scholarly journals The Effects of Rotation and Ice Shelf Topography on Frazil-Laden Ice Shelf Water Plumes

2006 ◽  
Vol 36 (12) ◽  
pp. 2312-2327 ◽  
Author(s):  
Paul R. Holland ◽  
Daniel L. Feltham
Keyword(s):  
Freezing Temperature ◽  
Shelf Water ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Frazil Ice ◽  
Ice Shelf Water ◽  
Effects Of Rotation ◽  
Realistic Topography ◽  
First Time

Abstract A model of the dynamics and thermodynamics of a plume of meltwater at the base of an ice shelf is presented. Such ice shelf water plumes may become supercooled and deposit marine ice if they rise (because of the pressure decrease in the in situ freezing temperature), so the model incorporates both melting and freezing at the ice shelf base and a multiple-size-class model of frazil ice dynamics and deposition. The plume is considered in two horizontal dimensions, so the influence of Coriolis forces is incorporated for the first time. It is found that rotation is extremely influential, with simulated plumes flowing in near-geostrophy because of the low friction at a smooth ice shelf base. As a result, an ice shelf water plume will only rise and become supercooled (and thus deposit marine ice) if it is constrained to flow upslope by topography. This result agrees with the observed distribution of marine ice under Filchner–Ronne Ice Shelf, Antarctica. In addition, it is found that the model only produces reasonable marine ice formation rates when an accurate ice shelf draft is used, implying that the characteristics of real ice shelf water plumes can only be captured using models with both rotation and a realistic topography.

scholarly journals Vertical Modification on Depth-Integrated Ice Shelf Water Plume Modeling Based on an Equilibrium Vertical Profile of Suspended Frazil Ice Concentration

2017 ◽  
Vol 47 (11) ◽  
pp. 2773-2792 ◽  
Author(s):  
Chen Cheng ◽  
Zhaomin Wang ◽  
Chengyan Liu ◽  
Ruibin Xia
Keyword(s):  
Freezing Point ◽  
Nonlinear Effects ◽  
Freezing Temperature ◽  
Shelf Water ◽  
Ice Shelf ◽  
Frazil Ice ◽  
Ice Concentration ◽  
Plume Modeling ◽  
Ice Shelf Water ◽  
Western Side

AbstractThe ice shelf water (ISW) plume is a prevalent phenomenon at the base of an ice shelf or sea ice adjacent to the ice shelf front. Such plumes may become supercooled and deposit marine ice when they rise. In the existing frazil ice–laden ISW plume models, it is generally assumed that supercooling and frazil ice growth can be adequately treated by using depth-averaged freezing temperature and vertically uniform frazil ice concentration within a plume. In reality, however, the temperature deficit and frazil ice concentration both increase toward the top of the plume. Hence, frazil crystals typically experience a greater deficit than that suggested by the plume’s temperature subtracted from its depth-averaged freezing point. In this study, the authors considered the combined nonlinear effects of vertical structures of frazil ice concentration and thermal forcing within an ISW plume by introducing equilibrium vertical profiles of frazil ice concentration into a horizontal two-dimensional depth-integrated ISW plume model. A series of idealized numerical experiments and an observation-based simulation beneath the western side of Ronne Ice Shelf have been conducted by using the vertically modified and original depth-integrated ISW plume models. It was found that the supercooled area, supercooling level, and suspended frazil ice and marine ice productivities are all substantially underestimated by the original models. Moreover, the differences are sensitive to the selected frazil ice size configuration. These results suggest that the vertical modification introduced in this study can significantly improve simulated marine ice distribution and its corresponding production, in comparison with those estimated by previous depth-integrated models.

A model for the spreading and sinking of the Deep Ice Shelf Water in the Ross Sea

2003 ◽  
Vol 15 (1) ◽  
pp. 25-30 ◽  
Author(s):  
ANGELO RUBINO ◽  
GIORGIO BUDILLON ◽  
STEFANO PIERINI ◽  
GIANCARLO SPEZIE
Keyword(s):  
Ross Sea ◽  
Deep Ocean ◽  
Ocean Dynamics ◽  
Shelf Water ◽  
Density Structure ◽  
Ice Shelf ◽  
Ice Shelf Water ◽  
Realistic Topography ◽  
Good Agreement

