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DOM is one of the largest of the bioreactive pools of carbon in the ocean (680-700 Pg C; Williams and Druffel, 1987; Hansell and Carlson, 1998, Hansell et al., 2009), second only to TCO2. The size of the reservoir (comparable to that of atmospheric CO2), as well as its role as a sink for autotrophically fixed carbon, as a substrate to heterotrophic microbes (Carlson, 2002; Carlson and Hansell 2014), and as a sink/source of carbon involved in climate variations over long time scales (Sexton et al. 2011), highlights the importance of DOM in the ocean carbon and nitrogen cycles. DOC exports 1.9 PgC yr-1 out of the epipelagic zone, contributing ~20% to the biological pump via meridional overturning circulation (Hansell et al. 2002; Carlson et al., 2010). Mechanisms that control DOM accumulation, allowing it to persist and be transported to the regions of overturn, are still poorly understood. Small perturbations in the production or sink terms of the oceanic DOC pool could strongly impact the balance between oceanic and atmospheric CO2. In this global ocean repeat hydrography, carbon and tracer program D. Hansell (University of Miami) and C. Carlson of UCSB will be responsible for at sea sampling and analyses of dissolved organic carbon (DOC) and nitrogen (DON) measurements. The proposed program includes 14 legs over 11 cruises conducted in various ocean basins from 2015 – 2020. The tentative break down of Carlson’s cruise coverage is as follows:
Year Cruise At sea participation
2015 P16N Leg 2 Yes
2016 I08S, I09N, I01E Yes- all legs
2017 P06 leg 1 Yes
2018 I05 Yes – all legs
2019 I06S Yes
2020 S4P No –sample analyses only
Sample throughput will track that of the dissolved inorganic carbon and total alkalinity measurements. DOC will be measured by high temperature combustion using a Shimadzu TOC-V or TOC –L systems with auto injection (CV of 1.5-2.5%). DON is calculated as the difference between total dissolved nitrogen concentrations this group will measure and dissolved inorganic nitrogen, measured by the hydrographic team. Oversight of project management for the UCSB component will be under the direction of C. Carlson. Sample analyses for each cruise takes approximately 9 – 16 months from receipt of samples depending on the length of the cruise. The at sea sampling personnel will be covered through a combination of PI, senior technician and student participation.
Sample analyses for each cruise takes approximately 9 – 16 months from receipt of samples depending on the length of the cruise.