scholarly journals Microstructure evolution of young sea ice from a Svalbard fjord using micro-CT analysis

2021 ◽  
pp. 1-20
Author(s):  
Martina Lan Salomon ◽  
Sönke Maus ◽  
Chris Petrich
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Strong Dependence ◽  
Ice Cores ◽  
Total Porosity ◽  
Arctic Sea Ice ◽  
Vertical Position ◽  
Micro Computed Tomography ◽  
Pore Sizes ◽  
Over Time

Abstract We analysed the three-dimensional microstructure of sea ice by means of X-ray-micro computed tomography. Microscopic (brine- and air- pore sizes, numbers and connectivity) and macroscopic (salinity, density, porosity) properties of young Arctic sea ice were analysed. The analysis is based on ice cores obtained during spring 2016. Centrifuging of brine prior to CT imaging has allowed us to derive confident relationships between the open, vertically connected and total porosity of young sea ice at relatively high temperatures. We analysed the dependence of the microscopic properties on vertical position and total brine porosity. Most bulk properties (salinity, density) and pore space properties (pore sizes and their distribution) show a strong dependence on total brine porosity, but did not change significantly over the course of the field work. However, significant changes were observed for pore numbers (decreasing over time) and pore connectivity (increasing over time). CT-based salinity determinations are subject to larger than standard uncertainties (from conductivity), while the CT method yields important information about the salinity contributions from closed and open pores. We also performed a comparison of CT-based air porosity with calculations based on density from hydrostatic weighing. The consistency is encouraging and gives confidence to our CT-based results.

scholarly journals Physical and optical characteristics of heavily melted “rotten” Arctic sea ice

2019 ◽  
Vol 13 (3) ◽  
pp. 775-793 ◽  
Author(s):  
Carie M. Frantz ◽  
Bonnie Light ◽  
Samuel M. Farley ◽  
Shelly Carpenter ◽  
Ross Lieblappen ◽  
...  
Keyword(s):  
Light Scattering ◽  
Sea Ice ◽  
Pore Space ◽  
Total Porosity ◽  
Arctic Sea Ice ◽  
Micro Computed Tomography ◽  
Structural Anisotropy ◽  
Scattering Coefficients ◽  
Ice Melt ◽  
Arctic Sea

Abstract. Field investigations of the properties of heavily melted “rotten” Arctic sea ice were carried out on shorefast and drifting ice off the coast of Utqiaġvik (formerly Barrow), Alaska, during the melt season. While no formal criteria exist to qualify when ice becomes rotten, the objective of this study was to sample melting ice at the point at which its structural and optical properties are sufficiently advanced beyond the peak of the summer season. Baseline data on the physical (temperature, salinity, density, microstructure) and optical (light scattering) properties of shorefast ice were recorded in May and June 2015. In July of both 2015 and 2017, small boats were used to access drifting rotten ice within ∼32 km of Utqiaġvik. Measurements showed that pore space increased as ice temperature increased (−8 to 0 ∘C), ice salinity decreased (10 to 0 ppt), and bulk density decreased (0.9 to 0.6 g cm−3). Changes in pore space were characterized with thin-section microphotography and X-ray micro-computed tomography in the laboratory. These analyses yielded changes in average brine inclusion number density (which decreased from 32 to 0.01 mm−3), mean pore size (which increased from 80 µm to 3 mm), and total porosity (increased from 0 % to > 45 %) and structural anisotropy (variable, with values of generally less than 0.7). Additionally, light-scattering coefficients of the ice increased from approximately 0.06 to > 0.35 cm−1 as the ice melt progressed. Together, these findings indicate that the properties of Arctic sea ice at the end of melt season are significantly distinct from those of often-studied summertime ice. If such rotten ice were to become more prevalent in a warmer Arctic with longer melt seasons, this could have implications for the exchange of fluid and heat at the ocean surface.

scholarly journals Physical and optical characteristics of heavily melted "rotten" Arctic sea ice

2018 ◽  
Author(s):  
Carie M. Frantz ◽  
Bonnie Light ◽  
Samuel M. Farley ◽  
Shelly Carpenter ◽  
Ross Lieblappen ◽  
...  
Keyword(s):  
Light Scattering ◽  
Sea Ice ◽  
Pore Space ◽  
Total Porosity ◽  
Arctic Sea Ice ◽  
Micro Computed Tomography ◽  
Structural Anisotropy ◽  
Scattering Coefficients ◽  
Ice Melt ◽  
Arctic Sea

