12th Pacific Science Inter-Congress, 8-12 July 2013
University of the South Pacific, Laucala Bay Campus, Suva, Fiji
PROJECTED SEASONALITY IN OCEAN ACIDIFCATION IN THE
WESTERN PACIFIC REGION
Sri Nandini1, *, Helene Jacot Des Combes1, Andrew Lenton2
and Mareva Kuchinke2
1PACE-SD, University of the South Pacific, Private Mail Bag,
Suva, Fiji Islands
*corresponding author: s.nandini42@gmail.com
2CSIRO Wealth from Oceans National Research Flagship, PO
Box 1538, Hobart, TAS 7001, Australia
Abstract
Oceans play a vital role by taking up atmospheric CO2, thus
altering the seawater chemistry. The pH and aragonite
saturation state (Ωar) are reduced, collectively known as
ocean acidification. Previous studies indicate that coral
growth (calcification) rates typically decline as saturation
states decrease. Consequently, island nations that rely on
coral reefs may be adversely impacted. In this study, we
investigate how the seasonal and long-term Ωar and its key
drivers: Sea Surface Temperature (SST), Salinity (SALT), Total
Alkalinity (TA) and Total CO2 (TCO2) change under the high
(A2) and control atmospheric CO2 emission scenarios. We
focus on the Pacific region (35°S: 30°N; 120°E: 220°E) and its
subregions: the West Pacific Warm Pool (WPWP) and the East
Equatorial Pacific (EEQ) due to their contrasting
characteristics. We evaluate the coupled carbon Community
Climate System Model (CCSM3) against upper ocean seasonal
data, where surface Ωar values drop from 3.8 to 2.3 by 2100
12th Pacific Science Inter-Congress, 8-12 July 2013
University of the South Pacific, Laucala Bay Campus, Suva, Fiji
for the whole region. The mean seasonal amplitude in Ωar
decreases by 4% from while the seasonal phase remains
unchanged till 2100. It was found that TCO2 is the main driver
in the seasonal variability in Ωar in the different regions and
that CCSM3 overestimates the TA response towards Ωar at
the equator, in the WPWP and in the EEQ. In the WPWP TA
compensates effects of TCO2 due to the dilution caused by
intensified hydrological cycle by 2100. In the EEQ, wind driven
seasonal upwelling is the main driver of seasonal changes in
Ωar by 2100.
Key Words: (ocean acidification; aragonite saturation
state; seasonal variability; Pacific)