科研之友
微信
新浪微博
Facebook
分享链接
摘要
Concentrations of oxygen (O-2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (z(mix)) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that z(mix) defined using oxygen may be different than z(mix) defined using temperature or density. Here, we propose to define an O-2-based mixed layer depth, z(mix)(O-2), as the depth where the relative difference between the O-2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O-2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of z(mix)(O-2) with zmix based on potential temperature differences, i.e., z(mix)(0.2 degrees C) and z(mix)(0.5 degrees C), and potential density differences, i.e., z(mix)(0.03 kgm(-3)) and z(mix)(0.125 kgm(-3)), showed that z(mix)(O-2) closely follows z(mix)(0.03 kgm(-3)). Further comparisons with published z(mix) climatologies and z(mix) derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O-2 profiles, we suggest using zmix(0.03 kgm(-3)), which is also the basis for the climatology by de Boyer Montegut et al. (2004).
- 出版日期2012