Abstract. Field investigations of the properties of heavily melted "rotten" Arctic sea ice were carried out on shorefast and drifting ice off the coast of Utqiaġvik (formerly Barrow), Alaska during the melt season. While no formal criteria exist to qualify when ice becomes "rotten", the objective of this study was to sample melting ice at the point where its structural and optical properties are sufficiently advanced beyond the peak of the summer season. Baseline data on the physical (temperature, salinity, density, microstructure) and optical (light scattering) properties of shorefast ice were recorded in May and June 2015. In July of both 2015 and 2017, small boats were used to access drifting "rotten" ice within ~ 32 km of Utqiaġvik. Measurements showed that pore space increased as ice temperature increased (−8 °C to 0 °C), ice salinity decreased (10 ppt to 0 ppt), and bulk density decreased (0.9 g cm-3 to 0.6 g cm-3). Changes in pore space were characterized with thin-section microphotography and X-ray micro-computed tomography in the laboratory. These analyses yielded changes in average brine inclusion number density (which decreased from 32 mm-3 to 0.01 mm-3), mean pore size (which increased from 80 μm to 3 mm) as well as total porosity (increased from 0 % to > 45 %) and structural anisotropy (variable, with values generally less than 0.7). Additionally, light scattering coefficients of the ice increased from approximately 0.06 cm-1 to > 0.35 cm-1 as the ice melt progressed. Together, these findings indicate that Arctic sea ice at the end of melt season is physically different from the often-studied summertime ice. If such rotten ice were to become more prevalent in a warmer Arctic, this could have implications for the exchange of fluid and heat at the ocean surface.

scholarly journals Dissolved organic matter in Antarctic sea ice

2001 ◽  
Vol 33 ◽  
pp. 297-303 ◽  
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%.

scholarly journals Variability of light transmission through Arctic land-fast sea ice during spring

2013 ◽  
Vol 7 (3) ◽  
pp. 977-986 ◽  
Author(s):  
M. Nicolaus ◽  
C. Petrich ◽  
S. R. Hudson ◽  
M. A. Granskog
Keyword(s):  
Sea Ice ◽  
Spatial Variability ◽  
Physical Properties ◽  
Snow Cover ◽  
Light Transmission ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Optical Measurements ◽  
Light Transmittance ◽  
Seasonal Evolution

Abstract. The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.

Dissolved Neodymium Isotopes Trace Origin and Spatiotemporal Evolution of Modern Arctic Sea Ice

2020 ◽  
Author(s):  
Georgi Laukert ◽  
Dorothea Bauch ◽  
Ilka Peeken ◽  
Thomas Krumpen ◽  
Kirstin Werner ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Surface Waters ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Spatiotemporal Evolution ◽  
Arctic Sea ◽  
The Arctic Ocean ◽  
Ice Floes

<p>The lifetime and thickness of Arctic sea ice have markedly decreased in the recent past. This affects Arctic marine ecosystems and the biological pump, given that sea ice acts as platform and transport medium of marine and atmospheric nutrients. At the same time sea ice reduces light penetration to the Arctic Ocean and restricts ocean/atmosphere exchange. In order to understand the ongoing changes and their implications, reconstructions of source regions and drift trajectories of Arctic sea ice are imperative. Automated ice tracking approaches based on satellite-derived sea-ice motion products (e.g. ICETrack) currently perform well in dense ice fields, but provide limited information at the ice edge or in poorly ice-covered areas. Radiogenic neodymium (Nd) isotopes (ε<sub>Nd</sub>) have the potential to serve as a chemical tracer of sea-ice provenance and thus may provide information beyond what can be expected from satellite-based assessments. This potential results from pronounced ε<sub>Nd</sub> differences between the distinct marine and riverine sources, which feed the surface waters of the different sea-ice formation regions. We present the first dissolved (< 0.45 µm) Nd isotope and concentration data obtained from optically clean Arctic first- and multi-year sea ice (ice cores) collected from different ice floes across the Fram Strait during the RV POLARSTERN cruise PS85 in 2014. Our data confirm the preservation of the seawater ε<sub>Nd</sub>signatures in sea ice despite low Nd concentrations (on average ~ 6 pmol/kg) resulting from efficient brine rejection. The large range in ε<sub>Nd</sub> signatures (~ -10 to -30) mirrors that of surface waters in various parts of the Arctic Ocean, indicating that differences between ice floes but also between various sections in an individual ice core reflect the origin and evolution of the sea ice over time. Most ice cores have ε<sub>Nd</sub> signatures of around -10, suggesting that the sea ice was formed in well-mixed waters in the central Arctic Ocean and transported directly to the Fram Strait via the Transpolar Drift. Some ice cores, however, also revealed highly unradiogenic signatures (ε<sub>Nd</sub> < ~ -15) in their youngest (bottom) sections, which we attribute to incorporation of meltwater from Greenland into newly grown sea ice layers. Our new approach facilitates the reconstruction of the origin and spatiotemporal evolution of isolated sea-ice floes in the future Arctic.</p>

