2,488 results on '"Fast ice"'
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2. First Calibrated Methane Bubble Wintertime Observations in the Siberian Arctic Seas: Selected Results from the Fast Ice.
- Author
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Chernykh, Denis, Shakhova, Natalia, Yusupov, Vladimir, Gershelis, Elena, Morgunov, Boris, and Semiletov, Igor
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ICE ,WINTER ,SEA ice ,ATMOSPHERIC methane ,WATER levels ,EBULLITION ,BOTTOM water (Oceanography) - Abstract
This paper presents the results of an acoustic survey carried out from the fast ice in the shallow waters of the East Siberian Arctic Shelf (ESAS) using a single beam echosounder. The aim of this paper is to demonstrate an improved approach to study seafloor seepages in the Arctic coastal zone with an echosounder calibrated on site. During wintertime field observations of natural rising gas bubbles, we recorded three periods of their increased activity with a total of 63 short-term ejections of bubbles from the seabed. This study presents quantitative estimates of the methane (CH
4 ) flux obtained in wintertime at two levels of the water column: (1) at the bottom/water interface and (2) at the water/sea ice interface. In winter, the flux of CH4 transported by rising bubbles to the bottom water in the shallow part of the ESAS was estimated at ~19 g·m−2 per day, while the flux reaching the water/sea ice interface was calculated as ~15 g·m−2 per day taking into account the diffusion of CH4 in the surrounding water and the enrichment of rising bubbles with nitrogen and oxygen. We suggest that this bubble-transported CH4 flux reaching the water /sea ice interface can be emitted into the atmosphere through numerous ice trenches, leads, and polynyas. This CH4 ebullition value detected at the water/sea ice interface is in the mid high range of CH4 ebullition value estimated for the entire ESAS, and two orders higher than the upper range of CH4 ebullition from the northern thermocarst lakes, which are considered as a significant source to the atmospheric methane budget. [ABSTRACT FROM AUTHOR]- Published
- 2023
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3. Antarctic Landfast Sea Ice: A Review of Its Physics, Biogeochemistry and Ecology.
- Author
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Fraser, A. D., Wongpan, P., Langhorne, P. J., Klekociuk, A. R., Kusahara, K., Lannuzel, D., Massom, R. A., Meiners, K. M., Swadling, K. M., Atwater, D. P., Brett, G. M., Corkill, M., Dalman, L. A., Fiddes, S., Granata, A., Guglielmo, L., Heil, P., Leonard, G. H., Mahoney, A. R., and McMinn, A.
- Abstract
Antarctic landfast sea ice (fast ice) is stationary sea ice that is attached to the coast, grounded icebergs, ice shelves, or other protrusions on the continental shelf. Fast ice forms in narrow (generally up to 200 km wide) bands, and ranges in thickness from centimeters to tens of meters. In most regions, it forms in autumn, persists through the winter and melts in spring/summer, but can remain throughout the summer in particular locations, becoming multi‐year ice. Despite its relatively limited extent (comprising between about 4% and 13% of overall sea ice), its presence, variability and seasonality are drivers of a wide range of physical, biological and biogeochemical processes, with both local and far‐ranging ramifications for the Earth system. Antarctic fast ice has, until quite recently, been overlooked in studies, likely due to insufficient knowledge of its distribution, leading to its reputation as a “missing piece of the Antarctic puzzle.” This review presents a synthesis of current knowledge of the physical, biogeochemical and biological aspects of fast ice, based on the sub‐domains of: fast ice growth, properties and seasonality; remote‐sensing and distribution; interactions with the atmosphere and the ocean; biogeochemical interactions; its role in primary production; and fast ice as a habitat for grazers. Finally, we consider the potential state of Antarctic fast ice at the end of the 21st Century, underpinned by Coupled Model Intercomparison Project model projections. This review also gives recommendations for targeted future work to increase our understanding of this critically‐important element of the global cryosphere.Plain Language Summary: Landfast ice (known more simply as fast ice) is sea ice that doesn't move horizontally, unlike pack ice. It can cover extensive regions of the Southern Ocean, and ranges in thickness up to several tens of meters. In many regions it melts or breaks out each summer, but can survive the melt season in others regions. Antarctic fast ice is critically important for a wide variety of coastal processes, and has far‐reaching consequences for the Earth system, however our knowledge of it is limited. This first review of Antarctic fast ice provides a synthesis of the current state of knowledge, including its baseline properties and its major roles in key glaciological, oceanographic, atmospheric, biogeochemical and biological interactions and processes, highlighting its crucial and far‐reaching importance. Antarctic fast ice is likely to reduce by the end of the 21st Century, in terms of its season length, thickness and possibly extent, but projections are highly uncertain due to a current lack of inclusion of fast ice in climate models. Observations of fast ice, including both ground‐ and satellite‐based, should be coordinated and expanded to allow deeper understanding of this important part of the global cryosphere and Antarctic coastal environment.Key Points: Antarctic landfast ice is a crucial but often overlooked part of the Antarctic coastal environmentOur review draws together the body of work which is wide‐ranging but tends to lack coordinationObservation programs need to be expanded and coordinated, and models need to incorporate realistic landfast ice [ABSTRACT FROM AUTHOR]
- Published
- 2023
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4. Fast Ice Thickness Distribution in the Western Ross Sea in Late Spring.
- Author
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Langhorne, P. J., Haas, C., Price, D., Rack, W., Leonard, G. H., Brett, G. M., and Urbini, S.
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ICE ,ICE crystals ,OCEAN currents ,AIRPLANES ,SEA ice ,ICE shelves ,AREA measurement ,MARINE habitats ,GLACIERS - Abstract
We present a 700 km airborne electromagnetic survey of late‐spring fast ice and sub‐ice platelet layer (SIPL) thickness distributions from McMurdo Sound to Cape Adare, providing a first‐time inventory of fast ice thickness close to its annual maximum. The overall mode of the consolidated ice (including snow) thickness was 1.9 m, less than its mean of 2.6 ± 1.0 m. Our survey was partitioned into level and rough ice, and SIPL thickness was estimated under level ice. Although level ice, with a mode of 2.0 m and mean of 2.0 ± 0.6 m, was prevalent, rough ice occupied 41% of the transect by length, 50% by volume, and had a mode of 3.3 m and mean of 3.2 ± 1.2 m. The thickest 10% of rough ice was almost 6 m on average, inclusive of a 2 km segment thicker than 8 m in Moubray Bay. The thickest ice occurred predominantly along the northwestern Ross Sea, due to compaction against the coast. The adjacent pack ice was thinner (by ∼1 m) than the first‐year fast ice. In Silverfish Bay, offshore Hells Gate Ice Shelf, New Harbor, and Granite Harbor, the SIPL transect volume was a significant fraction (0.30) of the consolidated ice volume. The thickest 10% of SIPLs averaged nearly 3 m thick, and near Hells Gate Ice Shelf the SIPL was almost 10 m thick, implying vigorous heat loss to the ocean (∼90 W m−2). We conclude that polynya‐induced ice deformation and interaction with continental ice influence fast ice thickness in the western Ross Sea. Plain Language Summary: Sea ice held stationary by the coast is named fast ice. Around Antarctica, it is often observed near floating land ice and grounded icebergs. Fast ice is a critical habitat for marine life and known to be a sensitive indicator to changing weather and oceanic processes. Despite its importance, satellite measurements of its area are recent, and little is known about its thickness. Using a specialized instrument on a fixed wing aircraft, we measured the 2017 November fast ice thickness in the western Ross Sea. Most of the fast ice surveyed was 2 m thick on average and had formed in sheltered embayments. Where floating glaciers are in contact with fast ice, a 3–10 m thick layer of loose ice crystals was sometimes observed beneath, which contributed to its thickness. However, most of the thicker ice was rough ice, formed when ferocious offshore winds pushed ice from the coast. It then drifted with the prevailing ocean currents until eventually becoming frozen in place against coastal topography. This rough ice, 3.3 m thick on average and comprising half the surveyed volume, was significantly thicker than adjacent freely moving pack ice. Our survey provides a baseline from which future change can be measured. Key Points: Annual maximum fast ice and sub‐ice platelet layer thickness distributions are surveyed by airborne electromagnetics over 700 km of Ross SeaDeformed against the coast, 50% of transect volume was rough first‐year fast ice (mode 3.3 m thick), that was thicker than nearby pack iceSub‐ice platelet layers over 0.5 m thick underlay level ice over large parts of four embayments, revealing land ice‐fast ice interaction [ABSTRACT FROM AUTHOR]
- Published
- 2023
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5. The decline of Svalbard land-fast sea ice extent as a result of climate change
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Jacek A. Urbański and Dagmara Litwicka
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Svalbard ,Fast ice ,Warming ,Machine learning ,Random Forest ,Oceanography ,GC1-1581 - Abstract
The Svalbard Archipelago has experienced some of the most severe temperature increases in the Arctic in the last three decades. This temperature rise has accelerated sea-ice melting along the coast of the archipelago, thus bringing changes to the local environment. In view of the importance of the near-future distribution of land-fast sea ice along the Svalbard coast, the available observation data on the ice extent between 1973 and 2018 are used herein to create a random forest (RF) model for predicting the daily ice extent and its spatial distribution according to the cumulative number of freezing and thawing degree days and the duration of the ice season. Two RF models are constructed by using either regression or classification algorithms. The regression model makes it possible to estimate the extent of land-fast ice with a root mean square error (RMSE) of 800 km2, while the classification model creates a cluster of submodels in order to forecast the spatial distribution of land-fast ice with less than 10% error. The models also enable the reconstruction of the past ice extent, and the prediction of the near-future extent, from standard meteorological data, and can even analyze the real-time spatial variability of land-fast ice. On average, the minimum two-monthly extent of land-fast sea ice along the Svalbard coast was about 12,000 km2 between 1973 and 2000. In 2005–2019, however, the ice extent declined to about 6,000 km2. A further increase in mean winter air temperatures by two degrees, which is forecast in 10 to 20 years, will result in a minimum two-monthly land-fast ice extent of about 1,500 km2, thus indicating a trend of declining land-fast ice extent in this area.
- Published
- 2022
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6. The Contribution of Sea-Ice Contamination to Inaccuracies in Sea-Ice Concentration Retrieval from Satellite Microwave Radiometry Data during the Ice-Melt Period.
