An intercomparison between AMSR-E snow-depth and satellite C- and Ku-band radar backscatter data for Antarctic sea ice

AbstractAdvanced Microwave Scanning Radiometer (AMSR-E) snow-depth data for Antarctic sea ice are compared with ship-based visual observations of snow depth, ice type and ridged-ice fraction, and with satellite C-band and Ku-band radar backscatter observations for two ship cruises into the Weddell Sea (ISPOL 2004–05,WWOS 2006) and one cruise into the Bellingshausen Sea (SIMBA 2007) during late winter/spring. Most (>75%) AMSR-E and ship-based snow-depth observations agree within 0.2 m during WWOS and SIMBA. Remaining observations indicate substantial underestimations of snow depths by AMSR-E data. These underestimations tend to increase with the ridged-ice fraction for WWOS and SIMBA. In areas with large snow depths, a combination of relatively stable low C-band radar backscatter and variable Ku-band radar backscatter is associated with undeformed first-year ice and may indicate snow metamorphism at this time of year during SIMBA. In areas with small snow depths, a combination of relatively stable low Ku-band radar backscatter, high C-band radar backscatter and low C-band radar backscatter standard deviations is associated with rough first-year ice during SIMBA. This information can help to better understand causes of the observed AMSR-E snow-depth bias during late-winter/spring conditions with decreasing average snow depth and to delineate areas where this bias occurs.

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Dissolved organic matter in Antarctic sea ice

Annals of Glaciology ◽

10.3189/172756401781818338 ◽

2001 ◽

Vol 33 ◽

pp. 297-303 ◽

Cited By ~ 68

Author(s):

David N. Thomas ◽

Gerhard Kattner ◽

Ralph Engbrodt ◽

Virginia Giannelli ◽

Hilary Kennedy ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Sea Ice ◽

Pore Space ◽

Ice Cores ◽

Weddell Sea ◽

Poor Correlation ◽

First Year ◽

Mean Values ◽

Antarctic Sea Ice

AbstractIt has been hypothesized that there are significant dissolved organic matter (DOM) pools in sea-ice systems, although measurements of DOM in sea ice have only rarely been made. The significance of DOM for ice-based productivity and carbon turnover therefore remains highly speculative. DOM within sea ice from the Amundsen and Bellingshausen Seas, Antarctica, in 1994 and the Weddell Sea, Antarctica, in 1992 and 1997 was investigated. Measurements were made on melted sea-ice sections in 1994 and 1997 and in sea-ice brines in 1992. Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations in melted ice cores were up to 1.8 and 0.78 mM, respectively, or 30 and 8 times higher than those in surface water concentrations, respectively. However, when concentrations within the brine channel/pore space were calculated from estimated brine volumes, actual concentrations of DOC in brines were up to 23.3 mM and DON up to 2.2 mM, although mean values were 1.8 and 0.15 mM, respectively. There were higher concentrations of DOM in warm, porous summer second-year sea ice compared with colder autumn first-year ice, consistent with the different biological activity supported within the various ice types. However, in general there was poor correlation between DOC and DON with algal biomass and numbers of bacteria within the ice. The mean DOC/DON ratio was 11, although again values were highly variable, ranging from 3 to highly carbon-enriched samples of 95. Measurements made on a limited dataset showed that carbohydrates constitute on average 35% of the DOC pool, with highly variable contributions of 1−99%.

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Uncertainties in Antarctic sea-ice thickness retrieval from ICESat

Annals of Glaciology ◽

10.3189/2015aog69a736 ◽

2015 ◽

Vol 56 (69) ◽

pp. 107-119 ◽

Cited By ~ 31

Author(s):

Stefan Kern ◽

Gunnar Spreen

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Sensitivity Study ◽

Weddell Sea ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Earth Observing System ◽