Permeability of growing sea ice - observations, modelling and some implications for thinning Arctic sea ice

2020 ◽  
Author(s):  
Sönke Maus
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Arctic Sea Ice ◽  
Heat Fluxes ◽  
Onset Of Convection ◽  
Permeability Model ◽  
Electrically Conducting ◽  
Melt Pond ◽  
Starting Point

<p>The permeability of sea ice is an important property with regard to the role of sea ice in the earth system. It controls fluid flow within sea ice, and thus processes like melt pond drainage, desalination and to some degree heat fluxes between the ocean and the atmosphere. It also impacts the role of sea ice in hosting sea ice algae and organisms, and the uptake and release of nutrients and pollutants from Arctic surface waters. However, as it is difficult to measure in the field, observations of sea ice permeability are sparse and vary, even for similar porosity, over orders of magnitude. Here I present progress on this topic in three directions. First, I present results from numerical simulations of the permeability of young sea ice based on 3-d X-ray microtomographic images (XRT). These results provide a relationship between permeability and brine porosity of young columnar sea ice for the porosity range 2 to 25 %. The simulations also show that this ice type is permeable and electrically conducting down to a porosity of 2 %, considerably lower than what has been proposed in previous work. Second, the XRT-based simulations are compared to predictions based on a novel crystal growth modelling approach, finding good agreement. Third, the permeability model provides a relationship between sea ice growth velocity and permeability. Based on this relationshiop interesting aspects of the growth of permeable sea ice can be deduced: The predictions consistently explain observations of the onset of convection from growing sea ice. They also allow for an evaluation of expected permeability changes for a thinning sea ice cover in a warmer climate. As the model is strictly valid for growing and cooling sea ice, the results are mostly relevant for sea ice desalination processes during winter. Modelling permeability of summer ice (and melt pond drainage) will require more observations of the pore space evolution in warming sea ice, for which the present results can be considered as a resonable starting point.</p>

Structural characteristics and development of sea ice in the western Ross Sea

1993 ◽  
Vol 5 (1) ◽  
pp. 63-75 ◽  
Author(s):  
M. O. Jeffries ◽  
W. F. Weeks
Keyword(s):  
Sea Ice ◽  
Internal Structure ◽  
Ross Sea ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Weddell Sea ◽  
The Arctic ◽  
Ice Thickness ◽  
Pack Ice ◽  
Western Ross Sea

The internal structure of ice cores from western Ross Sea pack ice floes showed considerable diversity. Snow-ice formation made a small, but significant contribution to ice growth. Frazil ice was common and its growth clearly occurred during both the pancake cycle and deformation events. Congelation ice was also common, in both its crystallographically aligned and non-aligned varieties. Platelet ice was found in only one core next to the Drygalski Ice Tongue, an observation adding to the increasing evidence that this unusual ice type occurs primarily in coastal pack ice near ice tongues and ice shelves. The diverse internal structure of the floes indicates that sea ice development in the Ross Sea is as complex as that in the Weddell Sea and more complex than in the Arctic. The mean ice thickness at the ice core sites varied between 0.71 m and 1.52 m. The thinnest ice generally occurred in the outer pack ice zone. Regardless of latitude, the ice thickness data are further evidence that Antarctic sea ice is thinner than Arctic sea ice.

