Ocean margins: The missing term in oceanic element budgets?

Abstract

The amount of carbon dioxide (CO2) in the atmosphere is a function of many interrelated processes in atmospheric, oceanic, hydrological, biological, and human realms. Constraining the contributions of these realms to global carbon budgets hinges on knowledge of the ocean's role in carbon cycling, which in turn depends on the ocean's chemical state and biological activity. Both are dependent on element and nutrient inputs from continental sourcesthe more elements that reach the ocean in a form readily consumable by life, the more productive micro-organisms that form the foundation of the ocean's food supply can be. Thus, on a fundamental level it is important to know how and where continental inputs reach the ocean. Fluxes traditionally considered in seawater element budgets are dissolved river inputs, dissolution of atmospheric dust, hydrothermal inputs, diffusive fluxes from deep-sea sediments, and submarine groundwater discharge. Interestingly, though most of the marine element budgets include a provision for small contributions from dust dissolution [Jickells et al., 2005], the dissolution of solids deposited along the ocean margins is usually ignored. Yet recent studies show that sediments on continental slopes and shelves contribute significantly to the dissolved elements found in seawater. Tracing and understanding these contributions will help scientists to get a better picture of ocean circulation, biological productivity, and carbon cycling.