Antarctic Sea Ice ◽

Snow Properties ◽

The Mean

AbstractA sensitivity study was carried out for the lowest-level elevation method to retrieve total (sea ice + snow) freeboard from Ice, Cloud and land Elevation Satellite (ICESat) elevation measurements in the Weddell Sea, Antarctica. Varying the percentage (P) of elevations used to approximate the instantaneous sea-surface height can cause widespread changes of a few to ˃10cm in the total freeboard obtained. Other input parameters have a smaller influence on the overall mean total freeboard but can cause large regional differences. These results, together with published ICESat elevation precision and accuracy, suggest that three times the mean per gridcell single-laser-shot error budget can be used as an estimate for freeboard uncertainty. Theoretical relative ice thickness uncertainty ranges between 20% and 80% for typical freeboard and snow properties. Ice thickness is computed from total freeboard using Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) snow depth data. Average ice thickness for the Weddell Sea is 1.73 ± 0.38 m for ICESat measurements from 2004 to 2006, in agreement with previous work. The mean uncertainty is 0.72 ± 0.09 m. Our comparison with data of an alternative approach, which assumes that sea-ice freeboard is zero and that total freeboard equals snow depth, reveals an average sea-ice thickness difference of ∼0.77m.

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Snow Depth and Air Temperature Seasonality on Sea Ice Derived From Snow Buoy Measurements

Frontiers in Marine Science ◽

10.3389/fmars.2021.655446 ◽

2021 ◽

Vol 8 ◽

Author(s):

Marcel Nicolaus ◽

Mario Hoppmann ◽

Stefanie Arndt ◽

Stefan Hendricks ◽

Christian Katlein ◽

...

Keyword(s):

Sea Ice ◽

Snow Cover ◽

Air Temperature ◽

Snow Depth ◽

Snow Accumulation ◽

Arctic Sea Ice ◽

Weddell Sea ◽

The Arctic ◽

Validation Data ◽

Antarctic Sea Ice

Snow depth on sea ice is an essential state variable of the polar climate system and yet one of the least known and most difficult to characterize parameters of the Arctic and Antarctic sea ice systems. Here, we present a new type of autonomous platform to measure snow depth, air temperature, and barometric pressure on drifting Arctic and Antarctic sea ice. “Snow Buoys” are designed to withstand the harshest environmental conditions and to deliver high and consistent data quality with minimal impact on the surface. Our current dataset consists of 79 time series (47 Arctic, 32 Antarctic) since 2013, many of which cover entire seasonal cycles and with individual observation periods of up to 3 years. In addition to a detailed introduction of the platform itself, we describe the processing of the publicly available (near real time) data and discuss limitations. First scientific results reveal characteristic regional differences in the annual cycle of snow depth: in the Weddell Sea, annual net snow accumulation ranged from 0.2 to 0.9 m (mean 0.34 m) with some regions accumulating snow in all months. On Arctic sea ice, the seasonal cycle was more pronounced, showing accumulation from synoptic events mostly between August and April and maxima in autumn. Strongest ablation was observed in June and July, and consistently the entire snow cover melted during summer. Arctic air temperature measurements revealed several above-freezing temperature events in winter that likely impacted snow stratigraphy and thus preconditioned the subsequent spring snow cover. The ongoing Snow Buoy program will be the basis of many future studies and is expected to significantly advance our understanding of snow on sea ice, also providing invaluable in situ validation data for numerical simulations and remote sensing techniques.

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Microzooplankton composition in the winter sea ice of the Weddell Sea

Antarctic Science ◽

10.1017/s0954102016000717 ◽

2017 ◽

Vol 29 (4) ◽

pp. 299-310 ◽

Cited By ~ 1

Author(s):

Marina Monti-Birkenmeier ◽

Tommaso Diociaiuti ◽

Serena Fonda Umani ◽

Bettina Meyer

Keyword(s):

