Auxiliary material for "North-South asymmetry in the modeled phytoplankton community response to climate change over the 21st century" Irina Marinov Department of Earth and Environmental Science, University of Pennsylvania, 240 S. 33rd Street, Hayden Hall 153, Philadelphia, PA 19104, USA. and Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA. Scott C. Doney and Ivan D. Lima Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, 266 Woods Hole Road, Woods Hole, MA 02543, USA. K. Lindsay Climate and Global Dynamics Division, National Center for Atmosphere Research, P.O. Box 3000, Boulder, CO 80307, USA. J. K. Moore Department of Earth System Science, Croul Hall 3214, Univ. of California at Irvine, Irvine, CA 92697-3100, USA. N. Mahowald Department of Earth and Atmospheric Sciences, 2140 Snee Hall, Cornell University, Ithaca, NY 14850. Global Biogeochemical Cycles Introduction The supplementary material includes (1) a description of how the ecological biome areas are changing over the 21st century with climate change; (2) caption for the supplementary table showing these changes; (3) detailed captions for four supplementary figures referenced in the main text; (4) additional references. (1) Ecological biomes are changing over the 21st century We define a set of ecological biomes based on physical criteria, closely following the definitions employed by Sarmiento et al. [2004] and conceptually along the lines of Longhurst [1994]. Details of the ecological partitioning are presented in Appendix B of the paper; the resulting biomes are shown in Figure 6 in the main paper. Climate change over the 21st century results in changes in the size of the various ecological biomes, as summarized in Supplementary Table 1. Generally speaking, the geographical boundaries separating different biomes migrate poleward with climate change, and the most pronounced biome change is the contraction of the marginal sea ice biomes. Because of more accelerated surface ocean warming in the north, the fractional contraction in the ice biome is larger in the Northern than in the Southern hemisphere (19% versus 15%). The retreating ice biome is replaced by the subpolar biome. As a consequence, the subpolar biome moves poleward and expands more in the Northern hemisphere (by 9%) compared to the Southern hemisphere (a 3.5% expansion). The poleward expansion of the Hadley cells and poleward shift in mid-latitude westerlies result in a net poleward expansion of the low nutrient, low chlorophyll Subtropical biomes and Subtropical gyres in all basins in both the Northern and Southern hemispheres. This expansion agrees in principle with the claim based on recent satellite observations that extreme ocean oligotrophic provinces are getting larger over time [Irwin et al., 2009; Polovina et al., 2008] and has consequences for global ocean productivity and ecosystem composition. (2) Supplementary Table 1 (ts01.pdf): Present area of the modeled ecological biomes (calculated for years 1980-1999) and the response of the biome areas to global warming in the 21st century. Areas are given in 10^12 m^2. Table columns shows the present area of the biomes, followed by the net change in areas and the % change in areas. Net area change is the difference between the model average warming conditions (2080-2099) minus present conditions (1980-1999). % change in area is the percent change in area relative to the (1980-1999) mean area. Note that the average control biome areas for years (1980-1999) are used for all calculations in the main body of the paper, and are illustrated in Figure 6 of the main text. (3) Supplementary Figure Captions: Figure S1 (fs01.pdf): Zonal averages of: (a) Relative (fractional) abundance of small phytoplankton (black) and diatoms (red) for years 1980-1999 (no units); (b) Trend in relative abundance of phytoplankton from 1980 to 2100; (c) Nutrient contribution to the 1980-2100 trend in specific growth rate () as calculated from Eq. A6b; (d) Light contribution to 1980-2100 trend in growth rate () as calculated from Eq. A6a. (e) Southward transport of small phytoplankton (black) and diatom biomass (red) in the Southern Hemisphere Atlantic basin in 102 molC/s. Trends in (b,c,d) above are calculated from the respective 1980-2100 modeled linear trends multiplied by 120 years, in units of day-1. Figure S2 (fs02.pdf): Global maps of the limiting nutrients at the ocean surface at present (averaged over the control period, years 1980-1999) and in the future (averaged over years 2080-2099) for (a,b) diatoms, (c,d) small phytoplankton and (e-f) diazotrophs. Figure S3 (fs03.pdf): Temporal trends in (a) surface diatom biomass and (c) surface nutrient limitation calculated from Eq. A3 (Appendix A of the paper). (b) Temporal trend in diatom biomass congruent with the nutrient limitation trend. (d) The residual trend in diatom biomass, or the trend in biomass unexplained by the nutrient limitation trend. Trends are calculated from the 120 years (1980-2100) of monthly data. Figure S4 (fs04.pdf): Global maps of the present values (average over years 1980-1999) and climate change signal (difference between years 1980-1999 and years 2080-2099) for (a,b) surface iron (nmol/m3); (c,d) Fe vertical advection at the maximum annual MLD in nmol Fe/m2/day; (e,f) Fe horizontal convergence vertically integrated up to the maximum annual MLD (nmol Fe/m2/day). These values were approximated off-line from monthly nitrate and flow values. (4) References: Irwin, A. J. and M. J. Oliver (2009), Are ocean deserts getting larger?, Geophysical Research Letters, 36, L18609, doi:10.1029/2009GL039883. Longhurst, A. (1994), Ecological Geography of the Ocean, 176 pp., Academic, San Diego, Calif. Polovina, J. J., E. A. Howell, and M. Abecassis (2008), OceanŐs least productive waters are expanding, Geophys. Res. Lett., 35, L03618, doi:10.1029/2007GL031745. Sarmiento, J. L., R. Slater, R. Barber, L. Bopp, S. C. Doney, A. C. Hirst, J. Kleypas, R. Matear, U. Mikolajewicz, P. Monfray, V. Soldatov, S. A. Spall and R. Stouffer (2004), Response of ocean ecosystems to climate warming, Global Biogeochem. Cycles, 18(3), GB3003, doi: 10.1029/2003GB002134.