Decadal variability of the air‐sea CO₂ fluxes in the equatorial Pacific Ocean

Abstract

[1] In order to determine the interannual and decadal changes in the air-sea carbon fluxes of the equatorial Pacific, we developed seasonal and interannual relationships between the fugacity of CO 2 (fCO 2 ) and sea surface temperature (SST) from shipboard data that were applied to high-resolution temperature fields deduced from satellite data to obtain high-resolution large-scale estimates of the regional fluxes. The data were gathered on board research ships from November 1981 through June 2004 between 95°W and 165°E. The distribution of fCO 2sw during five El Niño periods and four La Niña periods were documented. Observations made during the warm boreal winter-spring season and during the cooler boreal summer-fall season of each year enabled us to examine the interannual and seasonal variability of the fCO 2sw -SST relationships. A linear fit through all of the data sets yields an inverse correlation between SST and fCO 2sw , with both interannual and seasonal differences in slope. On average, the surface water fCO 2 in the equatorial region has been increasing at a rate similar to the atmospheric CO 2 increase. In addition, there appears to be a slight increase ($27%) in the outgassing flux of CO 2 after the 1997-1998 Pacific Decadal Oscillation (PDO) regime shift. Most of this flux increase is due to increase in wind speeds after the spring of 1998, although increases in fCO 2sw after 1998 are also important. These increases are coincident with the recent rebound of the shallow water meridional overturning circulation in the tropical and subtropical Pacific after the regime shift.

Spatial and temporal variations in dissolved and particulate organic nitrogen in the equatorial Pacific: biological and physical influences

“…One would ask if such a difference is ascribed to the spatial variability (i.e., 125 • W-140 • W vs. 150 • W), the interannual variability (i.e., 1992 vs. 1994), or both? Previous observation and modeling studies have shown large spatial and temporal variations in physical and biogeochemical processes occurring in the equatorial Pacific (Feely et al, 2002(Feely et al, , 2006Chavez et al, 1999;Murtugudde et al, 1999;Wang et al, 2006a, b). However, little is known about the large scale spatial and temporal variations of DON and PON in the equatorial Pacific.…”

Ocean acidification off the south coast of Japan: A result from time series observations of CO2parameters from 1994 to 2008

“…[2] Long-term increases of CO 2 levels in seawater and the atmosphere have been observed in various oceanic zones such as subtropical North Pacific and North Atlantic [e.g., Inoue et al, 1995;Midorikawa et al, 2005;Takahashi et al, 2006;Bates, 2007;Dore et al, 2009], the equatorial Pacific [e.g., Feely et al, 2006;Ishii et al, 2009], subarctic North Pacific and North Atlantic [e.g., Schuster et al, 2009;Metzl et al, 2010;Wakita et al, 2010;Wong et al, 2010] and the Southern Ocean Metzl, 2009]. Although it is important to understand the changes in ocean circulation, biogeochemical processes and their roles in changing oceanic CO 2 levels, the longterm CO 2 increase in the ocean is predominantly attributable to the absorption of CO 2 that is rapidly increasing in the atmosphere, primarily as a result of human activities such as fossil fuel combustion and land-use changes.…”

Monitoring and interpreting the ocean uptake of atmospheric CO 2

“…During El Niño conditions, the warm pool expands considerably and the thermocline deepens in the eastern Pacific, both leading to a reduction of the equatorial outgassing of CO 2 to the atmosphere, so that there is a strong El Niño/La Niña signal in the resulting CO 2 fluxes. Feely et al [17] also identified a change in regime which they associated with the changing phase of the Pacific Decadal Oscillation (PDO), evident when comparing periods before 1986 and after 1990. Before this transition, the region seems to have been a slowly decreasing source of CO 2 to the atmosphere, with the surface pCO 2 changing little while atmospheric CO 2 rose steadily.…”

“…We briefly describe these regional time series below. [17]. In addition to the TAO-related observations, the equatorial Pacific has been the focus of many oceanographic studies during the Joint Global Ocean Flux Study (JGOFS) era (e.g.…”