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Natural variability and anthropogenic change in equatorial Pacific surface ocean p CO 2 and pH
Author(s) -
Sutton Adrienne J.,
Feely Richard A.,
Sabine Christopher L.,
McPhaden Michael J.,
Takahashi Taro,
Chavez Francisco P.,
Friederich Gernot E.,
Mathis Jeremy T.
Publication year - 2014
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/2013gb004679
Subject(s) - thermocline , upwelling , pacific decadal oscillation , seawater , el niño southern oscillation , mooring , environmental science , oceanography , carbon dioxide , climatology , sea surface temperature , ocean acidification , pacific ocean , geology , atmospheric sciences , chemistry , organic chemistry
The equatorial Pacific is a dynamic region that plays an important role in the global carbon cycle. This region is the largest oceanic source of carbon dioxide (CO 2 ) to the atmosphere, which varies interannually dependent on the El Niño‐Southern Oscillation (ENSO) and other climatic and oceanic drivers. We present high‐resolution observations of surface ocean CO 2 partial pressure ( p CO 2 ) at four fixed locations in the Niño 3.4 area with data sets encompassing 10 ENSO warm and cold events from 1997 to 2011. The mooring observations confirm that ENSO controls much of the interannual variability in surface seawater p CO 2 with values ranging from 315 to 578 µatm. The mooring time series also capture the temporal variability necessary to make the first estimates of long‐term pH trends in the equatorial Pacific, which suggests that the combination of ocean acidification and decadal variability creates conditions for high rates of pH change since the beginning of the mooring record. Anthropogenic CO 2 increases play a dominant role in significant observed seawater p CO 2 trends of +2.3 to +3.3 µatm yr −1 and pH trends of −0.0018 to −0.0026 yr −1 across the full time series in this region. However, increased upwelling driven by increased trade winds, a shallower thermocline, and increased frequency of La Niña events also contribute an average of 40% of the observed trends since 1998. These trends are higher than previous estimates based on underway observations and suggest that the equatorial Pacific is contributing a greater amount of CO 2 to the atmospheric CO 2 inventory over the last decade.