Donald Olson - US grants

In this project the principal investigators will analyze data obtained on two hydrographic cruises in the northern Indian Ocean during December, 1986 - January, 1987, and July - August, 1988. The hydrographic data cover the height of both the northeast and southwest monsoons, and contain nearly 120 CTD profiles on each cruise (including tracer samples) and shipboard acoustic doppler current profiles. Forty ARGOS surface current drifters launched on the first cruise in the Arabian Sea and in late fall, 1985 in the Bay of Bengal will also be included. Principal goals are to analyze the surface velocity field along the cruise tracks, and water mass modification during the monsoons using temperature-salinity and other tracer techniques.

In this project a team of 3 US P.I.'s will collaborate with collaborators from several other countries to deploy an array of surface drifters in the equatorial Pacific in support of the TOGA (Tropical Ocean and Global Atmosphere) Programme. The drifters will provide data on surface and subsurface temperature and surface currents. Scientific goals are to map Sea Surface Temperature (SST) and currents, understand processes responsible for annual and interannual variability in SST, and improve operational Pacific Ocean models.

In this project, the P.I.'s will analyze a unique variety of oceanographic and satellite-derived data taken from 1988 to 1990 in the confluence region of the Brazil Current and the Malvinas Current east of Argentina. Data were collected in a joint effort involving US, Argentine, and French scientists. Studies will be made of the relation between local atmospheric forcing and local circulation, meridional motions of the Brazil Current, and the transport of the two currents separately.

New schemes to accurately parameterize the sub-grid effects of bottom topography in Ocean General Circulation Models (OGCMs) will be tested. Of particular interest is a more realistic prediction of the separation point of topographically steered boundary current like the Gulf Stream.

9314447 Olson In this project, the PIs will deploy approximately 210 Lagrangian surface drifters in the Indian Ocean as part of the Indian Ocean Expedition (IOE), a U.S. component of the World Ocean Circulation Experiment (WOCE). Drifters provide both surface currents and surface temperature measurements. In addition to contributing to measuring temperature measurements. In addition to contributing to measuring near-surface variability during the IOE, these data will fill a major gap in providing a surface layer data set of Lagrangian current measurements over the entire globe during WOCE, a major objective of that program. ***

Smith
9904689

This project outlines three research tasks designed to develop, validate, and improve a biological/chemical /physical model for the Arabian Sea. A focus of the research is to understand the Arabian-Sea carbon cycle, which requires that biological and physical processes be properly represented. To understand a problem of this complexity requires the development of a hierarchy of models that vary in dynamical complexity. The present approach is to begin with a dynamically simple system, to compare its solutions carefully with available data, identify model deficiencies and to develop and test various hypotheses for overcoming them.

The investigators initial system will consist of three components: a 51/2-layer physical model, a 4-compartment (NAHD) biological model, and a chemical model that simulates carbon and oxygen cycling. The system has the advantage that it is computationally very efficient. Consequently, the scientists will be able to carry out extensive test runs, and hence can carefully assess the influence of individual processes. Versions of each component model have already proven successful at simulating observations in the Arabian Sea and elsewhere, and this prior success gives the researchers confidence that the coupled system will also produce useful solutions. The initial system will be gradually improved and expanded as the investigators identify deficiencies and modify the model to correct them.

The central goal of the U.S. JGOFS Synthesis and Modeling Project (SMP) is to synthesize observational data into a set of models that can be used for prediction. Here, the investigators will bring together a group of scientists with the collective expertise necessary to achieve this goal for the Arabian Sea. Specifically, Sharon Smith contributes her knowledge of Arabian Sea biological and chemical fields, Raleigh Hood and Don Olson contribute their expertise in biological and chemical modeling, and Julian McCreary contributes his modeling experience of physical processes in the region. Each Principal Investigator thus performs an important function in the overall research effort.

In this effort the researchers will test fundamental hypotheses concerning the factors that control biogeochemical fluxes in the Arabian Sea. This region was selected to be the location of one of the four U.S. JGOFS Process Studies because of its strong monsoonal forcing and large seasonal oscillations, and indeed the project acquired the most complete seasonal and spatial resolution of carbon cycling among the four Studies. These field observations, in combination with concurrent ONR measurements, historical data and new satellite ocean color observations, thus provide an ideal data set for developing a coupled model that can respond realistically under a wide range of oceanic conditions. Consequently, the investigators expect that the results will be readily generalizable to other regions of the World Ocean.

This study will examine the population dynamics of two dominant grazing copepod species, Calanoides carinatus and Eucalanus crassus, in the context of a coupled biological?physical model in the northwestern Indian Ocean. The model populations will include a diapausing fifth copepodite stage (CV) believed to have evolved as the result of a predictably intermittent food supply associated with upwelling caused by seasonal monsoonal forcing within the region. The primary objectives of this study are: 1) to determine the significance of ontogenetic migration and diapause of the copepods Calanoides carinatus and Eucalanus crassus for the success of these populations in the northwestern and equatorial Indian Ocean, with respect to timing of migration and onset and collapse of phytoplankton blooms associated with monsoonal upwelling; 2) to test hypotheses of mechanisms underlying the initiation and cessation of diapause in CV stage of C. carinatus and E. crassus; and 3) to ascertain the importance of physical advection in transporting populations to the Oman coast, Gulf of Aden and Gulf of Oman, and potentially more distant areas such as Mozambique and Java, using the Great Whirl off Somalia as the epicenter of distribution of C. carinatus and E. crassus.

