Evolution of new ice and turbulent fluxes over freezing winter leads

Alam, Afshan; Curry, Judith A.

doi:10.1029/98jc01188

Cited by 44 publications

(50 citation statements)

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“…So, the fluxes depend on z 0 , which in turn may depend on the stormy conditions on the sea. This may partially explain the spread of the measured fluxes for the close conditions [e.g., Alam and Curry, 1998;Zulauf and Krueger, 2002;Gultepe et al, 2003].…”

Section: Surface Turbulent Fluxes and The Abl Dynamical Structurementioning

confidence: 99%

“…[49] The corresponding values of SHF and LHF observed from aircraft at an altitude of 120 m were 53.3 ± 108 and 23.3 ± 35 W m À2 respectively in the flight across polynya [Gultepe et al, 2003] [Zeng et al, 1998] used here may not contain the complete physics required for simulation of surface fluxes over a polynya, and a more complex model may be required [e.g., Alam and Curry, 1998;Andreas and Cash, 1999]; (2) the surface temperature and roughness over the polynya may be incorrectly specified if the polynya is partially frozen, or the wavy conditions cause larger roughness height than assumed by the Charnock formula; (3) the aircraft measurements are obtained at a height above the surface layer, and are not directly comparable to the simulated fluxes; and (4) specific mesoscale circulations may occur over polynya (e.g., organized convection), which may increase the fluxes; these effects are not accounted for by this hydrostatic model version with the mean vertical velocities of ±1 to 3 cm s À1 for this case.…”

Section: Surface Turbulent Fluxes and The Abl Dynamical Structurementioning

confidence: 99%

“…These clouds form from the intense surface fluxes of heat and moisture associated with the cold air flowing over the open water [e.g., Andreas, 1980;Andreas and Cash, 1999;Alam and Curry, 1998;Renfrew and Moore, 1999;Brummer and Pohlmann, 2000]. The evolution downstream of the boundary layer and clouds associated with wide leads and polynyas is, however, fundamentally different from the cold air outbreak schematized by Agee [1987].…”

Section: Introductionmentioning

confidence: 99%

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A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

Khvorostyanov

Curry

Gültepe³

et al. 2003

J. Geophys. Res.

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[1] This paper addresses the formation of a cloud system associated with an arctic polynya in Beaufort Sea during springtime. Data were obtained as a part of the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) Arctic Clouds Experiment from the Canadian Convair 580 aircraft during 25 April 1998. These data include in situ observations of cloud microphysics and meteorological variables and remote measurements from satellite and airborne lidar. A three-dimensional cloud-resolving model with explicit bin-resolving cloud microphysics is used to simulate the atmospheric boundary layer and cloud evolution associated with the polynya. After initialization with the aircraft sounding profiles, a quasi-steady polynya-induced atmospheric boundary layer (ABL) and a cloud system form. Strong turbulence in the ABL occurs above the polynya, the internal thermal boundary layer (ITBL) develops and grows upward in the downwind direction, and the ABL downwind of the polynya is separated into two decoupled layers. The cloud forms in the middle of the polynya, and its upper boundary lifts downwind while the lower boundary lowers and reaches the surface beyond the polynya southern boundary as a light fog. Farther to the south, the fog evaporates and transforms into an elevated cloud plume that extends for several tens of kilometers downwind. This cloud morphology is in good agreement with the lidar observations, which showed a cloud layer extending for more than 100 km downwind, and with the numerous previous observations. The simulated microphysical properties of a mixed cloud are similar to those observed. A new ice nucleation scheme resulted in cloud plume gradual crystallization along the wind and eventual transformation into diamond dust. Detailed evaluation of the water budget, supersaturation, and crystal size spectra showed that the ice crystal supersaturation relaxation times are 10-60 min; thus deposition on the crystals is rather slow, and only 1-5% of the available vapor is deposited on the crystals. The large ice crystal supersaturation relaxation time explains the relatively slow growth and gravitational fallout of the ice crystals, as well as the extensive propagation downwind of the plume.

