Time Series Particle Flux Measurements in the Sargasso Sea

Bermuda Institute Of Ocean Sciences (Bios), Inc., St. George'S

Investigators

Abstract

ABSTRACT OCE-0623505 Understanding ocean variability over interannual and decadal time-scales is of widespread interest and increasing relevance given the concerns over anthropogenic perturbations on global climate due to increases in greenhouse gases. It is certain that ocean ecosystems will be affected by altered climate patterns, and an imperative exists to assess and model the ocean's response to possible climate change scenarios. This requires a fundamental understanding of how the ocean and its biota naturally respond to climate and environmental forcing variables. Ocean observation is a necessary first step. The contributions of long-term studies to our knowledge of how the ocean works are numerous and far-reaching. Yet, such studies are exceedingly rare- especially those with a biogeochemical focus. Since 1978, the Oceanic Flux Program (OFP) has continuously measured particle fluxes in the deep Sargasso Sea. The 28 year 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 "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. With funding from this award, researchers at the Bermuda Biological Station for Research and the Marine Biological Laboratory will continue operation of 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 concurrence of three co-coordinated and complementary time-series at Bermuda -- the OFP, the Bermuda Atlantic Time-Series (BATS) and the Bermuda Testbed Mooring (BTM) --and new ocean technology presents 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. This project is expected to have a number of 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 panels have termed the OFP program a "community resource". The project 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 horizons of many young research investigators at a critical juncture. Of particular value are opportunities to become directly involved with observational oceanography, time-series research and integrated activities of the Bermuda Observatory.