Vertical distribution of nutrient tracers in the western Arctic Ocean and its relationship to water structure and biogeochemical processes

摘要

During the 3rd Chinese National Arctic Research Expedition cruise in the summer of 2008,nutrients(NO3^-,NO2^-,SiO3^2-,and PO4^3-)and dissolved oxygen were measured in the western Arctic Ocean,to derive the vertical distribution of nutrient tracers and its relationship to water structure and biogeochemical processes.The nutrient data show that surface waters had the lowest NO3^-/PO4^3-(mean of 0.5)and SiO3^2-/PO3^-(mean of 2.8)values in the water column,suggesting an excess of phosphate.Winter Bering Shelf water(wBSW)had high Si^*(16.7μmol/L;Si^*=[Si(OH)4]–[NO3^-])with negative N^*(−11.7μmol/L;N^*=[PO4^3-]−16[PO4^3-]+3.5μmol/L)in the water column,indicating nitrate deficiency.The warm Atlantic layer had positive N^*(0.8μmol/L)and negative Si^*(−5.4μmol/L)compared with Pacific source water.The vertical distribution of nutrients indicates that wBSW can be characterized by N^* minimum and Si^* maximum.In contrast,minima of Si^* and SiO3^2-/PO4^3- below 200 m indicate the distribution of Atlantic warm water.