- Author
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Alekseeva, T. A., Sokolova, J. V., Afanasyeva, E. V., Tikhonov, V. V., Raev, M. D., Sharkov, E. A., Kovalev, S. M., and Smolyanitsky, V. M.
- Subjects
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SEA ice , *MICROWAVE radiometry - Abstract
Sea-ice concentrations retrieved from satellite microwave radiometry data are influenced by many natural factors. In the work we consider sea-ice contamination. The values of sea-ice concentration derived with the use of the ASI, TUD, OSI-401-b, BT, NT, and CDR algorithms are analyzed on the example of fast ice in the East Siberian Sea. These algorithms are chosen because they are available for open access and are commonly used in scientific research. All of the algorithms return lower ice concentrations in contaminated ice as compared to clean ice during the active ice-melt period, from late May to early July. The ASI and TUD are the two most sensitive to sea-ice contamination, which is due to the high-frequency channels, 85–91 GHz, used in them. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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7. Effects of Snow and Remineralization Processes on Nutrient Distributions in Multi‐Year Antarctic Landfast Sea Ice.
- Author
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Sahashi, Reishi, Nomura, Daiki, Toyota, Takenobu, Tozawa, Manami, Ito, Masato, Wongpan, Pat, Ono, Kazuya, Simizu, Daisuke, Naoki, Kazuhiro, Nosaka, Yuichi, Tamura, Takeshi, Aoki, Shigeru, and Ushio, Shuki
- Subjects
SEA ice ,SNOWMELT ,ALGAL communities ,BIOLOGICAL productivity ,SNOW accumulation ,MARINE ecology ,ESSENTIAL nutrients - Abstract
We elucidated the effects of snow and remineralization processes on nutrient distributions in multi‐year landfast sea ice (fast ice) in Lützow‐Holm Bay, East Antarctica. Based on sea‐ice salinity, oxygen isotopic ratios, and thin section analyses, we found that the multi‐year fast ice grew upward due to the year‐by‐year accumulation of snow. Compared to ice of seawater origin, nutrient concentrations in shallow fast ice were low due to replacement by clean and fresh snow. In deeper ice of seawater origin (the lower half of the multi‐year fast ice column), remineralization was dominated by the degradation of organic matter. By comparison between first‐ and muti‐year ice, the biological uptake and the remineralization were dominated in relatively young ice and older ice, respectively, under the physical process of brine drainage. Plain Language Summary: Multi‐year landfast sea ice (fast ice) is abundant around the coast of Antarctica. Fast ice is an important component of Antarctic coastal marine ecosystems, providing a prolific habitat for ice algal communities. Although nutrients are essential for biological productivity within sea ice, the status of nutrients and processes affecting nutrient concentrations were previously not known for multi‐year fast ice. Here, we collected sea‐ice cores from multi‐year fast ice in Lützow‐Holm Bay, East Antarctica, and we analyzed nutrient concentrations using physical and biogeochemical parameters. Nutrient concentrations in the upper parts of the sea ice decreased due to the accumulation of clean (nutrient‐free) snow through melting and refreezing processes, contributing to upward ice growth. In deeper parts of the sea ice, nutrient concentrations were greatly affected by biological processes such as remineralization during the degradation of organic matter within sea ice. Key Points: Antarctic multi‐year landfast ice grew upward due to the year‐by‐year accumulation of snowNutrient concentrations decreased in the upper sea ice due to the replacement by clean snowIn deeper sea ice, remineralization by degradation of organic matter drove nutrient concentrations [ABSTRACT FROM AUTHOR]
- Published
- 2022
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8. Multiyear variability of the fast ice thickness in the Laptev Sea according to the polar station data
- Author
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A.B. Timofeeva and M.V. Sharatunova
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ice thickness ,fast ice ,polar stations ,ice conditions ,laptev sea ,sum of frost degree-days ,Geography (General) ,G1-922 - Abstract
The series of data on the fast ice thickness and the surface air temperature at the Roshydromet land-based polar stations in the Laptev Sea are analyzed. Observations for the last 15-year period (2005-2020) are compared to observations prior to 2004, and the changes corresponding to the new climatic conditions are revealed. Over the past 15 years ice thicknesses during the period of maximum ice growth (maximum ice thickness) have decreased by 6% on average. The ice growth process has become much slower, transition between the sequentional stages of ice development is observed 1-2 ten-days periods later. The surface air temperature at the considered stations was on average 3°C higher than for the previous period. The most significant changes are observed in the autumn months (October, November) and in April. The cumulative sum of the degree-day of frost averaged for the Laptev Sea stations, decreased by 15%; all 15 recent winter seasons can be classified as mild. It was revealed that the decrease of the cumulative sum of degree-day of frost is in a good agreement with the decrease of the mean-seasonal ice thickness (averaged for November-May) at the stations. This indicator seems to be more informative than the maximum ice thickness for estimation of the changes. Averaging over all stations revealed a 10% decrease of the mean-seasonal ice thickness during the past 15 years.
- Published
- 2021
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9. Sea-Ice Parameters from Satellite Remote Sensing
- Author
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Kern, Stefan, Willmes, Sascha, Barale, Vittorio, editor, and Gade, Martin, editor
- Published
- 2019
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10. Optical properties and surface energy flux of spring fast ice in the Arctic.
- Author
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Zhu, Jialiang, Liu, Yilin, Wang, Xiaoyu, and Li, Tao
- Abstract
Over the past decades, sea ice in the polar regions has been significantly affecting local and even hemispheric climate through a positive ice albedo feedback mechanism. The role of fast ice, as opposed to drift ice, has not been well-studied due to its relatively small coverage over the earth. In this paper, the optical properties and surface energy balance of land fast ice in spring are studied using in situ observations in Barrow, Alaska. The results show that the albedo of the fast ice varied between 0.57 and 0.85 while the transmittance increased from 1.3×10
−3 to 4.1×10−3 during the observation period. Snowfall and air temperature affected the albedo and absorbance of sea ice, but the transmittance had no obvious relationship with precipitation or snow cover. Net solar shortwave radiation contributes to the surface energy balance with a positive 99.2% of the incident flux, with sensible heat flux for the remaining 0.8%. Meanwhile, the ice surface loses energy through the net longwave radiation by 18.7% of the total emission, while the latent heat flux accounts for only 0.1%. Heat conduction is also an important factor in the overall energy budget of sea ice, contributing 81.2% of the energy loss. Results of the radiative transfer model reveal that the spectral transmittance of the fast ice is determined by the thickness of snow and sea ice as well as the amount of inclusions. As major inclusions, the ice biota and particulates have a significant influence on the magnitude and distribution of the spectral transmittance. Based on the radiative transfer model, concentrations of chlorophyll and particulate in the fast ice are estimated at 5.51 mg/m2 and 95.79 g/m2 , which are typical values in the spring in Barrow. [ABSTRACT FROM AUTHOR]- Published
- 2021
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11. Grounded icebergs as maternity denning habitat for polar bears (Ursus maritimus) in North and Northeast Greenland.
- Author
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Laidre, Kristin L. and Stirling, Ian
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POLAR bear ,ICEBERGS ,RINGED seal ,SEA ice ,ICE shelves ,SNOW - Abstract
This study provides the first documentation of polar bear (Ursus maritimus) maternity denning in snowdrifts around icebergs frozen into the fast ice or grounded on the seafloor. Based on six den observations in north and northeast Greenland during spring surveys in 2018 and 2019 (109 flight hours), together with observations of 20 adult females with 35 cubs of the year (COYs) in adjacent sea ice, we hypothesize that the use of snowdrifts around icebergs for maternity denning is an established behavior in the region and not a random event. Factors influencing maternity denning in snowdrifts around icebergs may include limited suitable drifts on the nearby terrestrial polar desert due to low precipitation, the presence of suitable wind-blown snow banks regardless of the direction of autumn storm winds, cold and stable habitat throughout the winter denning period, and access to ringed seal (Pusa hispida) pupping habitat in the nearby Northeast Water polynya. This type of maternity denning habitat is only available in glaciated regions of the Arctic where marine-terminating glaciers deposit mélange large enough to become grounded offshore and remain in place for months or years. This habitat may become less stable or disappear with long-term climate warming. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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12. Coastal fast ice in the Shokalski Strait
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V. A. Borodkin, A. P. Makshtas, and P. V. Bogorodsky
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fast ice ,ice polygon ,model ,snow cover ,structure ,Science - Abstract
Field investigations of coastal fast ice near the research station Ice Base on the «Cape Baranova», carried out in 2013–2014, made possible to reveal a number of characteristics of the sea ice cover formation. It has been shown that during winter and early spring the sea ice thickness, being formed due to intensive snow drift and caused by that flooding of the ice cover just near the coast of the Bolshevik Island, substantially grows at its upper boundary, that is typical for the Antarctic seas. At the same time, similar process of the ice growth at a relatively short distance from the coast shows all features characteristic for the ice cover in the Arctic seas, and that is well reproduced by the conceptual numerical sea ice model. Thus, the region of the Ice Base «Cape Baranova» represents a natural laboratory for studying the processes of the sea ice formation in both, the Arctic and Antarctic seas under condition of the same atmospheric forcing. Transformation of the fast ice structure during the summer time is described. Results of the investigations has demonstrated that despite the radical changes in the structure thicknesses of the fast ice remained almost unchanged due to the ice growth on the bottom boundary of the ice cover until a destruction of it in August.
- Published
- 2016
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13. Enhanced bottom-ice algal biomass across a tidal strait in the Kitikmeot Sea of the Canadian Arctic
- Author
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Laura A. Dalman, Brent G.T. Else, David Barber, Eddy Carmack, William J. Williams, Karley Campbell, Patrick J. Duke, Sergei Kirillov, and Christopher J. Mundy
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Ice algae ,Fast ice ,Tidal strait ,Nutrients ,Under-ice current ,Environmental sciences ,GE1-350 - Abstract
Sea ice algae are an important contributor of primary production in the Arctic ecosystem. Within the bottom-ice environment, access to nutrients from the underlying ocean is a major factor controlling production, phenology, and taxonomic composition of ice algae. Previous studies have demonstrated that tides and currents play an important role in driving the flux of nutrients to bottom-ice algal communities when biological demand during the spring bloom is high. In this study we investigate how surface currents under landfast first-year ice influence nutrient supply based on stoichiometric composition, algal chlorophyll a biomass and species composition during spring 2016, in Dease Strait, Nunavut. Stronger water dynamics over a shoaled and constricted strait dominated by tidal currents (tidal strait) supported turbulent flow more than 85% of the deployment duration in comparison to outside the tidal strait in an embayment where turbulent flow was only evidenced a small percentage (
- Published
- 2019
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14. Dynamic Fine‐Scale Sea Icescape Shapes Adult Emperor Penguin Foraging Habitat in East Antarctica.
