热带与南极海域表层海水N_2O饱和度异常差异性比较

COMPARISON OF SURFACE WATER N_2O SATURATION ANOMALIES BETWEEN TROPICAL AND THE ANTARCTIC WATERS

比较从30°N西太平洋至30°S东印度洋等热带海域与南大洋至东南极普里兹湾等南极海域的大气和表层海水N2O分压分布特征,表层海水pNO2饱和异常,分析引起异常差异性的主要影响因子。南极海域普里兹湾表层水中N2O分压(pN2O)平均为311.9±7.6 nL.L-1(14.1±0.4 nM),与大气中N2O混合比(318.5 nL.L-1)相比显略不饱和,融冰水的输入是导致不饱和的主要原因。海气N2O通量为-0.3±0.8μmol.m-2.d-1。而热带海域多数表层海水中N2O饱和度异常值都高于10%,在赤道海域发现最高值达54.7%,次高值则位于10°N的苏禄海为31%,计算出在赤道和苏禄海的海气通量分别为～12.4μmol.m-2.d-1和～4μmol.m-2.d-1。表明高纬度的普里兹湾是大气中N2O的弱汇,而低纬度热带海域表现为大气中N2O的源。造成热带与南极海域海洋N2O饱和度异常的影响因素,可能是低纬度的热带海域由于海气间的气体交换较弱、上升流影响强,而高纬度的南极海域由于融冰分层和强偏西风的影响;而海表面风速是影响N2O的海气交换和N2O通量的重要因素。

Characteristics of surface water partial pressure of N2 O and their saturation anomalies were compared between the tropic waters from 30°N in the Western Pacific to 30°S in East Indian Ocean and the Antarctic waters from the Southern Ocean to Prydz Bay, East Antarctica. Several major factors were analyzed for driving differences of satura- tion anomalies between the tropic and the Antarctic waters. The surface water pN20 from Prydz Bay was an average of 311.9 ±7.6 nL L-1 （ 14.1± 0.4 nM）, less unsaturated relative to atmospheric mixing ratio （318.5 nL L- 1 ）. This instauration would be attributed from melted seaice water being mixed to bring lower pN20. Air-sea flux of N20 was about -0.3 ±0.8 μmol m-2 d-1. However, N20 saturation anomalies appeared in most tropical surface waters higher than 10% with the maximum of 54.7% found in Equatorial waters and higher of 31% around 10°N in the Sulu sea. Air-sea fluxes were calculated for the tropic waters and Sulu Sea respectively as （ 12.4 μmol m-2 d-1 and -4 μmol m-2 d -1 , suggesting that low latitudinal tropical waters would play a significant role as an atmospheric N20 source. This might be caused due to weak air-sea exchange and strong upwelling. However in the high latitudinal Antarctic waters, stratification by melted seaice waters would Bay and persistent strong westerly would enhance air-sea exchange rate, especially prevent from upwelling in Prydz surface wind would be an important factor to impact air-sea flux of N2O.