Modeling the interplay between sea ice formation and the oceanic mixed layer: Limitations of simple brine rejection parameterizations

2015 ◽  
Vol 86 ◽  
pp. 141-152 ◽  
Author(s):  
Antoine Barthélemy ◽  
Thierry Fichefet ◽  
Hugues Goosse ◽  
Gurvan Madec
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Ice Formation ◽  
Oceanic Mixed Layer ◽  
Brine Rejection

scholarly journals Winter Convection Transports Atlantic Water Heat to the Surface Layer in the Eastern Arctic Ocean*

2013 ◽  
Vol 43 (10) ◽  
pp. 2142-2155 ◽  
Author(s):  
Igor V. Polyakov ◽  
Andrey V. Pnyushkov ◽  
Robert Rember ◽  
Laurie Padman ◽  
Eddy C. Carmack ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Heat Loss ◽  
Mixed Layer ◽  
Atlantic Water ◽  
Velocity Shear ◽  
The Arctic ◽  
Ice Formation ◽  
Surface Mixed Layer ◽  
Winter Convection

Abstract A 1-yr (2009/10) record of temperature and salinity profiles from Ice-Tethered Profiler (ITP) buoys in the Eurasian Basin (EB) of the Arctic Ocean is used to quantify the flux of heat from the upper pycnocline to the surface mixed layer. The upper pycnocline in the central EB is fed by the upward flux of heat from the intermediate-depth (~150–900 m) Atlantic Water (AW) layer; this flux is estimated to be ~1 W m−2 averaged over one year. Release of heat from the upper pycnocline, through the cold halocline layer to the surface mixed layer is, however, seasonally intensified, occurring more strongly in winter. This seasonal heat loss averages ~3–4 W m−2 between January and April, reducing the rate of winter sea ice formation. This study hypothesizes that the winter heat loss is driven by mixing caused by a combination of brine-driven convection associated with sea ice formation and larger vertical velocity shear below the base of the surface mixed layer (SML), enhanced by atmospheric storms and the seasonal reduction in density difference between the SML and underlying pycnocline.

scholarly journals Application of an atmospheric boundary layer model to a large-scale coupled sea-ice-oceanic mixed-layer model for the Southern Ocean

1991 ◽  
Vol 15 ◽  
pp. 191-195 ◽  
Author(s):  
Achim Stössel
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Layer Model ◽  
Oceanic Mixed Layer ◽  
Boundary Layer Model ◽  
Ice Model ◽  
Mixed Layer Model

A coupled sea-ice-oceanic mixed-layer model for the Southern Ocean is forced with daily atmospheric variables from the global analyses of the European Center for Medium Range Weather Forecasts (ECMWF). Using the analyses of the lowest level in the calculations of the turbulent heat fluxes and stresses with the appropriate bulk formulae, the simulation results resemble earlier ones with climatological forcing. In order to avoid a predetermination of the simulated sea-ice conditions from the (climatological) specification of the surface boundary conditions in the atmospheric general circulation model (AGCM), the sea-ice model is coupled additionally to a one-dimensional atmospheric boundary layer model. Using the global ECMWF-analyses as before, the coupled model is now forced from the geostrophic level (850 hPa). Without any changes of the original model parameters and physics, the results are rather poor in that the ice extent as well as the ice velocities are generally too low and that the ice thickness distribution resembles the results of a pure thermodynamic sea-ice model. The results with the forcing from the higher level are more realistic when snow and mixed-layer effects are neglected, thus resembling those of Koch (1988) in the Weddell Sea. This indicates that the parameterizations in the atmospheric boundary layer model have to be readjusted in order to interact realistically with the snow-sea-ice-oceanic mixed-layer model. Additionally, it will be demonstrated that the pattern of the wind field, whether from the geostrophic or the surface level, has a significant influence on the sea-ice model results.

scholarly journals Arctic Ocean Heat Impact on Regional Ice Decay: A Suggested Positive Feedback

2016 ◽  
Vol 46 (5) ◽  
pp. 1437-1456 ◽  
Author(s):  
Vladimir Ivanov ◽  
Vladimir Alexeev ◽  
Nikolay V. Koldunov ◽  
Irina Repina ◽  
Anne Britt Sandø ◽  
...  
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Positive Feedback ◽  
Heat Content ◽  
Ice Cover ◽  
Atlantic Water ◽  
Arctic Sea Ice ◽  
Ice Formation ◽  
Thermohaline Convection ◽  
Upper Mixed Layer