Billfishes are a complex of large pelagic fishes that occur in the tropical and subtropical waters of the world's oceans. They are top predators in the pelagic food web and, simultaneously, the most sought-after fishes for saltwater anglers. These oceanic "giants" support a multi-million dollar sportfishing industry and comprise a significant bycatch of tuna longline efforts. Unfortunately, human activities have led to significant declines in billfish stocks; blue marlin are thought to be at less than 40% of that necessary to sustain fishing at maximum sustainable yields. Despite their critical ecological status, the biological information available on these organisms is extremely limited.
Focusing on the early life history stages of billfishes is a tractable means of obtaining valuable biological data. For example, collection of early larval stages can be used, in conjunction with data on circulation, as a means of determining when and where spawning occurs. Investigation of the pelagic habitat variables associated with the occurrence of billfish larvae may provide insight into environmental conditions required for spawning and early survival. Even in their early life history, billfishes are likely important constituents of the pelagic food chain, especially as predators on zooplankton and larval fishes.
The overall objective of this study is a seasonally resolved understanding of the annual cycle of billfish spawning, larval growth, feeding, and transport within the complex environment of the Straits of Florida. As top predators, billfishes play a critical yet undefined role in the pelagic food web. Here we examine the early life history of billfishes within the oceanographic context of the Straits of Florida (SSF). The SSF is a complex system of discrete, interacting water masses and pelagic environments. Preliminary data suggest that billfish larvae occur predictably in three distinct patches across the SSF. The project is designed to 1) identify the sources of the three distinct larval billfish patches within the SSF; 2) determine how the these patches differ in terms of the trophic and growth environment of the billfish larvae; and 3) investigate the transport fates of larval billfishes from these different patches.
The fieldwork is divided into three separate study components: The first study will address the temporal qualities of cross-Strait features (i.e., water mass distribution, larval billfish patches, and zooplankton community structure). Monthly sampling (consisting of ichthyoplankton and zooplankton tows, CTD, fluorometry, and ADCP measurements) over two years will be linked via otolith aging studies and circulation patterns to estimates of spawning locations. Further otolith work on larval growth rates will be coupled to zooplankton work on community composition and dynamics to identify trophodynamic differences among patches. The second study will expand the spatial scale of our efforts to examine the along-Strait dynamics relating to the formation, maintenance, and fate of larval billfish patches. A single cruise will be made during the second year and will include the same suite of measurements as above as well as ARGOS-tracked drifter measurements. The third study during year 3 will incorporate Lagrangian techniques to track larval billfishes from hypothesized spawning sites through the Straits of Florida system to link these trajectories to the observed cross-Strait spatial patchiness and ultimate fate of the discrete patches. Sampling will consist of a similar set of measurements conducted at stations normal to the track of a group of drifters.
Results of the proposed study will provide critical new information regarding the early life history and ecology of these important pelagic predators as well as the interaction between different water masses and the trophodynamics of pelagic food webs. A further understanding of the formation, maintenance and fate of particular chl. a/zooplankton/larval fish patches also will provide insights into understanding the role of upwelling and water mass exchange across frontal boundaries and shallow banks.

Agriculture plays a central role in global food production and food security, and is among the societal sectors most vulnerable to climate variability and change. A marked increase in rainfall since the 1970s has contributed to major changes in land use in the Pampas of Argentina, the focus of this study: continuous cropping has widely replaced ecologically-sound agriculture-pasture rotations. Nevertheless, production systems that evolved partly in response to increased rainfall may not be viable if (as is entirely possible) climate reverts to a drier epoch. As there is much uncertainty about projected paths of future climate, particularly on regional scales and short time horizons (25-30 years hence), this project will explore various plausible climate scenarios to anticipate potential impacts on agricultural systems together with advances in agricultural technology that may affect productivity and vulnerability to climate. The central goal of this study is to improve understanding of linkages between agricultural ecosystems, uncertain decadal climate trajectories, technological innovations that decrease vulnerability to climate stresses, human decision-making, and land use and tenure changes over periods of a few decades. To achieve this goal, the investigators will build scenarios of inter-decadal climate variability; assess the impacts of climate variability on current and adapted agricultural production systems; simulate biological and economic effects of genetically-improved crops tolerant to drought stress; study the diffusion of this technological innovation; (5) develop models of individual decision-making and use these models to assess emerging regional-scale patterns of land use and land tenure and their implications for sustainability of production systems.

Agricultural production involves real-world decisions with important economic consequences, and thus is a useful test bed to understand decision-making in complex natural-human systems. This project will develop new insights on decision-making processes in agriculture, including individual and group learning, and adaptation to plausible climate changes. On a broader scale, the research will implement tools to assess the regional implications of climate change in the next 25-30 years, a scale relevant to resource management, and infrastructure and investment planning. Climate fluctuations will be explored in the context of important technological changes that may shape agriculture over the next decades. One highlight of the project is the active involvement of farmers and operational producers of climate information (the Argentine Met Service) that guarantee the relevance of the research, facilitate and demand outreach, and ensures stakeholders'' ownership of the process. Finally, similarity in experienced climate fluctuations, production scale, technology and crops grown, and land tenure regimes of the Pampas to those in the US Midwest suggest a broader relevance of the project''s results.