Abstract:

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.