scholarly journals Frazil Ice in the Antarctic Marginal Ice Zone

2021 ◽  
Vol 9 (6) ◽  
pp. 647
Author(s):  
Felix Paul ◽  
Tommy Mielke ◽  
Carina Schwarz ◽  
Jörg Schröder ◽  
Tokoloho Rampai ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Flow Behavior ◽  
Real Data ◽  
Ocean Waves ◽  
Ice Cover ◽  
Ice Crystals ◽  
Frazil Ice ◽  
Marginal Ice Zone ◽  
The Antarctic

Frazil ice, consisting of loose disc-shaped ice crystals, is the first ice that forms in the annual cycle in the marginal ice zone (MIZ) of the Antarctic. A sufficient number of frazil ice crystals form the surface “grease ice” layer, playing a fundamental role in the freezing processes in the MIZ. As soon as the ocean waves are sufficiently damped by a frazil ice cover, a closed ice cover can form. In this article, we investigate the rheological properties of frazil ice, which has a crucial influence on the growth of sea ice in the MIZ. An in situ test setup for measuring temperature and rheological properties was developed. Frazil ice shows shear thinning flow behavior. The presented measurements enable real-data-founded modelling of the annual ice cycle in the MIZ.

scholarly journals Brief communication: Grease Ice in the Antarctic Marginal Ice Zone

2021 ◽  
Author(s):  
Felix Paul ◽  
Tommy Mielke ◽  
Carina Nisters ◽  
Jörg Schröder ◽  
Tokoloho Rampai ◽  
...  
Keyword(s):  
Sea Ice ◽  
Rheological Properties ◽  
Annual Cycle ◽  
Flow Behavior ◽  
Ocean Waves ◽  
Ice Cover ◽  
Ice Crystals ◽  
Frazil Ice ◽  
Marginal Ice Zone ◽  
The Antarctic

Abstract. Frazil ice, consisting of loose disc-shaped ice crystals, is the very first ice that forms in the annual cycle in the marginal ice zone (MIZ) of the Antarctic. A sufficient number of frazil ice crystals forms the surface grease ice layer taking a fundamental role in the freezing processes in the MIZ. As soon as the ocean waves are sufficiently damped, a closed ice cover can form. In this brief communication we investigate the rheological properties of frazil ice, which has a crucial influence on the growth of sea ice in the MIZ. Grease ice shows shear thinning flow behavior.

scholarly journals A conceptual model for pancake-ice formation in a wave field

2001 ◽  
Vol 33 ◽  
pp. 361-367 ◽  
Author(s):  
Hayley H. Shen ◽  
Stephen F. Ackley ◽  
Mark A. Hopkins
Keyword(s):  
Wave Field ◽  
Ice Cover ◽  
Ice Crystals ◽  
Ice Formation ◽  
Governing Equations ◽  
Time Rate ◽  
Wave Condition ◽  
Frazil Ice ◽  
Marginal Ice Zone ◽  
Theoretical Paper

AbstractIt is well known that waves jostle frazil-ice crystals together, providing opportunities for them to compact into floes. The shape of these consolidated floes is nearly circular, hence the name: pancakes. From field and laboratory observations, the size of these pancakes seems to depend on the wavelength. Further aggregation of these individual pancakes produces the seasonal ice cover. Pancake-ice covers prevail in the marginal ice zone of the Southern Ocean and along the edges of many polar and subpolar seas. This theoretical paper describes conceptually the formation process of a pancake-ice cover in a wave field. The mechanisms that affect the evolution of the entire ice cover are discussed. Governing equations for the time-rate change of the floe diameter, its thickness and the thickness of the ice-cover are derived based on these mechanisms. Two criteria are proposed to determine the maximum floe size under a given wave condition, one based on bending and the other on stretching. Field and laboratory observations to date are discussed in view of this theory.

scholarly journals In situ measurements and analysis of ocean waves in the Antarctic marginal ice zone

2014 ◽  
Vol 41 (14) ◽  
pp. 5046-5051 ◽  
Author(s):  
Michael H. Meylan ◽  
Luke G. Bennetts ◽  
Alison L. Kohout
Keyword(s):  
Ocean Waves ◽  
In Situ Measurements ◽  
Marginal Ice Zone ◽  
The Antarctic

scholarly journals In-situ aircraft observations of ice concentrations within clouds over the Antarctic Peninsula and Larsen Ice Shelf

2012 ◽  
Vol 12 (7) ◽  
pp. 17295-17345
Author(s):  
D. P. Grosvenor ◽  
T. W. Choularton ◽  
T. Lachlan-Cope ◽  
M. W. Gallagher ◽  
J. Crosier ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Particle Production ◽  
Supercooled Liquid ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic ◽  
Larsen Ice Shelf

