Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2005 Modeling the Effect of Eddies and Advection on the Lower Trophic Ecosystem in the Northeast Tropical Pacific Annette Samuelsen Follow this and additional works at the FSU Digital Library. For more information, please contact [email protected] THE FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES MODELING THE EFFECT OF EDDIES AND ADVECTION ON THE LOWER TROPHIC ECOSYSTEM IN THE NORTHEAST TROPICAL PACIFIC by ANNETTE SAMUELSEN A dissertation submitted to the Department of Oceanography in partial fulfillment of the requirements for the degree of Doctor of Philosophy Degree Awarded: Spring Semester, 2005 The members of the committee approved the dissertation of Annette Samuelsen, defended on 14 March 2005. --------------------------------------------- James J. O'Brien Professor Directing Dissertation --------------------------------------------- Gordon Erlebacher Outside Committee Member --------------------------------------------- William K. Dewar Committee Member --------------------------------------------- Nancy H. Marcus Committee Member --------------------------------------------- Richard L. Iverson Committee Member --------------------------------------------- Eileen E. Hofmann Committee Member The office of Graduate Studies have verified and approved the above named committee members. ii ACKNOWLEDGEMENT I would like to thank the members on my committee and particularly my major professor James J. O'Brien for help and encouragement during this work. Eileen Hofmann and Richard Iverson made helpful suggestions regarding the biological model. John Kindle and Sergio deRada for provided the global NCOM data. Chlorophyll a and PAR data were obtained from the NASA/GSFA/DAAC. I am also very grateful to Paul Fiedler for providing the ship-based observations. This work was partially sponsored by the School of Computational Science and Information Technology, Florida State University. Steve Morey and Erik Kvaleberg kindly read and commented on the manuscript. iii TABLE OF CONTENTS List of Figures ............................................................................................................... vi List of Tables ................................................................................................................ xi Abstract ........................................................................................................................ xii 1. INTRODUCTION .................................................................................................... 1 2. METHODS ............................................................................................................... 9 2.1 Physical Model ............................................................................................. 9 2.2 Ecosystem Model ....................................................................................... 12 2.2.1 Nitrate ......................................................................................... 16 2.2.2 Ammonium ................................................................................. 19 2.2.3 Small Phytoplankton ................................................................... 19 2.2.4 Large Phytoplankton ................................................................... 20 2.2.5 Microzooplankton ....................................................................... 21 2.2.6 Mesozooplankton ........................................................................ 21 ` 2.2.7 Detritus ........................................................................................ 22 2.2.8 Light ............................................................................................ 22 3. NUMERCAL EXPERIMENTS .............................................................................. 26 3.1 Initial and Boundary Conditions ................................................................ 26 3.2 Sensitivity Analysis ................................................................................... 27 3.3 Cross-Shelf Flux at the Coast .................................................................... 28 3.4 Processes at the Costa Rica Dome ............................................................. 28 3.5 Model Validation ....................................................................................... 28 iv 4. RESULTS ............................................................................................................... 30 4.1 General Model Results and Model Validation ........................................... 30 4.1.1 Model Results ............................................................................. 31 4.1.2 Model Validation ....................................................................... 39 4.3 Gulf of Tehuantepec .................................................................................. 49 4.3 Costa Rica Dome ....................................................................................... 55 5. DISCUSSION .......................................................................................................... 60 5.1 Costa Rica Dome ....................................................................................... 60 5.2 Gulf of Tehuantepec .................................................................................. 62 5.3 Model ......................................................................................................... 64 6. SUMMARY AND CONCLUSION .......................................................................... 69 APPENDIX A. SENSITIVITY ANALYSIS ............................................................... 71 REFERENCES ............................................................................................................ 81 BIOGRAPHICAL SKETCH ....................................................................................... 87 v LIST OF FIGURES Figure 1.1. .................................................................................................................... 2 The geography and major currents of the northeast tropical Pacific. The Costa Rica Dome is indicated by a solid circle and the location of the wind-jets are indicated by blue arrows. The wind jets are named after the gulfs that they influence: Tehuantepec jet, Papagayo jet, and Panama jet. The two lines running parallel to the coast represent the 500 and 1000 m isobath. Notice than the continental shelf is very narrow along most of the coast, and that the continental slope is very steep. Figure 1.2. ..................................................................................................................... 3 Monthly mean fields of chlorophyll a in the eastern tropical Pacific. The 35 meter contour line for the thermocline (solid line) indicates the position of the CRD . In the fall and winter, there is low chlorophyll concentration at the CRD, although the thermocline is close to the surface (From Fiedler, 2002). Figure 1.3. ..................................................................................................................... 4 Nine-day composite (February 2 to 9, 2002) of SeaWiFS mean chlorophyll a showing an eddy (a) that has propagated from 95° W to 110° W, retaining a relatively high chlorophyll a concentration. Two other eddies are located closer to the coast, one west of the Gulf of Tehuantepec (b) and one in the Gulf of Papagayo (c). Figure 2.1. ................................................................................................................... 13 Synoptic maps of daily PAR used as input to the ecosystem model. The fields are derived from the SeaWiFS 8-day product by regridding onto the model grid and temporally interpolating down to 1-day temporal resolution. Figure 2.2. ................................................................................................................... 14 A flow diagram of the biological model. The different processes indicated by numbers in the diagram are: (1) denitrification, (2) nitrification, (3) grazing on small phytoplankton by microzooplankton, (4) predation on microzooplankton by mesozooplankton, (5) grazing unassimilated by microzooplankton that adds to the ammonium, (6) grazing unassimilated by microzooplankton that adds to the detritus pool, (7) food unassimilated by mesozooplankton that adds to the ammonium, (8) food unassimilated by mesozooplankton that adds to the detritus pool, (9) remineralization of detritus, (10) small phytoplankton mortality, (11) nitrate uptake by small and large phytoplankton, (12) ammonium uptake by small and large phytoplankton, (13) ingestion of detritus by mesozooplankton, (14) grazing on large phytoplankton by mesozooplankton, (15) mortality of microzooplankton, (16) large phytoplankton mortality, (17) influence of light in growth rate, (18) mesozooplankton mortality, and (19) sinking. Figure 2.3. ................................................................................................................... 18 Levitus climatology of temperature plotted against Levitus climatology of oxygen (open circles). The data are taken from the northeast tropical pacific (4.5ºN to 19.5ºN and vi 109.5ºW to 75.5ºW) from the surface down to 600 meters. The thick solid line represents the relationship between the temperature and oxygen that is used in the model (eq. 2.2.5). Figure 4.1. ....................................................................................................................