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Seasonal data for pCO2 and the concentrations of CO2 and nutrients in high‐latitude surface oceans obtained by the Lamont‐Doherty CO2 group and Marine Research Institute, Reykjavik, are presented and analyzed. The seasonal progression and relationships between these properties are described, and their inter‐ocean variation is compared. Spring phytoplankton blooms in the surface water of the North Atlantic Ocean and Iceland Sea caused a precipitous reduction of surface water pCO2 and the concentrations of CO2 and nutrients within two weeks, and proceeded until the nutrient salts were exhausted. This type of seasonal behavior is limited to the high‐latitude (north of approximately 40°N) North Atlantic Ocean and adjoining seas. In contrast, seasonal changes in CO2 and nutrients were more gradual in the North Pacific and the nutrients were only partially consumed in the surface waters of the subarctic North Pacific Ocean and Southern Ocean. The magnitude of seasonal changes in nutrient concentrations in the North Pacific and Southern Oceans was similar to that observed in the North Atlantic and adjoining seas. In the subpolar and polar waters of the North and South Atlantic and North Pacific Oceans, pCO2 and the concentrations Of CO2 and nutrients were much higher during winter than summer. During winter, the high latitude areas of the North Atlantic, North Pacific, and Weddell Sea were sources for atmospheric CO2; during summer, they became CO2 sinks. This is attributed to the upwelling of deep waters rich in CO2 and nutrients during winter, and the intense photosynthesis occurring in strongly stratified upper layers during summer. On the other hand, subtropical waters were a CO2 source in summer and a sink in winter. Since these waters were depleted of nutrients and could only sustain low levels of primary production, the seasonal variation of pCO2 in subtropical waters and the CO2 sink/source condition were governed primarily by temperature. An intense CO2 sink zone was found along the confluence of the subtropical and subpolar waters (or the subtropical convergence). Its formation is attributed to the combined effects of cooling in subtropical waters and photosynthetic drawdown of CO2 in subpolar waters.

Climatological mean monthly distributions of pH in the total H + scale, total CO 2 concentration (TCO 2 ), and the degree of CaCO 3 saturation for the global surface ocean waters (excluding coastal areas) are calculated using a data set for pCO 2 , alkalinity and nutrient concentrations in surface waters (depths <50 m), which is built upon the GLODAP, CARINA and LDEO databases. The mutual consistency among these measured parameters is demonstrated using the inorganic carbon chemistry model with the dissociation constants for carbonic acid by Lueker et al. (2000) and for boric acid by Dickson (1990). Linear potential alkalinity-salinity relationships are established for 24 regions of the global ocean. The mean monthly distributions of pH and carbon chemistry parameters for the reference year 2005 are computed using the climatological mean monthly pCO 2 data adjusted to a reference year 2005 and the alkalinity estimated from the potential alkalinity-salinity relationships. The equatorial zone (4°N-4°S) of the Pacific is excluded from the analysis because of the large interannual changes associated with ENSO events. The pH thus calculated ranges from 7.9 to 8.2. Lower values are located in the upwelling regions in the tropical Pacific and in the Arabian and Bering Seas; higher values are found in the subpolar and polar waters during the spring-summer months of intense photosynthetic production. The vast areas of subtropical oceans have seasonally varying pH values ranging from 8.05 during warmer months to 8.15 during colder months. The warm tropical and subtropical waters are supersaturated by a factor of as much as 4.2 with respect to aragonite and 6.3 for calcite, whereas the cold subpolar and polar waters are supersaturated by 1.2 for aragonite and 2.0 for calcite because of the lower pH values resulting from greater TCO 2 concentrations. In the western Arctic Ocean, aragonite undersaturation is observed. The time-series data from the Bermuda (BATS), Hawaii (HOT) and the Drake Passage show that pH has been declining at a mean rate of about -0.02 pH per decade, and that pCO 2 has been increasing at about 19 atm per decade tracking the atmospheric pCO 2 increase rate. This suggests that the ocean acidification is caused primarily by the uptake of atmospheric CO 2 . The relative A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT2 importance of the four environmental drivers (temperature, salinity, alkalinity and total CO 2 concentration) controlling the seasonal variability of carbonate chemistry at these sites is quantitatively assessed. The ocean carbon chemistry is governed sensitively by the TA/TCO 2 ratio, and the rate of change in TA is equally important for the future ocean environment as is the TCO 2 in ocean waters increases in the future.