加拿大海盆的营养盐极大

根据 1 999年和 2 0 0 3年中国北极科学考察航次 ,从Canada海盆收集温、盐、深和营养盐浓度数据 ,用文献报道的低浓度1 2 9I和高浓度金属钡 (Ba)来指示太平洋源水、用相应的高浓度1 2 9I和低浓度Ba来指示大西洋源水 ,划分了该海盆物理化学特征的 4个水团。表层水 ( <40m)的盐度从 2 5至 31 .6;硝酸盐处于耗尽水平 ,而磷酸盐和硅酸盐处于最低水平。营养盐再生水大致位于 40- 2 0 0m ;盐度特征为 31 .6- 33.1 ;营养盐浓度一致增至最高 ;极大峰的盐度在 33.1附近 ,其位温则处于最低水平 (约 - 1 .5°C)。混合水 (深约 2 0 0- 385m)盐度从 33.1至 34.8;位温从局域最低升至整个水柱最高的 0 .5 0- 0 .65 7°C ;营养盐则逐渐降低。深层水深度变化较大 ( 385m至 1 90 0m以下海底 ) ;但其盐度变化较小 ( 34.8- 34.9) ;位温则从最高降低到 - 0 .4至 - 0 5 4°C ;营养盐均轻微增加。结合文献中对于营养盐极大的年际观测 ,1 2 9I、Ba与氯氟烃CFC 1 1的浓度及3H 3He示踪年龄的结果分析表明 ,营养盐再生水是无季节性变化的、高年龄 (约 8- 1 5年 )的太平洋源水 ;深层为大西洋源水 ;而混合水团即为上述 2大源水的混合层。硅酸盐和磷酸盐的强极大指示优势种硅藻及其再生主导太平洋源水。

NUTRIENT MAXIMUM IN THE CANADA BASIN

Data of potential temperature (θ), salinity (S), depth and nutrient concentrations were collected during 1999 and 2003 Chinese Arctic Expedition cruises. Together with high barium (Ba) of Falkner et al. and low 129 I concentrations of McLaughlin et al. that indicate Pacific-origin water, with low Ba and high 129 I concentrations that indicate Atlantic-origin water, we defined four water masses of physical and chemical characteristics in the Canada basin. Surface water (< 40 m) had S from 25 to 31.6, where nitrate concentrations were consumed and limited, and phosphate and silicate concentrations were in the lowest level. Nutrient regeneration water (40—200 m) is characterized by S of 31.6—33.1 with θ decreasing to the lowest (to about -1.5 °C ), and nutrient concentrations approaching the maximum. Mixed water (200—385 m) are marked by S of 33.1 to 34.8 with θ increasing to the maximum of 0.50—0.657 °C , where nutrient values decrease considerably. Salinity of deep water changes a little (34.8—34.9) and the θ decreased from the highest to -0.4 or -0.54 °C , but its depth greatly increases from 400 m to 1900 m or deeper bottom, in contrast to its nutrient data increase slightly. McLaughlin et al.' annual nutrient observations with 129 I and Ba data mentioned above and the 3H- 3He age of Smethie et al. suggest that the nutrient regeneration water is Pacific-origin water with no seasonal alteration but with high tracer ages (about 8—15 a); the Atlantic layer waters are in the deep water; and mixed water is the mixed layer of both waters in the Canada Basin. The robust maximums of both silicate and phosphate imply that diatoms and their regeneration dominate the Pacific-origin water.