AbstractBroad, long-living, ice-free areas in midwinter northeast of Svalbard between 2011 and 2014 are investigated. The formation of these persistent and reemerging anomalies is linked, hypothetically, with the increased seasonality of Arctic sea ice cover, enabling an enhanced influence of oceanic heat on sea ice and, in particular, heat transported by Atlantic Water. The “memory” of ice-depleted conditions in summer is transferred to the fall season through excess heat content in the upper mixed layer, which in turn transfers to midwinter via thinner and younger ice. This thinner ice is more fragile and mobile, thus facilitating the formation of polynyas and leads. When openings in ice cover form along the Atlantic Water pathway, weak density stratification at the mixed layer base supports the development of thermohaline convection, which further entrains warm and salty water from deeper layers. Convection-induced upward heat flux from the Atlantic layer retards ice formation, either keeping ice thickness low or blocking ice formation entirely. Certain stages of this chain of events have been examined in a region north of Svalbard and Franz Joseph Land, between 80° and 83°N and 15° and 60°E, where the top hundred meters of Atlantic inflow through the Fram Strait cools and freshens rapidly. Complementary research methods, including statistical analyses of observations and numerical modeling, are used to support the basic concept that the recently observed retreat of sea ice northeast of Svalbard in winter may be explained by a positive feedback between summer ice decay and the growing influence of oceanic heat on a seasonal time scale.

Dynamics of Eddies Generated by Sea Ice Leads

2021 ◽  
Author(s):  
Kaylie Cohanim ◽  
Ken X. Zhao ◽  
Andrew L. Stewart
Keyword(s):  
Sea Ice ◽  
Mixed Layer ◽  
Baroclinic Instability ◽  
Eddy Diffusivity ◽  
Coherent Vortices ◽  
Brine Rejection ◽  
Ice Floes ◽  
Ice Leads ◽  
Length Scaling ◽  
Salt Forms

AbstractInteraction between the atmosphere and ocean in sea ice-covered regions is largely concentrated in leads, which are long, narrow openings between sea ice floes. Refreezing and brine rejection in these leads injects salt that plays a key role in maintaining the polar halocline. The injected salt forms dense plumes that subsequently become baroclinically unstable, producing submesoscale eddies that facilitate horizontal spreading of the salt anomalies. However, it remains unclear which properties of the stratification and leads most strongly influence the vertical and horizontal spreading of lead-input salt anomalies. In this study, the spread of lead-injected buoyancy anomalies by mixed layer and eddy processes are investigated using a suite of idealized numerical simulations. The simulations are complemented by dynamical theories that predict the plume convection depth, horizontal eddy transfer coefficient and eddy kinetic energy as functions of the ambient stratification and lead properties. It is shown that vertical penetration of buoyancy anomalies is accurately predicted by a mixed layer temperature and salinity budget until the onset of baroclinic instability (~3 days). Subsequently, these buoyancy anomalies are spread horizontally by eddies. The horizontal eddy diffusivity is accurately predicted by a mixing length scaling, with a velocity scale set by the potential energy released by the sinking salt plume and a length scale set by the deformation radius of the ambient stratification. These findings indicate that the intermittent opening of leads can efficiently populate the polar halocline with submesoscale coherent vortices with diameters of around 10 km, and provide a step toward parameterizing their effect on the horizontal redistribution of salinity anomalies.

scholarly journals Application of an atmospheric boundary layer model to a large-scale coupled sea-ice-oceanic mixed-layer model for the Southern Ocean

1991 ◽  
Vol 15 ◽  
pp. 191-195
Author(s):  
Achim Stössel
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Layer Model ◽  
Oceanic Mixed Layer ◽  
Boundary Layer Model ◽  
Ice Model ◽  
Mixed Layer Model

A coupled sea-ice-oceanic mixed-layer model for the Southern Ocean is forced with daily atmospheric variables from the global analyses of the European Center for Medium Range Weather Forecasts (ECMWF). Using the analyses of the lowest level in the calculations of the turbulent heat fluxes and stresses with the appropriate bulk formulae, the simulation results resemble earlier ones with climatological forcing. In order to avoid a predetermination of the simulated sea-ice conditions from the (climatological) specification of the surface boundary conditions in the atmospheric general circulation model (AGCM), the sea-ice model is coupled additionally to a one-dimensional atmospheric boundary layer model. Using the global ECMWF-analyses as before, the coupled model is now forced from the geostrophic level (850 hPa). Without any changes of the original model parameters and physics, the results are rather poor in that the ice extent as well as the ice velocities are generally too low and that the ice thickness distribution resembles the results of a pure thermodynamic sea-ice model. The results with the forcing from the higher level are more realistic when snow and mixed-layer effects are neglected, thus resembling those of Koch (1988) in the Weddell Sea. This indicates that the parameterizations in the atmospheric boundary layer model have to be readjusted in order to interact realistically with the snow-sea-ice-oceanic mixed-layer model. Additionally, it will be demonstrated that the pattern of the wind field, whether from the geostrophic or the surface level, has a significant influence on the sea-ice model results.

