The world's oceans can potentially be used as an extended target for achieving a radiometric calibration of space borne lidar if the reflective properties of the surface can be accurately predicted from available environmental data such as wind speed. To test current understanding of ocean reflectance we compare surface pulse returns measured with the 1064 nm altimetry channel of the Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat) with the predictions of near-IR reflectance from current ocean models. Measurements of wind speed retrieved from the SeaWinds database of the QuikSCAT satellite provide the model input. We find that while ocean models do not provide a full description of the nadir lidar observations this calibration technique yields a precision that exceeds that accomplished using White Sands as a target and that does not require the coordination that accompanies specialized calibration experiments.