Investigations of skeletal layer microstructure in the context of remote sensing of oil in sea ice

2017 ◽  
Vol 2017 (1) ◽  
pp. 2237-2255 ◽  
Author(s):  
Zoe R. Courville ◽  
Ross Lieb-Lappen ◽  
Keran Claffey ◽  
Bruce Elder
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Ice Sheet ◽  
Sensor Data ◽  
The Arctic ◽  
Army Corps ◽  
Water Interface ◽  
Micro Ct ◽  
X Ray ◽  
Ice Water

ABSTRACT (2017-159) The Arctic Oil Spill Response Technology – Joint Industry Program (JIP) funded a controlled basin experiment in November 2014 to assess the relative capabilities of a variety of oil in ice remote sensing techniques. An 80-cm sheet of level salt-water ice was grown in the Test Basin facility at the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire. The basin ice was representative of natural level sea ice grown under quiescent conditions. This created a controlled baseline environment to compare different sensors with a manageable number of variables. The sensor testing spanned a two-month ice growth phase and a one-month decay/melt period. The detailed physical and electrical properties of the lab-grown ice sheet were monitored over the course of the experiment. Analysis of preliminary sensor data revealed that the skeletal layer--the soft, porous band of new ice crystals at the growing ice water interface--plays a significant role in the process of incorporation of oil into the ice sheet, with oil infiltration occurring between the small lamellae structures. In addition, the underwater sensors, particularly acoustic sensors, appeared to be very sensitive to skeletal layer properties, especially the surface roughness of the ice/water interface and the density of the skeletal layer. Preliminary X-ray micro-computed tomography (micro-CT) data collected as part of the experiment demonstrated a qualitative scale dependence of sensor response to the skeletal layer microstructure. We used a cold-hardened Bruker SkyScan 1173 micro-CT scanner, housed in a −10 °C cold room, to generate full 3-dimensional x-ray images of the sea ice samples. We have demonstrated that the system is capable of distinguishing areas of void space, brine, ice, and oil at 40 micron resolution. The micro-CT scans were used to characterize the skeletal layer of the ice, including measuring density, thickness, orientation and spacing of the lamellae at 39 – 71 micron voxel resolution. Characterizing the ice structure with high resolution micro-CT imaging may resolve some of the ambiguity in the sensor measurements and lead to improved accuracy of the numerical models that predict sensor performance in different oil and ice scenarios.

scholarly journals Ice Growth and Platelet Crystals in Antarctica

2021 ◽  
Author(s):  
◽  
Jonathan Crook
Keyword(s):  
Sea Ice ◽  
Single Crystal ◽  
Ice Cores ◽  
The Arctic ◽  
First Year ◽  
Water Interface ◽  
Ice Growth ◽  
Brine Rejection ◽  
Ice Water ◽  
The Antarctic

<p>First-year land-fast sea ice growth in both the Arctic and the Antarctic is characterised by the formation of an initial ice cover, followed by the direct freezing of seawater at the ice-water interface. Such growth usually results, through geometric selection, in congelation ice. This is, in general, the typical crystal structure observed in first-year ice growth in the Arctic. However, in certain regions of the Antarctic, platelet crystals are observed to contribute significantly to the ice growth, beyond a depth of 1 m. This thesis will investigate a number of ideas as to why the platelet crystals only appear in the ice after a significant amount of congelation growth has occurred. One of the key premises will be that platelet ice forms when smaller frazil crystals, beneath the ice, rise up and attach to the interface. They are then incorporated into the ice cover and become the platelets seen in ice cores.  The Shields criterion is used to find the strength of turbulence, associated with tidal flow, required to keep a frazil crystal from adhering to the interface. It is shown that the sub-ice flow is sufficient to keep most crystals in motion. However, this turbulence may weaken or dissipate completely as the tide turns. The velocity associated with brine rejection is suggested as an alternative to keep the crystals in suspension during these periods of low shear turbulence. Brine rejection occurs as the sea ice grows, rejecting salt into the seawater below. By comparing this velocity with a model for the frazil rise velocity it is shown that brine rejection has sufficient strength to keep crystals in suspension. This effect weakens as the ice gets thicker, allowing larger frazil crystals to rise to the interface. The early work in this thesis shows that a flow can keep a single crystal from adhering to the interface. This can be regarded as the competence of a flow to keep a crystal in suspension. However, of equal importance is the capacity of a flow to keep a mass of crystals in suspension. It is shown that, given a sufficiently large mass of crystals beneath the ice, the same flow that can hold a single crystal in suspension will not be able to keep all the crystals in motion. The deposition of crystals is predicted to occur in a gradual manner if there is a steady build-up of crystals beneath the ice. The largest crystals, close to the interface, will settle against the ice as the flow is unable to support the entire mass of crystals Also considered is whether frazil crystals may be similar to cohesive sediments. If this is the case, a sudden influx of crystals from outside of the system may lead to the formation of a layer of unattached crystals beside the ice-water interface. This can cause a critical collapse of the turbulent field, resulting in the settling of a large quantity of frazil crystals. Though the emphasis of much of this thesis is on the effect of the flow on the crystals, it is also found that a mass of crystals can have a stabilising effect on the flow. The change in the density profile induced by an increase in the frazil concentration towards the ice-water interface (and hence a decrease in the density of the ice-water mixture) damps the turbulence produced by shear. The mass and size of crystals in suspension play major roles in the strength of stabilisation.  Measurements of turbulence and the suspension of frazil crystals beneath sea ice are difficult to make. This thesis aims to present and analyse a number of models which may explain the platelet puzzle - the delayed appearance of the platelet crystals in ice cores. These are compared with the observations which are available, and conclusions made on the validity of the theories presented.</p>