- Author
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Labrousse, Sara, Fraser, Alexander D., Sumner, Michael, Tamura, Takeshi, Pinaud, David, Wienecke, Barbara, Kirkwood, Roger, Ropert‐Coudert, Yan, Reisinger, Ryan, Jonsen, Ian, Porter‐Smith, Rick, Barbraud, Christophe, Bost, Charles‐André, Ji, Rubao, and Jenouvrier, Stéphanie
- Subjects
- *
GREENLAND ice , *POLYNYAS , *PENGUINS , *EMPERORS , *ANTARCTIC ice , *SEA ice - Abstract
The emperor penguin, an iconic species threatened by projected sea ice loss in Antarctica, has long been considered to forage at the fast ice edge, presumably relying on large/yearly persistent polynyas as their main foraging habitat during the breeding season. Using newly developed fine‐scale sea icescape data and historical penguin tracking data, this study for the first time suggests the importance of less recognized small openings, including cracks, flaw leads and ephemeral short‐term polynyas, as foraging habitats for emperor penguins. The tracking data retrieved from 47 emperor penguins in two different colonies in East Antarctica suggest that those penguins spent 23% of their time in ephemeral polynyas and did not use the large/yearly persistent, well‐studied polynyas, even if they occur much more regularly with predictable locations. These findings challenge our previous understanding of emperor penguin breeding habitats, highlighting the need for incorporating fine‐scale seascape features when assessing the population persistence in a rapidly changing polar environment. Plain Language Summary: Polar ecosystems are threatened by future loss of sea ice. The availability of satellite sea ice products has facilitated a better assessment of the impact of sea ice on polar species. Yet most studies have focused on coarse spatial scale sea ice products hampering an understanding of the mechanisms by which sea ice affects species. The development of fine‐scale sea ice products now provides an unprecedented opportunity to better understand the responses of sea ice obligate species to climate change. The emperor penguin is an iconic species threatened by projected sea ice loss in Antarctica. Here we used fine‐scale satellite sea ice observations to understand the emperor penguin's sea ice habitat during the entire breeding and Antarctic winter season. Sea ice characteristics affect both the foraging routes and effort of polar species, with consequences for their reproduction and survival, ultimately affecting population dynamics and species persistence. Emperor penguins dived at the edge of the landfast sea ice in cracks, flaw leads and open water areas called polynyas, formed by winds on both long and short time scales. By using daily passive microwave observations, we identified that emperor penguins did not venture into the large/persistent polynyas but dived instead in the ephemeral polynyas associated with daily changes in wind direction. Key Points: Dynamic fine‐scale sea icescape in East Antarctica affects the foraging routes and effort of emperor penguins during the breeding seasonEmperor penguins used short‐term ephemeral polynya openings to forage during the breeding season instead of using the persistent onesThe breeding foraging habitat was consistent among months, years, sexes, and sites despite the highly dynamic sea ice environment [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
15. Chlorophyll‐a in Antarctic Landfast Sea Ice: A First Synthesis of Historical Ice Core Data.
- Author
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Meiners, K. M., Vancoppenolle, M., Carnat, G., Castellani, G., Delille, B., Delille, D., Dieckmann, G. S., Flores, H., Fripiat, F., Grotti, M., Lange, B. A., Lannuzel, D., Martin, A., McMinn, A., Nomura, D., Peeken, I., Rivaro, P., Ryan, K. G., Stefels, J., and Swadling, K. M.
- Subjects
CHLOROPHYLL in water ,SHORE-fast ice ,SEA ice ,ICE cores ,ANTARCTIC climate - Abstract
Historical sea ice core chlorophyll‐a (Chla) data are used to describe the seasonal, regional, and vertical distribution of ice algal biomass in Antarctic landfast sea ice. The analyses are based on the Antarctic Fast Ice Algae Chlorophyll‐a data set, a compilation of currently available sea ice Chla data from landfast sea ice cores collected at circum‐Antarctic nearshore locations between 1970 and 2015. Ice cores were typically sampled from thermodynamically grown first‐year ice and have thin snow depths (mean = 0.052 ± 0.097 m). The data set comprises 888 ice cores, including 404 full vertical profile cores. Integrated ice algal Chla biomass (range: <0.1–219.9 mg/m2, median = 4.4 mg/m2, interquartile range = 9.9 mg/m2) peaks in late spring and shows elevated levels in autumn. The seasonal Chla development is consistent with the current understanding of physical drivers of ice algal biomass, including the seasonal cycle of irradiance and surface temperatures driving landfast sea ice growth and melt. Landfast ice regions with reported platelet ice formation show maximum ice algal biomass. Ice algal communities in the lowermost third of the ice cores dominate integrated Chla concentrations during most of the year, but internal and surface communities are important, particularly in winter. Through comparison of biomass estimates based on different sea ice sampling strategies, that is, analysis of full cores versus bottom‐ice section sampling, we identify biases in common sampling approaches and provide recommendations for future survey programs: for example, the need to sample fast ice over its entire thickness and to measure auxiliary physicochemical parameters. Plain Language Summary: Antarctic sea ice is a key driver of physical, chemical, and biological processes in the Southern Ocean. Importantly, sea ice serves as a substrate for microscopic algae which grow in the bottom, interior, and surface layers of the ice. These algae are considered an important food source for Antarctic marine food webs. Using a newly collated database of historical sea ice core chlorophyll‐a data (a proxy for ice algal biomass) from coastal sites, we describe the seasonal and vertical variability of algal biomass in Antarctic landfast sea ice. The seasonal chlorophyll‐a development is consistent with the current understanding of physical drivers of ice algal biomass, including the seasonal cycle of irradiance and surface temperatures driving landfast sea ice growth and melt. Our analyses show that algae in the lowermost third of ice cores drive the annual cycle of integrated biomass, but internal and surface communities are also important. Through comparison of biomass estimates based on different sea ice sampling strategies, that is, analysis of full cores versus bottom‐ice section sampling, we identify biases in common sampling approaches and provide recommendations for future survey programs: for example, the need to sample fast ice over its entire thickness and to measure auxiliary physical parameters, in particular snow‐thickness data. Key Points: First comprehensive collation of Antarctic landfast sea‐ice core chlorophyll‐a data establishedAlgae in lowermost third of ice cores drive annual cycle of integrated biomass, but internal and surface communities are also importantFull‐profile ice‐core sampling and systematic collection of auxiliary physico‐chemical parameters is recommended for future studies [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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16. Resolving and Analyzing Landfast Ice Deformation by InSAR Technology Combined with Sentinel-1A Ascending and Descending Orbits Data
- Author
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Zhiyong Wang, Jian Liu, Jinning Wang, Lihua Wang, Meng Luo, Zihao Wang, Ping Ni, and Hao Li
- Subjects
InSAR ,deformation measurement ,fast ice ,Baltic Sea ,Sentinel-1A ,Chemical technology ,TP1-1185 - Abstract
Detailed mapping of landfast ice deformation can be used to characterize the rheological behavior of landfast ice effectively and to improve sea ice modeling subsequently. In order to analyze the characteristics, trends and causes of deformation comprehensively and accurately, the Sentinel-1A ascending and descending orbits data were used to detect the horizontal and vertical deformation of the fast ice in the Baltic Sea. Firstly, the fast ice edge lines were acquired through feature extraction with interferometric coherence images and SAR amplitude images. Then, the deformation transformed model was constructed according to the geometric relationship of multi-orbits deformation measurements. Finally, the landfast ice deformations were resolved and the horizontal and vertical deformations were obtained. The results showed that the maximum deformation was—44 cm in horizontal direction and 16 cm in vertical direction within the fast ice region of 960 km2 during the time from 2 to 16 February 2018. The southwest wind was the principal reason for the deformation, which made the deformation mainly occur in the horizontal direction from east to west. Moreover, the inner fast ice kept stable due to the protection of outer consolidated ice. The results showed that the deformation trend and characteristics can be better understood by using InSAR technology that was combined with multi-orbits SAR data to resolve and analyze the landfast ice deformation.
- Published
- 2020
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17. Variability of Antarctic sea ice extent over the past 200 years
- Author
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Shutong Li, Jiao Yang, Cunde Xiao, Jiping Liu, and Dahe Qin
- Subjects
geography ,Multidisciplinary ,Oceanography ,geography.geographical_feature_category ,Ice core ,Fast ice ,Interdecadal Pacific Oscillation ,Sea ice ,Environmental science ,Antarctic sea ice ,Forcing (mathematics) ,Arctic ice pack ,Latitude - Abstract
While Arctic sea ice has been decreasing in recent decades that is largely due to anthropogenic forcing, the extent of Antarctic sea ice showed a positive trend during 1979–2015, followed by an abrupt decrease. The shortness of the satellite record limits our ability to quantify the possible contribution of anthropogenic forcing and internal variability to the observed Antarctic sea ice variability. In this study, ice core and fast ice records with annual resolution from six sites are used to reconstruct the annual-resolved northernmost latitude of sea ice edge (NLSIE) for different sectors of the Southern Ocean, including the Weddell Sea (WS), Bellingshausen Sea (BS), Amundsen Sea (AS), Ross Sea (RS), and the Indian and western Pacific Ocean (IndWPac). The linear trends of the NLSIE are analyzed for each sector for the past 100–200 years and found to be −0.08°, −0.17°, +0.07°, +0.02°, and −0.03° per decade (≥95% confidence level) for the WS, BS, AS, RS, and IndWPac, respectively. For the entire Antarctic, our composite NLSIE shows a decreasing trend (−0.03° per decade, 99% confidence level) during the 20th century, with a rapid decline in the mid-1950s. It was not until the early 1980s that the observed increasing trend occurred. A comparison with major climate indices shows that the long-term linear trends in all five sectors are largely dominated by the changes in the Southern Annular Mode (SAM). The multi-decadal variability in WS, BS, and AS is dominated by the Interdecadal Pacific Oscillation, whereas that in the IndWPac and RS is dominated by the SAM.
