Since 1978, the Oceanic Flux Program (OFP) has continuously measured particle fluxes in the deep Sargasso Sea. The three decade OFP time-series is, by far, the longest of its kind and unique in its focus on the deep ocean. OFP has produced a unique, albeit edited, record of temporal variability in the so-called biological pump, a term loosely applied here to material transfer from the surface to the deep ocean. The OFP provided the first direct evidence for seasonality in the deep ocean and the tight coupling between deep fluxes and upper ocean processes. It has provided clear evidence of the intensity of biological reprocessing of flux and scavenging of suspended material in mesopelagic waters. The record has documented interannual and longer variations in deep fluxes and shorter term fluctuations driven by the interactions between mesoscale variability and meteorological forcing. The time-series is becoming long enough to begin study of variability in terms of multiyear basin-scale climatic forcing, such as the North Atlantic Oscillation.
This award will provide renewal funding for this unique and fundamental oceanographic time-series. As the record gets longer, we are better able to put into perspective the observed fluctuations in terms of the interplay between climate and ocean functioning. The colocation of coordinated and complementary research programs at the Bermuda Time-Series Site- the OFP mooring, the Bermuda Atlantic Time-Series (BATS) shipbased biogeochemical observations, and anticipated future moored and autonomous technologies such as gliders present unparalleled opportunities to study the coupled interactions among ocean physics, biology and chemistry and material fluxes, and how these in turn are linked to atmospheric and climatic forcing. New analytical techniques, unimaginable when the OFP first began, are being applied to the sample archive, revealing new information about ocean processes that is embodied in the composition of recovered flux materials.
There will be several significant broader impacts: (1) Systematic, long-term biogeochemical observations, such as those provided by the OFP, are essential to gain an understanding of natural oceanic variability and to provide a reference point in which to interpret the repercussions of possible future climate change scenarios. (2) Previous NSF review panels have recognized the OFP as an invaluable "community resource". The OFP will continue to share its resources- sample material, data, ancillary shiptime, and use of the mooring platform- with researchers and students to make possible a diverse range of investigations at a very low cost to the community. (3) The OFP sample archive is a rare treasure. The sample material to be collected will continue to be invaluable for current and future biogeochemical and climate studies. (4) Educational experiences provided by the OFP will broaden the research experiences and science horizons of many young investigators at a critical juncture. Of particular value are opportunities to become directly involved with observational oceanography, time-series research and integrated ship-based research activities occuring at the Bermuda Time Series site.
The Oceanic Flux Program (OFP) sediment trap time series, the longest running time series of its kind, has continuously measured particle fluxes in the deep Sargasso Sea since 1978. OFP results provided the first direct observation of seasonality in the deep ocean, and have documented the tight coupling between deep fluxes and upper ocean processes and the intensity of biological reprocessing of sinking flux in the ocean interior. The synergy among OFP and other research programs co-located at the Bermuda time-series site has provided unprecedented opportunities to study the linkages between ocean physics, biology and chemistry and particle flux generation and particle recycling in the ocean interior. The OFP time-series is beginning to reveal how the deep ocean is affected by large-scale climatic forcing, such as the North Atlantic Oscillation. Understanding the oceanic particle flux is important as this process regulates many aspects of ocean health and global element cycles. Excepting deep vent communities, the export flux of organic matter from the ocean's surface waters- including the particle flux and a smaller contribution from vertically migrating zooplankton - ultimately provides the food source for all life in the ocean interior. The overall fluxes and flux ratio of organic matter and carbonate shells produced by microscopic marine organisms control, in part, the ocean’s ability to absorb excess carbon dioxide from the atmosphere. The depths at which nutrient and bioreactive elements that are incorporated into sinking organic debris are released as particles undergo degradation and dissolution, coined the "length scale of remineralization", affects the redistribution of nutrients by ocean currents which, in turn, regulates geographic patterns of ocean productivity. Particle flux also efficiently transfers suspended materials, such as continentally-derived clays advected by currents from ocean margins, to the deep ocean and eventually to the seafloor, as these materials are ingested by zooplankton during nonselective feeding and repackaged into larger sinking particles such as fecal pellets and aggregates. Additionally, particulate pollutants, deposited from the atmosphere or transported by ocean currents, are also transferred via the particle flux from surface waters to the deep ocean and eventually to the seafloor, where they contaminate deep ocean and benthic ecosystems. One of the central objectives of OFP research is to elucidate the processes that control particle flux generation and particle cycling within the ocean interior. This is not a straightforward task. The particle flux is an aggregate of materials from diverse sources: organic and mineral remains of microscopic phytoplankton and animals, fecal pellets and amorphous aggregates produced by zooplankton, repackaged clay particles sourced from continental margins, minerals formed in situ as particles degrade, and other materials scavenged from the surrounding seawater. Only rarely do sinking particles formed in surface waters survive the trip to the abyssal seafloor. Rather, as particles sink they are subjected to microbial remineralization, dissolution, consumption by deeper-dwelling zooplankton, particle dissaggregation and desorption/adsorption reactions. The result is a continuing evolution in particle flux concentration and composition from the surface to the ocean seafloor. While globally only a small fraction (<1% of surface production) survives its trip to the seafloor, this residual material retains a wealth of information about past ocean conditions which can be used to reconstruct the earth’s history. Two overarching goals drive core OFP research activities. The first is to extend the time-series by collection of new flux samples that are of the highest possible sample quality and that have maximal oceanographic context. The second is to elucidate the causal processes that drive oceanic particle flux through comparative studies of flux magnitude and composition and concurrent observations of external forcing (e.g. weather and climate patterns), surface water physics and biology (e.g. ocean eddies and fronts, blooms, etc.) and interior processes (eg midwater biological activity, chemical scavenging). A second OFP goal is to provide research and training opportunities for scientists and students. The OFP collaborates with PIs at academic institutions in the US and Europe in support of MS and PhD research, including seagoing opportunities. In recent years, the OFP has also provided extensive hand-on and theoretical training to graduate scholars from developing countries who were participants in the Center of Excellence in Observational Oceanography program at BIOS. OFP has provided extensive training in the sciences, including chemical methods and statistics to numerous undergraduate summer researchers, as well as to talented high-school students who work as student research assistants in the lab. Finally, the OFP contributes to middle and high school science teacher training, and also to public education through lectures and tours, and sea-going opportunities for educators.
