Space‐time variation of mixed‐layer properties, heat and salt fluxes, and ice melt in the Newfoundland marginal ice zone

Oceanographic data collected in the Newfoundland marginal ice zone in March 1992 are analyzed to study the variation of mixed-layer properties across the ice zone. The mixed-layer depth decreases from 80 m in the interior of the pack ice to 25 m at the eastern ice edge over a distance of 120 km. In the open ocean without ice cover, the depth is considerably greater, 150∼200 m. The temperature under the pack ice is near freezing. A sharp increase in both the temperature and salinity occurs across the ice edge. The variation of the mixed-layer properties is simulated by integrating a one-dimensional bulk mixed-layer model coupled to sea ice, from November 1991 to March 1992. The initial ocean conditions are obtained from an objective analysis of archived data of November 1991. The forcings are 6-hourly meteorological data from the European Centre for Medium-Range Weather Forecasts. Ice concentration and thickness are treated as prescribed functions of time extracted from daily ice maps since ice in the area is not locally formed. The model simulation is in good agreement with the observations. From the model results, a detailed analysis of the roles of wind stress, ice melt, surface cooling, and shortwave radiation in the water mass transformation of the upper ocean is carried out. There are large differences in the melt rate and water-ice heat flux between the times when ice enters the shelf and after the water has been cooled by the ice to near freezing: 15∼20 cm d−1 and 500∼700 Wm−2, and 0∼2 cm a−1 and 20∼50 Wm−2 respectively. A large portion of the heat in the water column is expended for ice melting from January to March. Calculations that use surface data such as surface wind and sea surface temperature without considering ice melt can underestimate the net ocean-to-air heat flux, especially at the eastern ice edge in March.

[1]  C. Tang,et al.  A dynamical model for wind‐driven ice motion: Application to ice drift on the Labrador Shelf , 1996 .

[2]  J. I. MacPherson,et al.  Investigating the marginal ice zone on the Newfoundland Shelf , 1994 .

[3]  A. Omstedt,et al.  Ice growth and oceanic heat flux: Models and measurements , 1992 .

[4]  C. Tang.  Oceanographic features in the Newfoundland marginal ice zone, March‐April 1990 , 1992 .

[5]  John S. Wettlaufer,et al.  Heat flux at the ice‐ocean interface , 1991 .

[6]  C. Tang.  A two‐dimensional thermodynamic model for sea ice advance and retreat in the Newfoundland marginal ice zone , 1991 .

[7]  A. Warn-Varnas,et al.  Predictions and Studies with a One-Dimensional Ice/Ocean Model. , 1990 .

[8]  M. Ikeda,et al.  A model of sea ice and the upper ocean mixed layer off Labrador , 1990 .

[9]  J. Willebrand,et al.  Fine Adjustment of Large Scale Air-Sea Energy Flux Parameterizations by Direct Estimates of Ocean Heat Transport , 1989 .

[10]  G. Mellor,et al.  A two‐dimensional coupled ice‐ocean model of the Bering Sea marginal ice zone , 1989 .

[11]  George L. Mellor,et al.  An Ice-Ocean Coupled Model , 1989 .

[12]  L. Mysak,et al.  A Simple Steady-State Coupled Ice-Ocean Model, with Application to the Greenland-Norwegian Sea , 1989 .

[13]  Stuart D. Smith.  Coefficients for sea surface wind stress, heat flux, and wind profiles as a function of wind speed and temperature , 1988 .

[14]  M. Houssais.  Testing a Coupled Ice-Mixed-Layer Model Under Subarctic Conditions , 1988 .

[15]  Ralph J. Slutz,et al.  A Comprehensive Ocean-Atmosphere Data Set , 1987 .

[16]  S. Häkkinen.  A coupled dynamic‐thermodynamic model of an ice‐ocean system in the marginal ice zone , 1987 .

[17]  E. Josberger.  Bottom ablation and heat transfer coefficients from the 1983 Marginal Ice Zone Experiments , 1987 .

[18]  J. Morison,et al.  Dynamics and thermodynamics of the ice/upper ocean system in the marginal ice zone of the Greenland Sea , 1987 .

[19]  M. Steele,et al.  Ice-Seawater Turbulent Boundary Layer Interaction with Melting or Freezing , 1986 .

[20]  G. Symonds.  Seasonal ice extent on the northeast Newfoundland shelf , 1986 .

[21]  G. R. Stegen,et al.  A Heat Balance for the Bering Sea Ice Edge , 1985 .

[22]  L. Røed.  A Thermodynamic Coupled Ice-Ocean Model of the Marginal Ice Zone , 1984 .

[23]  P. Lemke,et al.  The seasonal variation of the mixed layer and the pycnocline under polar sea ice , 1984 .

[24]  Fred W. Dobson,et al.  The heat budget at ocean weather station Bravo , 1984 .

[25]  D. Pollard,et al.  Development of a Simple Upper-Ocean and Sea-lce Model , 1983 .

[26]  R. Reed,et al.  On Estimating Insolation over the Ocean , 1977 .

[27]  A. Semtner.  A MODEL FOR THE THERMODYNAMIC GROWTH OF SEA ICE IN NUMERICAL INVESTIGATIONS OF CLIMATE , 1975 .