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50 Years of Ocean Discovery: National Science Foundation 1950—2000
as photochemistry, vertical particle flux and scavenging, and organic complexation of metals.
producing trustworthy measurements of concentrations of most of the elements in seawater and realizing that the concentrations generally followed patterns that are predictable based on a combination of elemental chemistry, biological processes, and global water circulation patterns. Previously we had either zero or erroneous values for concentrations of a majority of the elements in the ocean.
uncovering the relationships between biological processing and chemical diagenesis in sediments, critical to areas such as the coupling of water column and sediment processes, mineral formation, and paleoceanographic interpretations.
assessing the crucial role that hydrothermal processes play in chemical budgets of the oceans, as well as the role of chemical processes in the very dynamic biological and geological phenomena found in rift zones.
determining the importance of coastal margins as locations of very high productivity, high carbon flux, and high sedimentary carbon storage as compared to the rest of the open ocean.
FUTURE RESEARCH TRAJECTORIES
We used our review of past progress and our sense of impending issues to guess at the future of the science. Our time horizon forward is on the order of two decades, roughly that used for our backward look. Forecasting progress in a field as broad as ocean chemistry requires that we break it into smaller chunks amenable to handling. Organizing this effort along the lines of our review of progress, however, allows the past to rule the future. To avoid the smaller tribalisms that exist in our (or any) field, it was necessary to keep the participants from breaking into their natural caucuses. We needed a means to shake up the traditional thinking patterns.
We therefore chose to divide oceanic processes (not necessarily chemical processes) along the lines of the time scales within which their characteristic patterns emerge. We focused on processes occurring at (1) seasonal and shorter time scales, (2) seasonal to annual time scales, (3) annual to millennial time scales and (4) greater than millennial time scales. Of course, this choice forces its own structure onto the field, so we also considered possible omissions and overlaps. This time-scale approach reinforces the role of ocean chemistry in the solution of a variety of interdisciplinary oceanic problems.
Synthesizing questions raised using the time-scale approach required identification of major themes that the field of ocean chemistry will address over the next few decades. We attempted to balance a desire to identify exciting problems, apparent at this time, with the need to provide umbrellas likely to contain the unexpected discoveries of coming decades. The results of our deliberations can be grouped into eight themes.
Major and minor plant nutrients—how they are transported to the euphotic zone and affect community structure, and how these processes are influenced by natural and anthropogenic changes. The ocean's ability to support life and the role of life in maintaining the chemical constitution of the ocean are strongly affected by the transport and redistribution of nutrients. Despite exciting progress over many decades, it is clear that unknown processes are controlling the patterns of these mutual controls. Rapid progress will show how subtleties in nutrient dynamics affect end states of great importance, such as fisheries and harmful algal blooms.
Land-sea exchange at the ocean margins. Margins influence biogeochemical cycles to an extent much more than their areal extent might imply, while being especially susceptible to anthropogenic influence. Processes that occur disproportionately in margin environments, such as organic matter burial, mineral formation, and denitrification affect the oceanic balances of many elements. Unraveling the highly variable complex of chemical, physical, geological, and biological linkages in margins will provide needed context for human colonization of the coastline.
Organic matter assemblies, at molecular to supra-molecular scales, their reactivity and interactions with other materials. Organic matter must be characterized at scales including, but also greater than, its molecular constituents, to enable understanding its preservation, transport, and interactions with inorganic materials. The "micro-architecture" with which constituents are assembled controls reactivity with important implications for primary and secondary production, photochemical processes, mineral formation, and trace metal dynamics.
Advective chemical transport through the ocean ridge system (ridges and flanks), ocean margin sediments, and coastal aquifers. Fluid flow through these environments appears to have greater importance than previously appreciated, and may strongly influence many oceanic chemical cycles. Greater understanding of the magnitude and variability of these advective transports will improve budgeting of chemicals in the ocean and provide explanations for many regional processes affected by the flow, such as mineral formation and nutrient inputs.
Forecasting and characterization of anthropogenic changes in ocean chemistry: consequences at local and global scales. Climatic as well as chemical changes to the oceans will affect many different biogeochemical cycles. Assessing natural variability will be critical to determination of anthropogenic effects. Linkage to other oceanographic variables, such as biological and physical processes, will enable better assessment of the role of the oceans in global environmental change.
Air-sea exchange rates of gases that directly influ