BIO-PHYSICAL MODELING OF THE NORTHERN HUMBOLDT CURRENT

1. BIO-PHYSICAL MODELING OF THE NORTHERN HUMBOLDT CURRENT Alexander von Humboldt (1769-1859) was a nature researcher and explorer, universal genius and cosmopolitan, scientist and patron. His lengthy Latin American journey from 1799 to 1804 was celebrated as the second scientific discovery of South America. Members of natural science disciplines such as physical geography, climatology, ecology or oceanography see Humboldt as their founder. The masterpiece of his advanced years, the five-volume "Cosmos. Draft of a Physical Description of the World," has remained unique in its comprehensive approach.

2. OVERVIEW This workshop is held at the Escuela de Oceanografia of the Universidad Catolica deValparaiso with the support of the Inter-American Institute for Global Change Research (IAI), The Instituto de Fomento Pesquero de Chile, The Instituto del Mar del Peru and with the participation of biological and physical oceanographers and fishery scientists from the United States, Chile and Peru. The long-term goal is to develop a bio-physical modeling system for the Chile-Peru coastal marine ecosystem region that could be useful as a fisheries management system and to advance our understanding on the effects of climate changes on ecosystem components. WORKING GROUPS: (i) Establish the conceptual framework for developing the model system, and summarize existing modeling activities in Peru and Chile. (ii) Assess the existing modeling capabilities and needs of the collaborating groups. (iii) Identify local sources (Peru and Chile) of environmental forcing data. (iv) Identify other research collaborators from the United States, Peru and Chile. (v) Select specific physical, biological and ecosystem models to be implemented, and identify a model validation plan. (vi) Define a first set of short-term specific research proposals to be submitted to IAI and other funding agencies at local and international levels. (vii) Identify and define the participation of marine science graduate students from the participant countries in the development of the proposed bio-physical modeling system. KEY-SPECIFIC TOPICS ARE: (i) Characterize interannual, seasonal and synoptic variability of: the near-shore upwelling circulation, upwelling fronts, atmospheric forcing, fish populations, major zooplankton, recruitment, population sizes, egg and larval mortality rates, primary production, nutrients inputs, El Nino events, coastal trapped waves, phytoplankton biomass, and species composition. (ii) Define spatial and temporal scales relevant for bio-physical modeling: establishing boundaries and scales of variability (e.g. upwelling events, seasonal, ENSO), especially with regard to cross-shelf transport, inner-shelf and near shore hydrography, identifying key bio- ecosystem model components. (iii) Identify key bio-physical variables for field measurements and gathering of historical data sets for the purpose of initialization, data assimilation and evaluation of a bio-physical model system: atmospheric variables and data; high-resolution surveys of three- dimensional hydrographics, velocity, bio-optical, and zooplankton fields; turbulence, nutrients, phytoplankton, photosynthesis parameters, particulate and dissolved organic material, trace metals; moorings spanning the continental shelf.

4. THE PARTICIPANTS Avijit Gangopadhyay Jorge Mesias Sergio Salinas Ruben Escribano Juan Tarazona Luis Pizarro Vivian Montecino Sergio Rosales Patricio Barria, Rodolfo Serra Wolfgang Schneider Tim Baumgartner James J. Bisagni Dian Gifford Jesus Pineda Jose Blanco THE INSTITUTIONS Universidad Catolica de Valparaiso (UCV) Instituto de Fomento Pesquero (IFOP) Instituto del Mar del Peru (IMARPE) Facultad de Cienciasde la Universidad de Chile Universidad de Concepcion Centro de Investigacion Cientifica de Educacion Superior de Ensenada (CICESE) Mexico. School for Marine Sciences and Technology (SMAST), University of Massachusetts Dartmouth Inter-American Institute for Global Change Research (IAI) University of Rhode Island (URI) Woods Hole Oceanographic Institution (WHOI) Old Dominion University (ODU) concejo NACIONAL DE INVESTIGACION Y TECNOLOGIA DEL PERU(CONCYTEC)

