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Intraseasonal Hydrographic Variations and Nearshore Carbonates System Off Northern Chile During the 2015 El Niño Event
Author(s) -
Aguilera Victor M.,
Vargas Cristian A.,
Dewitte Boris
Publication year - 2020
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2020jg005704
Subject(s) - hydrography , upwelling , downwelling , oceanography , salinity , environmental science , sea surface temperature , alkalinity , kelvin wave , phytoplankton , climatology , sea surface height , atmospheric sciences , geology , chemistry , organic chemistry , nutrient
Little is known on the El Niño‐related impacts affecting the CO 2 dynamic and fluxes in productive Eastern Boundary Upwelling Systems (EBUS). Through 35 oceanographic campaigns conducted between January 2015 and April 2016 in the Humboldt EBUS (23°S), intraseasonal (i.e., daily‐to‐bimonthly) hydrographic variations and nearshore changes in surface carbonates system were assessed during the 2015 El Niño event. Collected hydrographic and carbonates system data (sea surface temperature (SST), subsurface temperature, salinity, oxygen, chlorophyll a , pH, total alkalinity ( A T ) and p CO 2 ), were analyzed and interpreted considering local (i.e., satellite winds and tide gauge sea level) and remote (i.e., equatorial Kelvin waves) forcing. Permanent alongshore wind conditions prompted a relatively deep mixed layer favoring elevated acidity (7.8–7.9 pH T ) and CO 2 saturated (>450 μatm) conditions throughout most of the study period. Between austral summer‐fall and fall‐winter transitions, intermittent warm events increased water temperature (SST) above the long‐term climatological state (2000–2010), and gave rise to high acidity‐warm conditions. However, despite warm water particularly high in salinity (>35) and A T (>2,300 μmol kg −1 ) associated with downwelling Kelvin waves activity observed during the developing phase of the 2015 El Niño event, phytoplankton production and CO 2 uptake were favored because of the maintenance of mean upwelling conditions. These results are discussed in terms of data limitations, coastal processes adding variability to carbonates system variability, and requirements for a better understanding of hydrographic forcing and responses in the Humboldt EBUS.