- Published
- 2021
18. An on-ice aerial survey of the Kane Basin polar bear (Ursus maritimus) subpopulation
- Author
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Seth Stapleton, Stephen N. Atkinson, Eric V. Regehr, Markus Dyck, Kristin L. Laidre, Nicholas J. Lunn, Erik W. Born, Øystein Wiig, and Todd W. Arnold
- Subjects
geography ,Distance sampling ,geography.geographical_feature_category ,Aerial survey ,Ursus maritimus ,Fjord ,Biology ,Arctic ice pack ,Fast ice ,Arctic ,biology.animal ,Physical geography ,General Agricultural and Biological Sciences ,Transect - Abstract
There is an imminent need to collect information on distribution and abundance of polar bears (Ursus maritimus) to understand how they are affected by the ongoing decrease in Arctic sea ice. The Kane Basin (KB) subpopulation is a group of high-latitude polar bears that ranges between High Arctic Canada and NW Greenland around and north of the North Water polynya (NOW). We conducted a line transect distance sampling aerial survey of KB polar bears during 28 April–12 May 2014. A total of 4160 linear kilometers were flown in a helicopter over fast ice in the fjords and over offshore pack ice between 76° 50′ and 80° N′. Using a mark-recapture distance sampling protocol, the estimated abundance was 190 bears (95% lognormal CI: 87–411; CV 39%). This estimate is likely negatively biased to an unknown degree because the offshore sectors of the NOW with much open water were not surveyed because of logistical and safety reasons. Our study demonstrated that aerial surveys may be a feasible method for obtaining abundance estimates for small subpopulations of polar bears.
- Published
- 2021
19. Optical properties and surface energy flux of spring fast ice in the Arctic
- Author
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Yilin Liu, Xiaoyu Wang, Jialiang Zhu, and Tao Li
- Subjects
Surface energy flux ,Fast ice ,Aquatic Science ,Spring (mathematics) ,Oceanography ,Atmospheric sciences ,Geology ,The arctic - Published
- 2021
20. Response of fast ice to ground penetrating radar and backscattering coefficient from scatterometer in Larsemann Hills, East Antarctica.
- Author
-
Bothale, Rajashree Vinod, Anoop, S., Gopaiah, Manne, and Sherief, Mehanaz
- Subjects
- *
SHORE-fast ice , *GROUND penetrating radar , *SCIENTIFIC expeditions , *GEOPHYSICS - Abstract
The study presents inter-annual variations in the backscatter response of fast ice (sea ice attached to the coast) to C band Advanced Scatterometer (ASCAT) (2012–2016). It also analyses the Ground Penetrating Radar (GPR) observations collected during the 35th Indian Scientific Expedition to Antarctica (ISEA, 2015–16) for identification of different fast ice features and to measure fast ice depth in the Larsemann Hills area, East Antarctica. Apart from clear demarcation of features like melt water channels, frozen icebergs within fast ice and underlying topography near island, GPR provided fast ice depth information, which was used to understand backscatter response. The seasonal variations of C band backscatter were caused due to changes in snow thickness, time of freezing and sporadic melt/freeze events apart from summer melt. The backscatter response to NOAA high resolution blended daily sea surface temperature (SST) variations indicate that sudden rise/fall in backscatter during winter is probably due to sporadic melt/freeze events caused by rise/fall in SST. The results show volumetric contribution from sheet ice and domination of snow metamorphism towards increase in backscatter over fast ice. This study highlights the importance of monitoring backscatter response of fast ice to determine its state and condition. Depending on the characteristics of backscatter inter-annual curve, information about time of freeze up, melt season, ice build-up, and sporadic freeze/ thaw events can be inferred which play an important role in the energy budget of Antarctica. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
21. Glacial and tidal strain of landfast sea ice in Terra Nova Bay, East Antarctica, observed by interferometric SAR techniques.
- Author
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Han, Hyangsun and Lee, Hoonyol
- Subjects
- *
SEA ice , *INTERFEROMETRY , *POLYNYAS , *MARINE ecology - Abstract
The dynamics of landfast sea ice, also called fast ice for short, has a large influence on the variability of polynyas and marine ecosystems, and the logistics for research stations near the Antarctic coast. Therefore, it is important to accurately measure the strain of fast ice and its seasonal variations, and to identify the cause of stresses on the ice. In this paper, we separate the strains from glacial stress and tidal stress of fast ice near the Campbell Glacier Tongue (CGT) in Terra Nova Bay, East Antarctica. This was done using observations from a series of one-day tandem COSMO-SkyMed Interferometric Synthetic Aperture Radar (InSAR) images obtained from December 2010 to January 2012. Firstly, we discriminated fast ice from pack ice and open water by analyzing the interferometric coherence values. We then identified the characteristics of the strains by investigating the equi-displacement lines of fringes in weekly InSAR and double-differential InSAR (DDInSAR) images. The weekly InSAR images predominantly showed glacial shear strain of the fast ice with fringes parallel to the sides of the CGT. This was due to the cumulative flow of the CGT for a week, while oscillating tidal signals were relatively small. The DDInSAR images, which cancelled glacial strain rates in two one-day InSAR images, showed a deformation of the fast ice by tidal sea surface tilt, with the fringes parallel to the coastline. Based on the unique characteristics of these strains, we separated them from the one-day InSAR images by decomposing the fringe patterns into glacial and tidal strain. Glacial shear strain rates of fast ice attached to the east of the CGT decreased from May to August owing to ice thickening and then stabilized until December. Those to the west of the CGT increased from May to July. This was possibly due to bottom melting of the ice by the increased ocean circulation during the expansion period of the nearby polynya. The glacial strain then decreased until December because of reduced polynya activity. The fast ice near the Jang Bogo Station (JBS) only showed tidal strain as it was isolated from the CGT by cracks and leads. Tidal strain rates of the fast ice were strongly correlated with the magnitude of tidal variations in all these regions, which represents shows that the tidal strain represents tidal sea surface tilt. The tidal response of fast ice to the west of the CGT and near the JBS was stronger than that to the east of the CGT, probably owing to thinner ice thickness there. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
22. ПРОЯВЛЕНИЕ КЛИМАТИЧЕСКИХ ИЗМЕНЕНИЙ В ЛЕДОВОМ РЕЖИМЕ ЛАДОЖСКОГО ОЗЕРА ЗА ПОСЛЕДНИЕ 55 ЛЕТ
- Subjects
Global and Planetary Change ,Ice formation ,Fast ice ,Geochemistry and Petrology ,Phenology ,Air temperature ,Environmental science ,Climate change ,Physical geography ,Cold period ,Earth-Surface Processes ,Water Science and Technology - Abstract
The article presents results of monitoring changes in some phenological characteristics of the ice cover of Lake Ladoga over the past 55 years. A steady tendency has been observed for a decrease in the duration of ice formation and the area of fast ice since the beginning of the 90s. A comparison is made of the average spatial patterns of ice formation dynamics between the periods 1964–1994 and 1993–2019. Since the beginning of the 90s, there has been a change in the ice characteristics of Lake Ladoga, directly related to a reduction in the duration of the cold period. The duration of ice events averaged over the past 30 years has decreased by about a month compared with the previous thirty-year period. Fast ice began to cover only 30% of the lake surface compared to 80% in previous years. The frequency of winters with incomplete freeze-up (remaining ice free areas) increased from two to six years per decade. The warming effect is most clearly seen in the central part of the lake. Such significant changes in the dynamics of ice phenology cannot but affect the functioning of the entire ecosystem of Lake Ladoga.
- Published
- 2021
23. INTERANNUAL VARIATIONS OF MAXIMAL FAST ICE EXTENT IN THE EAST SIBERIAN SEA
- Author
-
V.V. Selyuzhenok
- Subjects
Fast ice ,Climatology ,General Earth and Planetary Sciences ,Geology - Published
- 2021
24. ДИНАМИКА БЕРЕГОВ ОСТРОВОВ СЕВЕРНОЙ ЧАСТИ КАРСКОГО МОРЯ (ст. 1. Остров Ушакова)
- Subjects
geography ,Oceanography ,geography.geographical_feature_category ,Fast ice ,Dome ,Sea ice ,Glacier ,Glacial period ,Quaternary ,Cretaceous ,Geology ,Iceberg ,Earth-Surface Processes - Abstract
The analysis of a large complex of materials – satellite images, UAV surveys, meteorological observations of polar stations, and archival data made it possible to establish the shoreline retreat rates of Ushakov Island. The island is entirely coved by the glacial dome formed above the late Cretaceous and Quaternary rock formations. The ice/rock interface is partially located below sea level. lying on the Ushakov island is located in the northern part of the Central Kara Upland and was discovered in 1935 by Soviet sea expedition visited by scientific expeditions extremely rare. For a long time, Ushakov Island was maintained by slightly negative (up to 1% volume annually) ice balance, a short ice-free period, and protected from storm waves by fast ice. At the beginning of the XXI century, the situation changed – the air temperature began to increase noticeably, the area of sea ice decreased, and the wave activity increased during the warm season. The edges of Ushakov ice dome began to break off and float into the sea as icebergs evenly around the perimeter with an increasing rate: from 10.9 m/year in 1954–2011, up to 27.3 m/year in 2011–2019. The area of the island decreased in 2002–2019 by 230.8 ha/year, in 2015–2019 – up to 294 ha/year. The glacier surface around the polar station has decreased by 15 m in 65 years. A monument of science and technology - the polar station (built in 1954, 800 m from the edge of the glacier) was washed away to the sea in 2018. The subtype of ice shores has changed from ice barriers up to 3 m high (low cliffs of floating ice) to ice walls up to 45 m and more.
- Published
- 2021
25. Fast ice dynamics of the sea of Azov in the XXI centure
- Author
-
Natalia Yaitskaya and Anastasiia A. Magaeva
- Subjects
Oceanography ,Fast ice ,Dynamics (mechanics) ,Geology - Abstract
The article is dedicated to the investigation of the fast ice dynamics for the period 2000–2020 according to satellite data and field observations using GIS technologies. We used data from International Data Center – Sea Ice and coastal observation points to analyze long-term changes. Data processing and analysis was carried out using the ArcGIS 10.4 software package. As a result, data were obtained on the spatial and temporal variability of fast ice in the Sea of Azov for the 2000–2020. The area and width of fast ice, the periods of formation, destruction and duration were analyzed. The maps of the fast ice formation frequency were constructed for each month of the winter period: December–March. It is shown that the duration of fast ice on all coastal observation points decreased: for points on the northern coast Taganrog and Mariupol—by 3–5 days, for points on the southern coast of Taganrog Bay—Yeisk and Dolzhanskaya—by 10–12 days, for point Genichesk—7 days. Average long-term fast ice area for 2000–2020 is 1800 km2. But against the background of an increase in winter air temperatures, the fast ice area is decreasing, and in the last winter periods it is not observed. The width of the fast ice at the northern coast of the Sea of Azov and the Taganrog Bay is 5–10 km. In the western and southeastern parts of the sea (sections Temryuk, Arabatskaya and Obitochny), the fast ice width is 2–5 km on average over the winter and was observed in 25 % of cases.