Sea Ice ◽

Ice Cores ◽

Complete Loss ◽

Weddell Sea ◽

Late Winter ◽

Ice Melt ◽

Antarctic Sea Ice ◽

Carbon Biomass ◽

The Antarctic ◽

Carbon Concentrations

AbstractSympagic microzooplankton were studied during late winter in the northern Weddell Sea for diversity, abundance and carbon biomass. Ice cores were collected on an ice floe along three dive transects and seawater was taken from under the ice through the central dive hole from which all transects were connected. The areal and vertical microzooplankton distributions in the ice and water were compared. Abundance (max. 1300 ind. l-1) and biomass (max. 28.2 µg C l-1) were high in the ice cores and low in the water below the sea ice (max. 19 ind. l-1, 0.15 µg C l-1, respectively). The highest abundances were observed in the bottom 10 cm of the ice cores. The microzooplankton community within the sea ice comprised mainly aloricate ciliates, foraminifers and micrometazoans. In winter, microzooplankton represent an important fraction of the sympagic community in the Antarctic sea ice. They can potentially control microalgal production and contribute to particulate organic carbon concentrations when released into the water column during the ice melt in spring. Continued reduction of the sea ice may undermine the roles of microzooplankton, leading to a reduction or complete loss of diversity, abundance and biomass of these sympagic protists.

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Comparison of sea ice classification methods based on satellite scatterometer and radiometer data in the Weddell Sea, Antarctica

Antarctic Science ◽

10.1017/s0954102019000154 ◽

2019 ◽

Vol 31 (3) ◽

pp. 150-164

Author(s):

Xiaoping Pang ◽

Xiang Gao ◽

Qing Ji

Keyword(s):

Sea Ice ◽

Satellite Remote Sensing ◽

Remote Sensing Data ◽

Weddell Sea ◽

First Year ◽

Sea Ice Concentration ◽

Antarctic Sea Ice ◽

Ice Concentration ◽

Type Information

AbstractInformation on sea ice type is an important factor for deriving sea ice parameters from satellite remote sensing data, such as sea ice concentration, extent and thickness. In this study, sea ice in the Weddell Sea was classified by the histogram threshold (HT) method, the Spreen model (SM) method from satellite scatterometer data and the strong contrast (SC) method from radiometer data, and this information was compared with Antarctic Sea Ice Processes and Climate (ASPeCt) sea ice-type ship-based observations. The results show that all three methods can distinguish the multi-year (MY) ice and first-year (FY) ice using Ku-band scatterometer data and radiometer data during the ice growth season, while C-band scatterometer data are not suitable for MY ice and FY ice discrimination using HT and SM methods. The SM model has a smaller MY ice classification extent than the HT method from scatterometer data. The classification accuracy of the SM method is the higher compared to ship-based observations. It can be concluded that the SM method is a promising method for discriminating MY ice from FY ice. These results provide a reference for further retrieval of long-term sea ice-type information for the whole of Antarctica.

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A Textural Approach to Improving Snow Depth Estimates in the Weddell Sea

Remote Sensing ◽

10.3390/rs12091494 ◽

2020 ◽

Vol 12 (9) ◽

pp. 1494

Author(s):

M. Jeffrey Mei ◽

Ted Maksym

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Thickness Distribution ◽

Radar Data ◽

Weddell Sea ◽

Ice Thickness ◽

Two Dimensional ◽

Snow Surface ◽

Sea Ice Thickness ◽

Antarctic Sea Ice

The snow depth on Antarctic sea ice is critical to estimating the sea ice thickness distribution from laser altimetry data, such as from Operation IceBridge or ICESat-2. Snow redistributed by wind collects around areas of deformed ice and forms a wide variety of features on sea ice; the morphology of these features may provide some indication of the mean snow depth. Here, we apply a textural segmentation algorithm to classify and group similar textures to infer the distribution of snow using snow surface freeboard measurements from Operation IceBridge campaigns over the Weddell Sea. We find that texturally-similar regions have similar snow/ice ratios, even when they have different absolute snow depth measurements. This allows for the extrapolation of nadir-looking snow radar data using two-dimensional surface altimetry scans, providing a two-dimensional estimate of the snow depth with ∼22% error. We show that at the floe scale (∼180 m), snow depth can be directly estimated from the snow surface with ∼20% error using deep learning techniques, and that the learned filters are comparable to standard textural analysis techniques. This error drops to ∼14% when averaged over 1.5 km scales. These results suggest that surface morphological information can improve remotely-sensed estimates of snow depth, and hence sea ice thickness, as compared to current methods. Such methods may be useful for reducing uncertainty in Antarctic sea ice thickness estimates from ICESat-2.