Spreading and sinking of the Deep Ice Shelf Water (DISW) in the Ross Sea are analysed using in situ observations and the results of a nonlinear, reduced gravity, layered numerical model, which is able to simulate the motion of a bottom trapped current over realistic topography. The model is forced by prescribing thickness and density of the DISW layer at the southern model boundary as well as ambient density stratification above the DISW layer. This density structure is imposed using hydrographic data acquired by the Italian PNRA-CLIMA project. In the model water of the quiescent ambient ocean is allowed to entrain in the active deep layer due to a simple entrainment parameterization. The importance of forcing the model with a realistic ambient density is demonstrated by carrying out a numerical simulation using an idealized ambient density. In a more realistic simulation the path and the density structure of the DISW vein flowing over the Challenger Basin are obtained and are found to be in good agreement with data. It is found that entrainment, which is particularly active in regions of strong topographic variation, significantly influences the pattern followed by the DISW layer. The evolution of the DISW layer beyond the continental shelf, i.e., in a region where the paucity of experimental data does not allow for a detailed description of the deep ocean dynamics, is also investigated.

scholarly journals Response of sub-ice platelet layer thickening rate to variations in Ice Shelf Water supercooling in McMurdo Sound, Antarctica

2018 ◽  
Author(s):  
Chen Cheng ◽  
Adrian Jenkins ◽  
Paul R. Holland ◽  
Zhaomin Wang ◽  
Chengyan Liu ◽  
...  
Keyword(s):  
Nonlinear Effects ◽  
Crystallographic Structure ◽  
Shelf Water ◽  
Ice Shelf ◽  
Mcmurdo Sound ◽  
Frazil Ice ◽  
Ice Concentration ◽  
Vertical Distributions ◽  
Ice Shelf Water ◽  
The Vertical Distribution

Abstract. Persistent outflow of supercooled Ice Shelf Water (ISW) from beneath McMurdo Ice Shelf creates a sub-ice platelet layer (SIPL) having a unique crystallographic structure under the sea ice in McMurdo Sound (MMS), Antarctica. A new frazil-ice-laden ISW plume model that encapsulates the combined nonlinear effects of the vertical distributions of supercooling and frazil ice concentration (FIC) on frazil ice growth is applied to MMS, and is shown to reproduce the observed ISW supercooling and SIPL distributions. Using this model, the dependence of SIPL thickening rate on ISW supercooling in MMS is investigated. Results are found to be sensitive to the choice of frazil ice suspension index, which determines the vertical distribution of FIC. For each suspension index, SIPL thickening rate can be expressed as an exponential function of ISW supercooling. The complex dependence on FIC highlights the need to improve frazil ice observations within the ice-ocean boundary layer.

scholarly journals Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

2018 ◽  
Vol 12 (1) ◽  
pp. 25-38 ◽  
Author(s):  
David W. Rees Jones ◽  
Andrew J. Wells
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Large Scale ◽  
Freezing Temperature ◽  
Ice Shelf ◽  
Secondary Nucleation ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Frazil Ice ◽  
Microphysical Processes

Abstract. The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest that crystals grow much faster than previously thought. In this paper, we consider models of a population of ice crystals with different sizes to provide insight into the treatment of frazil ice in large-scale models. We consider the role of crystal growth alongside the other physical processes that determine the dynamics of frazil ice. We apply our model to a simple mixed layer (such as at the surface of the ocean) and to a buoyant plume under a floating ice shelf. We provide numerical calculations and scaling arguments to predict the occurrence of frazil-ice explosions, which we show are controlled by crystal growth, nucleation, and gravitational removal. Faster crystal growth, higher secondary nucleation, and slower gravitational removal make frazil-ice explosions more likely. We identify steady-state crystal size distributions, which are largely insensitive to crystal growth rate but are affected by the relative importance of secondary nucleation to gravitational removal. Finally, we show that the fate of plumes underneath ice shelves is dramatically affected by frazil-ice dynamics. Differences in the parameterization of crystal growth and nucleation give rise to radically different predictions of basal accretion and plume dynamics, and can even impact whether a plume reaches the end of the ice shelf or intrudes at depth.

scholarly journals Observations of the Size Distribution of Frazil Ice in an Ice Shelf Water Plume

2020 ◽  
Vol 47 (21) ◽  
Author(s):  
Eamon K. Frazer ◽  
Pat J. Langhorne ◽  
Greg H. Leonard ◽  
Natalie J. Robinson ◽  
Dániel Schumayer
Keyword(s):  
Size Distribution ◽  
Shelf Water ◽  
Ice Shelf ◽  
Frazil Ice ◽  
Ice Shelf Water

scholarly journals Frazil-ice growth rate and dynamics in mixed layers and sub-ice-shelf plumes

2017 ◽  
Author(s):  
David W. Rees Jones ◽  
Andrew J. Wells
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Large Scale ◽  
Freezing Temperature ◽  
Ice Shelf ◽  
Secondary Nucleation ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Frazil Ice ◽  
Microphysical Processes

