Massive nitrous oxide emissions from the tropical South Pacific Ocean

Water column biogeochemistry of oxygen minimum zones in the eastern tropical North Atlantic and eastern tropical South Pacific oceans

“…Although OMZs are usually not in direct contact with the atmosphere, their vicinity to coastal upwelling systems plays an important role for oceanic emissions of climate-relevant trace gases such as N 2 O, CH 4 , and DMS with potential feedbacks on global warming, which then may again impact on ocean deoxygenation. Our studies from the ETSP (Arévalo-Martínez, 2015, 2016 confirm intense production of N 2 O in the coastal upwelling. This is in line with an increase in N 2 O production from OMZ areas as concluded from forced climate models.…”

“…This is especially important since some OMZs are connected to coastal upwelling regions where OMZ waters -enriched in both nutrients and trace gases such as CO 2 , N 2 O and CH 4 -are brought to the surface, fueling phytoplankton blooms and releasing trace gases to the atmosphere (see, e.g., Capone and Hutchins, 2013). Thus, although they are usually not in direct contact with the atmosphere, OMZs play an important role for oceanic emissions of climate-relevant trace gases (see, e.g., Arévalo-Martínez et al, 2015).…”

Distributions and sea-to-air fluxes of nitrous oxide in the South China Sea and the West Philippines Sea

“…Denitrification occurs under low oxygen (o6 μmol L À 1 ) to anoxic conditions (Nevison et al, 2003). Denitrification produces and consumes N 2 O in oxygen minimum zones and the net result is that oxygen minimum zones have some of the highest N 2 O concentrations in the ocean (LaMontagne et al, 2003;Naqvi et al, 2010;Zamora et al, 2012;Arévalo-Martínez et al, 2015). In the water column with low oxygen concentrations and in sediments or inside suspended particles, nitrification and denitrification can occur simultaneously and are often closely coupled (Seitzinger, 1988;Ward et al, 1989;Capone, 1991;Middelburg et al, 1996;Barnes and Owens, 1998;Naqvi et al, 1998;Robinson et al, 1998;Usui et al, 2001;Nevison et al, 2003;Codispoti et al, 2005;Bange, 2008).…”

The Air-Sea Nitrous Oxide Flux along Cruise Tracks to the Arctic Ocean and Southern Ocean

“…In situ observations have covered a large area of the world ocean, and the N 2 O concentrations in the the N2O concentrations in the surface waters are ~3% higher than the equilibrium concentration [4]. Significant N2O sources have been found in tropical oceans where upwelling occurs, such as the Peru upwelling of the subtropical Pacific Ocean [7] and the Arabian Sea [8], which contribute ~0.2-0.9 Tg·N·a −1 and ~0.5-1 Tg·N·a −1 , respectively. Another potentially significant source is the Southern Ocean.…”