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May 28, 2010Journal of Physical Oceanography248 citations

Observation and Parameterization of Ablation at the Base of Ronne Ice Shelf, Antarctica

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AJAdrian JenkinsKNKeith W. NichollsHCHugh F. J. Corr

Key Points

  • To test and validate bulk parameterizations of turbulent heat and salt transfer through the oceanic boundary layer against direct measurements of ice shelf basal ablation.
  • Measured ice shelf thinning and basal ablation over month-long and year-long intervals using phase-sensitive radar situated approximately 500 km from open water in the southwestern Ronne Ice Shelf.
  • Collected ocean temperature data within 25 m of the ice shelf base and derived tidal current velocities via tidal analysis of collocated current records.
  • Calculated basal ablation rates using multiple bulk turbulent transfer parameterizations and compared them directly with radar-derived ablation observations.
  • A parameterization explicitly incorporating ocean current effects on the turbulent transfer of heat and salt matched observed basal ablation rates within 40%.
  • Calibrating the drag coefficient reduced the discrepancy between modeled ablation rates and radar observations to below observational error thresholds.
  • Simpler current-dependent parameterizations utilizing constant turbulent transfer coefficients produced equally accurate melt rate estimates.

Abstract

Abstract Parameterizations of turbulent transfer through the oceanic boundary layer beneath an ice shelf are tested using direct measurements of basal ablation. Observations were made in the southwestern part of Ronne Ice Shelf, about 500 km from open water. The mean basal ablation rate was measured over a month-long and a year-long period using phase-sensitive radar to record the thinning of the ice shelf. Ocean temperatures were observed within about 25 m of the ice shelf base over the period of the radar observations, while the tidally dominated ocean currents were estimated from tidal analysis of collocated current observations from an earlier period. Ablation rates derived using these ocean data and a number of bulk parameterizations of turbulent transfer within the boundary layer are compared with the direct measurements. The ablation rates derived using a parameterization that explicitly includes the impact of ocean currents on the turbulent transfer of heat and salt match the observations to within 40%; with suitable tuning of the drag coefficient, the mismatch can be reduced below the level of the observational errors. Equally good agreement can be obtained with two slightly simpler, current-dependent parameterizations that use constant turbulent transfer coefficients, and the optimal values for the coefficients at this particular location on Ronne Ice Shelf are given.

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Cite This Study

Jenkins et al. (2010) studied this question.

synapsesocial.com/papers/6a10d3fdcfa01e990d9f9f63https://doi.org/10.1175/2010jpo4317.1
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