5. BACKGROUND STRONG FISHERIES ACTIVITY IN AN OCEANICENVIRONMENT CHARACTERIZED BY STRONG ATMOSPHERIC FORCING AFFECTING THE OCEAN PROPERTIES AND THE DYNAMICS OF THE FISH POPULATIONS. THIS DEPENDENCE ON ENVIRONMENTAL CONDITIONS IS MANIFESTED AT SEVERAL SPATIAL AND TEMPORAL SCALES WHERE THE UPWELLING ACTIVITY IS CHARACTERISTICALLY DOMINANT AND PERSISTENT. OVERALL, THE PERU-CHILE AREA PRESENT A REGIME OF HIGH-NUTRIENT AND HIGH-CHLOROPHYLL CONCENTRATIONS, WITH NUTRIENT AVAILABILITY ROUTINELY EXCEEDING THOSE REQUIRED BY PHYTOPLANKTON (BARBER, 1992). THE REGIME OF HIGH-NUTRIENT CONCENTRATIONS FOUND IN THE COASTAL AREAS CAN BE PARTIALLY LINKED TO THE DYNAMICS OF THE UNDERCURRENT, WHICH PLAYS A ROLE SIMILAR TO THAT OF THE UNDERCURRENT IN THE NORTHERN-CONNECTED EQUATORIAL REGION, INDUCING HIGH-CONCENTRATION OF NUTRIENTS IN THE UPPER LAYERS OF THE OPEN OCEAN (FRIEDRICHS AND HOFFMAN, 2001). RECENT FIELD STUDIES HAVE SHOWN THAT ECOSYSTEM COMPONENTS IN THE REGION PRESENT COMPLEX RESPONSE TO EL NINO EVENTS, WITH NO EFFECTS ON THE PHYTOPLANKTON AND ZOOPLANKTON BIOMASSES WHILE SECONDARY PRODUCTION IS SIGNIFICANTLY REDUCED BY CHANGES IN THE FOOD SUPPLY (ULLOA ET AL., 2001). CONDITIONS NEAR REGIONS WITH MARKED COASTLINE FEATURES LIKE CAPES AND BAYS HAVE SHOWN "UPWELLING SHADOWS" THAT LARGELY AFFECT THE ECOLOGY OF COASTAL UPWELLING AREAS, PARTICULARLY THE RETENTION OF MEROPLANKTONIC LARVAE (MARIN ET AL., 2002; GRAHAM AND LARGIER, 1997). RELAXATION OF UPWELLING FAVORABLE WINDS AND SUBSEQUENT WATER MASS ADVECTION INTO CLOSE OR SEMI-ENCLOSED AREAS MAY EXPLAIN THE INCREASE IN RETENTION TIME (MARIN AND MORENO, 2002). MODELING STUDIES HAVE ALSO SHOWN THAT OCEAN COASTAL REGIONS NEAR CAPES PRESENT STRONG NONLINEAR DYNAMICS AND TRANSPORT OF VORTICITY TOWARD THE COAST WHICH COULD INDUCE TRANSPORT OF BIOMASS (PHYTO, EGGS AND LARVAE) INTO THESE EMBAYMENTS AND EXPLAIN INCREASED RETENTION TIMES (MESIAS ET AL., 2001 AND 2002; LETH AND SHAFFER 2001). THE CROSS-SHELF AND ALONG-SHELF TRANSPORT PROCESSES ARE AFFECTED BY CHANGES IN THE WIND FORCING DURING EL NINO YEARS WHICH INDUCE A SIGNIFICANT REDUCTION IN THE UPWELLING ACTIVITY (MESIAS ET AL., 2002). FROM A RESOURCE MANAGEMENT POINT OF VIEW, THE STRONG FISHERIES ACTIVITY IN THE EASTERN BOUNDARY CURRENT REGION OF NORTHERN CHILE AND SOUTHERN PERU PRESENT SEVERAL UNSOLVED ISSUES RELATED TO INSUFFICIENT SCIENTIFIC KNOWLEDGE ON THE DYNAMICS OF THE FISH POPULATIONS AND THEIR DEPENDENCE ON ENVIRONMENTAL CONDITIONS (PENA-TORRES ET AL., 2000; GUTIERREZ, 2001).

6. Overall, past field and satellite observations and modeling studies have shown evidences that a large portion of the changes in primary production (and fish populations) occur due to ENSO and climate variability of the wind-driven upwelling conditions in the Chile-Peru region (Theme I of IAI Research), and that the regional ecosystem and environmental variability is related to climatic changes of global scale (Schwartzlose, 1999) (Theme II of IAI Research) modulated by effects of the local topography and coastline geometry. To further advance in our understanding on the effects of climate changes on the regional Chile-Peru ecosystem (Themes I and II), we propose to develop a research program with a combined data analysis and numerical modeling approach. This research program envisions to address a specific set of scientific hypotheses related to biological and physical processes over a wide range of time scales in the upwelling system of the Chile-Peru region by uses of data and the to-be-developed modeling system. Some of the scientific hypotheses are: (i) Physical control of biomass and fertilization in the coastal ocean is due to persistent equatorward winds and upwelling processes. (ii) Latitudinal changes in fertilization and biomass abundance are linked to alongshore variations in mixing activity. (iii) Local geometry of upwelling jets and fronts in the surface and subsurface layers is strongly linked to local geometry of the coastline and bottom topography. (iv) Ecosystem and environmental variability regimes at transient-synoptic and intra-annual scales are linked to regimes of climatic scale (e.g. ENSO and interannual). (v) Regional ecosystem and environmental variability are linked to changes in global-scale climatic regimes. To develop the bio-physical modeling system for the Chile-Peru coastal marine ecosystem region, we will make uses of other Similar experiences such as The Advanced Fisheries Management Information System (AFMIS), built through a collaboration of Harvard University and the School for Marine Science and Technology at the University of Massachusetts at Dartmouth, which uses state-of-the-art multidisciplinary and computational capabilities to operational fisheries management for the Georges Bank region in the north-eastern coast of the United States.