Distributions of N2O and its air-sea fluxes in seawater along cruise tracks between 30°S-67°S and in Prydz Bay, Antarctica

Abstract

Air and surface seawater samples were taken during the 22nd Chinese National Antarctic Research Expedition, November 2005 to March 2006, and analyzed for N2O concentrations. The results show that the concentration of N2O in surface seawater increased from 8.9 ± 0.2 nM to 17.9 ± 0.3 nM along the cruise tracks southward from 30°S-67°S latitude and correlated well with sea surface temperature (SST). The saturation anomaly along the cruise tracks changed from negative (south) to positive (north) with the turning point located between 50 and 55°S latitude coincident with the location of the Subantarctic Front (SAF). Positive saturation found north of the SAF is due to the seasonal SST variation, while the undersaturation of N2O south of the SAF may be due to a combination of SST variation and intrusion of N2O-depleted ice meltwater during summer. Air-sea fluxes measured on the cruise tracks north of the SAF were positive, ranging between 5 and 10 μmol m-2 d -1, while fluxes south of the SAF were close to zero. N2O in the surface water of Prydz Bay was in near equilibrium with the atmosphere: the corresponding air-sea flux was about -0.3 ± 0.8 μmol m -2 d-1, not different from zero. Copyright 2009 by the American Geophysical Union.