Impact of the large-scale Arctic circulation and the North Water Polynya on nutrient inventories in Baffin Bay -: art. no. 3112

[1] The distributions of nitrate, phosphate, and silicate in northern Baffin Bay were determined from 90 bottle casts taken between April 11 and July 21, 1998. During late spring, low-salinity Arctic water entered northern Smith Sound and mixed with Baffin Bay water (BBW) within the North Water Polynya. The Arctic water originated from the Bering Sea and contained high concentrations of phosphate and silicate (referred to as silicate-rich Arctic water (SRAW)). The distribution of the two water masses was established using a new tracer, Si-ex, which showed moderate penetration of SRAW into Smith Sound during April and a very strong incursion in May and June, consistent with the intensification of southward current velocities. Biological depletion of macronutrients in BBW began in April and continued until nitrate was exhausted from the upper mixed layer in early June. Beneath the Polynya the deep waters (>450 m) showed a marked increase in nutrient concentration toward the bottom, which was most pronounced in the south and much stronger for silicate than nitrate and phosphate. The silicate enrichment was consistent with dissolution of diatom-derived biogenic silica in deep waters. The results indicate that the North Water acts as a silicate trap in which the biota differentially transports surface silicate to depth, thereby influencing local and downstream nutrient signatures.