OUR MAIN OBJECTIVE IS TO LEVERAGE THE CONSTRAINTS FROM GLINT OCO-2 DATA AND FROM ATMOSPHERIC OXYGEN (O2) DATA IN PARTICULAR THE NASA ATOM PROGRAM AND SCRIPPS NETWORK TO QUANTIFY THE OCEAN CARBON FLUX RESPONSE TO EL NINO-SOUTHERN OSCILLATION (ENSO). ENSO IS THE MAIN SOURCE OF YEAR-TO-YEAR FLUCTUATIONS IN ATMOSPHERIC CO2. THE OCEAN ACCOUNTS FOR 15 TO 50% OF THESE INTERANNUAL VARIATIONS (I.E 0.5-1 PGC/Y). DURING THE 2015/2016 EL NINO EVENT GLINT OCO-2 DATA DETECTED A STRONG DECREASE OF 1 PPM IN COLUMN CO2 OVER THE CENTRAL EQUATORIAL PACIFIC WHICH IS ATTRIBUTED TO AN INCREASE IN THE OCEAN SINK. YET THE MAGNITUDE OF THIS INCREASE IN THE OCEAN SINK AND THE PROCESSES DRIVING IT REMAIN LARGELY UNKNOWN. THESE UNCERTAINTIES HAVE FAR REACHING IMPLICATIONS FOR OUR UNDERSTANDING OF THE CARBON CYCLE AND ITS RESPONSE TO CLIMATE VARIABILITY. FIRST THE STRONGER OCEAN SINK COMPETES WITH THE WEAKER LAND SINK OBSERVED DURING EL NINO EVENTS AND IMPACT THE DETECTION AND ATTRIBUTION OF THE LAND SINK VARIABILITY. SECOND UNCERTAINTIES IN THE DRIVING MECHANISMS STRONGLY LIMIT SEASONAL AND LONG TERM PREDICTION OF ENSO IMPACTS.