Hawaii Ocean Time-series (HOT)
in the School of Ocean and Earth Science and Technology at the University of Hawai'i


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Interdisciplinary Research in Ocean Sciences

During the past decade, oceanographic field studies have focused on co-ordinated, multi-investigator research questions that are well beyond the scope of most single investigator programs. More recently, programs have been initiated to study oceanographic processes occurring on basin-wide or global space scales and annual to decadal time scales. One such endeavor is the Hawaii Ocean Time-Series (HOT) Program. This brief introduction section to the HOT Program Field and Laboratory Protocols manual provides a summary of the motivation behind this program and the analytical framework used for making our field observations and conducting our laboratory measurements. In addition to the inherent scientific importance of the HOT program, it also serves to strengthen the academic programs of the University by involving our graduate and undergraduate students in research that is at the forefront of the various sub-disciplines of oceanography.

Global Geoscience Research Initiative

In fiscal year 1987, NSF established a new special-focus research program termed "The Global Geosciences Research Initiative" which is intended to support studies of the earth as a system of inter-related physical, chemical and biological processes that act together to regulate the habitability of our planet. The stated goals of this program are two-fold. The first goal is to understand the earth-ocean-atmosphere system. The second goal is to describe, and eventually predict, major cause-and-effect relationships. Two of the major components of the Global Geosciences Initiative are the World Ocean Circulation Experiment (WOCE) and the Global Ocean Flux Study (GOFS) programs. The former is focused on physical oceanographic processes and the latter on biogeochemical processes.

WOCE Program objectives include:
  • to complete a basic description of the physical state of the ocean and the atmosphere-ocean boundary

  • to understand the role of ocean heat transport and ocean heat storage on global climate

  • to determine the representativeness of the specific WOCE data sets for the long-term behavior of the ocean, and to find methods of determining long-term changes in the ocean circulation

GOFS Program objectives include:
  • to determine the mean and fluctuating components of world-wide oceanic productivity and its relationship to ocean physics

  • to understand the processes and rates of removal of biogenic materials from the surface waters to the ocean's interior

  • to provide an understanding of the processes governing the rates of sedimentation and burial rates of biogenic matter

Beyond intrinsic academic interest, the Global Geosciences Research Initiative program has important practical implications for the maintenance of the quality of life on our planet. For example, twenty-five years ago few would have predicted that acid rain, ozone holes above Antarctica and toxic waste contamination of potable water supplies would be important issues today. What will be the environmental concerns twenty-five years into the future? In recent years we have become aware of the potentially deleterious effects of anthropogenic pollution on global climate. The accelerated use of fossil fuels in the post-industrial period and the mass deforestation activities which have taken place as a result of global agricultural and urban expansion have resulted in the accumulation of "greenhouse" gases (e.g., carbon dioxide and methane) in the atmosphere. Because these gases impede the return to space of energy received from the sun, the earth's surface becomes a bit warmer. Therefore, like the glass in a greenhouse, carbon dioxide and methane gases create a warmer planet. The more recent introduction of anthropogenic pollutants, including freons and a variety of radioactive and non-radioactive waste products, comprise new challenges to and demands on global homeostasis. In order to assess these environmental concerns and to predict accurately the effects of anthropogenic inputs, long-term observations are urgently needed to document time-dependent changes in the earth-ocean-atmosphere system and to establish cause-and-effect relationships.

We know that the ocean plays a central role in maintaining global homeostasis. It is a turbulent fluid responsible for the storage and transport of vast quantities of heat on our planet that, through interactions with the atmosphere, cause variations in weather. We also know that the ocean has the capacity to assimilate excess carbon dioxide from the atmosphere thereby potentially controlling the magnitude of the greenhouse effect and the devastating global environmental changes which might otherwise occur. The transfer of carbon dioxide from the atmosphere to the surface ocean and from the surface ocean to greater depths is controlled by both physical and biological processes. The latter processes, collectively termed the "biological pump" because of their potential ability to "pump" anthropogenically-produced carbon dioxide into the deep sea, are not particularly well-documented or understood in spite of their recognized importance in global biogeochemical cycling. Finally, the production of organic matter in the ocean is approximately equal to that on land, but the factors controlling the growth rates of the microscopic oceanic plants are poorly known. In spite of the recognized importance of the marine environment in global food production, there is great uncertainty in the accuracy of our estimate of oceanic primary productivity. This is, in part, due to an undersampling of open ocean marine habitats and the inability to extrapolate the occasional expeditionary data to annual rates of primary production.

