The Gulf of Mexico is known for its numerous natural seeps as well as a very active drilling program for the oil located in its sediments. This study examines water column in an active drilling and seep region in two different years, assessing the carbonate system chemistry in the deep northern Gulf of Mexico waters. There were two summer cruises in the Northern Gulf of Mexico two years apart, 2012 and 2014. Over 350 samples were collected for DIC and TA measurements on the first cruise and 115 samples were collected on the second cruise. The remaining carbon system parameters, such as pH and pCO2, were determined for each sample. The cruises were compared to GOMECC cruises in nearby region and showed that surface DIC was statistically more variable for this sample region but surface TA was not as statistically variable, suggesting a larger biological activity gradient than in the GOMECC cruises. The Mississippi River plume extended into the sampling areas on both cruises but to different extents and directions, likely due to the 227% increased discharge rate between the two years. Saturation states of calcite and aragonite approach an average of one only in the densest water sampled, suggesting favorable values for calcite and aragonite structure builders. The deepwater in the northern Gulf of Mexico was statistically significant to similar density water in the Atlantic, suggesting that the deepwater has returned to pre spill conditions, according to the carbonate chemistry.
