Historial nitrate, phosphate, and dissolved oxygen data from the central Arctic Ocean are examined with particular emphasis on the conservative parameters NO (9*NO3+O2) and PO (135*PO4+O2). The NO/PO ratio is shown to increase with depth in the Canada Basin, being ~0.78 in Surface and Upper Halocline Waters and ~1.0 in the Atlantic Layer and Deep Waters. Lower Halocline Water is marked by NO and PO minima and intermediate NO/PO. NO/PO ratios from the Arctic shelf seas are examined to determine possible source regions for the various water masses. The NO/PO ratio of Canada Basin Deep Water implies an upper bound of ~11% shelf water contribution to this water mass. A slight oxygen maximum core in the Lower Halocline Water is identified at a salinity of S=34.5 in the vicinity of the Alpha Ridge. This core appears to be diminished by diapycnal mixing and does not extend into the Beaufort Gyre. ¿ American Geophysical Union 1990