Flux comparisons between sediments and sediment traps in the eastern tropical Pacific: Implications for atmospheric C02 variations during the Pleistocene1

Regeneration rates of labile elements and biogenic components were measured at two sites in the Guatemala Basin by comparing fluxes of material caught in sediment traps to fluxes of that preserved in the sediments. From 95 to 99% of the N, P, organic C, CaCO 3 , opal, and Br reaching the sea floor are regenerated at the two sites. For elements bound largely in refractory phases (e.g. Al, Sc, Ti, and Fe), the particle‐associated flux to the bottom is within 20% of the accumulation rate in the sediment. The two MANOP sites, about 800 km apart, have similar fluxes of organically associated N, P, and C, reflecting similar and relatively high primary productivity. There is a marked contrast in the opal/carbonate fluxes which leads to differences in CO 2 cycling at the two locations. At least 95% of the total particulate organic carbon and >97% of the total particulate phosphate are regenerated at <1,500‐m depth in the oceans. In contrast, much of the CaCO 3 is destroyed at the sea floor. By a simple three‐box ocean model we show that the recycling and storage depths of organic C, CaCO 3 , and P can be important factors in the control of the CO 2 content of the atmosphere. We suggest that Pleistocene CO 2 variations were due in part to global increases in upwelling during glacial periods with synchronous increases in total oceanic productivity and differences in diatom vs. carbonate productivity.