Abstract. In-situ aircraft observations of ice crystal concentrations in Antarctic clouds are presented for the first time. Orographic, layer and wave clouds around the Antarctic Peninsula and Larsen Ice shelf regions were penetrated by the British Antarctic Survey's Twin Otter Aircraft, which was equipped with modern cloud physics probes. The clouds studied were mostly in the free troposphere and hence ice crystals blown from the surface are unlikely to have been a major source for the ice phase. The temperature range covered by the experiments was 0 to −21°C. The clouds were found to contain supercooled liquid water in most regions and at heterogeneous ice formation temperatures ice crystal concentrations (60 s averages) were often less than 0.07 l−1, although values up to 0.22 l−1 were observed. Estimates of observed aerosol concentrations were used as input into the DeMott et al., 2010 ice nuclei (IN) parameterisation. The observed ice crystal number concentrations were generally in broad agreement with the IN predictions, although on the whole the predicted values were higher. Possible reasons for this are discussed and include the lack of IN observations in this region with which to characterise the parameterisation, and/or problems in relating ice concentration measurements to IN concentrations. Other IN parameterisations significantly overestimated the number of ice particles. Generally ice particle concentrations were much lower than found in clouds in middle latitudes for a given temperature. Higher ice crystal concentrations were sometimes observed at temperatures warmer than −9 °C, with values of several per litre reached. These were attributable to secondary ice particle production by the Hallett Mossop process. Even in this temperature range it was observed that there were regions with little or no ice that were dominated by supercooled liquid water. It is likely that in some cases this was due to a lack of seeding ice crystals to act as rimers to initiate secondary ice particle production. This highlights the complicated nature of this process and indicates that the accurate representation of it in global models is likely to represent a challenge. However, the contrast between Hallett Mossop zone ice concentrations and the fairly low concentrations of heterogeneously nucleated ice suggests that the Hallet Mossop process has the potential to be very important in remote, pristine regions such as around the Antarctic coast.

scholarly journals Mapping and assessing variability in the Antarctic marginal ice zone, pack ice and coastal polynyas in two sea ice algorithms with implications on breeding success of snow petrels

2016 ◽  
Vol 10 (4) ◽  
pp. 1823-1843 ◽  
Author(s):  
Julienne C. Stroeve ◽  
Stephanie Jenouvrier ◽  
G. Garrett Campbell ◽  
Christophe Barbraud ◽  
Karine Delord
Keyword(s):  
Sea Ice ◽  
Breeding Success ◽  
Ice Cover ◽  
Passive Microwave ◽  
Phytoplankton Productivity ◽  
Pack Ice ◽  
Coastal Polynya ◽  
Marginal Ice Zone ◽  
Bootstrap Algorithm ◽  
The Antarctic

Abstract. Sea ice variability within the marginal ice zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore, mapping their spatial extent as well as seasonal and interannual variability is essential for understanding how current and future changes in these biologically active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of MIZ, consolidated pack ice and coastal polynyas in the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent record for assessing the proportion of the sea ice cover that is covered by each of these ice categories. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depend strongly on which sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap, and applies the same thresholds to the sea ice concentrations to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal that the seasonal cycle in the MIZ and pack ice is generally similar between both algorithms, yet the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice area as the Bootstrap algorithm. Trends also differ, with the Bootstrap algorithm suggesting statistically significant trends towards increased pack ice area and no statistically significant trends in the MIZ. The NASA Team algorithm on the other hand indicates statistically significant positive trends in the MIZ during spring. Potential coastal polynya area and amount of broken ice within the consolidated ice pack are also larger in the NASA Team algorithm. The timing of maximum polynya area may differ by as much as 5 months between algorithms. These differences lead to different relationships between sea ice characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.

scholarly journals In-situ aircraft observations of ice concentrations within clouds over the Antarctic Peninsula and Larsen Ice Shelf

2012 ◽  
Vol 12 (23) ◽  
pp. 11275-11294 ◽  
Author(s):  
D. P. Grosvenor ◽  
T. W. Choularton ◽  
T. Lachlan-Cope ◽  
M. W. Gallagher ◽  
J. Crosier ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Particle Production ◽  
Supercooled Liquid ◽  
Ice Crystals ◽  
Ice Crystal ◽  
Ice Shelf ◽  
Aircraft Observations ◽  
The Antarctic ◽  
Larsen Ice Shelf

Abstract. In-situ aircraft observations of ice crystal concentrations in Antarctic clouds are presented for the first time. Orographic, layer and wave clouds around the Antarctic Peninsula and Larsen Ice shelf regions were penetrated by the British Antarctic Survey's Twin Otter aircraft, which was equipped with modern cloud physics probes. The clouds studied were mostly in the free troposphere and hence ice crystals blown from the surface are unlikely to have been a major source for the ice phase. The temperature range covered by the experiments was 0 to −21 °C. The clouds were found to contain supercooled liquid water in most regions and at heterogeneous ice formation temperatures ice crystal concentrations (60 s averages) were often less than 0.07 l−1, although values up to 0.22 l−1 were observed. Estimates of observed aerosol concentrations were used as input into the DeMott et al. (2010) ice nuclei (IN) parameterisation. The observed ice crystal number concentrations were generally in broad agreement with the IN predictions, although on the whole the predicted values were higher. Possible reasons for this are discussed and include the lack of IN observations in this region with which to characterise the parameterisation, and/or problems in relating ice concentration measurements to IN concentrations. Other IN parameterisations significantly overestimated the number of ice particles. Generally ice particle concentrations were much lower than found in clouds in middle latitudes for a given temperature. Higher ice crystal concentrations were sometimes observed at temperatures warmer than −9 °C, with values of several per litre reached. These were attributable to secondary ice particle production by the Hallett Mossop process. Even in this temperature range it was observed that there were regions with little or no ice that were dominated by supercooled liquid water. It is likely that in some cases this was due to a lack of seeding ice crystals to act as rimers to initiate secondary ice particle production. This highlights the chaotic and spatially inhomogeneous nature of this process and indicates that the accurate representation of it in global models is likely to represent a challenge. However, the contrast between Hallett Mossop zone ice concentrations and the fairly low concentrations of heterogeneously nucleated ice suggests that the Hallet Mossop process has the potential to be very important in remote, pristine regions such as around the Antarctic coast.