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A comparison between Envisat and ICESat sea ice thickness in the Antarctic

10.5194/tc-2021-227 ◽

2021 ◽

Author(s):

Jinfei Wang ◽

Chao Min ◽

Robert Ricker ◽

Qian Shi ◽

Bo Han ◽

...

Keyword(s):

Sea Ice ◽

Snow Depth ◽

Spatial Variations ◽

Weddell Sea ◽

Ice Thickness ◽

Sea Ice Thickness ◽

Temporal And Spatial Variations ◽

Antarctic Sea Ice ◽

Temporal And Spatial ◽

The Antarctic

Abstract. The crucial role that Antarctic sea ice plays in the global climate system is strongly linked to its thickness. While field observations are too sparse in the Antarctic to determine long-term trends of the Antarctic sea ice thickness (SIT) on a hemispheric scale, satellite radar altimetry data can be applied with a promising prospect. European Space Agency Climate Change Initiative – Sea Ice Project (ESA SICCI) includes sea ice freeboard and sea ice thickness derived from Envisat, covering the entire Antarctic year-round from 2002 to 2012. In this study, the SICCI Envisat SIT in the Antarctic is first compared with a conceptually new ICESat SIT product retrieved from an algorithm employing modified ice density. Both data sets are compared to SIT estimates from upward-looking sonar (ULS) in the Weddell Sea, showing mean differences (MD) and standard deviations (SD) of 1.29 (0.65) m for Envisat-ULS, while we find 1.11 (0.81) m for ICESat-ULS, respectively. The inter-comparisons are conducted for three seasons except winter, based on the ICESat operating periods. According to the results, the differences between Envisat and ICESat SIT reveal significant temporal and spatial variations. More specifically, the smallest seasonal SIT MD (with SD shown in brackets) of 0.00 m (0.39 m) for Envisat-ICESat for the entire Antarctic is found in spring (October–November) while larger MD of 0.52 m (0.68 m) and 0.57 m (0.45 m) exist in summer (February–March) and autumn (May–June), respectively. It is also shown that from autumn to spring, mean Envisat SIT decreases while mean ICESat SIT increases. Our findings suggest that overestimation of Envisat sea ice freeboard, potentially caused by radar backscatter originating from inside the snow layer, primarily accounts for the differences between Envisat and ICESat SIT in summer and autumn, while the uncertainties of snow depth product are not the dominant cause of the differences.To get a better understanding of the characteristics of the Envisat-derived sea ice thickness product, we firstly conduct a comprehensive comparison between Envisat and ICESat-1 sea ice thickness. Their differences reveal significant temporal and spatial variations. Our findings suggest that overestimation of Envisat sea ice freeboard primarily accounts for the differences in summer and autumn, while the uncertainties of snow depth product are not the dominant cause of the differences.

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Salinity effects on cultured Neogloboquadrina pachyderma (sinistral) from high latitudes: new paleoenvironmental insights

Geo-Marine Letters ◽

10.1007/s00367-020-00677-1 ◽

2021 ◽

Vol 41 (1) ◽

Author(s):

Jacqueline Bertlich ◽

Nikolaus Gussone ◽

Jasper Berndt ◽

Heinrich F. Arlinghaus ◽

Gerhard S. Dieckmann

Keyword(s):