scholarly journals Ice Growth and Platelet Crystals in Antarctica

2021 ◽  
Author(s):  
◽  
Jonathan Crook
Keyword(s):  
Sea Ice ◽  
Single Crystal ◽  
Ice Cores ◽  
The Arctic ◽  
First Year ◽  
Water Interface ◽  
Ice Growth ◽  
Brine Rejection ◽  
Ice Water ◽  
The Antarctic

<p>First-year land-fast sea ice growth in both the Arctic and the Antarctic is characterised by the formation of an initial ice cover, followed by the direct freezing of seawater at the ice-water interface. Such growth usually results, through geometric selection, in congelation ice. This is, in general, the typical crystal structure observed in first-year ice growth in the Arctic. However, in certain regions of the Antarctic, platelet crystals are observed to contribute significantly to the ice growth, beyond a depth of 1 m. This thesis will investigate a number of ideas as to why the platelet crystals only appear in the ice after a significant amount of congelation growth has occurred. One of the key premises will be that platelet ice forms when smaller frazil crystals, beneath the ice, rise up and attach to the interface. They are then incorporated into the ice cover and become the platelets seen in ice cores.  The Shields criterion is used to find the strength of turbulence, associated with tidal flow, required to keep a frazil crystal from adhering to the interface. It is shown that the sub-ice flow is sufficient to keep most crystals in motion. However, this turbulence may weaken or dissipate completely as the tide turns. The velocity associated with brine rejection is suggested as an alternative to keep the crystals in suspension during these periods of low shear turbulence. Brine rejection occurs as the sea ice grows, rejecting salt into the seawater below. By comparing this velocity with a model for the frazil rise velocity it is shown that brine rejection has sufficient strength to keep crystals in suspension. This effect weakens as the ice gets thicker, allowing larger frazil crystals to rise to the interface. The early work in this thesis shows that a flow can keep a single crystal from adhering to the interface. This can be regarded as the competence of a flow to keep a crystal in suspension. However, of equal importance is the capacity of a flow to keep a mass of crystals in suspension. It is shown that, given a sufficiently large mass of crystals beneath the ice, the same flow that can hold a single crystal in suspension will not be able to keep all the crystals in motion. The deposition of crystals is predicted to occur in a gradual manner if there is a steady build-up of crystals beneath the ice. The largest crystals, close to the interface, will settle against the ice as the flow is unable to support the entire mass of crystals Also considered is whether frazil crystals may be similar to cohesive sediments. If this is the case, a sudden influx of crystals from outside of the system may lead to the formation of a layer of unattached crystals beside the ice-water interface. This can cause a critical collapse of the turbulent field, resulting in the settling of a large quantity of frazil crystals. Though the emphasis of much of this thesis is on the effect of the flow on the crystals, it is also found that a mass of crystals can have a stabilising effect on the flow. The change in the density profile induced by an increase in the frazil concentration towards the ice-water interface (and hence a decrease in the density of the ice-water mixture) damps the turbulence produced by shear. The mass and size of crystals in suspension play major roles in the strength of stabilisation.  Measurements of turbulence and the suspension of frazil crystals beneath sea ice are difficult to make. This thesis aims to present and analyse a number of models which may explain the platelet puzzle - the delayed appearance of the platelet crystals in ice cores. These are compared with the observations which are available, and conclusions made on the validity of the theories presented.</p>

scholarly journals Sea-ice habitat minimizes grazing impact and predation risk for larval Antarctic krill

