Coastal areas

In general, enhanced N2O emissions in coastal areas are found in upwelling systems and nitrogen-rich estuaries (Seitzinger et al, 2000; Nevison et al, 2004). However, as in the case of the open ocean emissions, flux estimates from coastal areas are heavily biased by a seasonal variability, which is, in the majority of the studies, only inadequately resolved.

The narrow bands of coastal upwelling systems such as those found in the northwestern Indian Ocean (Arabian Sea) and in the southeastern Pacific Ocean (off central Chile) have been identified as 'hot spots' for extremely high N2O anomalies with N2O saturations of up to 8250 per cent and 2426 per cent, respectively (Naqvi et al, 2005; Cornejo et al, 2007). In nitrogen-rich estuarine systems, high N2O anomalies are usually only found in the estuaries themselves, whereas the adjacent shelf waters, which are not influenced by the river plumes, are close to equilibrium with the atmosphere. Bange (2006b), for example, computed mean N2O saturations of 113 per cent and 467 per cent for European shelf and estuarine systems, respectively.

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