Air–Sea Heat Flux Measurements from Nearly Neutrally Buoyant Floats

The ability of neutrally buoyant, high-drag floats to measure the air–sea heat flux from within the turbulent oceanic boundary layer is investigated using float data from four different winter and fall float deployments. Two flux estimates can be made: Q0A measures the vertical advection of heat, and Q0D integrates the Lagrangian heating rate. Because the floats are only imperfectly Lagrangian, a key issue is diagnosing the ability of a given set of float data to make accurate flux measurements. A variety of diagnostics are explored and evaluated. Here Q0A and Q0D are compared to heat flux measurements computed using bulk formulas and shipboard measurements for one 2-week cruise. Quality controlled float-based fluxes agree with bulk fluxes to within 10 W m−2 for both positive and negative values. The differences are well within the expected statistical errors in the float measurements and the bias errors of the bulk measurements.