Figure 1 from the PHC 2.0 Paper (shown below), illustrates the density of data observations at the surface in winter and summer of the WOA and EWG (AOA) data fields. The color scale ranges from 1 observation to 10+. For information about the temporal distribution of this data, refer to Table 1 in the PHC Paper. Note the lack of winter data in the Canadian Archepeligo, Hudson Bay, and Baffin Bay in both data sets.
PHC 2.0 used only the analyzed data fields provided by WOA and EWG as a bases for generating the climatology. The poor data representation in the Archepeligo region resulted in inaccurate values in these fields, which were then propogated into PHC 2.0. This is the subject of point #2 under "Motivations for Upgrading to PHC 2.1" on the PHC 2.1 overview page.
(Read the figure caption for additional information about how this data was binned, and the fields provided by WOA and EWG)