Basin-scale extrapolation of shipboard pCO2 data by using satellite SST and Chla

A new method for the estimation of basin-scale distribution of pressure of carbon dioxide on the sea surface (pCO2) by satellite-derived sea surface temperature (SST) and chlorophyll-a concentration (Chla) is presented. 28 557 shipboard pCO2 data were regressed by second-order multiple regression equations of SST and Chla with a regression error of ±14 µatm and ±17 µatm in the subtropical and subarctic domain, respectively. The monthly-average SST and monthly-maximum Chla (Chlmax) field determined from the Advanced Earth Observing Satellite/Ocean Color Temperature Scanner (ADEOS/OCTS) level 3 Daily Binned Map data were substituted into the multi-regression equation to generate the ‘monthly-typical’ basin-scale pCO2 field in the North Pacific, and the results agreed well with the climatological field of shipboard pCO2 observations with an error bar of ±21 µatm except in the case of springtime subarctic North Pacific. The satellite-pCO2 field also satisfactorily reproduced the principle distribution of pCO2 in the springtime subarctic North Pacific such as the location of each low-pCO2 patch observed by the shipboard measurements. The extent of pCO2 depletion in each pCO2 patch, however, was not well approximated by the satellite-pCO2 field. This was caused by the underestimation of Chlmax in these low-pCO2 patches due to the low frequency of satellite-Chla observations in the springtime subarctic North Pacific due to the cloudiness.