A parameter model of gas exchange for the seasonal sea ice zone
- 1Graduate School of Oceanography, University of Rhode Island, 215 South Ferry Rd., Narragansett, RI, 02882, USA
- 2Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, USA
- 3US Army Corps of Engineers Cold Regions Research and Engineering Laboratory, 72 Lyme Rd., Hanover, NH, 03755, USA
- 4Department of Earth and Environmental Sciences, Columbia University, Room 106 Geoscience Bldg., Palisades, NY 10964, USA
- 5Department of Earth and Environmental Engineering, Columbia University, 918 Seeley Mudd Bldg., Columbia University, 500 West 120th St, New York, NY 10027, USA
Abstract. Carbon budgets for the polar oceans require better constraint on air–sea gas exchange in the sea ice zone (SIZ). Here, we utilize advances in the theory of turbulence, mixing and air–sea flux in the ice–ocean boundary layer (IOBL) to formulate a simple model for gas exchange when the surface ocean is partially covered by sea ice. The gas transfer velocity (k) is related to shear-driven and convection-driven turbulence in the aqueous mass boundary layer, and to the mean-squared wave slope at the air–sea interface. We use the model to estimate k along the drift track of ice-tethered profilers (ITPs) in the Arctic. Individual estimates of daily-averaged k from ITP drifts ranged between 1.1 and 22 m d−1, and the fraction of open water (f) ranged from 0 to 0.83. Converted to area-weighted effective transfer velocities (keff), the minimum value of keff was 10−55 m d−1 near f = 0 with values exceeding keff = 5 m d−1 at f = 0.4. The model indicates that effects from shear and convection in the sea ice zone contribute an additional 40% to the magnitude of keff, beyond what would be predicted from an estimate of keff based solely upon a wind speed parameterization. Although the ultimate scaling relationship for gas exchange in the sea ice zone will require validation in laboratory and field studies, the basic parameter model described here demonstrates that it is feasible to formulate estimates of k based upon properties of the IOBL using data sources that presently exist.