- Published
- 2021
26. High-resolution mapping of circum-Antarctic landfast sea ice distribution, 2000–2018
- Author
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A. D. Fraser, R. A. Massom, K. I. Ohshima, S. Willmes, P. J. Kappes, J. Cartwright, and R. Porter-Smith
- Subjects
Biogeochemical cycle ,010504 meteorology & atmospheric sciences ,0211 other engineering and technologies ,Distribution (economics) ,Climate change ,02 engineering and technology ,01 natural sciences ,Sea ice ,14. Life underwater ,lcsh:Environmental sciences ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,lcsh:GE1-350 ,geography ,geography.geographical_feature_category ,business.industry ,lcsh:QE1-996.5 ,lcsh:Geology ,Fast ice ,Habitat ,13. Climate action ,Climatology ,Compositing ,General Earth and Planetary Sciences ,Satellite ,business ,Geology - Abstract
Landfast sea ice (fast ice) is an important component of the Antarctic nearshore marine environment, where it strongly modulates ice sheet–ocean–atmosphere interactions and biological and biogeochemical processes, forms a key habitat, and affects logistical operations. Given the wide-ranging importance of Antarctic fast ice and its sensitivity to climate change, improved knowledge of its change and variability in its distribution is a high priority. Antarctic fast-ice mapping to date has been limited to regional studies and a time series covering East Antarctica from 2000 to 2008. Here, we present the first continuous, high-spatio-temporal resolution (1 km, 15 d) time series of circum-Antarctic fast-ice extent; this covers the period March 2000 to March 2018, with future updates planned. This dataset was derived by compositing cloud-free satellite visible and thermal infrared imagery using an existing methodology, modified to enhance automation and reduce subjectivity in defining the fast-ice edge. This new dataset (Fraser et al., 2020) has wide applicability and is available at https://doi.org/10.26179/5d267d1ceb60c. The new algorithm presented here will enable continuous large-scale fast-ice mapping and monitoring into the future.
- Published
- 2020
27. Circulation and fjord-shelf exchange during the ice-covered period in Young Sound-Tyrolerfjord, Northeast Greenland (74°N).
- Author
-
Boone, W., Rysgaard, S., Kirillov, S., Dmitrenko, I., Bendtsen, J., Mortensen, J., Meire, L., Petrusevich, V., and Barber, D.G.
- Subjects
- *
OCEAN circulation , *FJORDS , *OCEAN surface topography , *SILLS (Geology) , *BAROTROPY , *SEA ice - Abstract
Fjords around Greenland connect the Greenland Ice Sheet to the ocean and their hydrography and circulation are determined by the interplay between atmospheric forcing, runoff, topography, fjord-shelf exchange, tides, waves, and seasonal growth and melt of sea ice. Limited knowledge exists on circulation in high-Arctic fjords, particularly those not impacted by tidewater glaciers, and especially during winter, when they are covered with sea-ice and freshwater input is low. Here, we present and analyze seasonal observations of circulation, hydrography and cross-sill exchange of the Young Sound-Tyrolerfjord system (74°N) in Northeast Greenland. Distinct seasonal circulation phases are identified and related to polynya activity, meltwater and inflow of coastal water masses. Renewal of basin water in the fjord is a relatively slow process that modifies the fjord water masses on a seasonal timescale. By the end of winter, there is two-layer circulation, with outflow in the upper 45 m and inflow extending down to approximately 150 m. Tidal analysis showed that tidal currents above the sill were almost barotropic and dominated by the M2 tidal constituent (0.26 m s −1 ), and that residual currents (∼0.02 m s −1 ) were relatively small during the ice-covered period. Tidal pumping, a tidally driven fjord-shelf exchange mechanism, drives a salt flux that is estimated to range between 145 kg s −1 and 603 kg s −1 . Extrapolation of these values over the ice-covered period indicates that tidal pumping is likely a major source of dense water and driver of fjord circulation during the ice-covered period. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
28. Recent and historic occurrences of leopard seals (Hydrurga leptonyx) at Easter Island (Rapa Nui), Eastern Polynesia
- Author
-
Annette Kühlem, Jack S. Grove, Marcelo Flores, and Brent S. Stewart
- Subjects
0106 biological sciences ,education.field_of_study ,geography ,geography.geographical_feature_category ,Range (biology) ,010604 marine biology & hydrobiology ,Population ,Leopard ,Biology ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Arctic ice pack ,Oceanography ,Fast ice ,Peninsula ,biology.animal ,Hydrurga leptonyx ,Sea ice ,General Agricultural and Biological Sciences ,education - Abstract
Though leopard seals live and reproduce almost exclusively in fast ice and pack ice habitats surrounding the Antarctic Continent, they have been reported to range northward to South Georgia in the South Atlantic Ocean, South Africa, Patagonia, New Zealand and several islands in the South Atlantic, South Pacific, and southern Indian oceans. We summarize recent (2011 through 2018) sightings of leopard seals at Easter Island (Rapa Nui), Eastern Polynesia, and we discuss archeological and anthropological records (i.e., rock art, legends, archeological specimens, Rongorongo script) that arguably indicate that leopard seals have periodically appeared at the island for several centuries. We think that the most likely origin of these visits of leopard seals to Easter Island is from the Antarctic Peninsula to southwestern South America in austral winter as seasonal sea ice expands northward, or perhaps more recently from a small resident population in Tierra del Fuego, via the broad, cold Humboldt Current that flows northward along the Chilean coast from the Southern Ocean.
- Published
- 2020
29. Dispersed Sedimentary Matter in the Marine Cryosystem: Snow–Drifting Ice–Icewater of the Arctic and Antarctic
- Author
-
Alexander N Novigatsky, A. A. Klyuvitkin, and Alexander P Lisitzin
- Subjects
Drift ice ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,010505 oceanography ,Circumpolar star ,Oceanography ,Snow ,01 natural sciences ,The arctic ,Arctic ,Fast ice ,Sea ice ,Sedimentary rock ,Geology ,0105 earth and related environmental sciences - Abstract
A comparative description of sedimentary matter in the snow–ice cover of the Circumpolar Arctic and fast ice of the Antarctic is given. The main distribution patterns of dispersed sedimentary matter in the marine cryosystem of snow–sea ice–ice water of the Arctic and Antarctica are obtained. Sedimentary matter fluxes from the bottom of sea ice to the ocean bottom are calculated.
- Published
- 2020
30. Weddell seal observations on female and pup behavior and breeding status for four overwintering periods (2015 to 2018) at Barton Peninsula, King George Island, Antarctica
- Author
-
Yejin Kim, In-Young Ahn, Ji Kang Park, and Won Young Lee
- Subjects
0106 biological sciences ,Seal (emblem) ,Leptonychotes weddellii ,geography.geographical_feature_category ,biology ,010604 marine biology & hydrobiology ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Fishery ,Geography ,Fast ice ,Peninsula ,Animal ecology ,George (robot) ,General Earth and Planetary Sciences ,General Agricultural and Biological Sciences ,Overwintering ,General Environmental Science - Abstract
In animal ecology studies, it is a fundamental monitoring work to observe annual breeding cycle. In this study, we report the detailed observations on seven mother and pup pairs of Weddell seal (Leptonychotes weddellii) at Barton peninsula, King George Island, Antarctica. Two or three pairs had been observed along the coast on the fast ice in 2015, 2017, and 2018 and no breeding was recorded in 2016. Although it varied among individuals, pups were recorded to be born on 19−25 Sept., began swimming at day 18−19 after birth, and molted at day 21−25. Our observations may provide fundamental breeding information of Weddell seals in our study site and contribute to the future long-term monitoring research of seals.
- Published
- 2020
31. Fast Ice Prediction System (FIPS) for land-fast sea ice at Prydz Bay, East Antarctica: an operational service for CHINARE
- Author
-
Qi Shu, Bin Cheng, Timo Vihma, Lin Zhang, Petra Heil, Fengming Hui, Jiechen Zhao, and Qinghua Yang
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Correlation coefficient ,0211 other engineering and technologies ,Mode (statistics) ,02 engineering and technology ,Prediction system ,Snow ,01 natural sciences ,Fast ice ,Climatology ,Sea ice ,Hindcast ,Bay ,Geology ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
A Fast Ice Prediction System (FIPS) was constructed and is the first regional land-fast sea-ice forecasting system for the Antarctic. FIPS had two components: (1) near-real-time information on the ice-covered area from MODIS and SAR imagery that revealed, tidal cracks, ridged and rafted ice regions; (2) a high-resolution 1-D thermodynamic snow and ice model (HIGHTSI) that was extended to perform a 2-D simulation on snow and ice evolution using atmospheric forcing from ECMWF: either using ERA-Interim reanalysis (in hindcast mode) or HERS operational 10-day predictions (in forecast mode). A hindcast experiment for the 2015 season was in good agreement with field observations, with a mean bias of 0.14 ± 0.07 m and a correlation coefficient of 0.98 for modeled ice thickness. The errors are largely caused by a cold bias in the atmospheric forcing. The thick snow cover during the 2015 season led to modeled formation of extensive snow ice and superimposed ice. The first FIPS operational service was performed during the 2017/18 season. The system predicted a realistic ice thickness and onset of snow surface melt as well as the area of internal ice melt. The model results on the snow and ice properties were considered by the captain of R/VXuelongwhen optimizing a low-risk route for on-ice transportation through fast ice to the coastal Zhongshan Station.
