Relationships between total alkalinity in surface water and sea surface dynamic height in the Pacific Ocean

Abstract

Improved spatial and temporal representation of total alkalinity (TA) is expected to be an important component in monitoring changes in the oceanic carbon cycle and acidification over the coming decades. For this reason, previous authors have sought to develop and apply empirical methods to characterize TA in the surface ocean. However, there are regions such as the North Pacific that have proven difficult to successfully represent through empirical relationships based on temperature and salinity with linear regression. Here we propose a new empirical approach for reconstructing TA for the Pacific basin using sea surface salinity and sea surface dynamic height (SSDH). We propose five zones of the Pacific basin where the empirical relationships are applied separately. The root-mean-square error of the fittings of these equations to the measured TA is 7.8 lmol kg 21 . The SSDH-based empirical equation helps especially to represent the TA in the North Pacific subtropical-subarctic frontal zone where salinity-normalized TA as well as other oceanographic variables exhibits a large meridional gradient and sizeable formation of Central Mode Water and Subtropical Mode Water occurs.

Remotely Forced Decadal Physical and Biogeochemical Variability of North Pacific Subtropical Mode Water Over the Last 40 Years

“…From these data, we calculated AOU, DIC normalized at S = 35 (nDIC), pH in total scale at in situ temperature, Ω arag , and preformed nDIC. Such calculation is justified because our observations (Midorikawa et al, 2010;Takatani et al, 2014) have indicated that nTA in the surface water is almost invariable in latitude and time in the western North Pacific subtropical region and is vertically uniform from the sea surface to the STMW depth. Such calculation is justified because our observations (Midorikawa et al, 2010;Takatani et al, 2014) have indicated that nTA in the surface water is almost invariable in latitude and time in the western North Pacific subtropical region and is vertically uniform from the sea surface to the STMW depth.…”

Investigating ENSO‐Related Temperature Variability in Equatorial Pacific Core‐Tops Using Mg/Ca in Individual Planktic Foraminifera

“…Under such conditions, the direct thermal and pH influences on Mg/Ca may work in partial opposition, theoretically resulting in lower Mg/Ca variance. Total variability in sea surface pH ranges from ~0.01 to 0.03 pH units for our core‐top locations, with maximum variance in the cold tongue east of Galapagos (Iida et al, ; Takatani et al, ). In terms of Mg/Ca, this pH variability should have a much smaller impact than temperature, but it also implies that pH and temperature are not strongly additive in the equatorial Pacific.…”

Physical forcing of late summer chlorophyll a blooms in the oligotrophic eastern North Pacific

“…Climatological data were calculated by averaging over 1982–2012. JMA also provided monthly mean oceanic total alkalinity estimates (from 2001) mapped with 1° resolution [ Takatani et al ., ].…”

“…We used the total alkalinity data to evaluate the effect of this process. Note that total alkalinity is a quasi‐conservative property, slightly affected by biological activity (e.g., formation of calcium carbonate; change in nitric acid concentration through photosynthesis) in this region [ Takatani et al ., ]. In this study, the total alkalinity data were not affected by local biological activity because they were estimated from the sea surface salinity and dynamic height fields through an empirical relationship.…”