Water column denitrification rates in the oxygen minimum layer of the Pacific Ocean along 32 degrees S

作者：Kim Il Nam^*; Min Dong Ha; Macdonald Alison M

来源：Global Biogeochemical Cycles, 2013, 27(3): 816-827.

DOI：10.1002/gbc.20070

• Water column denitrification
• eOMP analysis
• N*
• South Pacific Ocean
• Oxygen minimum layer

To date, estimates of water column denitrification rates in global- and basin-scale nitrogen budgets do not include any values obtained in the open ocean outside the oxygen minimum zones (OMZs). The high-quality, 32 degrees S Pacific repeat hydrographic surveys conducted in 1992, 2003, and 2010 offer an opportunity to estimate denitrification rates on basin scales in the open ocean away from the Eastern Tropical Pacific (ETP) oxygen minimum zones. Here, extended optimum multiparameter analysis and N-* are used to estimate water column denitrification (N-deni) in the oxygen minimum layer (OML; 1100-2000 dbar). Water column denitrification rates for 2003 and 2010 are estimated from the regression analysis using N-deni and transit time distribution ages based on CFC12. Estimated mean denitrification rates in the OML at 32 degrees S range from 3.1 to 7.5 mu molNm(-3)yr(-1) (=2.6-6.8mmolNm(-2)yr(-1) with a thickness of 900m). The OML denitrification rates are 2-3 orders of magnitudes lower than those estimated in the OMZs of ETP. However, their significance to Pacific nitrogen budget needs to be investigated in the future. Although uncertainties remain, our results may ultimately contribute to an improved understanding of marine nitrogen cycles.

• 出版日期2013-9