Polar Biology ◽  
2021 ◽  
Author(s):  
Carmen L. David ◽  
Fokje L. Schaafsma ◽  
Jan A. van Franeker ◽  
Evgeny A. Pakhomov ◽  
Brian P. V. Hunt ◽  
...  
Keyword(s):  
Sea Ice ◽  
Predation Risk ◽  
Water Column ◽  
Antarctic Krill ◽  
Standing Stock ◽  
Euphausia Superba ◽  
Grazing Impact ◽  
Water Interface ◽  
Winter Habitat ◽  
Ice Water

AbstractSurvival of larval Antarctic krill (Euphausia superba) during winter is largely dependent upon the presence of sea ice as it provides an important source of food and shelter. We hypothesized that sea ice provides additional benefits because it hosts fewer competitors and provides reduced predation risk for krill larvae than the water column. To test our hypothesis, zooplankton were sampled in the Weddell-Scotia Confluence Zone at the ice-water interface (0–2 m) and in the water column (0–500 m) during August–October 2013. Grazing by mesozooplankton, expressed as a percentage of the phytoplankton standing stock, was higher in the water column (1.97 ± 1.84%) than at the ice-water interface (0.08 ± 0.09%), due to a high abundance of pelagic copepods. Predation risk by carnivorous macrozooplankton, expressed as a percentage of the mesozooplankton standing stock, was significantly lower at the ice-water interface (0.83 ± 0.57%; main predators amphipods, siphonophores and ctenophores) than in the water column (4.72 ± 5.85%; main predators chaetognaths and medusae). These results emphasize the important role of sea ice as a suitable winter habitat for larval krill with fewer competitors and lower predation risk. These benefits should be taken into account when considering the response of Antarctic krill to projected declines in sea ice. Whether reduced sea-ice algal production may be compensated for by increased water column production remains unclear, but the shelter provided by sea ice would be significantly reduced or disappear, thus increasing the predation risk on krill larvae.

scholarly journals Tank study of physico-chemical controls on gas content and composition during growth of young sea ice

2002 ◽  
Vol 48 (161) ◽  
pp. 177-191 ◽  
Author(s):  
Jean-Louis Tison ◽  
Christian Haas ◽  
Marcia M. Gowing ◽  
Suzanne Sleewaegen ◽  
Alain Bernard
Keyword(s):  
Sea Ice ◽  
Sea Water ◽  
Bubble Nucleation ◽  
Water Dynamics ◽  
Gas Content ◽  
First Year ◽  
Water Interface ◽  
Atmospheric Gases ◽  
Physico Chemical ◽  
Ice Water

AbstractDuring an ice-tank experiment, samples were taken to study the processes of acquisition and alteration of the gas properties in young first-year sea ice during a complete growth–warming–cooling cycle. The goal was to obtain reference levels for total gas content and concentrations of atmospheric gases (O2, N2, CO2) in the absence of significant biological activity. The range of total gas-content values obtained (3.5–18 mL STP kg−1) was similar to previous measurements or estimates. However, major differences occurred between current and quiet basins, showing the role of the water dynamics at the ice–water interface in controlling bubble nucleation processes. Extremely high CO2concentrations were observed in all the experiments (up to 57% in volume parts). It is argued that these could have resulted from two unexpected biases in the experimental settings. Concentrations in bubbles nucleated at the interface are controlled by diffusion both from the ice–water interface towards the well-mixed reservoir and between the interface water and the bubble itself. This double kinetic effect results in a transition of the gas composition in the bubbles from values close to solubility in sea water toward values close to atmospheric, as the ice cover builds up.

scholarly journals Variability scaling and consistency in airborne and satellite altimetry measurements of Arctic sea ice

2020 ◽  
Vol 14 (2) ◽  
pp. 751-767
Author(s):  
Shiming Xu ◽  
Lu Zhou ◽  
Bin Wang
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Snow Depth ◽  
Spatial Scales ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
First Year ◽  
Noise Levels ◽  
Wide Range