Abstract. The growth of frazil or granular ice is an important mode of ice formation in the cryosphere. Recent advances have improved our understanding of the microphysical processes that control the rate of ice-crystal growth when water is cooled beneath its freezing temperature. These advances suggest that crystals grow much faster than previously thought. In this paper, we consider models of a population of ice crystals with different sizes to provide insight into the treatment of frazil ice in large-scale models. We consider the role of crystal growth alongside the other physical processes that determine the dynamics of frazil ice. We apply our model to a simple mixed layer (such as at the surface of the ocean) and to a buoyant plume under a floating ice shelf. We provide numerical calculations and scaling arguments to predict the occurrence of frazil-ice explosions, which we show are controlled by crystal growth, nucleation and, gravitational removal. Faster crystal growth, higher secondary nucleation and slower gravitational removal make frazil-ice explosions more likely. We identify steady-state crystal size distributions, which are largely insensitive to crystal growth rate but are affected by the relative importance of secondary nucleation to gravitational removal. Finally, we show that the fate of plumes underneath ice shelves is dramatically affected by frazil-ice dynamics. Differences in the parameterization of crystal growth and nucleation give rise to radically different predictions of basal accretion and plume dynamics; and can even impact whether a plume reaches the end of the ice shelf or intrudes at depth.

scholarly journals Measurements of Ice Shelf Water beneath the front of the Ross Ice Shelf using gliders

2017 ◽  
Vol 58 (74) ◽  
pp. 41-50 ◽  
Author(s):  
Monica J.S. Nelson ◽  
Bastien Y. Queste ◽  
Inga J. Smith ◽  
Gregory H. Leonard ◽  
Benjamin G.M. Webber ◽  
...  
Keyword(s):  
Freezing Point ◽  
Potential Temperature ◽  
Open Water ◽  
Shelf Water ◽  
Ice Shelf ◽  
Point Temperature ◽  
Ross Ice Shelf ◽  
Ice Shelf Water ◽  
Surface Freezing

ABSTRACTMeasurements made by an underwater glider deployed near the Ross Ice Shelf were used to identify the presence of Ice Shelf Water (ISW), which is defined as seawater with its potential temperature lower than its surface freezing point temperature. Properties logged by the glider included in situ temperature, electrical conductivity, pressure, GPS location at surfacings and time. For most of the first 30 recorded dives of its deployment, evidence suggests the glider was prevented from surfacing due to being under the ice shelf. For dives under the ice shelf, farthest from the ice shelf front, ISW layers of varying thicknesses and depth locations were observed; between 2 m thick (centred at 231 m depth) to >93 m thick (centred at >360 m). For dives under the ice shelf, close to the ice shelf front, either no ISW was observed or ISW layers were centred at shallower depths (116–127 m). Thicker ISW layers (e.g. up to 250 m thickness centred at 421 m) were observed for some glider dives in open water in front of the Ross Ice Shelf. No in situ supercooling (water colder than the pressure-dependent freezing point temperature) was observed.

scholarly journals Responses of sub-ice platelet layer thickening rate and frazil-ice concentration to variations in ice-shelf water supercooling in McMurdo Sound, Antarctica

2019 ◽  
Vol 13 (1) ◽  
pp. 265-280 ◽  
Author(s):  
Chen Cheng ◽  
Adrian Jenkins ◽  
Paul R. Holland ◽  
Zhaomin Wang ◽  
Chengyan Liu ◽  
...  
Keyword(s):  
Sea Ice ◽  
Crystallographic Structure ◽  
Shelf Water ◽  
Ice Shelf ◽  
Mcmurdo Sound ◽  
Frazil Ice ◽  
Ice Concentration ◽  
Vertical Distributions ◽  
Linear Effects ◽  
Ice Shelf Water

Abstract. Persistent outflow of supercooled ice-shelf water (ISW) from beneath McMurdo Ice Shelf creates a rapidly growing sub-ice platelet layer (SIPL) with a unique crystallographic structure under the sea ice in McMurdo Sound, Antarctica. A vertically modified frazil-ice-laden ISW plume model that encapsulates the combined non-linear effects of the vertical distributions of supercooling and frazil concentration on frazil-ice growth is applied to McMurdo Sound and is shown to reproduce the observed ISW supercooling and SIPL distributions. Using this model, the dependence of the SIPL thickening rate and depth-averaged frazil-ice concentration on ISW supercooling in McMurdo Sound is investigated and found to be predominantly controlled by the vertical distribution of frazil concentration. The complex dependence on frazil concentration highlights the need to improve frazil-ice observations within the sea-ice–ocean boundary layer in McMurdo Sound.

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