The authors and supporters of these new NSF initiatives are certain that a much improved global perspective of ocean processes is both achievable and necessary; the time for action is now. Recent technological advances including the development of earth observing satellite systems, acoustic tomography, in situ sensors and remotely-operated instrumentation, the availability of sophisticated laboratory facilities (e.g., accelerator mass spectrometers, laser-based flow cytometers, super-computers) and the development of comprehensive numerical models provide us with the tools necessary to begin our global observation programs. Furthermore, the human resources are also available and significant academic interest now exists for the study of global-scale phenomena. Finally, the earth-ocean-atmosphere system is already in trouble, and all indications are that things will only get worse. We need to obtain sound data for the planning and implementation of future environmental policy.

The Hawaii Ocean Time-series (HOT) Program

In June 1988, a team of scientists at the University of Hawaii received funding from the NSF Global Geosciences Program to establish and maintain a deep water hydrographic station at a site approximately 100 km north of the island of Oahu. The program was funded initially for a five-year period but is expected to continue for at least 10-15 years, and possibly longer. This hydrostation will serve as the open ocean benchmark for combined GOFS- and WOCE-related research activities, and will comprise the single most extensive investigation of its kind in the Pacific Ocean. The Hawaii Ocean Time-Series site has been named Station ALOHA (A Long-term Oligotrophic Habitat Assessment) to reflect the international scientific collaboration which we eventually hope to establish.

One significant feature of long time-series observations is that they allow one to study slow processes, rare and unpredictable events as well as complex physical and biogeochemical interactions. Serial data can also yield unexpected insights into the organization and functioning of oceanic ecosystems. Variability of biological processes in the tropical oligotrophic ocean is generally assumed to be small relative to most temperate ecosystems where seasonal cycles can be substantial. However, there are few studies with sufficient data collected from a single site to describe accurately the temporal variability of the oligotrophic ocean. There are processes on at least three time scales which might be important: atmospheric storms with a time scale of hours to days, seasonal variability with time scales of weeks to months and interannual variability. Because of the generally small size of oligotrophic ocean plankton and their potentially high rates of production we expect the response time, for example to an infusion of nutrients from storm-induced mixing of the water column, to be rapid.

The HOT program will initially support monthly research cruises for the purpose of obtaining detailed information on the physics, chemistry and biology at Station ALOHA. The specific parameters routinely measured include: (1) temperature, salinity and oxygen, (2) optical properties of the upper water column (PAR, fluorescence), (3) dissolved inorganic and organic nutrients, (4) suspended particulate organic matter, (5) dissolved inorganic carbon, (6) pigments, (7) microbial biomass, (8) primary production and (9) particle flux. Taken together, these data will adequately characterize the physical, chemical and biological conditions of the water column which ultimately determine the rates of organic matter production and particle flux from the surface layers of the ocean (i.e., the biological pump). In the near future, we hope to establish the capability of continuous monitoring of several of the above-mentioned properties (temperature, salinity, currents, oxygen, nutrients, pigments, optical properties) of the system using remotely-operated instruments deployed from permanent bottom-moored platforms or surface buoys. This combination of comprehensive monthly sampling from research vessels with the remotely-collected, high-frequency data should greatly enhance our understanding of the dynamics of ocean mixing and its effects on biological communities in the central ocean gyres.

In summary, the Hawaii Ocean Time-Series research program is designed to be a co-ordinated, interdisciplinary scientific study of physical and biogeochemical variability in the oligotrophic North Pacific Ocean. The principal HOT Program objectives are to:

  • observe/interpret seasonal and interannual variations in water mass characteristics and biogeochemical parameters

  • help achieve GOFS and WOCE program objectives and generate meaningful, testable hypotheses

  • serve as a data backbone for additional GOFS/WOCE process-oriented field programs

  • provide a deep-water "laboratory" for the development and testing of new techniques and instruments

  • contribute to international data network on global climate change

  • contribute to marine science research and education in Hawaii

The HOT Program is just the beginning of what may eventually become the most intensive investigation of the Pacific Ocean ever conducted. We fully anticipate and encourage international collaboration which should serve to enhance further the reputation of the marine science research programs at the University of Hawaii.