Abstract. Satellite and airborne remote sensing provide complementary capabilities for the observation of the sea ice cover. However, due to the differences in footprint sizes and noise levels of the measurement techniques, as well as sea ice's variability across scales, it is challenging to carry out inter-comparison or consistently study these observations. In this study we focus on the remote sensing of sea ice thickness parameters and carry out the following: (1) the analysis of variability and its statistical scaling for typical parameters and (2) the consistency study between airborne and satellite measurements. By using collocating data between Operation IceBridge and CryoSat-2 (CS-2) in the Arctic, we show that consistency exists between the variability in radar freeboard estimations, although CryoSat-2 has higher noise levels. Specifically, we notice that the noise levels vary among different CryoSat-2 products, and for the European Space Agency (ESA) CryoSat-2 freeboard product the noise levels are at about 14 and 20 cm for first-year ice (FYI) and multi-year ice (MYI), respectively. On the other hand, for Operation IceBridge and NASA's Ice, Cloud, and land Elevation Satellite (ICESat), it is shown that the variability in snow (or total) freeboard is quantitatively comparable despite more than a 5-year time difference between the two datasets. Furthermore, by using Operation IceBridge data, we also find widespread negative covariance between ice freeboard and snow depth, which only manifests on small spatial scales (40 m for first-year ice and about 80 to 120 m for multi-year ice). This statistical relationship highlights that the snow cover reduces the overall topography of the ice cover. Besides this, there is prevalent positive covariability between snow depth and snow freeboard across a wide range of spatial scales. The variability and consistency analysis calls for more process-oriented observations and modeling activities to elucidate key processes governing snow–ice interaction and sea ice variability on various spatial scales. The statistical results can also be utilized in improving both radar and laser altimetry as well as the validation of sea ice and snow prognostic models.

scholarly journals Sea ice circulation in the Laptev Sea and ice export to the Arctic Ocean: Results from satellite remote sensing and numerical modeling

2000 ◽  
Vol 105 (C7) ◽  
pp. 17143-17159 ◽  
Author(s):  
Vitaly Y. Alexandrov ◽  
Thomas Martin ◽  
Josef Kolatschek ◽  
Hajo Eicken ◽  
Martin Kreyscher ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Numerical Modeling ◽  
Sea Ice ◽  
Arctic Ocean ◽  
Satellite Remote Sensing ◽  
The Arctic ◽  
Laptev Sea ◽  
The Arctic Ocean ◽  
The Laptev Sea

scholarly journals Visualizing brine channel development and convective processes during artificial sea-ice growth using Schlieren optical methods

2016 ◽  
Vol 62 (231) ◽  
pp. 1-17 ◽  
Author(s):  
C. A. MIDDLETON ◽  
C. THOMAS ◽  
A. DE WIT ◽  
J.-L. TISON
Keyword(s):  
Sea Ice ◽  
Growth Period ◽  
Transport Processes ◽  
Optical Methods ◽  
Water Interface ◽  
Ice Growth ◽  
Convective Processes ◽  
Ice Water ◽  
Brine Channel ◽  
Channel Development

ABSTRACTTwo non-invasive optical Schlieren methods have been adapted to visualize brine channel development and convective processes in experimentally grown sea ice obtained when a NaCl aqueous solution is cooled from above in a quasi-two-dimensional Hele–Shaw cell. The two different visualization methods, i.e. traditional and synthetic Schlieren optical imaging, produce high spatial resolution images of transport processes during ice growth, without any external perturbation. These images allow observations of the flow dynamics simultaneously within the ice layer, around the ice/water interface, and in the liquid water layer, revealing connections between the processes occurring within the two phases. Results from these methods show that desalination of the growing ice layer occurs by two concurrent, yet independent, mechanisms: (1) boundary layer convection persisting throughout the ice growth period, with short fingers present just below the ice/water interface, and (2) gravity-driven drainage from the brine channels producing deep penetrating convective streamers, which appear after a given time from the beginning of ice growth. The improved visualization and qualitative characterization of these processes show that Schlieren optical methods have exciting potential applications for future study of convective processes during sea-ice growth.

