Nutrient fluxes in the eastern North Atlantic Clare Johnson (1), Stuart Cunningham (1), Penny Holliday (2) and Stefan Gary (1) (1) Scottish Association of Marine Science (2) National Oceanography Centre, Southampton
Subpolar North Atlantic 64 N 56 N 48 N 72 N 40 N 15 W 30 W 45 W 0 UK North Atlantic Nordic Seas Greenland 0°25 W20 W 15 W10 W5 W 60 N 63 N 57 N 54 N 51 N UK Iceland Rockall Trough Iceland Basin Extended Ellett Line 1997 onwards Annual hydrographic section
Mean geostrophic transports ( ) Holliday et al., accepted, JGR, early view. ≈ total transports (difference between geostrophic-derived surface velocities and altimeter-derived surface velocities minimised)
Nutrient data quality assessment Mean ± stdev (no QC) Sherwin et al., 2012, ICES Journal of Marine Science, 69, Black: all data Red: data from 1 cruise Decision: ‘good’ data mode ± 1 stdev Johnson et al., 2013, DSR, 82, [NO 3 ] (µM) [SiO 3 ] (µM) NO 3 PO 4 SiO 3
Example nutrient sections NO 2+3 PO 4 SiO 3 IcelandRockall Scotland (µM)
Calculation of nutrient fluxes Two water masses defined by density: (1) Upper water < kg m -3 (2) Overflow water > kg m -3 Nutrient (µM) Holliday et al., accepted, JGR, early view.
Volume and nutrient transports 3.9 ± ± ± ± 0.9 NO 2+3 (kmol s -1 ) UW OW Total Volume (Sv) UW +6.7 OW -2.1 Total +2.5
Volume and nutrient transports 1.3 SiO 3 (kmol s -1 ) UW OW Total PO 4 (kmol s -1 ) UW +4.4 OW -1.9 Total
Nutrient distribution in eastern North Atlantic shows water mass structure as well as non-conservative behaviour. Eastern North Atlantic net source of nutrients to Nordic Seas and Arctic Ocean. First look mean values 1997 to 2013: NO kmol s -1, PO kmol s -1, SiO kmol s -1 (likely to be slightly on high side). Summary Future work More sophisticated nutrient transport calculation. Calculation of variability around mean transports. Produce time-series of volume and nutrient transports between 1997 and present.
The research leading to these results has received funding from the European Union 7th Framework Programme (FP ), under grant agreement n NACLIM