UC San Diego

The convergence of freshwater from polar and subpolar waters influences nutrient (nitrate, phosphate, and silicate) concentrations on the southeastern Greenland shelf. Interannual variability of nutrient distributions from the shoreline to 150 km offshore were determined by using hydrographic and nutrient measurements from June to September of 2002 to 2016 to produce high-resolution transects. Although no significant trend was observed during the period analyzed, in-situ observations from 1991 to 2018 revealed considerable interannual variability and that nutrient concentrations in polar-origin waters (POLW) were two to three times less than those of Atlantic-origin (AW). In POLW, the mean nitrate, phosphate, and silicate concentrations (in µmol/kg) were 5.02, 0.51, and 3.10, respectively, compared to that of AW, with means of 15.16, 0.98, and 7.80, respectively over the same area. Waters of Pacific-origin, transported through the Arctic Ocean circulation and western Fram Strait, were observed furthest inshore in southeastern Greenland from 1997 to 2018 with increased fractions of Pacific Water concentration in 2004 (0.15) and 2018 (0.16). From relationships observed between nutrients, nitrate was identified as the least biologically-available nutrient, followed by phosphate, and then, silicate, which concurred with previous studies in the North Atlantic region. The accepted global stochiometric relationships for N:P, N:Si, and Si:P are 16, 1.07, and 15, respectively. As expected, results differed slightly throughout the cross section, as the area from the shoreline to 72 km exhibited ratios of 17.71, 1.66, and 9.70, respectively, while the area from 72 km to 150 displayed ratios of 13.56, 1.00, and 10.14, respectively.