New insights of pco2 variability in the tropical eastern Pacific Ocean using SMOS SSS and OSTIA SST C W Brown, J Boutin, L Merlivat, LOCEAN Paris Results
SMOS 10 day Sea Surface Salinity Ostia Sea Surface Temperature/ KNMI ASCAT wind
Summertime (April- October) - Fresher SSS, - Warmer SST - No jet winds Early Winter (October- December) - Upwelling in Gulf of Tecuantec - Intensified jet winds in Tecuantec - Freshpool remains in Panama Late Winter (January- March) - Upwelling in all three gulfs - Freshpool eroded 3-7 ms-1 7-12 ms-1 12+ ms-1
K x (pco2sea-pco2atm) Air-Sea CO2 flux Sea surface partial pressures of CO2 Two pco2 databases: SOCAT (Surface Ocean CO2 Atlas, Bakker et al. 2014) ~10 million obs, 1968-2011 LDEO v2013 (Lamont-Doherty Earth Observatory, Takahashi et al. 2013) ~9 million obs, 1957-2013
Region: Eastern Tropical Pacific Annual increase of pco2: Computed from SOCAT observations within ETPO: 1.92 μatm yr-1 since 1990 ~ Atmospheric increase in CO2 between 1990-2014 All calculated pco2 data corrected to 2014 values.
All SOCAT data 1990-2011 The Eastern Tropical Pacific
Watermasses in the 3 Gulfs of the Eastern Tropical Pacific The same TS environment is observed in each gulfs
How is pco2 and air sea flux influenced? 1. Strong winds: -Increase Air-Sea CO2 flux Air-Sea FluxCO2 = kco2 CO2 (pco2sea-pco2atm) Where CO2 is the solubility of CO2 (Weiss, 1974), pco2sea the partial pressure of CO2 in seawater (μatm), pco2atm the partial pressure of CO2 in the atmosphere (μatm), and kco2 (cm/h) is the gas transfer velocity for CO2. k = 0.27 U2(660/Sc)0.5 Where U is the 10 m wind speed, and Sc is the Schmidt number -Upwelling introduces high DIC 13 C water into the mixed layer 2. Rainfall: Rainfall dilutes both DIC and total alkalinity, and results in under-saturated pco2
Look-Up-Table (LUT) RMSE = 14.89uatm Works well at low salinity, Works well at low temperature Larger error at intermediate values A B C
Original data vs LUT SOCAT Measured data Modelled using SOCAT temperature and salinity, using LUT
Applying the LUT to 4 years Of Satellite SST + SSS data - Upwelling strongest under axis of Jet wind - Highest pco2 during winter - Low pco2 year-round in - Gulf of Panama
Summer- Low pco2 Winter- High pco2 Gulf of Papaguay and Tecuantec - net outgassing Gulf of Panama -net ingassing
In-situ pco2 Satellite data variability Conclusions Conclusions -SMOS satellite SSS improves the constraint of sea surface processes influencing pco2 variability. - Jet winds and rainfall are first order controls of air-sea fluxes of CO2 - Ship based measurements, SMOS, OSTIA and ASCAT products can be used to produce high - resolution surface ocean CO2 data via the use of a statistical model Panama Gulf region: Lower pco2 due to high rainfall, year round in-gassing except February-March Papaguay Gulf region: High year-round pco2 due to upwelling caused by jet winds (winter) or gyre (summer) Tecuantec Gulf region: Low pco2 during summer, high wintertime pco2 due to upwelling caused by jet winds ETPO average: Mean of pco2: 20 µatm oversaturated Sea-Air flux: 1.06 mmol m-2 d-1 sea -> air flux Christopher.brown@locean-ipsl.upmc.fr Data Sources LOCEAN 0.25 SMOS SSS SOCAT OSTIA SST KNMI ASCAT 0.25 wind velocity Cats.ifremer.fr/Products socat.info ghrsst-pp.metoffice.com Knmi.nl/scatterometer