Calibrating the ECCO Ocean General Circulation Model Using WOCE Data and Model Green's Functions Dimitris Menemenlis, Ichiro Fukumori, Tong Lee, and Lee-Lueng Fu Model Green's functions provide a simple, yet effective, method to test and calibrate General-Circulation-Model (GCM) parameterizations, to study and quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products. These properties are demonstrated within the context of the ECCO (Estimating the Circulation and Climate of the Ocean, http://www.ecco-group.org) ocean data assimilation project using a subset of WOCE data.