HR: 0800h
AN: OS31A-0548    [Abstracts]
TI: The Advective Nutricline: The Impact of Subtropical Mode Water on the North Atlantic Subsurface Nutrient Gradient and Primary Productivity
AU: * Palter, J B
EM: jbp3@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Box 90227, Durham, NC 27708 United States
AU: Lozier, M S
EM: s.lozier@duke.edu
AF: Duke University, Division of Earth and Ocean Sciences, Nicholas School of the Environment and Earth Sciences, Box 90227, Durham, NC 27708 United States
AU: Barber, R T
EM: 2525047578
AF: Nicholas School of the Environment and Earth Science, Duke Marine Laboratory, 135 Duke Marine Lab Rd, Beaufort, NC 28516 United States
AB: The ocean's ability to act as a sink for atmospheric carbon dioxide is subject to considerable spatial and temporal variability. Not least of the causes of this variability is the strength of the biological pump, which is critically dependent on the physical supply of nutrients from the subsurface ocean to the euphotic zone. Using hydrographic data from the World Ocean Circulation Experiment (WOCE), the NODC historical data, and time series data from Hydrostation S and Bermuda Atlantic Time Series, we have found that the North Atlantic Subtropical Mode Water (STMW) is a source of spatial and temporal variability in the vertical nutrient gradient in the subtropical gyre. The STMW essentially injects low nutrient water between the seasonal and permanent pycnocline. STMW is likely depleted in nutrients by biological uptake and the convective mixing of zero-nutrient surface water with subsurface water during formation. After formation, the water mass is advected around the subtropical gyre and spread along isopycnals. It can be characterized by low potential vorticity and low nutrient concentrations up to 1500 km from the formation region, suggesting that in the region of tight subtropical recirculation, the advective time scale is faster than the remineralization time scale. The weak vertical nutrient gradient imposed by the STMW impacts all vertical processes that supply nutrients to the euphotic zone. Using ship based primary productivity data and satellite observations of sea surface chlorophyll, we also examine the hypothesis that the presence of STMW influences rates of primary productivity and the size and location of the low productivity region in the subtropical North Atlantic.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4845 Nutrients and nutrient cycling
DE: 4215 Climate and interannual variability (3309)
DE: 4532 General circulation
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting