Award: OCE-0961660

The Great Calcite Belt (GCB) is an area in the Southern Ocean characterized by high reflectance (as observed annually from satellite since the mid 1970's) (see Fig. 1). For decades, scientists have hypothesized the cause of this massive feature which covers ~16% of the global ocean, and with only anecdotal evidence as to its source. One hypothesis was that the high reflectance was due to elevated abundance of coccolithophores, a common group of microscopic phytoplankton that are covered with calcium carbonate scales (called coccoliths, which are highly reflective). The goal of this project was to describe the fundamental cause of this feature, the oceanographic processes responsible for the long-term presence of the GCB (e.g. physical, chemical, biological), as well as feedbacks to the CO2 cycle and particle sinking fluxes that sustain the ocean's biological carbon pump. We performed two field campaigns to survey half of the Southern Ocean GCB feature between South America, eastwards to Australia (Fig. 1). Our results indeed show that coccolithophores were elevated in abundance in the GCB. Moreover, there was a significant, but complex, relationship between coccolithophore calcite concentrations and pCO2; a relationship which is affected by seasonality, frontal boundaries and overall phytoplankton species composition. The significance of this (from a CO2 perspective) is that the GCB is >50 times larger than the next-smaller coccolithophore-rich area in the N. Atlantic Ocean with enormous biogeochemical importance. We developed a conceptual model describing how the balance of macro-nutrients (nitrate and silicate) and trace metals (iron and cobalt) control the phytoplankton competitors, which, in turn, allows the coccolithophores to dominate in the GCB. Our work (for the first time) describes the resultant feedbacks of the GCB to the CO2 cycle and vertical flux of POC and PIC in this enormous ocean region. We produced a massive data set of biogeochemical properties from a vastly under-sampled region of the world ocean. Our data from these cruises now reside at the Biological and Chemical Oceanography Data Management Office (BCODMO) and for these regions of the Southern Ocean (particularly the Indian Sector), represent some of the few recent cruises to this region. Because of this, we also deployed ARGOS profiling floats during our cruises, for investigators at Scripps Inst. Of Oceanography. These floats telemeter data for years as they drift through the world ocean. The broader impact for understanding the seasonal development of areas of high PIC/pCO2 in the GCB and its ocean biogeochemical function has significant implications for control and modulation of the exchange of CO2 between ocean and atmosphere, and the relative strength of the biological pump of carbon in this region of the SO. Several endeavors extended the field and research components of the project into educational opportunities, well beyond the oceanographic community. Seventeen students were trained as part of this project, including a number of undergraduates. Five undergraduate students participated on the research cruises and all of these are now pursuing graduate degrees in science or combined science and law. These students came from Colby College, University of Maine and Dalhousie University. We also brought a high school-level educator on both cruises for public and classroom outreach. This work involved making initial contact with multiple schools around the U.S. to introduce the scientific problem of the GCB, then the teacher devoted half their ship time to daily interactions with the students, answering questions, blogging and video conferencing and the other half to helping with deck and lab operations. Public lay-presentations were made at the BigelowÆs Café Scientifique program held annually in Boothbay Harbor each summer (which attracts >1000 participants each year; http://www.bigelow.org). ...