The A tlantic M eridional T ransect Programme - past, present and future

1. The Atlantic Meridional Transect Programme - past, present and future Carol Robinson & the AMT team RRS James Clark Ross AMT 1995-2000 Rationale Major scientific outcomes AMT 2002-2006 Rationale Improvements Scientific hypotheses

2. AMT-5 Sept 1997 Universidad de Vigo • AMT 1995-2000 : Rationale • UK NERC (~ £280,000 over 3 years) • phytoplankton processes & bio-optical signatures • latitudinal distributions of zooplankton • JCR cruises UK to Falkland Islands Sept/Oct and • Falkland Islands to UK April/May • ~ 13,500 km, 50 oN – 52 oS • ~ 2-4 days extra to passage, ~ 2 hr day-1 station time • underway measurements + 1-2 vertical casts day-1 • optics, phytoplankton, PP, nutrients, zooplankton • UK NERC-PML, Spanish CANIGO & CIRCANA, USA NASA • AMT5 SeaWiFS Atlantic Characterisation Experiment

3. AMT 1995-2000 : Scientific achievements • Unique biogeochemical measurements over basin scales • 12 cruises : seasonal & interannual time series • data set : optics, phyto- & mesozooplankton • 70+ peer reviewed publications, 17 in 2001 • special issue Progress in Oceanography • 22 Ph.D. theses + 24 ongoing • definition of provinces • optics & calibration of remotely sensed data • sources & sinks of pCO2 • plankton community diversity • plankton community activity

4. AMT 2002-2006 : Rationale & Improvements UK NERC Consortium : Climate change & Biodiversity (~ £2.3 million) 9 specific hypotheses co-ordinated Plymouth Marine Laboratory 6 partner institutions, ~ 45 investigators directed cruise track - 2 x 1.5 h stns per day samples gyre & upwelling - 10 d extra deeper sampling, SAP time, links with PML/SOC time series : continue & enhance plankton community structure, atmospheric interactions, biogases scientific & data management student & technical training

5. 9 climatically important integrated hypotheses 4 FeIII FeII+OH SO2 +OH H2SO4 DUST NH4+ 9 Fe UV SO2 pCO2 7 DMS 1 2 CH4 Nutrients 3 8 N2O 6 5 Carbon AMT I AMT II new 6 1 4 2 5 3 7 8 9

6. Directed cruise track 1. Biodiversity • Characterise biological provinces • Requires cruise track to cover wide range of plankton communities • Size spectrum of plankton community • (bacteria, phytoplankton, micro-mesozooplankton) • Production to calcification ratio • Phytoplankton size structure • Primary production to respiration ratio

7. Composite satellite image of aerosols over the oceans Directed cruise track 2. Comparison N and S Atlantic • Differences in functioning of N and S Atlantic gyres despite similar phytoplankton biomass and rates of production • Requires cruise track to sample gyres • Imbalance production < respiration in N but not S Atlantic • Models predict lateral input of nutrients in N Atlantic • Different atmospheric supply of nutrients

8. Law et al Aiken Lefevre et al Chile upwelling Jan 1997 pCO2 Directed cruise track 3. Basin scale estimates of biogas fluxes • Climatically important gases - v. little data • Requires cruise track to cover range of plankton communities and particularly upwelling areas • Relationship plankton • biomass and N2O, CH4 • Species specific DMS • Oceans 20% atmospheric • N2O burden; N2O is 280 x CO2 • Relate to remotely sensed • parameters

9. The Atlantic Meridional Transect Programme 1995-2006 Conclusions • AMT 1995-2000 • 70++ publications • 20++ Ph.D. theses • significant findings : • Characterise physical and biogeochemical provinces • Distribution of pCO2 and other biogases • Variability in pico- to meso-plankton activity • Optics & remote sensor calibration • AMT 2002-2006 • continued & enhanced data coverage • decadal time series • biodiversity - wide range of oceanographic regimes • upper ocean biogeochemistry - comparison N & S Atlantic • climate change - basin scale flux of biogases