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Abstract Export rates of organic matter (OM) were determined based on PO₄³⁻, NO₃⁻and O₂budgets during GEOTRACES cruise GP15 in the Pacific Ocean that crossed subpolar, subtropical and equatorial regimes. Lowest OM export rates at 3–5 mmol C/m²/yr were found in the subtropical regions and highest rates at 9–12 mmol C/m²/yr were found in the equatorial and subpolar regions. Satellite based OM export rates showed similar regional trends but with a significantly larger range. The budget and satellite‐based OM export rates were 3–15× higher than estimates of particle loss rates based on²³⁴Th and sediment trap collections, with the differences primarily due to non‐particle forms of OM export and different integration times of methods. The efficiency of export varied from 0.1 to 0.3, with the lowest efficiencies in the subtropics and highest efficiencies in the subpolar and equatorial regions. 

Systematic regional variations in the ratio of nutrient depth gradients of dissolved inorganic carbon (ΔDIC): nitrate (ΔNO3): phosphate (ΔPO4) in the upper layer (300m) of the Pacific Ocean are observed. Regional variations in the ΔDIC/ΔNO3/ΔPO4 are primarily the result of three processes, that is, the C/N/P of organic matter (OM) being exported and subsequently degraded, nitrogen fixation and air-sea CO2 gas exchange. The link between the observed dissolved ΔDIC/ΔNO3/ΔPO4 and the C/N/P of exported OM is established using surface layer dissolved DIC, NO3 and PO4 budgets. These budgets, in turn, provide a means to indirectly estimate the C/N/P of OM being exported from the surface layer of the ocean. The indirectly estimated C/N/P of exported OM reach maxima in the subtropical gyres at 177/22/1 that is significantly greater than the Redfield ratio and a minimum in the equatorial ocean at 109/16/1 with both results agreeing with available observed particle C/N/P and ocean biogeochemical models. The budget approach was applied to a bioactive trace element (TE) using the measured dissolved Cadmium (Cd) to PO4 gradients to estimate the Cd/P of exported OM in the Pacific Ocean. Combining the budget method with the availability of high-quality dissolved nutrient and trace element data collected during the GOSHIP and GEOTRACES programs could potentially provide estimates of the C/N/P/TE of exported OM on global ocean scales which would significantly improve our understanding of the link between the ocean’s biological pump and dissolved nutrient distributions in the upper ocean. 

Abstract Systematic regional variations in the ratio of nutrient depth gradients of dissolved inorganic carbon (ΔDIC):nitrate (ΔNO₃):phosphate (ΔPO₄) in the upper layer (300 m) of the Pacific Ocean are observed. Regional variations in the ΔDIC/ΔNO₃/ΔPO₄are primarily the result of three processes, that is, the C/N/P of organic matter (OM) being exported and subsequently degraded, nitrogen fixation, and air‐sea CO₂gas exchange. The link between the observed dissolved ΔDIC/ΔNO₃/ΔPO₄and the C/N/P of exported OM is established using surface layer dissolved DIC, NO₃, and PO₄budgets. These budgets, in turn, provide a means to indirectly estimate the C/N/P of OM being exported from the surface layer of the ocean. The indirectly estimated C/N/P of exported OM reach maxima in the subtropical gyres at 177/22/1, that is, significantly greater than the Redfield ratio and a minimum in the equatorial ocean at 109/16/1 with both results agreeing with available observed particle C/N/P and ocean biogeochemical models. The budget approach was applied to a bioactive trace element (TE) using the measured dissolved Cadmium (Cd) to PO₄gradients to estimate the Cd/P of exported OM in the Pacific Ocean. Combining the budget method with the availability of high‐quality dissolved nutrient and TE data collected during the GOSHIP and GEOTRACES programs could potentially provide estimates of the C/N/P/TE of exported OM on global ocean scales which would significantly improve our understanding of the link between the ocean's biological pump and dissolved nutrient distributions in the upper ocean. 

Abstract The cycling of biologically produced calcium carbonate (CaCO₃) in the ocean is a fundamental component of the global carbon cycle. Here, we present experimental determinations of in situ coccolith and foraminiferal calcite dissolution rates. We combine these rates with solid phase fluxes, dissolved tracers, and historical data to constrain the alkalinity cycle in the shallow North Pacific Ocean. The in situ dissolution rates of coccolithophores demonstrate a nonlinear dependence on saturation state. Dissolution rates of all three major calcifying groups (coccoliths, foraminifera, and aragonitic pteropods) are too slow to explain the patterns of both CaCO₃sinking flux and alkalinity regeneration in the North Pacific. Using a combination of dissolved and solid‐phase tracers, we document a significant dissolution signal in seawater supersaturated for calcite. Driving CaCO₃dissolution with a combination of ambient saturation state and oxygen consumption simultaneously explains solid‐phase CaCO₃flux profiles and patterns of alkalinity regeneration across the entire N. Pacific basin. We do not need to invoke the presence of carbonate phases with higher solubilities. Instead, biomineralization and metabolic processes intimately associate the acid (CO₂) and the base (CaCO₃) in the same particles, driving the coupled shallow remineralization of organic carbon and CaCO₃. The linkage of these processes likely occurs through a combination of dissolution due to zooplankton grazing and microbial aerobic respiration within degrading particle aggregates. The coupling of these cycles acts as a major filter on the export of both organic and inorganic carbon to the deep ocean.