- Published
- 2020
32. Measurements of light transfer through drift ice and landfast ice in the northern Baltic Sea
- Author
-
Elina Kari, Susanne Kratzer, Arttu Jutila, Matti Leppäranta, Anna Friedrichs, Institute for Atmospheric and Earth System Research (INAR), and INAR Physics
- Subjects
1171 Geosciences ,0106 biological sciences ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Sea ice ,Ocean Engineering ,Coloured dissolved organic matter ,Aquatic Science ,Oceanography ,Atmospheric sciences ,01 natural sciences ,Physics::Geophysics ,Scattering ,lcsh:Oceanography ,14. Life underwater ,lcsh:GC1-1581 ,1172 Environmental sciences ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences ,Drift ice ,geography ,geography.geographical_feature_category ,010604 marine biology & hydrobiology ,Light transfer ,Particulates ,Snow ,Colored dissolved organic matter ,Fast ice ,13. Climate action ,Photosynthetically active radiation ,Environmental science ,Diffuse attenuation coefficient ,Seawater ,Astrophysics::Earth and Planetary Astrophysics - Abstract
The aim of this study was to investigate the light transfer through sea ice with a focus on bio-optical substances both in fast ice and in the drift ice zones in the northern Baltic Sea. The measurements included snow and ice structure, spectral irradiance and photo-synthetically active radiation below the sea ice. We also measured the concentrations of the three main bio-optical substances which are chlorophyll-a, suspended particulate matter, and coloured dissolved organic matter (CDOM). These bio-optical substances were determined for melted ice samples and for the underlying sea water. The present study provides the first spectral light transfer data set for drift ice in the Baltic Sea. We found high CDOM absorption values typical to the Baltic Sea waters also within sea ice. Our results showed that the transmittance through bare ice was lower for the coastal fast ice than for the drift ice sites. Bio-optical substances, in particular CDOM, modified the spectral distribution of light penetrating through the ice cover. Differences in crystal structure and the amount of gas inclusions in the ice caused variation in the light transfer. Snow cover on ice was found to be the dominant factor influencing the light field under ice, confirming previous studies. In conclusion, snow cover dominated the amount of light under the ice, but did not modify its spectral composition. CDOM in the ice absorbs strongly in the short wavelengths. As pure water absorbs most in the long wavelengths, the light transfer through ice was highest in the green (549-585 nm). (C) 2020 Institute of Oceanology of Polish Academy of Sciences. Published by Elsevier B.V.
- Published
- 2020
33. Grounded icebergs as maternity denning habitat for polar bears (Ursus maritimus) in North and Northeast Greenland
- Author
-
Ian Stirling and Kristin L. Laidre
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,biology ,Ursus maritimus ,010604 marine biology & hydrobiology ,Glacier ,Snow ,010603 evolutionary biology ,01 natural sciences ,Iceberg ,Habitat ,Fast ice ,biology.animal ,Sea ice ,Physical geography ,General Agricultural and Biological Sciences ,Polar desert - Abstract
This study provides the first documentation of polar bear (Ursus maritimus) maternity denning in snowdrifts around icebergs frozen into the fast ice or grounded on the seafloor. Based on six den observations in north and northeast Greenland during spring surveys in 2018 and 2019 (109 flight hours), together with observations of 20 adult females with 35 cubs of the year (COYs) in adjacent sea ice, we hypothesize that the use of snowdrifts around icebergs for maternity denning is an established behavior in the region and not a random event. Factors influencing maternity denning in snowdrifts around icebergs may include limited suitable drifts on the nearby terrestrial polar desert due to low precipitation, the presence of suitable wind-blown snow banks regardless of the direction of autumn storm winds, cold and stable habitat throughout the winter denning period, and access to ringed seal (Pusa hispida) pupping habitat in the nearby Northeast Water polynya. This type of maternity denning habitat is only available in glaciated regions of the Arctic where marine-terminating glaciers deposit melange large enough to become grounded offshore and remain in place for months or years. This habitat may become less stable or disappear with long-term climate warming.
- Published
- 2020
34. Foraging patterns of Antarctic minke whales in McMurdo Sound, Ross Sea
- Author
-
Trevor Joyce, Robert L. Pitman, Stacy Kim, John W. Durban, David G. Ainley, Ben Saenz, Grant Ballard, and Kendra L. Daly
- Subjects
0106 biological sciences ,Krill ,biology ,010604 marine biology & hydrobiology ,Foraging ,Adelie penguin ,Geology ,Oceanography ,biology.organism_classification ,Remotely operated vehicle ,010603 evolutionary biology ,01 natural sciences ,Predation ,Water column ,Fast ice ,Antarctic silverfish ,Environmental science ,Ecology, Evolution, Behavior and Systematics - Abstract
Evidence indicates that Antarctic minke whales (AMWs) in the Ross Sea affect the foraging behaviour, especially diet, of sympatric Adélie penguins (ADPEs) by, we hypothesize, influencing the availability of prey they have in common, mainly crystal krill. To further investigate this interaction, we undertook a study in McMurdo Sound during 2012–2013 and 2014–2015 using telemetry and biologging of whales and penguins, shore-based observations and quantification of the preyscape. The 3D distribution and density of prey were assessed using a remotely operated vehicle deployed along and to the interior of the fast-ice edge where AMWs and ADPEs focused their foraging. Acoustic surveys of prey and foraging behaviour of predators indicate that prey remained abundant under the fast ice, becoming successively available to air-breathing predators only as the fast ice retreated. Over both seasons, the ADPE diet included less krill and more Antarctic silverfish once AMWs became abundant, but the penguins' foraging behaviour (i.e. time spent foraging, dive depth, distance from colony) did not change. In addition, over time, krill abundance decreased in the upper water column near the ice edge, consistent with the hypothesis (and previously gathered information) that AMW and ADPE foraging contributed to an alteration of prey availability.
- Published
- 2020
35. Accounting for the Viscoplastic Properties of Ice to Optimize Design Solutions for Offshore Oil-and-Gas Field Structures in Sharapov Shar Bay
- Author
-
S. V. Solomatin
- Subjects
Viscoplasticity ,Field (physics) ,business.industry ,Energy Engineering and Power Technology ,Accounting ,computer.file_format ,shar ,Fast ice ,Submarine pipeline ,business ,computer ,Bay ,Offshore oil and gas ,Geology - Abstract
An individual approach to the determination of the ice loads on offshore oil-and-gas field structures in Sharapov Shar Bay, the Kara Sea, is presented. Sharapov Shar Bay is a rare example of fast ice that forms and remains stable over the entire period of maximum ice loads, offering an opportunity to optimize design solutions by accounting for the viscoplastic properties of ice. The results of field ice surveys in Sharapov Shar Bay are described, and an example of using them in ice load calculations is given.
- Published
- 2020
36. Morphometry and Internal Structure of Stamukhas in the Ice-covered Seas of Russia
- Author
-
Konstantin A. Kornishin, E. U. Mironov, Roman B. Guzenko, Victor V. Kharitonov, Ya. O. Efimov, and Viktor S. Porubaev
- Subjects
Fluid Flow and Transfer Processes ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Fast ice ,010505 oceanography ,01 natural sciences ,Geomorphology ,Layer thickness ,Geology ,0105 earth and related environmental sciences ,Water Science and Technology ,Ice thickness - Abstract
A method for studying stamukhas using the modern field equipment is considered. The peculiarities of morphometric characteristics and parameters of the internal structure of stamukhas are analyzed. The interrelation between the consolidated layer thickness and the accumulated freezing degree days is derived for different seas. The comparative analysis of morphometric characteristics and the consolidated layer in the ice-covered seas of Russia is carried out. It is shown that the formation of stamukhas in different regions has specific features depending on the depth, bottom topography, drift characteristics, ice thickness, and dates of fast ice formation. The maximum thickness of the consolidated layer is registered in the Kara and Laptev seas.
- Published
- 2020
37. Drivers of concentrated predation in an Antarctic marginal-ice-zone food web
- Author
-
Benjamin Saenz, Erin Conlisk, Kendra L. Daly, David G. Ainley, Grant Ballard, Megan Elrod, and Stacy Kim
- Subjects
0106 biological sciences ,Krill ,Food Chain ,010504 meteorology & atmospheric sciences ,Euphausia ,Ecosystem ecology ,Antarctic Regions ,lcsh:Medicine ,01 natural sciences ,Models, Biological ,Article ,Predation ,Animals ,lcsh:Science ,0105 earth and related environmental sciences ,Trophic level ,Marine biology ,Multidisciplinary ,biology ,010604 marine biology & hydrobiology ,Fur Seals ,lcsh:R ,Whales ,Food webs ,biology.organism_classification ,Spheniscidae ,Food web ,Perciformes ,Oceanography ,Fast ice ,Habitat ,Predatory Behavior ,Antarctic silverfish ,Environmental science ,lcsh:Q ,Euphausiacea - Abstract
Predators impact preyscapes (3-D distribution of forage species) by consuming prey according to their abilities or by altering prey behavior as they avoid being consumed. We elucidate prey (Antarctic silverfish[Pleuragramma antarctica] and crystal krill[Euphausia chrystallorophias]) responses to predation associated with the marginal ice zone (MIZ) of the McMurdo Sound, Antarctica, polynya. Prey abundance and habitat was sampled across a 30 × 15 km area by remotely-operated vehicle, and included locations that were accessible (ice edge) or inaccessible (solid fast ice) to air-breathing predators. Prey and habitat sampling coincided with bio-logging of Adélie penguins and observations of other air-breathing predators (penguins, seals, and whales), all of which were competing for the same prey. Adélie penguins dived deeper, and more frequently, near the ice edge. Lowered abundance of krill at the ice edge indicated they were depleted or were responding to increased predation and/or higher light levels along the ice edge. Penguin diet shifted increasingly to silverfish from krill during sampling, and was correlated with the arrival of krill-eating whales. Behaviorally-mediated, high trophic transfer characterizes the McMurdo Sound MIZ, and likely other MIZs, warranting more specific consideration in food web models and conservation efforts.
- Published
- 2020
38. Significant chick loss after early fast ice breakup at a high-latitude emperor penguin colony
- Author
-
Grant Ballard and Annie E. Schmidt
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Lead (sea ice) ,Climate change ,Geology ,Storm ,Oceanography ,Breakup ,010603 evolutionary biology ,01 natural sciences ,Ice shelf ,Latitude ,Fast ice ,Sea ice ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
Emperor penguins require stable fast ice, sea ice anchored to land or ice shelves, on which to lay eggs and raise chicks. As the climate warms, changes in sea ice are expected to lead to substantial declines at many emperor penguin colonies. The most southerly colonies have been predicted to remain buffered from the direct impacts of warming for much longer. Here, we report on the unusually early breakup of fast ice at one of the two southernmost emperor penguin colonies, Cape Crozier (77.5°S), in 2018, an event that may have resulted in a substantial loss of chicks from the colony. Fast ice dynamics can be highly variable and dependent on local conditions, but earlier fast ice breakup, influenced by increasing wind speed, as well as higher surface air temperatures, is a likely outcome of climate change. What we observed at Cape Crozier in 2018 highlights the vulnerability of this species to untimely storm events and could be an early sign that even this high-latitude colony is not immune to the effects of warming. Long-term monitoring will be key to understanding this species' response to climate change and altered sea ice dynamics.