scholarly journals Variability of light transmission through Arctic land-fast sea ice during spring

2012 ◽  
Vol 6 (5) ◽  
pp. 4363-4385 ◽  
Author(s):  
M. Nicolaus ◽  
C. Petrich ◽  
S. R. Hudson ◽  
M. A. Granskog
Keyword(s):  
Sea Ice ◽  
Spatial Variability ◽  
Physical Properties ◽  
Large Scale ◽  
Light Transmission ◽  
Ice Cores ◽  
Arctic Sea Ice ◽  
Optical Measurements ◽  
Light Transmittance ◽  
Seasonal Evolution

Abstract. The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along repeated (March, May, June 2010) transects under un-deformed land-fast sea ice at Barrow, Alaska. The objective was to quantify seasonal evolution and spatial variability of light transmittance through snow and sea ice. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for Chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt may cause as much spatial variability of relative light transmittance as the contrast of ponded and white ice during summer. In both instances, a spatial variability of up to three times above and below the mean was measured. In addition, we found a thirtyfold increase of light transmittance as a result of partial snowmelt. Hence, the seasonal evolution of transmittance through sea ice exceeded the spatial variability. Nevertheless, more comprehensive under-ice radiation measurements are needed for a more generalized and large-scale understanding of the under-ice energy budget for physical, biological, and geochemical applications.

scholarly journals Supplementary material to "Imprint of Arctic sea ice cover in North-Greenland ice cores"

2019 ◽  
Author(s):  
Damiano Della Lunga ◽  
Hörhold Maria ◽  
Birthe Twarloh ◽  
Behrens Melanie ◽  
Dallmayr Remi ◽  
...  
Keyword(s):  
Sea Ice ◽  
Ice Cores ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
Arctic Sea ◽  
Supplementary Material ◽  
North Greenland

scholarly journals Measurement report: Spatial variations in ionic chemistry and water-stable isotopes in the snowpack on glaciers across Svalbard during the 2015–2016 snow accumulation season

2021 ◽  
Vol 21 (4) ◽  
pp. 3163-3180
Author(s):  
Elena Barbaro ◽  
Krystyna Koziol ◽  
Mats P. Björkman ◽  
Carmen P. Vega ◽  
Christian Zdanowicz ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Sea Ice ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Aerosol Formation ◽  
Svalbard Archipelago ◽  
Snow Chemistry ◽  
Deposition Patterns

Abstract. The Svalbard archipelago, located at the Arctic sea-ice edge between 74 and 81∘ N, is ∼60 % covered by glaciers. The region experiences rapid variations in atmospheric flow during the snow season (from late September to May) and can be affected by air advected from both lower and higher latitudes, which likely impact the chemical composition of snowfall. While long-term changes in Svalbard snow chemistry have been documented in ice cores drilled from two high-elevation glaciers, the spatial variability of the snowpack composition across Svalbard is comparatively poorly understood. Here, we report the results of the most comprehensive seasonal snow chemistry survey to date, carried out in April 2016 across 22 sites on seven glaciers across the archipelago. At each glacier, three snowpits were sampled along the altitudinal profiles and the collected samples were analysed for major ions (Ca2+, K+, Na+, Mg2+, NH4+, SO42-, Br−, Cl−, and NO3-) and stable water isotopes (δ18O, δ2H). The main aims were to investigate the natural and anthropogenic processes influencing the snowpack and to better understand the influence of atmospheric aerosol transport and deposition patterns on the snow chemical composition. The snow deposited in the southern region of Svalbard is characterized by the highest total ionic loads, mainly attributed to sea-salt particles. Both NO3- and NH4+ in the seasonal snowpack reflect secondary aerosol formation and post-depositional changes, resulting in very different spatial deposition patterns: NO3- has its highest loading in north-western Spitsbergen and NH4+ in the south-west. The Br− enrichment in snow is highest in north-eastern glacier sites closest to areas of extensive sea-ice coverage. Spatial correlation patterns between Na+ and δ18O suggest that the influence of long-range transport of aerosols on snow chemistry is proportionally greater above 600–700 m a.s.l.

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