Seasonal variations in the properties and structural composition of sea ice and snow cover in the Bellingshausen and Amundsen Seas, Antarctica

1997 ◽  
Vol 43 (143) ◽  
pp. 138-151 ◽  
Author(s):  
M. O. Jeffries ◽  
K. Morris ◽  
W.F. Weeks ◽  
A. P. Worby
Keyword(s):  
Sea Ice ◽  
Isotopic Composition ◽  
Snow Cover ◽  
Sea Water ◽  
Ice Cores ◽  
Ice Cover ◽  
Snow Accumulation ◽  
Ice Formation ◽  
Frazil Ice ◽  
Core Sets

AbstractSixty-three ice cores were collected in the Bellingshausen and Amundsen Seas in August and September 1993 during a cruise of the R.V. Nathaniel B. Palmer. The structure and stable-isotopic composition (18O/16O) of the cores were investigated in order to understand the growth conditions and to identify the key growth processes, particularly the contribution of snow to sea-ice formation. The structure and isotopic composition of a set of 12 cores that was collected for the same purpose in the Bellingshausen Sea in March 1992 are reassessed. Frazil ice and congelation ice contribute 44% and 26%, respectively, to the composition of both the winter and summer ice-core sets, evidence that the relatively calm conditions that favour congelation-ice formation are neither as common nor as prolonged as the more turbulent conditions that favour frazil-ice growth and pancake-ice formation. Both frazil- and congelation-ice layers have an av erage thickness of 0.12 m in winter, evidence that congelation ice and pancake ice thicken primarily by dynamic processes. The thermodynamic development of the ice cover relies heavily on the formation of snow ice at the surface of floes after sea water has flooded the snow cover. Snow-ice layers have a mean thickness of 0.20 and 0.28 m in the winter and summer cores, respectively, and the contribution of snow ice to the winter (24%) and summer (16%) core sets exceeds most quantities that have been reported previously in other Antarctic pack-ice zones. The thickness and quantity of snow ice may be due to a combination of high snow-accumulation rates and snow loads, environmental conditions that favour a warm ice cover in which brine convection between the bottom and top of the ice introduces sea water to the snow/ice interface, and bottom melting losses being compensated by snow-ice formation. Layers of superimposed ice at the top of each of the summer cores make up 4.6% of the ice that was examined and they increase by a factor of 3 the quantity of snow entrained in the ice. The accumulation of superimposed ice is evidence that melting in the snow cover on Antarctic sea-ice floes ran reach an advanced stage and contribute a significant amount of snow to the total ice mass.

scholarly journals First record of the occurrence of sea ice in the Cordillera Darwin fjords (54°S), Chile

2021 ◽  
pp. 1-11
Author(s):  
Charles Salame ◽  
Inti Gonzalez ◽  
Rodrigo Gomez-Fell ◽  
Ricardo Jaña ◽  
Jorge Arigony-Neto
Keyword(s):  
Time Series ◽  
Sea Ice ◽  
First Record ◽  
Ice Formation ◽  
Future Research ◽  
Landsat 8 ◽  
Surface Salinity ◽  
Air Temperatures ◽  
Aerial Reconnaissance ◽  
High Precipitation

Abstract This paper provides the first evidence for sea-ice formation in the Cordillera Darwin (CD) fjords in southern Chile, which is farther north than sea ice has previously been reported for the Southern Hemisphere. Initially observed from a passenger plane in September 2015, the presence of sea ice was then confirmed by aerial reconnaissance and subsequently identified in satellite imagery. A time series of Sentinel-1 and Landsat-8 images during austral winter 2015 was used to examine the chronology of sea-ice formation in the Cuevas fjord. A longer time series of imagery across the CD was analyzed from 2000 to 2017 and revealed that sea ice had formed in each of the 13 fjords during at least one winter and was present in some fjords during a majority of the years. Sea ice is more common in the northern end of the CD, compared to the south where sea ice is not typically present. Is suggested that surface freshening from melting glaciers and high precipitation reduces surface salinity and promotes sea-ice formation within the semi-enclosed fjord system during prolonged periods of cold air temperatures. This is a unique set of initial observations that identify questions for future research in this remote area.

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