- Published
- 2020
39. First of an Arctic sea ice meiofauna food web analysis based on abundance, biomass and stable isotope ratios
- Author
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Rolf Gradinger and Bodil A. Bluhm
- Subjects
Biomass (ecology) ,geography ,geography.geographical_feature_category ,Ecology ,Stable isotope ratio ,Meiobenthos ,Aquatic Science ,Arctic ice pack ,Food web ,Oceanography ,Arctic ,Fast ice ,Abundance (ecology) ,Environmental science ,Ecology, Evolution, Behavior and Systematics - Published
- 2020
40. Interpreting englacial layer deformation in the presence of complex ice flow history with synthetic radargrams
- Author
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Dustin M. Schroeder, Cooper Elsworth, and Matthew R. Siegfried
- Subjects
geography ,geography.geographical_feature_category ,Ice stream ,Flow (psychology) ,Geophysics ,Deformation (meteorology) ,Tracking (particle physics) ,Rotation ,law.invention ,Fast ice ,law ,Ice sheet ,Radar ,Geology ,Earth-Surface Processes - Abstract
Fast ice flow on the Antarctic continent constitutes much of the mass loss from the ice sheet. However, geophysical methods struggle to constrain ice flow history at depth, or separate the signatures of topography, ice dynamics and basal conditions on layer structure. We develop and demonstrate a methodology to compare layer signatures in multiple airborne radar transects in order to characterize ice flow at depth, or improve coverage of existing radar surveys. We apply this technique to generate synthetic, along-flow radargrams and compare different deformation regimes to observed radargram structure. Specifically, we investigate flow around the central sticky spot of Whillans Ice Stream, West Antarctica. Our study suggests that present-day velocity flowlines are insufficient to characterize flow at depth as expressed in layer geometry, and streaklines provide a better characterization of flow around a basal sticky spot. For Whillans Ice Stream, this suggests that ice flow wraps around the central sticky spot, supported by idealized flow simulations. While tracking isochrone translation and rotation across survey lines is complex, we demonstrate that our approach to combine radargram interpretation and modeling can reveal critical details of past ice flow.
- Published
- 2020
41. КОНВЕКЦИЯ ВОЗДУХА В СНЕЖНОМ ПОКРОВЕ МОРСКОГО ЛЬДА
- Subjects
Convection ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Snow ,Atmospheric sciences ,Physics::Geophysics ,Atmosphere ,symbols.namesake ,Convective instability ,Fast ice ,13. Climate action ,Geochemistry and Petrology ,Heat transfer ,Sea ice ,symbols ,Astrophysics::Earth and Planetary Astrophysics ,Rayleigh scattering ,Physics::Atmospheric and Oceanic Physics ,Geology ,Earth-Surface Processes ,Water Science and Technology - Abstract
For the first time, data on stability of stationary convective filtration within infinite horizontal layer of snow covering the flat surface of floating ice is presented in this article. An analytical solution of the linearized problem was obtained with the use of the Galerkin method, and the parametric analysis of the problem was performed. It was found that the stability criteria (Rayleigh filtration numbers) obtained with consideration for the heat exchange of snow cover with the atmosphere did not exceed the known value of 4π2 for a horizontal porous layer with impermeable isothermal boundaries. As expected, the interaction with the atmosphere has the most significant impact on the critical Rayleigh numbers, while influence of variations in snow density and ice thickness and the thickness of the underlying layer of ice are small. Based on data of ice and meteorological observations made in the winter of 2015/16 in the Western part of the Laptev Sea together with calculations of the fast ice evolution, the values and temporal variability of temperature gradients and the Rayleigh numbers in the snow cover were obtained using a thermodynamic model. It was found that both, the model and observed magnitudes, exceeded their critical values determined by solving the stability problem. The conclusion is made that the convective regime of the heat transfer does really exist in the snow cover, and thus its contribution to the thermal and mass balance of sea ice during winter period should be taken into account.
- Published
- 2020
42. Enhanced Iron Flux to Antarctic Sea Ice via Dust Deposition From Ice‐Free Coastal Areas
- Author
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Ashley T. Townsend, Arnout Roukaerts, Delphine Lannuzel, L. Duprat, Julie Janssens, Klaus M Meiners, Florian Deman, Naoya Kanna, P. van der Merwe, Analytical, Environmental & Geo-Chemistry, Faculty of Sciences and Bioengineering Sciences, and Chemistry
- Subjects
Biogeochemical cycle ,010504 meteorology & atmospheric sciences ,Iron ,Antarctic sea ice ,Oceanography ,01 natural sciences ,Deposition (geology) ,Geochemistry and Petrology ,Phytoplankton ,Earth and Planetary Sciences (miscellaneous) ,Sea ice ,0105 earth and related environmental sciences ,geography ,geography.geographical_feature_category ,Particulates ,sea ice ,Coastal ,Geophysics ,Fast ice ,Space and Planetary Science ,Antarctica ,Environmental science ,Seawater ,dust ,human activities - Abstract
Antarctic sea ice is an important temporal reservoir of iron which can boost primary production in the marginal ice zone during the seasonal melt. While studies have reported that Antarctic fast ice bears high concentrations of iron due to the proximity to coastal sources, less clear is the biogeochemical changes this iron pool undergoes during late spring. Here we describe a 3-weeks? time series of physical and biogeochemical data, including iron, from first-year coastal fast ice sampled near Davis Station (Prydz Bay, East Antarctica) during late austral spring 2015. Our study shows that dissolved and particulate iron concentrations in sea ice were up to two orders of magnitude higher than in under-ice seawater. Furthermore, our results indicate a significant contribution of lithogenic iron from the Vestfold Hills (as deduced from the comparison with crustal element ratios) to the particulate iron pool in fast ice after a blizzard event halfway through the time series. Windblown dust represented approximately 75% of the particulate iron found in the ice and is a potential candidate for keeping concentrations of soluble iron stable during our observations. These results suggest that iron entrapped during ice formation, likely from sediments, as well as local input of coastal dust, support primary productivity in Davis fast ice. As ice-free land areas are likely to expand over the course of the century, this work highlights the need to quantify iron inputs from continental Antarctic dust and its bioavailability for ice algae and phytoplankton. Plain summary Oceanic single-celled algae are the base of the ocean food web and play an important role in the Earth climate. In the Southern Ocean, the growth of these microorganisms is limited by the naturally low concentration of iron in the seawater. Microalgae benefits from the presence of the Antarctic sea ice since iron there are many times concentrated relative to the seawater. Less clear though, is the contribution of the potential sources of iron to the sea ice. We collected and analyzed sea ice cores for a series of parameters, including iron, from first-year coastal sea ice sampled near Davis Station (Prydz Bay, East Antarctica) during late austral spring 2015. Our results suggest that iron entrapped during ice formation, likely from seafloor sediments, as well as dust blown by winds from the neighboring Vestfold Hills, are the main sources of iron to Davis coastal sea ice. Since we can expect the expansion of ice-free areas and exposed grounds over the course of this century, our results highlight the need to quantify the amount of iron coming from continental Antarctic dust and to access if sea algae can access this form of iron for their basic physiological needs.
- Published
- 2019
43. Cosmogenic 10Be exposure dating of glacial erratics on Horseshoe Island in western Antarctic Peninsula confirms rapid deglaciation in the Early Holocene
- Author
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M. Akif Sarıkaya, Yeong Bae Seong, Attila Çiner, Cengiz Yıldırım, and Byung Yong Yu
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Ice stream ,Geology ,Glacier ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Fast ice ,Deglaciation ,Physical geography ,Glacial period ,Ice sheet ,Ecology, Evolution, Behavior and Systematics ,Sea level ,Holocene ,0105 earth and related environmental sciences - Abstract
The rapid warming observed in the western Antarctic Peninsula gives rise to a fast disintegration of ice shelves and thinning and retreat of marine-terminating continental glaciers, which is likely to raise global sea levels in the near future. In order to understand the contemporary changes in context and to provide constraints for hindcasting models, it is important to understand the Late Quaternary history of the region. Here, we build on previous work on the deglacial history of the western Antarctic Peninsula and we present four new cosmogenic 10Be exposure ages from Horseshoe Island in Marguerite Bay, which has been suggested as a former location of very fast ice stream retreat. Four samples collected from erratic pink granite boulders at an altitude of ~80 m above sea level yielded ages that range between 12.9 ± 1.1 ka and 9.4 ± 0.8 ka. As in other studies on Antarctic erratics, we have chosen to report the youngest erratic age (9.4 ± 0.8 ka) as the true age of deglaciation, which confirms a rapid thinning of the Marguerite Trough Ice Stream at the onset of Holocene. This result is consistent with other cosmogenic age data and other proxies (marine and lacustrine 14C and optically stimulated luminescence) reported from nearby areas.
- Published
- 2019
44. Effects of snow and remineralization processes on nutrient distributions in multi-year Antarctic landfast sea ice
- Author
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Reishi Sahashi, Daiki Nomura, Takenobu Toyota, Manami Tozawa, Masato Ito, Pat Wongpan, Kazuya Ono, Daisuke Simizu, Kazuhiro Naoki, Yuichi Nosaka, Takeshi Tamura, Shigeru Aoki, and Shuki Ushio
- Subjects
Geophysics ,remineralization ,multi-year landfast ice ,Space and Planetary Science ,Geochemistry and Petrology ,nutrients ,fast ice ,Earth and Planetary Sciences (miscellaneous) ,East Antarctica ,snow ,Oceanography ,sea ice - Abstract
We elucidated the effects of snow and remineralization processes on nutrient distributions in multi-year landfast sea ice (fast ice) in Lutzow-Holm Bay, East Antarctica. Based on sea-ice salinity, oxygen isotopic ratios, and thin section analyses, we found that the multi-year fast ice grew upward due to the year-by-year accumulation of snow. Compared to ice of seawater origin, nutrient concentrations in shallow fast ice were low due to replacement by clean and fresh snow. In deeper ice of seawater origin (the lower half of the multi-year fast ice column), remineralization was dominated by the degradation of organic matter. By comparison between first- and muti-year ice, the biological uptake and the remineralization were dominated in relatively young ice and older ice, respectively, under the physical process of brine drainage.
