris Derksen, Stephen Howell, Fred Laliberté, Chad Thackeray, Reinel Sospedra-Alfonso, Vincent Vionnet, Paul J. Kushner i Ross Brown. "Canadian snow and sea ice: historical trends and projections". Cryosphere 12, nr 4 (4.04.2018): 1157–76. http://dx.doi.org/10.5194/tc-12-1157-2018.
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Abstract. The Canadian Sea Ice and Snow Evolution (CanSISE) Network is a climate research network focused on developing and applying state of the art observational data to advance dynamical prediction, projections, and understanding of seasonal snow cover and sea ice in Canada and the circumpolar Arctic. Here, we present an assessment from the CanSISE Network on trends in the historical record of snow cover (fraction, water equivalent) and sea ice (area, concentration, type, and thickness) across Canada. We also assess projected changes in snow cover and sea ice likely to occur by mid-century, as simulated by the Coupled Model Intercomparison Project Phase 5 (CMIP5) suite of Earth system models. The historical datasets show that the fraction of Canadian land and marine areas covered by snow and ice is decreasing over time, with seasonal and regional variability in the trends consistent with regional differences in surface temperature trends. In particular, summer sea ice cover has decreased significantly across nearly all Canadian marine regions, and the rate of multi-year ice loss in the Beaufort Sea and Canadian Arctic Archipelago has nearly doubled over the last 8 years. The multi-model consensus over the 2020–2050 period shows reductions in fall and spring snow cover fraction and sea ice concentration of 5–10 % per decade (or 15–30 % in total), with similar reductions in winter sea ice concentration in both Hudson Bay and eastern Canadian waters. Peak pre-melt terrestrial snow water equivalent reductions of up to 10 % per decade (30 % in total) are projected across southern Canada.
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Goodwin, Ian D. "Basal ice accretion and debris entrainment within the coastal ice margin, Law Dome, Antarctica". Journal of Glaciology 39, nr 131 (1993): 157–66. http://dx.doi.org/10.1017/s002214300001580x.
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AbstractBasal ice stratigraphy in coastal ice cliffs at the Law Dome margin has revealed the basal accretion of clean and debris-bearing ice, marine congelation ice and granular marine ice inland of the margin. Co-isotopic analysis of δ18O and δD isotopes together with solute chemistry were applied to determine the modes of accretion and debris entrainment. The marine congelation ice and the granular marine ice were formed from the basal freezing of desalinated sea water and the episodic mixture of basal meltwater and sea water, respectively. Two different debris-entrainment mechanisms were identified. Debris-band ice with debris concentrations of 6.3–33% (by volume) was formed from proglacial raised beach and shallow marine sediment incorporated by an over-riding advance of the margin. Two other debris-bearing ice types, dispersed debris-poor ice with debris concentrations <0.3% (by volume) and laminated debris ice with debris concentrations 0.9–1.9% (by volume) were accreted further inland from the margin by basal regelation processes associated with the Robin (1976) heat-pump effect.
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Goodwin, Ian D. "Basal ice accretion and debris entrainment within the coastal ice margin, Law Dome, Antarctica". Journal of Glaciology 39, nr 131 (1993): 157–66. http://dx.doi.org/10.3189/s002214300001580x.
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AbstractBasal ice stratigraphy in coastal ice cliffs at the Law Dome margin has revealed the basal accretion of clean and debris-bearing ice, marine congelation ice and granular marine ice inland of the margin. Co-isotopic analysis of δ18O and δD isotopes together with solute chemistry were applied to determine the modes of accretion and debris entrainment. The marine congelation ice and the granular marine ice were formed from the basal freezing of desalinated sea water and the episodic mixture of basal meltwater and sea water, respectively. Two different debris-entrainment mechanisms were identified. Debris-band ice with debris concentrations of 6.3–33% (by volume) was formed from proglacial raised beach and shallow marine sediment incorporated by an over-riding advance of the margin. Two other debris-bearing ice types, dispersed debris-poor ice with debris concentrations <0.3% (by volume) and laminated debris ice with debris concentrations 0.9–1.9% (by volume) were accreted further inland from the margin by basal regelation processes associated with the Robin (1976) heat-pump effect.