scholarly journals Data assimilation in sea-ice monitoring

2000 ◽  
Vol 31 ◽  
pp. 327-332 ◽  
Author(s):  
Ronald L. S. Weaver ◽  
Konrad Steffen ◽  
John Heinrichs ◽  
James A. Maslanik ◽  
Gregory M. Flato
Keyword(s):  
Remote Sensing ◽  
Data Assimilation ◽  
Sea Ice ◽  
Global Climate ◽  
Remote Sensing Data ◽  
The Arctic ◽  
Physical Processes ◽  
Error Statistics ◽  
Sensing Data ◽  
Ice Model

AbstractThe detection of small changes in concentration or thickness in the Arctic or Antarctic ice cover is an important topic in the current global-climate-change debate. Change detection using satellite data alone requires rigorous error analysis for their derived ice products, including inter-satellite validation for long time series. All models of physical processes are only approximations, and the best models of complicated physical processes have errors and uncertainties. A promising approach is data assimilation, combining model, in situ data and satellite remote-sensing data. Sea-ice monitoring from satellite, ice-model estimates, and the potential benefit of combining the two are discussed in some detail. In a case-study we demonstrate how the sea-ice backscatter for the Beaufort Sea region was derived using a backscattering model in combination with an ice model. We conclude that, for data assimilation, the first steps include the use of simple models, moving, with success at this level, to progressively more complex models. We also recommend reconfiguring the current remote-sensing data to include precise time tags with each pixel. For example, the current Special Sensor Microwave Imager data might be reissued in a time-tagged orbital (or gridded) format as opposed to the currently available daily averaged gridded data. Finally, error statistics and quality-control information also need to be readily available in a form useful for assimilation. The effectiveness of data-assimilation techniques is directly linked to the availability of data error statistics.

scholarly journals Oxygen exchange and ice melt measured at the ice-water interface by eddy correlation

2011 ◽  
Vol 8 (6) ◽  
pp. 11255-11284 ◽  
Author(s):  
M. H. Long ◽  
D. Koopmans ◽  
P. Berg ◽  
S. Rysgaard ◽  
R. N. Glud ◽  
...  
Keyword(s):  
Sea Ice ◽  
Primary Production ◽  
Eddy Correlation ◽  
Correlation Technique ◽  
Water Interface ◽  
Algal Communities ◽  
Ice Melt ◽  
Eddy Correlation Technique ◽  
Time Periods ◽  
Ice Water

Abstract. This study uses the eddy correlation technique to examine fluxes across the ice-water interface. Temperature eddy correlation systems were used to determine rates of ice melting and freezing, and O2 eddy correlation systems were used to examine O2 exchange rates as driven by biological and physical processes. The research was conducted below 0.7 m thick sea ice in mid March 2010 in a southwest Greenland fjord and revealed low average rates of ice melt amounting to a maximum of 0.80 ± 0.09 mm d−1 (SE, n=31). The corresponding calculated O2 flux associated with release of O2 depleted melt water was less than 13 % of the average daily O2 respiration rate. Ice melt and insufficient vertical turbulent mixing due to low current velocities caused periodic stratification immediately below the ice. This prevented the determination of fluxes during certain time periods, amounting to 66 % of total deployment time. The identification of these conditions was evaluated by examining the velocity and the linearity and stability of the cumulative flux. The examination of unstratified conditions through velocity and O2 spectra and their cospectra revealed characteristic fingerprints of well-developed turbulence. From the observed O2 fluxes, a photosynthesis/irradiance curve was established by least-squares fitting. This relation showed that light limitation of net photosynthesis began at 4.2 μmol photons m−2 s−1, and that the algal communities were well-adapted to low-light conditions as they were light saturated for 75 % of the day during this early spring period. However, the sea ice associated microbial and algal community was net heterotrophic with a daily gross primary production of 0.69 ± 0.02 mmol O2 m−2 d−1 (SE, n=4) and a respiration rate of −2.13 mmol O2 m−2 d−1 (no SE, see text for details) leading to a net primary production of −1.45 ± 0.02 mmol O2 m−2 d−1 (SE, n=4). Modeling the observed fluxes allowed for the calculation of fluxes during time periods when no O2 fluxes were extracted. This application of the eddy correlation technique produced high temporal resolution O2 fluxes and ice melt rates that were measured without disturbing the environmental conditions while integrating over a large area of approximately 50 m2 which encompassed the highly variable activity and spatial distributions of sea ice algal communities.

Sign in / Sign up

Export Citation Format

Share Document