- Published
- 2021
45. Elastic deformation plays a non-negligible role in Greenland’s outlet glacier flow
- Author
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Julia Christmann, Ralf Müller, Shfaqat Abbas Khan, Veit Helm, Mathieu Morlighem, Thomas Kleiner, Daniel Steinhage, Angelika Humbert, Ole Zeising, Martin Rückamp, and Niklas Neckel
- Subjects
QE1-996.5 ,geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Grounding line ,Ice stream ,Flow (psychology) ,Geology ,Glacier ,010502 geochemistry & geophysics ,01 natural sciences ,Viscoelasticity ,Environmental sciences ,Fast ice ,13. Climate action ,General Earth and Planetary Sciences ,Ocean tide ,GE1-350 ,Geomorphology ,Sea level ,0105 earth and related environmental sciences ,General Environmental Science - Abstract
Future projections of global mean sea level change are uncertain, partly because of our limited understanding of the dynamics of Greenland's outlet glaciers. Here we study Nioghalvfjerdsbr AE, an outlet glacier of the Northeast Greenland Ice Stream that holds 1.1 m sea-level equivalent of ice. We use GPS observations and numerical modelling to investigate the role of tides as well as the elastic contribution to glacier flow. We find that ocean tides alter the basal lubrication of the glacier up to 10 km inland of the grounding line, and that their influence is best described by a viscoelastic rather than a viscous model. Further inland, sliding is the dominant mechanism of fast glacier motion, and the ice flow induces persistent elastic strain. We conclude that elastic deformation plays a role in glacier flow, particularly in areas of steep topographic changes and fast ice velocities. Ice flow dynamics in Greenland's outlet glaciers are influenced by elastic deformation, both in the area of tidal influence up to 14 km inland from the grounding line and further upstream, suggest analyses of GPS observations and numerical simulations.
- Published
- 2021
46. Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability
- Author
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Mark S. Handcock, R Porter-Smith, Marilyn N. Raphael, Zhaohui Wang, Kay I. Ohshima, Phillip Reid, Robert A. Massom, Andrew R. Klekociuk, Jessica Cartwright, and Alexander D. Fraser
- Subjects
Biogeochemical cycle ,geography ,QE1-996.5 ,geography.geographical_feature_category ,Continental shelf ,Baseline (sea) ,Geology ,Oceanography ,Physical Geography and Environmental Geoscience ,Environmental sciences ,Fast ice ,Period (geology) ,Sea ice ,Cryosphere ,Meteorology & Atmospheric Sciences ,Bathymetry ,GE1-350 ,Physical geography ,Life Below Water ,Earth-Surface Processes ,Water Science and Technology - Abstract
Landfast sea ice (fast ice) is an important though poorly understood component of the cryosphere on the Antarctic continental shelf, where it plays a key role in atmosphere–ocean–ice-sheet interaction and coupled ecological and biogeochemical processes. Here, we present a first in-depth baseline analysis of variability and change in circum-Antarctic fast-ice distribution (including its relationship to bathymetry), based on a new high-resolution satellite-derived time series for the period 2000 to 2018. This reveals (a) an overall trend of -882±824 km2 yr−1 (-0.19±0.18 % yr−1) and (b) eight distinct regions in terms of fast-ice coverage and modes of formation. Of these, four exhibit positive trends over the 18-year period and four negative. Positive trends are seen in East Antarctica and in the Bellingshausen Sea, with this region claiming the largest positive trend of +1198±359 km2 yr−1 (+1.10±0.35 % yr−1). The four negative trends predominantly occur in West Antarctica, with the largest negative trend of -1206±277 km2 yr−1 (-1.78±0.41 % yr−1) occurring in the Victoria and Oates Land region in the western Ross Sea. All trends are significant. This new baseline analysis represents a significant advance in our knowledge of the current state of both the global cryosphere and the complex Antarctic coastal system, which are vulnerable to climate variability and change. It will also inform a wide range of other studies.
- Published
- 2021
47. Validating satellite derived and modelled sea-ice drift in the Laptev Sea with in situ measurements from the winter of 2007/2008
- Author
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Polona Rozman, Jens A. Hölemann, Thomas Krumpen, Rüdiger Gerdes, Cornelia Köberle, Thomas Lavergne, Susanne Adams, and Fanny Girard-Ardhuin
- Subjects
Shelf seas ,sea-ice drift ,sea-ice–ocean coupled model ,acoustic Doppler current profiler ,fast ice ,Environmental sciences ,GE1-350 ,Oceanography ,GC1-1581 - Abstract
A correct representation of the ice movement in an Arctic sea-ice–ocean coupled model is essential for a realistic sea-ice and ocean simulation. The aim of this study is to validate the observational and simulated sea-ice drift for the Laptev Sea Shelf region with in situ measurements from the winter of 2007/08. Several satellite remote-sensing data sets are first compared to mooring measurements and afterwards to the sea-ice drift simulated by the coupled sea-ice–ocean model. The different satellite products have a correlation to the in situ data ranging from 0.56 to 0.86. The correlations of sea-ice direction or individual drift vector components between the in situ data and the observations are high, about 0.8. Similar correlations are achieved by the model simulations. The sea-ice drift speed derived from the model and from some satellite products have only moderate correlations of about 0.6 to the in situ record. The standard errors for the satellite products and model simulations drift components are similar to the errors of the satellite products in the central Arctic and are about 0.03 m/s. The fast-ice parameterization implementation in the model was also successfully tested for its influence on the sea-ice drift. In contrast to the satellite products, the model drift simulations have a full temporal and spatial coverage and results are reliable enough to use as sea-ice drift estimates on the Laptev Sea Shelf.
- Published
- 2011
- Full Text
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48. Dynamics and mechanical integrity of a fast-ice stabilized ice tongue in Antarctica prior to break-off
- Author
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Oliver J. Marsh, Rodrigo Andres Gomez Fell, Heather Purdie, and Wolfgang Rack
- Subjects
Fast ice ,Ice tongue ,Magnitude (mathematics) ,Mechanical integrity ,Ice calving ,Growth rate ,Geomorphology ,Geology - Abstract
The full length of Parker Ice Tongue on the Victoria Land Coast, Antarctica, calved in March 2020. Calving of this magnitude (18 km) is not previously seen for this location. The mean growth rate (...
- Published
- 2021
49. Ice stream subglacial access for ice sheet history and fast ice flow: The BEAMISH Project on Rutford Ice Stream, West Antarctica and initial results on basal conditions
- Author
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Dominic A. Hodgson, Paul G. D. Anker, Keith W. Nicholls, Rebecca Schlegel, Sridhar Anandakrishnan, Keith Makinson, Andrew Smith, Alex Brisbourne, Tavi Murray, and S. Rios-Costas
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Fast ice ,Ice stream ,Flow (psychology) ,Ice sheet ,010502 geochemistry & geophysics ,01 natural sciences ,Geomorphology ,Geology ,0105 earth and related environmental sciences ,Earth-Surface Processes - Abstract
Three holes were drilled to the bed of Rutford Ice Stream, through ice up to 2154 m thick, to investigate the basal processes and conditions associated with fast ice flow and the glacial history of the West Antarctic Ice Sheet. A narrative of the drilling, measuring and sampling activities, as well as some preliminary results and initial interpretations of subglacial conditions, is given. These were the deepest subglacial access holes ever drilled using the hot-water drilling method. Samples of bed and englacial sediments were recovered, and a number of instruments were installed in the ice column and the bed. The ice–bed interface was found to be unfrozen, with an existing, well-developed subglacial hydrological system at high pressure, within ~1% of the ice overburden. The bed itself comprises soft, water-saturated sediments, consistent with previous geophysical interpretations. Englacial sediment quantity varies significantly between two locations ~2 km apart, and possibly over even shorter (~20 m) distances. Difficulties and unusual observations encountered while connecting to the subglacial hydrological system in one hole possibly resulted from the presence of a large clast embedded in the bottom of the ice.
- Published
- 2021
50. Satellite altimetry detection of ice-shelf-influenced fast ice
- Author
-
Gemma M. Brett, Daniel Price, Wolfgang Rack, and Patricia J. Langhorne
- Subjects
geography ,QE1-996.5 ,geography.geographical_feature_category ,Freeboard ,Geology ,Forcing (mathematics) ,Snow ,Ice shelf ,Environmental sciences ,Fast ice ,Sea ice ,Outflow ,GE1-350 ,Altimeter ,Geomorphology ,Earth-Surface Processes ,Water Science and Technology - Abstract
The outflow of supercooled Ice Shelf Water from the conjoined Ross and McMurdo ice shelf cavity augments fast ice thickness and forms a thick sub-ice platelet layer in McMurdo Sound. Here, we investigate whether the CryoSat-2 satellite radar altimeter can consistently detect the higher freeboard caused by the thicker fast ice combined with the buoyant forcing of a sub-ice platelet layer beneath. Freeboards obtained from CryoSat-2 were compared with 4 years of drill-hole-measured sea ice freeboard, snow depth, and sea ice and sub-ice platelet layer thicknesses in McMurdo Sound in November 2011, 2013, 2017 and 2018. The spatial distribution of higher CryoSat-2 freeboard concurred with the distributions of thicker ice-shelf-influenced fast ice and the sub-ice platelet layer. The mean CryoSat-2 freeboard was 0.07–0.09 m higher over the main path of supercooled Ice Shelf Water outflow, in the centre of the sound, relative to the west and east. In this central region, the mean CryoSat-2-derived ice thickness was 35 % larger than the mean drill-hole-measured fast ice thickness. We attribute this overestimate in satellite-altimeter-obtained ice thickness to the additional buoyant forcing of the sub-ice platelet layer which had a mean thickness of 3.90 m in the centre. We demonstrate the capability of CryoSat-2 to detect higher Ice Shelf Water-influenced fast ice freeboard in McMurdo Sound. Further development of this method could provide a tool to identify regions of ice-shelf-influenced fast ice elsewhere on the Antarctic coastline with adequate information on the snow layer.
- Published
- 2021
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