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Section: Surface Turbulent Fluxes and The Abl Dynamical Structurementioning

confidence: 99%

Section: Surface Turbulent Fluxes and The Abl Dynamical Structurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

Khvorostyanov

Curry

Gültepe³

et al. 2003

J. Geophys. Res.

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“…(1) The first ice to form is frazil and pancake ice. Its thickness is determined primarily by wind speed [see Martin and Kauffman (1981), Bauer and Martin (1983), and Alam and Curry (1998)]. In the work on frazil and pancake ice done by Toudal and Coon (1999), a simple approximation to the ice thickness can be given by…”

Section: Report Documentation Pagementioning

confidence: 99%

Sea Ice Mechanics Research

Coon¹

1999

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LONG-TERM GOALThe ultimate goal of this research is the development of a complete ice dynamics model that will include lead direction and ice thickness distribution in refrozen leads. OBJECTIVESNorthWest Research Associates, Inc. (NWRA) had two objectives during this past year. The first was to use stress data to develop a new formulation of ice strength to be used in the anisotropic model . The new formulation was developed and has been provided to Dr. R. S. Pritchard for his use in model development for PIPS3.0. The second objective for this year was to review other work being done on sea ice strength in Europe. APPROACHThe approach this year was to use measured sea ice stress and models to formulate the behavior of refrozen leads. Some of the data in the models was acquired by visits to several European universities. These visits were accomplished through an appointment as Adjunct Scientist to the International ONR Office in London. WORK COMPLETEDThe work with SIMI stress data analysis was completed and the results were presented in a paper, "Determination of Pack Ice Stress from Flatjack Sensors," submitted to the Journal of Cold Regions Science and Technology. Douglas C. Echert, Gerald S. Knoke and myself authored this paper. Important insight into sea ice strength was gained through visits to the Technical Universities of Denmark, Finland, and Norway, as well as a visit to the Scott Polar Institute of Cambridge University in England. On each visit, I made a presentation on the development of the Anisotropic Sea Ice Model and received useful review of the model. The findings from the visits are presented in the section below. The results of this year's work were also presented at the PIPS3.0 development meeting at NIC in July. RESULTSDuring my six-month visit to the Technical University of Denmark, I worked with Leif Toudal on a frazil/pancake ice model for the Greenland Sea that may have applications in support of PIPS3.0 for

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“…The momentum balance in the new-ice region is assumed to be such that the ice is constrained to move with a velocity close or equal to that of the pack ice, and so U X ≈ U p . Finally, H X is typically either prescribed (Pease 1987;Ou 1988), parameterised as a function of various oceanic and atmospheric variables such as polynya fetch and wind speed (Alam & Curry 1998;Winsor & Björk 2000), or derived from simple hydrodynamic models of the frazil ice-water mixture (Bauer & Martin 1983;Biggs, Morales Maqueda & Willmott 2000).…”

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confidence: 99%

The opening of wind-driven polynyas

2014

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The opening of wind-driven coastal polynyas has often been investigated using idealised flux models. Polynya flux models postulate that the boundary separating the region of thin ice adjacent to the coast within the polynya from the thicker ice piling up downstream is a mathematical shock. To conserve mass, any divergence of the ice flux across the shock translates into a change in the shock's position or, in other words, a change in the width of the thin-ice region of the polynya. Polynya flux models are physically incomplete in that, while they conserve ice mass, they do not conserve linear momentum. In this paper, we investigate the improvements that can be achieved in the simulation of polynyas by imposing conservation of momentum as well as mass. We start by adopting a mathematically solid formulation of the ice mass and momentum balances throughout the polynya region, from the coast to the pack ice. Hydrostatic and plastic versions of the ice internal forces are used in the model. Two different approaches are then explored. We first postulate the existence of a shock at the seaward edge of the thin-ice region of the polynya and derive jump conditions for the conservation of ice mass and momentum at the shock which are consistent with the continuous model physics. Polynyas simulated by this mass-and momentum-conserving shock model always reach a steady state if the polynya forcing is uniform in space and constant in time. This is also true for all polynya flux models presented previously in the literature, but the location of the steady-state polynya edge and the time required to reach it can greatly differ between shock formulations and more simplistic flux ones. We next relax the assumption that a shock exists and let the boundary between thin ice and piling up ice emerge naturally as part of the full solution of the continuous model equations. Polynyas simulated in this way are very different from those simulated by either shock or flux models. Most notably, we find that steady-state polynya solutions are not always attainable in the continuous model. We determine under which conditions this is so and explain how such unsteady solutions come about. We also show that, in those cases when a steady-state solution exists in the continuous model, the steady-state polynya width is considerably larger than in the shock model, and the time required to attain it is accordingly longer. The occurrence of such significant differences between the polynya solutions calculated with flux and shock models, on the one hand, and with more sophisticated continuous † Email address for correspondence: mamm@noc.ac.uk

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Evolution of new ice and turbulent fluxes over freezing winter leads

Cited by 44 publications

References 30 publications

A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

A springtime cloud over the Beaufort Sea polynya: Three‐dimensional simulation with explicit spectral microphysics and comparison with observations

Sea Ice Mechanics Research

The opening of wind-driven polynyas

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