scholarly journals Ocean wave speed in the Antarctic marginal ice zone

2001 ◽  
Vol 33 ◽  
pp. 350-354 ◽  
Author(s):  
Colin Fox ◽  
Tim G. Haskell
Keyword(s):  
Wave Propagation ◽  
Large Scale ◽  
Wave Speed ◽  
Ross Sea ◽  
Ocean Waves ◽  
Wave Speeds ◽  
Marginal Ice Zone ◽  
Scale Properties ◽  
Ice Floes ◽  
The Antarctic

AbstractThe propagation of ocean waves in the marginal ice zone (MIZ) is investigated with the aim of determining whether the loading and scattering of waves by ice floes is significant. Measurements made using instrumented ice floes in the MIZ north of the Ross Sea, Antarctica, during June 1998 are used to determine the frequency-wavelength relationship for propagating ocean waves in that region. This measured-dispersion equation is related to the effective large-scale properties of the MIZ that occur in models for wave propagation and scattering. We present the measured wave speeds to enable estimation of the parameters in these models.

Plumbing the depths - the waters of the Ross Sea

2003 ◽  
Vol 15 (1) ◽  
pp. 1-1
Author(s):  
STANLEY S. JACOBS
Keyword(s):  
Sea Ice ◽  
Continental Shelf ◽  
Ocean Circulation ◽  
Ross Sea ◽  
Ice Cover ◽  
Surface Layers ◽  
Sea Ice Extent ◽  
The Antarctic

The first oceanographic measurements in the Ross Sea were made by its discoverer James Clark Ross, from the Erebus, on 18 January 1841. Since that time its continental shelf, seasonally ice free in most years, has proved a magnet to explorers and scientists, if not to fishermen and tourists. Nevertheless, our knowledge of this environment is rapidly being outpaced by our ignorance of its variability. For example, the Ross Sea contains two of the largest, most persistent polynyas on the Antarctic coastline, but its sea ice extent has increased over recent decades while its salinity has steadily declined. Are regional winds now stronger, the ocean circulation faster, and the ice thinner now than at the time of the IGY? Are its winter polynyas characterized more by upwelling driven by offshore winds, or downwelling due to brine release when sea ice is formed? How are polynya surface layers stabilized and iron-enriched, reportedly enhancing summer productivity, if the ice cover is blown away before it can melt in situ?

scholarly journals Mapping and Assessing Variability in the Antarctic Marginal Ice Zone, the Pack Ice and Coastal Polynyas

2016 ◽  
Author(s):  
Julienne C. Stroeve ◽  
Stephanie Jenouvrier ◽  
G. Garrett Campbell ◽  
Christophe Barbraud ◽  
Karine Delord
Keyword(s):  
Sea Ice ◽  
Marine Ecosystem ◽  
Active Regions ◽  
Ice Cover ◽  
Passive Microwave ◽  
Phytoplankton Productivity ◽  
Pack Ice ◽  
Marginal Ice Zone ◽  
Data Record ◽  
The Antarctic

Abstract. Sea ice variability within the marginal ice zone (MIZ) and polynyas plays an important role for phytoplankton productivity and krill abundance. Therefore mapping their spatial extent, seasonal and interannual variability is essential for understanding how current and future changes in these biological active regions may impact the Antarctic marine ecosystem. Knowledge of the distribution of different ice types to the total Antarctic sea ice cover may also help to shed light on the factors contributing towards recent expansion of the Antarctic ice cover in some regions and contraction in others. The long-term passive microwave satellite data record provides the longest and most consistent data record for assessing different ice types. However, estimates of the amount of MIZ, consolidated pack ice and polynyas depends strongly on what sea ice algorithm is used. This study uses two popular passive microwave sea ice algorithms, the NASA Team and Bootstrap to evaluate the distribution and variability in the MIZ, the consolidated pack ice and coastal polynyas. Results reveal the NASA Team algorithm has on average twice the MIZ and half the consolidated pack ice area as the Bootstrap algorithm. Polynya area is also larger in the NASA Team algorithm, and the timing of maximum polynya area may differ by as much as 5 months between algorithms. These differences lead to different relationships between sea ice characteristics and biological processes, as illustrated here with the breeding success of an Antarctic seabird.

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