Sea Ice ◽

Cold Water ◽

Weddell Sea ◽

Wall Thickening ◽

High Latitudes ◽

Neogloboquadrina Pachyderma ◽

Antarctic Sea Ice ◽

The Antarctic ◽

Water Species ◽

Cold Water Species

AbstractThis study presents culture experiments of the cold water species Neogloboquadrina pachyderma (sinistral) and provides new insights into the incorporation of elements in foraminiferal calcite of common and newly established proxies for paleoenvironmental applications (shell Mg/Ca, Sr/Ca and Na/Ca). Specimens were collected from sea ice during the austral winter in the Antarctic Weddell Sea and subsequently cultured at different salinities and a constant temperature. Incorporation of the fluorescent dye calcein showed new chamber formation in the culture at salinities of 30, 31, and 69. Cultured foraminifers at salinities of 46 to 83 only revealed chamber wall thickening, indicated by the fluorescence of the whole shell. Signs of reproduction and the associated gametogenic calcite were not observed in any of the culture experiments. Trace element analyses were performed using an electron microprobe, which revealed increased shell Mg/Ca, Sr/Ca, and Na/Ca values at higher salinities, with Mg/Ca showing the lowest sensitivity to salinity changes. This study enhances the knowledge about unusually high element concentrations in foraminifera shells from high latitudes. Neogloboquadrina pachyderma appears to be able to calcify in the Antarctic sea ice within brine channels, which have low temperatures and exceptionally high salinities due to ongoing sea ice formation.

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Albedo of Young and First-Year Antarctic Sea Ice

Annals of Glaciology ◽

10.1017/s0260305500008909 ◽

1990 ◽

Vol 14 ◽

pp. 331 ◽

Cited By ~ 2

Author(s):

Richard Brandt ◽

Ian Allison ◽

Stephen Warren

Keyword(s):

Sea Ice ◽

Radiation Flux ◽

Open Water ◽

First Year ◽

Spectral Measurements ◽

Antarctic Sea Ice ◽

Antarctic Expedition ◽

Downward Radiation ◽

Radiation Measurements ◽

Snow Thickness

Reflection of solar radiation was studied in the seasonal sea-ice zone off East Antarctica on a cruise of the Australian Antarctic Expedition, October-December 1988. Spectral and total albedos were measured for grease ice, nilas, young grey ice, grey-white ice, snow-covered ice, and open water. Spectral measurements covered the region 400–1000 nm wavelength. For ice too thin to support our weight, the radiometers were mounted at the end of a 1.5 m rod extended out the door of a helicopter or from a basket hung from the ship's crane, using a positioning and leveling rack. Corrections had to be applied to the downward radiation flux because the helicopter or the crane was in the field of view of the cosine-collector. The fractional coverage of each of the ice types (and open water) was estimated hourly for the region near the ship, as well as the thickness of each ice type, and the snow thickness. Observations were carried out continuously during the four weeks the ship was in the ice, supplemented by occasional helicopter surveys covering larger areas. These observations, together with the radiation measurements, make possible the computation of area-average albedo for the East Antarctic sea-ice zone in spring.

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Characteristics of Sea-ice thickness and Snow-depth distributions of the Summer landfast ice in Lützow-Holm Bay, East Antarctica

Annals of Glaciology ◽

10.3189/172756406781811240 ◽

2006 ◽

Vol 44 ◽

pp. 281-287 ◽

Cited By ~ 9

Author(s):

Shotaro Uto ◽

Haruhito Shimoda ◽

Shuki Ushio

Keyword(s):

Sea Ice ◽

Interannual Variability ◽

Snow Depth ◽

East Antarctica ◽

Ice Thickness ◽

First Year ◽

Total Thickness ◽

Sea Ice Thickness ◽

Landfast Ice ◽

Northeasterly Wind

AbstractSea-ice observations have been conducted on board icebreaker shirase as a part of the Scientific programs of the Japanese Antarctic Research Expedition. We Summarize these to investigate Spatial and interannual variability of ice thickness and Snow depth of the Summer landfast ice in Lützow-Holm Bay, East Antarctica. Electromagnetic–inductive observations, which have been conducted Since 2000, provide total thickness distributions with high Spatial resolution. A clear discontinuity, which Separates thin first-year ice from thick multi-year ice, was observed in the total thickness distributions in two voyages. Comparison with Satellite images revealed that Such phenomena reflected the past breakup of the landfast ice. Within 20–30km from the Shore, total thickness as well as Snow depth decrease toward the Shore. This is due to the Snowdrift by the Strong northeasterly wind. Video observations of Sea-ice thickness and Snow depth were conducted on 11 voyages Since December 1987. Probability density functions derived from total thickness distributions in each year are categorized into three types: a thin-ice, thick-ice and intermediate type. Such interannual variability primarily depends on the extent and duration of the Successive break-up events.

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