FY 2002
Water column CO2 measurements during the Gas Ex-98 Expedition
Feely, R.A., R. Wanninkhof, D.A. Hansell, M.F. Lamb, D. Greeley, and K. Lee
In Gas Transfer at Water Surfaces,, M. Donelan, W. Drennan, E. Saltzman, and R. Wanninkhof (eds.), AGU, Washington, D.C., AGU Geophysical Monograph, 127, doi: 10.1029/GM127p0173, 173–180 (2002) |
During the recent GasEx-98 cruise in the North Atlantic aboard the NOAA ship Ronald H. Brown, carbon measurements were performed in the area of 46°N, 20.5°W. This process study followed a warm core ring tagged with the deliberately introduced tracer, SF6. Continuous surface water measurements were combined with vertical profiles sampled daily to depths up to 1000 m for carbon mass balance studies. Dissolved inorganic carbon (DIC) and fCO2 measurements were conducted onboard in both underway and discrete analysis modes. During the 25-day experiment in the tagged patch surface water fCO2 values averaged 275 ± 9 µatm, providing a constant condition of undersaturation and flux of CO2 into the ocean. Using the Wanninkhof [1992] exchange coefficient, the estimated CO2 flux ranged from approximately 1-27 mol m−2 yr−1. The largest CO2 flux occurred during a large wind event beginning on June 6. After the event, DIC and fCO2 values decreased for a few days, as a result of increased productivity associated with the strong mixing event. The DIC results were combined with the TOC, TON, and nutrient data to provide a mass balance for carbon within the patch. The results for the 25-day period indicate DIC increases in the mixed layer ranging from 0.2-1.8 µmol kg−1 d−1 due to gas exchange. |
